Want a change of scenery? Possess a detailed knowledge of birds? Then the Scottish Wildlife Trust (SWT) has a job for you. The SWT is hiring a ranger for a six-month position on Handa, an uninhabited island off the coast of the Scottish Highlands.

Handa is accessible from the mainland only by a 10-minute ferry. The ranger position, which covers the summer tourism season, requires weekly ferry trips to resupply at the nearby 200-person town of Scourie. The only visitors are summer volunteers and the 5,000-odd tourists who arrive each summer, mostly for birdwatching.

The island boasts thriving bird populations, including puffins, skuas, guillemots, and razorbills. Monitoring the species' health is a crucial part of the ranger's job. The guillemots and razorbills on Handa each contribute to about 10% of the populations in the British Isles.

The summer ranger will support wildlife conservation and tourism at the head of a team of volunteers. Despite the isolated location, the position is a social one.

"It's a challenging role, but the successful candidate will spend some warm, sunny days in one of the most beautiful and exciting places in Scotland," said Rab Potter, reserves area manager for the SWT.

Handa was not always uninhabited

People lived on Handa year-round until 1847, when the Highlands Potato Famine forced the population to emigrate to Nova Scotia. The remnants of a church can still be found on the island, as well as centuries of graves. Inhabitants of the mainland often buried their dead on Handa to prevent wolves from eating the bodies.

Connections between Handa and outsiders extended not just to the mainland but to the archipelago of St. Kilda, now also uninhabited. In 1876, a man named Donald MacDonald from St. Kilda first crossed the 24m gap between the shore of Handa and a 72m tower of rock called the Great Stack. He made the ascent by swinging hand over hand on a rope across open water. In 1969, a team that included well-known Scottish mountaineer Hamish MacInnes made the first ascent from the water.

During the summer, however, climbing the Great Stack is off-limits due to the presence of nesting birds. But if you'd like to spend six months monitoring puffins and guillemots, then the SWT ranger position may be for you. It runs from March to September and pays £26,112 ($35,311). The SWT provides free lodging in a ranger bothy.

Last week, a magnitude 7 earthquake ripped through the Hubbard Glacier, on the Alaska-Yukon border. Now, fieldwork by the Yukon Geological Survey (YGS) has revealed localized avalanches and serac falls. The reaction of the Hubbard Glacier to this earthquake offers warnings to mountaineers climbing on a warming planet.

2025's earthquake of the year

If it occurred in a densely populated area, the 2025 Hubbard Glacier earthquake could easily have killed thousands of people. Instead, it killed no one. In the mountaineering off-season, the American Wrangell-St. Elias National Park and the Canadian Kluane National Park lie abandoned by humans. Territorial lines notwithstanding, they both sit on the Hubbard Glacier, a roughly 100-km stretch of ice beginning at Mt. Hubbard and ending at Disenchantment Bay.

The recent earthquake struck a mere five kilometers under the surface of the ice and reached 7 on the Richter scale. Earthquake magnitudes are measured on a logarithmic scale, so a 7th magnitude earthquake shifts the ground 10 times more than a 6th magnitude, and so on. The 1906 San Francisco earthquake, for instance, which remains the deadliest in United States history, probably had a magnitude of about 7.9.

Cause not clear

Understanding how and why an earthquake happens takes rapid follow-up. Much of that comes from local witnesses via systems like Did You Feel It? Their reports help pin down the epicenter of an earthquake. If the aftershocks all trace a line, they can even identify the fault line responsible. But in the case of the Hubbard Glacier earthquake, aftershocks clustered along a 65km blob, rather than a clean line neatly defining where the fault runs.

There are many potential explanations for this, as outlined in this brilliant write-up. One is that multiple mechanisms triggered this earthquake, leading to smaller earthquakes along other fault lines nearby. These mechanisms can include one plate sliding next to the other, one plate sliding under another, or more exotic events like magma bubbles.

Another possibility is that Hubbard Glacier's placement along a geological transition zone -- from classic plate shifting to the north, to subduction of one plate under another in the south -- leads to messy, chaotic fault behavior. And finally, it's also possible that some of the aftershocks were not earthquakes at all, but rather local icequakes.

New results from the Yukon Geological Survey

The YGS posted preliminary results of their follow-up survey on Facebook. In that post, they state that the inciting event was one tectonic plate sliding two meters relative to its neighbor all at once. This is a significant amount of fault slip, but the team did not locate any places where the ground had ruptured.

Their results don't offer conclusive answers regarding the clumpiness of the aftershocks. But whether or not the earthquake triggered icequakes, it certainly disrupted the glacial environment around 3,741m Mt. King George at the epicenter. When the YGS team arrived in the area shortly after the earthquake, they found dust hanging in the air from recent rockfall.

Radiating out from the epicenter, they found numerous snow and ice avalanches, as well as evidence of recent serac falls. But the damage on Mt. King George was most intense.

"It is fortunate that this event did not occur during mountaineering season, as earthquake-triggered serac falls and avalanches have caused fatalities in the past," they wrote. "The damage to ice in the region and persistent rockfall from landslides scars may pose new additional hazards for mountaineering and skiing expeditions in the area."

Threat to mountaineers

The reaction of glaciers to shallow earthquakes is a pressing issue for mountaineers as global temperatures rise. When glaciers melt, the water runs downstream and rejoins the sea. Without the weight of ice on top of it, the Earth's crust rises. This process, known as isostatic rebound, is also responsible for some of Everest's current upward growth.

Isostatic rebound has been occurring gradually over the last 20,000 years, since the end of the last Ice Age. It causes earthquakes worldwide, some of which trigger avalanches. Human-induced climate change compounds this effect. With glacier melt accelerating at unprecedented rates, low-level seismic activity seems to have increased beneath the Greenland ice sheet.

Geologists and glaciologists can use events like the Hubbard Glacier earthquake to better understand the seismological warning signs for ice and snow hazards. Potentially, this information could be incorporated into mountaineering ventures the same way that weather forecasts currently are. But right now, the YGS has issued a call for athletes to help out scientists, rather than the other way around.

"If any mountaineers or skiers have photos of Mt. King George before these slides, we would love to hear from you! Pre-event photos will help us estimate total landslide volumes. Please send any relevant photos to geology@yukon.ca."

The National Institute of Standards and Technology (NIST) fulfills a vital role in national security: employing the sort of people who would, if they got bored, take over the world. It takes a specific kind of person to run the persnickety gravitational calculations of exactly how fast clocks tick on Mars relative to the Earth.

Thanks to NIST, two of these people have recently published their calculations, instead of building a lair under a volcano to perform evil experiments. They found that Mars time runs faster than Earth time, and considerably messier.

The purpose of clock rate models

In strong gravitational fields, time flows more slowly. Albert Einstein first described this effect, known as time dilation, in his 1915 theory of general relativity. Scientists working in precision timekeeping must account not only for the Earth's gravity, but also that of the Sun and Moon.

They have become very good at that. The evidence is on your phone: the accuracy of GPS is thanks to minute adjustments to clock rates in different locations around the Earth.

Future spacefarers will need to know the exact time on Mars relative to the Earth. Any kind of precision location system, such as GPS, depends on clock rate conversions. The new paper from NIST models the gravitational field on Mars at different points throughout its orbit to predict what that clock rate should be. They double-check their results using in-situ gravitational observations from Mars.

Mars' messy time

Modelling Martian time is a lot more complicated than it is for the Earth. Not only is it harder to actually take measurements that would allow scientists to check their math, but the math itself also involves more factors.

Mars' lower mass means gravity is a lot weaker on its surface than on Earth. Even without external effects, Martian time flows faster than Earth time.

But the Mars time to Earth time conversion depends on a lot more than Mars's gravitational field. The biggest complication for time on Mars is the eccentricity of its orbit. Eccentricity describes how elongated and oval-shaped an orbit is, as opposed to circular. Since Mars' orbit is considerably more eccentric than Earth's, its distance from the Sun varies much more.

Mars's lower mass, only 10% of the Earth's, also makes it easier for other bodies in the Solar System to push it around. While the motion of Mars doesn't affect the Earth's gravity much, the motion of Earth matters a lot to Mars.

The ever-changing locations of the Sun and the Earth push and pull on the surface gravity of Mars and, consequently, its clock rate.

We understand Earth time 100 times better than Mars time

Although Mars time changes over the course of a Martian year, the authors found an average difference of 421.5 microseconds (millionths of a second, or μs) per day between Mars and the Earth. It doesn't sound like much, but think of it this way: For every day that passes on Earth, Mars falls behind our clocks by 421.5 μs. If we don't model and compensate for the difference, that's enough to render 5G wireless, for instance, totally useless.

By predicting this discrepancy, the authors have theoretically enabled 5G cell service on Mars, although some minor technological advancements will be necessary to make this happen. But their model does come with big error bars.

Make no mistake: the new model of Martian time is vastly more precise than the previous model. (The previous model was created by the exact same people who made the new one, because NIST only employs people with worrying dedication.) Nonetheless, it fits the data about a hundred times worse than the current best model of Moon to Earth time conversion. You'll never guess who the authors are on that one.

When they compare their model of clock rate to real gravitational observations from Mars, their guesses are only off by an average of 100 ns (a billionth of a second) every day. This is astoundingly precise, but still a hundred times worse than their errors on the Moon, which are about 1 ns every day. Mars is a messier place to visit than the Moon, and time runs strangely there.

Despite its unmemorable name, J2322-2650 is a strange system. A Jupiter-sized exoplanet orbits an energetic neutron star, which constantly bombards it with gamma rays. Now, a team of astronomers has published its observations of the planet. They discovered strong westerly winds and an atmosphere unlike anything else.

So is it really a planet at all?

Pulsars and their companions

When massive stars die, they jettison their outer layers in a supernova. No longer able to support itself through nuclear fusion, the core collapses in on itself. If it's big enough, it forms a black hole. If it's not, it leaves behind a neutron star.

In many ways, these zombie stars are more dramatic objects than black holes. Many emit violent bursts of gamma rays and X-rays, the sort of light that would tear apart human cells. Periodic radio emission is also common, flung out from near the surface of the neutron star as a result of off-kilter magnetic fields. (Exactly how close to the surface this emission begins, and through what mechanism, remains a mystery.)

Neutron stars that emit in the radio band are known as pulsars, or zombie stars, because they are remnants of massive dead stars. These radio pulses are so regular, so seemingly artificial, that their discoverer, Jocelyn Bell, jokingly referred to them as "little green men."

Astronomers observe the radio waves of pulsars to study all sorts of phenomena. They can detect companion stars orbiting the pulsar -- everything from rocky planets to other neutron stars -- using slight delays in the pulse arrival times at the telescope.

That's how the team behind a new study on J2322-2650 knew to point the James Webb Space Telescope at this source, when no traditional exoplanet survey would have noticed the faint Jupiter-like companion. (In all but a few exciting cases, pulsars do not emit visible light.)

Carbon winds on a lemon-shaped planet

Jupiter-like planets tend to have atmospheres composed mostly of hydrogen and helium, similar to the Sun. Heavier atoms like nitrogen, carbon, and oxygen allow molecules such as ammonia and methane to form. While no two gas giant exoplanets are the same, astronomers have never found anything like the companion of J2322-2650 before.

Instead of a hydrogen-based atmosphere, they found mostly helium and an absurd amount of carbon. Not hydrocarbon chains, which commonly occur in outer space, but pure molecular carbon. In solid form, pure carbon forms minerals like graphite and diamonds. There is no earthly analog for gaseous clouds of carbon -- even the darkest soot also includes lots of oxygen and hydrogen.

Team co-author Peter Gao said that the observations stunned him. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It's extremely different from what we expected.”

The weird planet's nearness to a pulsar enables its gaseous, carbon-rich atmosphere. The two are so close together that the pulsar's gravity keeps the companion pinned with one side always facing it, a process known as tidal locking. (The Moon, for instance, is tidally locked to the Earth). Because the near side of the companion is slightly closer to the pulsar than the far side, the difference in gravitational attraction stretches it out like a football.

So that's the companion of this zombie star: an elongated, tidally locked object covered in carbon winds, whose nearside is pummeled by gamma rays all the time and whose far side never sees light.

What is it?

Black widow pulsars

Black widow is one of those wretched, jargon-y pulsar terms that baffle most other astronomers, let alone the general public. But unlike many offbeat pulsar terms (just what is a birdie, anyway, and what does it mean to zap one?), black widow is descriptive. A black widow pulsar is one that, like a female black widow spider, is "eating" the light, fluffy atmosphere of its companion. Many of these companions are brown dwarfs, failed stars more similar to Jupiter than to our Sun.

Most astronomers consider brown dwarfs to be planets. Like Jupiter, they have hydrogen atmospheres rich with common molecules like methane, and more exotic iron and silicate compounds. They are not dominated by helium and pure molecular carbon.

Even if we assume this system represents the end-stage of classical black widow formation, where the pulsar has already stripped most of the atmosphere off its companion, the carbon remains an anomaly. Carbon and oxygen form at the same stage of stellar evolution, so there should be a lot more oxygen floating around its atmosphere.

The authors of the study discuss more exotic scenarios, like a merger between one helium and one carbon-oxygen white dwarf. But these still can't explain the carbon concentration they observed. We may know what this companion looks like now, but what it used to be remains a mystery.

Above, an artist's conception of the system, as the lemon-shaped planet orbits the pulsar. Imagery: NASA/JWST/ESA/CSA/Ralf Crawford (STScI)

Tired, but can't sleep? Working, but can't focus? Need something mindless yet peaceful happening in the background? Check out our December picks for the best live wildlife cams from Explore.org. From surprising visitors to a bald eagle nest to the fuzziest penguins in all of Argentina, we have you covered for the best creature activity around the globe.

4. Muskoxen in Alaska

Until you have seen a muskox, you cannot comprehend how much fur they have. If you haven't, don't even finish reading this. Go take a look at the muskox live cam from the University of Alaska at Fairbanks. Here, half a dozen muskox meander in and out of view, attracted by a feeding stand. Some stand snacking, while others curl up on the ground, heedless of the cold, and scratch their heads against the snow.

Muskoxen went extinct in Alaska around the start of the 20th century. The U.S. government reintroduced them from Canadian populations in 1935 to support Yup'ik subsistence hunting. Since then, their population in Alaska has remained stable, and muskox continue to thrive in Canada and Greenland.

3. Elephants at a watering hole in South Africa

This one deserves a special shout-out for its soundscape. Insects and songbirds unite at all hours of the day to form a peaceful, evocative background for work or sleep.

But it's worth watching, too. At one point, a herd of strange, orange-red creatures thronged onscreen. Their heads looked like deer, they were striped like zebras, and they wagged their tails incessantly like dogs. Several larger, long-horned dark creatures wandered among them, equally obscure to me.

After much googling, I determined the orange creatures to be bongos, a type of antelope. (If you need a pick-me-up, go search for photos of baby bongos.) The cow-things were harder, but I eventually placed them as nyalas. Although also a type of antelope, nyalas have a bovine grace. They look like what teenage cows would compare themselves to when they look in the mirror.

As it turns out, bongos are both shy and nocturnal. Seeing them for so long during the day and interacting with a different species is a rare treat. Check them out when you have a moment.

2. Bald eagle nest in Iowa

Earlier this week, I was on the phone with a friend when I mentioned my hatred of raptor cams. "I check them on and off, and the birds are never there," I proclaimed. "Raptor cams are a scam. I'll never put a raptor cam on my best-of-the-month list."

But I decided to give raptors a last chance before my monthly ranking, and lo and behold, there was a little bird sauntering around the nest on the Decorah, Iowa cam. It was dark brown and strangely sleek for a chick. I watched it, entranced by the way its neck moved.

Slowly, like a character in a horror movie, the truth dawned on me. "Holy cow," I texted the same friend. "I just checked this eagle cam, and there's an owl in the nest."

"Brave owl right there," she wrote back. "Though maybe he too knows the rule of the eagle cam: As long as the eagles are on camera, they're never there."

1. Baby penguins on Isla Tova

Hey. Hey, you. Please take a look at these fuzzy little penguins.

It's been a rough day for me. These penguins have gotten me through it. I keep thinking about having a cry, and instead I switch back to the penguin tab. They're fuzzy and small, and they keep wiggling everywhere. I'm obsessed.

Magellanic penguins are native to Patagonia, and unlike many of the creatures featured on Explore.org, they're not endangered at all. These hardy two-foot birds are particularly thriving on Isla Tova off the coast of Argentina, where the live cams set up around the island also support biological research.

Right now, there are three chicks in this nest under a wiry bush. As I watch, one of them emerges from the mass of indistinguishable fluff. He opens and closes his mouth a bit like a cat chirping, annoys his siblings by rearranging his position, and then falls asleep with his mouth open. The other chicks settle back in for a long, tiring night of penguining.

Four hundred thousand years ago, someone took up a piece of pyrite, struck it against a stone, and started a fire. Archaeologists working on a site in Suffolk have found the pyrite and the scalded clay it left behind. But what species knew how to make fire in Britain almost half a million years ago?

About 1.5 million years ago, early hominins -- the group ranging from Australopithicus to modern humans, but not apes like chimpanzees or gorillas -- maintained fire in open-air sites in Kenya. And 50,000 years ago, Neanderthals may have struck the side of stone bifaces to catch a spark.

The newly discovered evidence in Barnham, Suffolk, fills in a crucial step along the way. It is also now the oldest known evidence for deliberate fire-starting, as opposed to fire maintenance, by an astonishing 350,000 years. Earlier hominins likely used fire arising from lightning strikes or wildfires, but did not know how to create it themselves.

Barnham has long been a fruitful archaeological site. The site attracted at least two separate species of hominin around 400,000 years ago. One of these, which contributed older tools to the site, may have been Homo heidelbergensis. This early human left behind tool remnants in Britain, referred to as the Clactonian culture.

Not dull cavemen, after all

The second culture probably left behind the evidence of fire-starting. They weren't Homo sapiens, who were still living it up in East Africa at the time. The most likely candidate is Homo neanderthalis. A Neanderthal site from approximately the same era was found at nearby Swanscombe, although no human remains have been discovered at Barnham.

Long stereotyped as dull cavemen, Neanderthals were our closest cousins. Recent research shows they made art and ritually buried their dead. Now, it seems they may have started fire as well.

This second, likely Neanderthal culture at Barnham used fire. It left its scars in reddened clayey silt scattered around the site, rich in haematite. Haematite forms when iron-rich minerals are heated.

The team behind the new research, published in Nature, experimented with burning sediments to recreate the distribution of haematite and the magnetic properties of the silt. The closest replica came from a dozen four-hour exposures to temperatures between 400-600°C, a typical hearth temperature.

But it's the flecks of pyrite found at the site that may have just rewritten our understanding of human technological evolution. They were found scattered among pieces of stained flint, and they didn't match any sediment in the immediate vicinity of the site. Someone had brought them there.

Striking pyrite against flint is one of the oldest methods of starting a fire. These pyrite pieces transform the Barnham site into an enigmatic glimpse into the creativity and technological advancement of early human species.

Unless bones are discovered at Barnham, however, we can't confirm exactly who these brilliant cousins of ours were.

At the bottom of a lake in Kyrgyzstan lie the ruins of a former trading hub along the Silk Road. Its remnants have lain undisturbed for 500 years, after a massive earthquake submerged it. Now, a joint team of Kyrgyz and Russian archaeologists has begun excavations under the lake. They discovered numerous buildings, fragments of pottery, and a vast funerary complex.

Lake Issyk-Kul lies in northeastern Kyrgyzstan, near the Kazakhstan border and on the edge of the Tien Shan Mountains. At 182km long and up to 60km wide, it is larger than many countries. Its salty waters prevent it from freezing over even in the cold mountain winters. They also hide the remnants of the medieval town of Toru-Aygyr. Like other settlements around Lake Issyk-Kul, Toru-Aygyr thrived off trade and travel.

The region was so connected in the high Middle Ages, in fact, that the bubonic plague outbreak known as the Black Death may have begun somewhere along the shores of Issyk-Kul. In the mid-1300s, the Black Death killed two out of every three residents of Europe.

A century after the first bubonic plague cases showed up around Issyk-Kul, an earthquake submerged Toru-Aygyr. It remained there for the next 600 years.

An underwater necropolis

This week, the Russian Geographic Society announced its first discoveries at the Toru-Aygyr site. Perhaps the most enigmatic of them is a 60,000-square-meter necropolis, dated to the 13th through 14th centuries. All the skeletons in the necropolis lie facing north towards the Kaaba in Mecca, in alignment with Muslim burial practice.

The necropolis is degrading rapidly, prompting swift excavation. This diving season, the team recovered two skeletons, one female and one male. Forensic results have yet to be released.

Fourteenth-century skeletons from Toru-Aygyr will be of particular interest, since bodies from two other cemeteries near Issyk-Kul show bubonic plague in their DNA. Their tombstones date their deaths to 1338 and 1339, perhaps marking the first outbreak of the Black Death.

Life along the Silk Road

The rest of the discoveries so far in Toru-Aygyr may not be as existential as the necropolis, but they offer valuable insights into life in Kyrgyzstan nearly a millennium ago. The remains of an ornately decorated building, for instance, hint at village social life. The archaeologists suspect it to have been a mosque, a madrasa, or a bathhouse.

They also found a millstone, many ceramic fragments, and an intact grain-storage vessel known as a khum. This last was embedded into the bottom of the lake, and the team will return in the future with specialized equipment to extract it.

Nearby, they found more burial sites outside the main necropolis. These burials appear to date from before Islam became the dominant religion, and indicate continued occupation of the settlement for many centuries.

"In the 10th century, the Kara-Khanid State was formed on this land," said expedition leader Maksim Menshikov in a press release. "People here practiced various religions: pagan Tengrianism, Buddhism, Nestorian Christianity. The ruling elite often turned to Islam throughout their rule, but this religion became widespread in Central Asia only in the 13th century."

One unsolved mystery at Toru-Aygyr is when and why it was abandoned. By the time the earthquake submerged the settlement at the beginning of the 15th century, its occupants had already left. Finding out why will take detective work through primary sources. The team hopes that Chinese records from the time may hold secrets.

"The Chinese considered this territory a zone of their interests, but they could not control it," said Menshikov. "Nevertheless, we see that this location is reflected in Chinese sources. This gives us hope to correlate historical materials with the results of our excavations."

Between the coastal lowlands and arid highlands of Peru lie about 5,200 holes. Carved before the Spanish invasion in 1532, the so-called "Valley of Holes" has long intrigued archaeologists and conspiracy theorists alike. New data suggest the site may have been an elaborate marketplace and, later, an Inca tax depot.

Situated in the Pisco Valley about 200km south of modern-day Lima, the Valley of Holes lies atop Monte Sierpe, or "Serpent Mountain." The name is not a coincidence. A 1.5km line of round holes snakes across the hilltop, evocative yet eluding obvious purpose. Explanations for the monument have included a grave site, a geoglyph (like the animal shapes at Nazca), an agricultural site, and, recently, a marketplace.

Holes at a crossroads

At the dawn of the first millennium, the Pisco Valley lurked at the edge of the Chincha Kingdom. Although a military society, the Chincha had advanced agricultural techniques. The remnants of their fields lie at the bottom of the foothills, the soil still rich thanks to their use of fertilizers like guano. They fished, too, and sailed the coast.

It was probably the Chincha who first dug the 5,200 holes atop Monte Sierpe. Their kingdom fell to the Inca around 1480, although the Chincha leaders retained much of their autonomy. If the Inca built the Valley of Holes, they had only 60-ish years to do so before the Spanish overthrew them. There are also no similar sites in the Inca heartland.

Monte Sierpe sits in the foothills of the Andes, at the intersection of major trade routes between agricultural plains, fishing coastlines, and mountain mines. Earlier archaeologists suggested that it was ideally positioned as a location for bartering. Now, they have the data to back that up.

Seeds in the ground

The team published their results this week in Antiquity. They surveyed the entire site with high-resolution aerial photography and sampled the soil in 19 holes. They found a variety of seeds and plants not present in the surrounding ground. These included maize, cotton, and brassica. Also present was Humboldt's willow, a coastal riparian plant used in basket-weaving.

While mountain plants could blow down from higher altitudes, the agricultural products and coastal plants required human transport. The structure of the site also suggests it hosted an activity with many participants. The holes are arranged in clusters of about a dozen rows each, with six or so holes per row.

These clusters could have served as categories in a marketplace, with goods laid out in each hole for easy display. There is enough space between holes to walk through the middle of each cluster, and busier traffic could have crossed between clusters.

Monte Sierpe under the Inca

The Inca did not use money, but their taxation system was rigorous and effective. They recorded census and financial information with a string-based writing system where the placement and type of knots on a string indicated numbers. Different strings combined together into quipus, the equivalent of books.

The authors of the new study suggest that one such quipu, found near Pisco Valley, may describe the Valley of Holes. This quipu recorded large-scale accounting functions, possibly including taxation quotas at the Monte Sierpe site. During the Inca period, it would have been an obvious center of taxation in their strict system.

Right now, the system of writing on quipus retains many mysteries. The exact purpose of this particular quipu is not known. But like many linguistic mysteries, advances in machine learning and encryption may mean answers are closer than ever before.

Watching animals go through their daily routines, even when there's not a lot happening, is a good way to relax -- hence the popularity of live wildlife cams. These cameras are often seasonal, as migrations or weather bring different species into the spotlight.

Below, a list of the best feeds currently on explore.org, a repository of nature films and live streams. From the secret lives of pandas and wolves to the deceptive richness of a Texas backyard, here's our roundup of the best cams to watch in November.

5. Lesser Flamingos in Kimberley, South Africa

This comforting livestream always has something feathered and spindly onscreen, no matter what time of day. Outside of the city of Kimberley lies Kamfers Dam, an artificial wetland that treats most of the urban runoff. In 2006, an ornithologist convinced a local diamond mining company to help him create a breeding island for Lesser Flamingos, since the dam waters were filled with their favorite algae.

The island was a hit among the flamingos. Unfortunately, Kimberley's growth has posed a threat to the site's safety in recent years. This livestream comes with an asterisk, but it's well worth the watch.

4. Waterhole at Nkorho Bush Lodge

There are a multitude of South African bush cams live this month, and after careful analysis, I have selected this one as my favorite.

Night or day, it seems like this is the waterhole to be at. If it were a club, there would always be a line of well-dressed young people queuing outside, a bouncer breaking up a fight, and a horde of drunk girls crying on the curb.

During the day, lions prowl the area. Wildebeest cross in cautious herds. At night, the hyenas and wild dogs come out, and insects criss-cross the field of view at all moments.

As of writing this, the same hippopotamus has been slouching in the center of the watering hole for the last 10 hours. None of the other visitors seemed to care. A pack of hyenas trotted by, their laughter mellowed out by the gentle sound of rain falling on the water.

3. Pandas in Gengda Valley, China

I have a thing about pandas: I'm opposed. Listen, I like charismatic megafauna as much as the next guy, but pandas aren't a keystone species for anything. They're useless, and I take their survival against the tides of evolution as a sign of God's existence. It's time to stop throwing conservation resources at them.

So it is with great regret that I have to admit the Gengda Valley Panda Yard is really entertaining. After watching for a few minutes, I found the great lumbering beasts reaching into my heart. Where before I had described them as stupid with derision, it now seemed a term of affection. Sure, they have no desire to reproduce in captivity unless shown videos of wild pandas copulating. But look at those great fuzzy heads. Isn't it worth putting zookeepers through awkward rituals to keep these things alive?

I've kept this livestream open on my browser for the last week. Every so often, I click back on it. There's always some great stupid bear onscreen, lazing about. All it does is eat and sleep. More power to you, panda.

2. Texas backyard wildlife

While many of the most popular livestreams on Explore.org shine in one particular season -- for instance, during the zebra migration or the salmon runs -- there's always something happening in this Texas backyard. The owners have arranged 68 cameras across their five-acre Austin property, and alternate between them for the best action.

On their cameras, I've seen gray fox pups cavorting around a field and raccoons huddling over a snack. Screech owls have flown at the camera before swooping away at the last instant. A garter snake hunted down and ate a frog.

This livestream showcases the incredible biodiversity of urban areas and the impact of rewilding, even on the scale of a single backyard. The owners of this property regularly post highlight videos and photos to their website. They even run a Discord server for their viewers to foster understanding of urban wildlife.

1. The International Wolf Center

It's strange to think, watching this livestream, that wolves were a nightmare beast to everyone from Alaska to Germany for much of human history. They look so startlingly dog-like and act so communally. But that's the magic of wildlife cams: that humans get an eye into how animals behave among themselves, without our presence.

Make no mistake, these are not wild wolves. They are living in a luxury compound designed just for them. Zoos rarely keep wolf packs, because their social lives are so complex. Without the ability for one wolf to leave, tensions may lead to violence. At the International Wolf Center (IWC), specialists continually monitor the dynamics between their "ambassador wolves" and relocate individuals, if necessary.

The IWC, like all the best zoos and aquariums, is primarily a research institution. They fund scholarships, conferences, and publish a magazine. Their ambassador wolves facilitate this research, allowing the staff to study pack behavior 24/7, but their real purpose is to encourage the public to care for wolves. The pack includes multiple breeds, including Arctic gray wolves and North American gray wolves. You can read each wolf's biography on the IWC website.

It doesn't look real, at first glance. There must be a green screen right behind the shadowed silhouette of a falling man. It must be AI-generated. But it's real: a snapshot of a man in freefall, eclipsing the high-resolution surface of the Sun behind him.

How?

Trigonometry preparation

Andrew McCarthy and Gabriel Brown came up with the idea for the shot while skydiving together. They knew it would be near-impossible.

"We had to find the right location, time, aircraft, and distance for the clearest shot, while factoring in the aircraft’s power-off glideslope for the optimal sun angle and safe exit altitude," wrote Brown on Instagram.

He volunteered to skydive for the project, while McCarthy, an experienced solar astrophotographer, would snap the shot. 

Brown posted screenshots of the math involved. In addition to the skydiving complications, the pair needed to calculate how far away the telescope should be to silhouette a man against sunspots and granulation (the pattern on the Sun's outer atmosphere made by little heat cells bursting).

These sunspots are tens of thousands of kilometers wide and 150 million kilometers away. The shot needed both the skydiver silhouette and the sunspots to be clear and visible. That wouldn't work if the silhouette is way smaller or larger than the sunspots. They had to fit into the frame at comparable sizes. This was one of the factors that set how far away from Brown the camera had to be. They calculated that the proper distance would be 1.5 miles, or 2.4 kilometers.

Four pilots and a paramotor

For maximum precision, McCarthy and Brown hired a paramotor pilot to give Brown a lift. They went through three pilots before finding Jim Hamberlin. Hamberlin was able to steer his paramotor directly in front of an active region on the Sun's surface. When McCarthy gave the call, Brown jumped from the motor, and Hamberlin revved it up out of the way of the central shot.

Typically, skydivers spend 10 seconds or so in freefall from Brown's 3,500-foot exit altitude before triggering their parachute. That's enough time for Brown to have reached terminal velocity at about 200kph -- the speed at which gravity balances with air resistance and a skydiver doesn't accelerate any further. (His head-down position would have given him an even faster terminal velocity, up to 320kph.) McCarthy filmed his freefall on a Lunt 60mm H-alpha camera and snapped single exposures on an ASI 1600mm.

One shot captured Brown's silhouette and the position of the Sun, but not the details of the solar chromosphere (the Sun's hot outer atmosphere) or its wider surface. As described in his highly readable write-up of his usual solar photography methods, McCarthy stacked hundreds of exposures. By tracking the Sun's minute motion through the sky, he prevented blurring while preserving the features of the chromosphere at that moment in time. The solar surface is highly turbulent, so the same sunspots a day later might have moved or faded.

Each exposure only covered a small tile of the solar surface, so for the fully zoomed-out version of the shot, McCarthy pieced them together into a composite image like a mosaic. (In fact, this method of imaging space objects is called mosaicing and is used in both astrophotography and scientific astronomy.)

Filters and focus

No matter how fast the shutter speed, a normal photo of the Sun oversaturates a camera's detector. That's why McCarthy used an H-alpha filter for this photo, like he uses for all his solar photography. "H-alpha" refers to a narrow frequency of reddish light that hydrogen emits when it decreases in energy.

With an H-alpha filter in place, photographs of the Sun only take in the outer edge of the chromosphere, where hydrogen is cooling and thus decreasing in energy. It's a favorite filter of astrophotographers because dramatic features such as sunspots and solar flares form on the chromosphere.

Unlike the chromosphere, humans are largely invisible in H-alpha. They reflect only what stray photons bounce off them from the Sun. That's why Brown's falling form stands out like a hole in space.

While keeping two objects of different distances in focus is usually difficult, especially with a long lens, McCarthy took the photo so far away from Brown that both he and the Sun came out sharp. They both fell within the so-called zone of focus that photographers are familiar with.

If you're interested in a print of either the close-up or full versions, you can find them on McCarthy's store, along with his other work. As for Brown, McCarthy reassured Redditors that he landed safely. And no, he wasn't anywhere near the Sun.

Astronomers have announced a candidate for the universe's first generation of stars. While sifting through observations of the earliest known galaxies, they flagged one small dwarf galaxy, GLIMPSE-16043. Unlike every galaxy we have observed before, it doesn't bear any signs of recycled stellar material.

Astronomers have theorized the existence of this first generation of stars, which formed not from the ashes of their ancestors but from primordial hydrogen and helium. Many candidates have previously cropped up, but none have won popular support. GLIMPSE-16043, however, may have what it takes to stand the test of time.

'Population III' Stars

The Big Bang only created four elements: hydrogen, helium, and tiny amounts of lithium and beryllium. No oxygen, no iron, no carbon. In short, none of the elements that make up our solid, dynamic world.

Those did not arrive until much later, when the first stars died in massive explosions called supernovae. Deep in the furnace of their cores, they had forged all of the elements up to iron. Their supernovae flung these elements out across interstellar space, seeding the gas with metals that would work their way into the next generation of stars. (Astronomers call any atom heavier than helium a metal, presumably because they want to drive chemists into a blind rage.)

When early astronomers observed the Milky Way, they found this second generation of stars lurking in the ancient center of the galaxy and at the far-flung edges. They called them Population II stars to distinguish them from the much more metallic, familiar Population I stars that make up the Milky Way. These include our Sun.

By the time astronomers got around to theorizing the existence of an even earlier generation of stars, the naming convention was set. The first stars in the universe are Population III.

A galaxy of only hydrogen and helium

People cannot exist without metals. Planets cannot exist without metals. Not even the dust grains that float in interstellar space can exist without metals. Without metals, there are only clouds of gas and stars.

That's what would comprise this possible candidate for Population III stars, a dwarf galaxy from only 900 million years after the Big Bang. GLIMPSE-16043 is only visible to us because it lies behind a much larger, much more nearby galaxy. The gravity of that foreground galaxy magnifies the light of GLIMPSE-16043 and reroutes it toward us. The James Webb Space Telescope (JWST) excels at photographing these "gravitationally lensed" galaxies.

The team that identified GLIMPSE-16043 investigated thousands of lensed galaxies observed with the JWST. GLIMPSE-16043 was the only one that matched their criteria. Hydrogen makes galaxies redder, so to identify galaxies dominated by hydrogen, the team restricted their search to galaxies that appear brighter when photographed through a red filter.

Then they used how bright a galaxy is under different colored filters to calculate its age. They kept only the hydrogen-dominated galaxies that dated from 700 million to 1.2 billion years after the Big Bang. That's when Population III stars would have existed.

GLIMPSE-16043 passed these tests with flying colors. At about 900 million years after the Big Bang, it seems to have almost no metals. When we look at this tiny little dot on a pixelated image, we may be looking at some of the first stars in the universe.

Confirming this will be difficult. The dwarf galaxy is very faint, and the JWST is probably not sensitive enough to do anything other than image it in different color filters. These filters are equivalent to putting giant buckets out in the rain to catch all the water you can. They miss the fine detail in each raindrop that would reveal the presence or lack of metals.

If this galaxy is indeed made of Population III stars, it is probably one of the last stragglers from that era. We may need to wait for a better bucket to confirm the nature of GLIMPSE-16043. Fortunately, the galaxy isn't going anywhere.

Members of a 500km expedition along the Hudson River sampled water at two high-elevation lakes in the Adirondacks. Their findings indicate that humans introduce microplastics into the environment through more than just water and air pollution. Modern clothing and gear also shed microplastics.

In 2024, an outdoor company and a youth wilderness company joined forces to lead eight high schoolers on this trek along the Hudson River. Starting in the Adirondack Mountains, they hiked, rafted, and kayaked to the New York Harbor, relying only on human power.

The students came from New York and California. All were juniors or seniors, and all were male for unspecified "practical considerations," although two had never hiked a mountain before. On the flip side, three were Eagle Scouts and two came from the Adirondacks.

The expedition took 18 days, some of which lasted 20 hours. They stayed in a combination of campsites and hotels. Challenges included canoe portaging and dealing with storms.

Surprising measurements

Along the way, the group took water samples to measure microplastics in two lakes. They expected Lake Tear, at the top of the watershed, to have the purest water they would encounter.

Moss Pond, only 13m lower than Lake Tear in elevation but further down the watershed, experiences similar airflow to Lake Tear. In contrast to Lake Tear, though, no trail leads to its shores.

Contrary to their expectations, the team found a 26-times higher concentration of microplastics in Lake Tear than in Moss Pond. This suggests that in the upper watershed, more microplastics arrive in the water carried on hikers' garments than floating in the air.

The team's findings agree with surveys that found increased amounts of microplastics on trails. Most of the plastic was microfibers from clothing.

What you can do

Many biochemists, environmental scientists, and public health specialists have devoted their careers to understanding the impact of microplastics on the world around us. They have uncovered effects ranging from respiratory illnesses in children to disrupted food chains in ecosystems worldwide.

While individuals may lack the power to effect wide-scale change in society's reliance on plastic, the Hudson River experiments show there are some ecosystems where we can have an impact.

Currently, most gear companies no longer sell natural rubber soles. And natural fiber clothes are often more difficult to find than their synthetic counterparts. But hard rubber soles shed fewer microplastics than soft ones. Additionally, natural fibers like cotton and linen don't release any microfibers.

Here, customers have more power for change than in most other areas of pollution.

Watching animals go through their daily routines, even when there's not a lot happening, is a good way to relax -- hence the popularity of live wildlife cams. These cameras are often seasonal, as migrations or weather bring different species into the spotlight.

Below, a list of the best feeds currently on explore.org, a repository of nature films and live streams. From bears snacking on salmon to wildebeest crossing the Okavango Delta, here are the best live streams for October.

5. Alligators and spoonbills, St. Augustine, Florida

When the sun is up, alligators flop like logs by the water in St. Augustine Alligator Farm Zoological Park. They don't do much, but that's okay. They're alligators.

At night, roseate spoonbills and herons dominate the scene. Spoonbills, once hunted nearly to extinction for their distinctive pink feathers, now thrive across the southeastern United States. A few of them are guaranteed to be curled up in front of the camera.

The nighttime soundscape is gentle but comforting, with the occasional birdcall. During the day, though, the conversation of human visitors makes muting a better option.

4. Polar Bears, Churchill, Manitoba

This live stream rewards patience. At night, a stationary camera focuses on the subarctic shrubbery outside the Tundra Buggy Lodge, a hotel in Canada's northern Manitoba, which hosts polar bear spotting tours. The only sound is the rush of the wind. During the day, the camera pans over the scrappy tundra.

But the thrill of spotting a polar bear sloping across the screen is worth it. The Churchill Wildlife Management Area heavily restricts visitors to protect this stretch of coast for polar bears and other keystone species.

Polar bears face existential threats in areas like this one, as climate change melts the sea ice on which they do most of their hunting. This is the best time of year to view polar bears at Churchill, because they're all hanging out, waiting for nearby Hudson Bay to freeze so they can start hunting and eating again.

3. Underwater Reef Cams, Utopia Village, Honduras

At night, the screen is pitch black, but the burble of water justifies the WiFi usage. When sunlight turns the water a striking turquoise, fish dart in and out of the corals. Occasionally, something larger looms up out of the distance and passes in front of the screen like a leviathan.

Utopia Village used to be a dive resort, but after the COVID-19 shutdown, its owners decided not to reopen. Now, they operate their location as a marine conservation center.

2. Boteti River zebra migration, Botswana

Of all the live streams currently on explore.org, this one stands out for its soundscape. Birds gibber and yowl. Wild dogs chirp. Other creatures of indeterminate species make noises that defy categorization. Even without the stunning video, this live stream is worth putting on in the background.

During much of the day, nothing moves across this sandy river in the Okavango Delta. But at night, the landscape comes alive. Zebras meander through the scenery, stopping to drink on their 500km migration to the Makgadikgadi salt pans. Wildebeest travel with them and frequent the river by themselves as well. Occasionally, a herd of elephants comes to splash in the water.

On tonight's stream, in the early hours of the Botswanan morning, a herd of wildebeest passed in front of the camera. When they had crossed the river, a sudden flurry of wild dog barks broke out. The wildebeest froze, scanning the shore near the camera for the threat. But no wild dogs appeared. The herd relaxed and moved on into the morning light.

1. Brooks Falls Brown Bears, Katmai, Alaska

There's a reason these bears consistently top the most-viewed list. With 40 bears often onscreen at any one time, there's no shortage of entertainment. The white noise of the water offers a pleasing background to emails, Excel sheets, or coding. And anytime a bear catches a salmon, it feels like a personal victory.

This live stream overlooks the rapids of a two-kilometer stretch of the Brooks River, right along the fall sockeye salmon run. The brown bears here eat up to 40 salmon a day in preparation for winter hibernation. As fall progresses, they will continue to fatten.

Cubs splash in the less oversubscribed stretches of the river, learning to catch salmon for the first time. Victorious old bears feast, turning wide brown eyes to the camera. Some bears, tired of fishing, sit down in the river and just enjoy the waves lapping their fur. There is plenty of salmon for everyone.

If you have a favorite planet or star, you're in good company. Astronomers who devote their lives to the study of peculiar outer space objects are all too happy to gush about the ones they like best. From the cradles of new planets to the violent graveyards of massive stars, here are some of the answers we got for the question: "What's your favorite thing in outer space?"

A planet factory far from Earth

Yifan Zhou is an assistant professor of Astronomy at the University of Virginia, where he studies exoplanets with high-powered optical and infrared telescopes like the James Webb Space Telescope. Predictably, his favorite thing in space is a distant star with planets orbiting it.

This system, PDS 70, was "One of the first objects I have looked at for my first research project in undergrad," Zhou says. "My analysis led to a sort of failed project. The object that we thought was a planet of PDS 70 turned out to be a background star."

But Zhou and his advisor's intuition that PDS 70 had planets turned out to be correct. In fact, the baby super-Jupiter orbiting PDS 70 was the first exoplanet to be directly imaged. In groundbreaking images from the European Southern Observatory, a glowing young planet carves out rings in the dust and gas accreting onto the star.

"The discovery reminded me of my undergraduate project," says Zhou. Inspired, he led a Hubble project that tracked how quickly gas is falling onto the young super-Jupiter. He credits that work with helping boost his career. "I'm still writing proposals about it now."

A star with a vaporized moon stuck in orbit

Most star systems are too far away and too faint to directly image any planets around them. Claire Rogers is a graduate student in Physics at the University of California Irvine who researches stars whose atmospheric fluctuations mimic the signs of planets. Her favorite object in space is Tabby's Star, an exoplanet system found in the Kepler survey, which she loves for its "super weirdly shaped transits." Transits are dips in starlight brought on by a planet passing in front of it.

The transits across Tabby's Star are so dramatic that they inspired theories of alien civilizations.

"For a bit, people thought it might be an artificial megastructure blocking the light, but it is probably actually dust from an exomoon that got broken up around it," she says.

Tabby's Star is a dramatic example of a common source of confusion for planet hunters: Dips in stellar brightness that hint at planets, but might just be the star.

"Stars vary naturally in their emission, and the variations...are roughly comparable to the variations we would expect from a small planet," Rogers explains.

A flashing star system hidden by dust

Dillon Dong, a postdoctoral fellow at the National Radio Astronomy Observatory in Socorro, New Mexico, picked a favorite star whose light varies even more wildly: Eta Carina.

Throughout the 19th century, the previously unobtrusive Eta Carina began to glow brighter and brighter. Once barely visible to the human eye, by 1837, it outshone Rigel. The following year, it dimmed once more. It kept fluctuating until 1845, when it rocketed up to the vaulted place of second-brightest star in the sky. Then it began to fade. By 1886, it was no longer visible at all.

This was not a supernova, those violent stellar death throes that go off in a blink and fade steadily over time. Eta Carina was inconsistent. Something stranger was going on.

"This system shows just how much we have to learn about the dramatic pre-explosion lives of massive stars," enthuses Dong, who researches radio signals from exotic stars. "The cause of the brightening was a great eruption where the star blew out dozens of solar masses of material, forming the Homunculus Nebula."

The dust obscures much of the inner workings of the Eta Carina system, including further evidence of what exactly happened to it in the 19th century. Many of the theories involve dramatic binary interactions. In one scenario, the system originally had three stars, and the brightening came from a collision between two of them. Another theory suggests that one star may have stolen matter from another as it passed by. It's hard to tell, because Eta Carina is unique in our sky. No other system exhibits fluctuations so shrouded in mystery.

"The thing that really gets me is that most massive stars are in binaries, triples, etc," says Dong. "This kind of thing surely happens all the time in the universe."

A dramatic stellar corpse

When massive stars like Eta Carina run out of fuel to burn, they explode into supernovae and leave behind neutron stars like the memorably named 1E2259+586, the favorite object of Victoria Kaspi. Kaspi is a professor physics at McGill University and director of the Trottier Space Institute. She observed 1E2259+586 uneventfully for years before it suddenly lit up with X-ray flares, thereby helping her answer a long-standing mystery.

Neutron stars are the condensed remnants of massive stars. Within them, frictionless superfluids flow through a crystal lattice of neutrons. They weigh more than our Sun, but all that matter is packed into a ball the size of San Francisco.

Some neutron stars emit regular X-rays through magnetic activity near their surfaces.  1E2259+586 is one of these, but its period is unusually low. This source, and a handful of other slow X-ray pulsars, were the focus of conflicting theories.

One theory posited that the slow X-ray emission was driven by material trickling onto the neutron star's surface. The other, more dramatic interpretation predicted that the rotation rate was slow because of a supersized magnetic field holding the neutron star back. This kind of theoretical object, called a magnetar, could also potentially explain neutron stars that emit sporadic low-energy gamma rays.

Kaspi monitored the slow X-ray pulsar 1E2259+586 for years with the Rossi X-ray Timing Explorer (RXTE), trying to determine its nature. "It was getting a little dull," she says of her now-favorite source. "Then one day, the [principal investigator] of RXTE called me on the phone to say it was having major X-ray bursts during one of my observations!"

These X-ray bursts were leagues more intense than the regular, repetitive emission Kaspi had observed up until then. Only the magnetar theory predicted this kind of behavior from anomalous X-ray pulsars like 1E2259+586. 

"In that instant, I knew those observations had proven it was a magnetar. It was a great feeling, a true 'eureka' moment."

The first light in the Universe

Up till now, all the astronomers in this article have been observers who use telescopes to advance our knowledge. I was curious to know what an astronomer who works in the field of computing would pick as the coolest thing in outer space, so I asked Mariangela Lisanti, a professor of Physics at Princeton. Her simulations predict how different models for dark matter affect galaxies.

"Am I allowed to say the Cosmic Microwave Background?" she says.

Her hesitation comes from the fact that the CMB is so much bigger and more singular than other sources in space. It's like being asked what your favorite rock is and saying the Moon. The CMB is the remnant radiation propagating through all space that has been traveling toward us since the entire universe was on fire. If you tune your TV between channels, then somewhere between 1%-10% of the static will be from the CMB. (Exactly how much depends on the frequency.)

But astronomers use the tiny variations across the CMB to probe everything from the formation of the first galaxies to how gravity behaves at the subatomic scale. It absolutely counts as a cool thing in space. It's kind of the ultimate cool thing in space.

In 1715, a violent hurricane off the Florida coast tore eleven Spanish ships to pieces and drowned most of their crew. That was only the start of the drama. Now, after the waterlogged ruins of the fleet have inspired piracy, arson, and archaeological theft, one of the shipwrecks has surrendered more treasure -- over $1 million in 18th-century coins.

So many rotting Spanish hulls litter the seabed off the central Floridian coast that this stretch of shoreline is called the Treasure Coast. This summer, a salvage company recovered over a thousand coins and other artifacts. “Every find helps piece together the human story of the 1715 fleet,” said director of operations Sal Guttuso. 

It's not just the monetary value of such a haul but also the historical significance that enraptures the hodgepodge of treasure hunters and amateur historians who obsess over the 1715 Fleet. The new discoveries will soon circulate in Florida museums, but in the meantime, many tantalizing questions remain unanswered. Where did they find the haul? Which ship, in particular, yielded the horde?

The comeback fleet

The Fleet of 1715 was intended to restore the Spanish Empire to its former glory. After half a century of economic mishaps and a decade of brutal war, Spain's once-regular deliveries of silver bullion had dwindled and then stopped entirely.

But from the get-go, mishaps plagued the project. Its commander, Juan Esteban de Ubilla, arrived in the Mexican port city of Veracruz in 1712. Ingots had been collected, coins minted, and ships refurbished. He was raring to go. But the year came and went, and no orders came. The Spanish Crown was engaged in complex peace negotiations and wanted Ubilla to hold off until the new world order set in.

Ubilla spent the next three years engaged in a series of first venomous, then sycophantic letters to his commanding officer in Mexico City. Both he and the fleet's sailors waited at Veracruz, wanting both in entertainment and back pay. In fact, the only thing of note that appears to have happened to Ubilla during this time was an unspecified "accident with his sword" that left him unable to travel for a time. (For a fascinating and often hilarious account of Ubilla's three-year bureaucratic nightmare, see this article.)

But on July 31, 1715, the Fleet did finally set sail -- straight into a hurricane, which sank eleven of its twelve ships and killed over a thousand men, including the unfortunate Ubilla.

Real-life Treasure Island

Eleven ships loaded with treasure, sunk in shallow Caribbean waters? The race was on to find them.

The Spanish had a head start. The largest ship in the Fleet, the Urca de Lima, floundered on a sandbank off the coast of Fort Pierce, Florida. The survivors evacuated the precious cargo to a salvage camp on the beach. Then they set the beached ship on fire to hide it from passing ships. Their captain hopped aboard a Spanish mail ship to carry news of the wreck to the Crown.

Unfortunately for Spain, word of the disaster had spread among nearby pirates. Charles Vane and Henry Jennings wasted no time fishing around the coastline for visible shipwrecks. Instead, they captured the mail ship and exhorted the captain of the Urca de Lima to give up the exact location. He did so.

Vane, Jennings, and their crew paid the survivors at the salvage camp a highly armed visit. Resistance was out of the question. They surrendered the modern equivalent of $23 million to Vane and Jennings.

Underwater art thieves

In 1932, the state of Florida authorized underwater excavations of a shipwreck they believed to be the Urca de Lima. Other wrecks followed, scattered along the Florida coastline. Exactly which ship became which wreck remains a hot topic of discussion among aficionados of the 1715 Fleet. Unspoken: the implication that the wrecks found so far may not even be the most exciting ships of the fleet.

Given the allure of the treasure ships, along with their historical importance, the government of Florida allows only one company at a time to excavate them. For the past decade, the lucky company has been Queens Jewels LLC. By law, Queens Jewels must donate up to 20 percent of each salvage haul to Florida museums.

While the ships themselves have mostly deteriorated in the warm Floridian water, artifacts remain buried beneath 300 years of sand. These artifacts include the silver coins known as pieces of eight and a variety of rarer gold coins. They're archaeological treasures -- and fetch a hefty price on the underground art market.

Queens Jewels has respected its donation requirements. But the temptation of making an extra million dollars or so proved too much for one of its subcontractor companies, a family of treasure hunters operating under the colorful name Booty Salvage. The family stole half of what they recovered from a 2015 dive before turning the rest over to Queens Jewels, according to one of the family's own members, Eric Schmitt, who was haunted by the theft.

A year after the crime, he dove back to the wreck and placed three of the coins in the sand. Then he sat on the secret.

That is, until last year, when Eric Schmitt texted the founder of Queens Jewels. Over a series of 36 messages, he confessed to the charade. Perhaps by this point, the stolen coins seemed trivial: He sent the texts from a jailhouse, following his arrest for assault with a deadly weapon.

Federal authorities have spent the past year tracking down as many of the stolen coins as they can.

The new find

After all this drama, Queens Jewels is back in the headlines. This time, it's with a success story. Divers directed by Captain Levin Shavers have recovered over a thousand artifacts from a 1715 Fleet wreck, valued at $1 million. This haul includes pieces of eight, gold escudos, and other unspecified gold pieces.

Queens Jewels has yet to release the details of the excavation. We do not yet know its location, nor do we know whether any of the artifacts bear clues to the identity of the ship. But the company is already liaising with local museums to restore and display some of the recovered pieces, which are fragile after 300 years of immersion in saltwater.

"Each coin is a piece of history, a tangible link to the people who lived, worked, and sailed during the Golden Age of the Spanish Empire," Guttuso commented in Queens Jewels' press release. "Finding 1,000 of them in a single recovery is both rare and extraordinary."

This does not mark the end of Queens Jewels' search for the 1715 Fleet shipwrecks. With only a handful of wrecks discovered, the secrets of July 31, 1715, remain a treasure for the future.

For tens of thousands of years, humans have observed the minute seasonal changes that make or break a harvest. Now, for the first time, satellites have caught up. A study published this week in Nature used cutting-edge satellite methods to map the fine detail of seasons around the world.

Studying plants from space

The simplest approach to studying seasons across the whole planet is to image the Earth from space and track green vegetation. In winter, for instance, the top half of North America sits gray and dismal. Green rushes up from the lush forests of the south, bringing spring rain and blooming flowers. Trees burst back into life. Then, as fall creeps in, a fire-red line sweeps south and once more leaves grayness in its wake.

This is the traditional method of remote sensing phenology, or the study of the seasons from satellites. But while green shows the ebb and flow of summer across much of inland North America, Europe, and North Africa, it starts to falter in arid regions and the tropics. How can you track seasonal changes across the Amazon or the South Pacific, where the leaves are always green?

Plant stress

This new study tracks seasons by how much plants are growing in a particular region. To do so, it applies techniques common in agriculture and ecology. When plants convert sunlight to energy, the chemical mechanisms in photosynthesis release red light at two very specific frequencies. This phenomenon, known as solar-induced chlorophyll fluorescence, helps farmers identify how stressed their plants are. Stressed plants do not photosynthesize as efficiently as happy ones. The new study uses plant stress to track seasonal changes across regions that don't have more obvious markers of summer or winter.

They also use near-infrared observations of plants' reflectivity, or how much sunlight they absorb versus what they reflect. When plants are thriving, they reflect a lot more near-infrared light than when they are stilted and slow-growing. This method, coupled with solar-induced chlorophyll fluorescence, offers a window into vegetation health even for evergreen plants.

A changing seasonal map

The team found that more factors predict seasons than simply the north-south dichotomy over what time of year is summer. Some regions, such as Amazon floodplains, don't have two distinct seasonal changes in the year. Instead, one major event -- such as a yearly flood -- dominates vegetation change.

Another curious outcome of the study is that despite what intuition might suggest, nearby regions with similar climates don't necessarily sync up their seasons. These regions of asynchronicity often pop up near mountain ranges. Mountains can dramatically alter airflow and weather patterns, creating micro-weather systems and thereby disconnecting regions as nearby as a few dozen kilometers. In an article for ScienceAlert, lead author Drew Terasaki Hart gave the example of Phoenix and Tucson, Arizona. Tucson experiences summer monsoons while the residents of nearby Phoenix bake in 50°C heat.

The effects of this seasonal mismatch

The team's research provides additional evidence for the hypothesis that posits high local seasonal variability increases biodiversity. If a species lives in both Tucson and Phoenix, the hypothesis runs, then the arrival of rain might cue mating at different times. Over the long term, this could result in the species splitting into two separate species.

While this hypothesis is far from accepted, the new study's findings do support it. For instance, the hypothesis predicts that tropical regions should see more local variability in seasons since they have higher biodiversity. This is exactly what the new study found.

If you're interested in exploring your local micro-climate through the eyes of plants, check out the team's interactive map here.

The devastating earthquake that hit Lisbon, Portugal in 1755 fueled de-Christianization in Europe. Satirical French writer Voltaire, writing just after the disaster that killed tens of thousands of people, wondered, "Was there more vice in Lisbon, now destroyed/than in licentious Paris and London?"

It didn't help that the disaster struck on All Saints' Day, when the populace was out celebrating in the streets. They had been good Christians, or no worse than any others, and yet God had struck them down. Theologically, the Lisbon Earthquake made no sense.

Geologically, it makes no sense either. Earthquakes cluster around fault lines and subduction zones, where one tectonic plate jostles for space with another. But the sea floor beneath Lisbon is smooth and blameless.

New models suggest there's something brewing under the surface, driving Lisbon's illogical earthquakes.

Fault lines and subduction

Two kinds of geological activity drive earthquakes. The first, which occurs on land, is called delamination. The top layer of the Earth, the crust, is hard and brittle. Beneath it lies the mantle. Continental mantle is squishy and dense, much denser than the magma asthenosphere beneath.

At the gaps between tectonic plates, the squishy mantle beneath one crust bumps into the other. They fight for dominance. When one loses and gets sucked beneath the other, it stretches and weakens. The lighter magma beneath starts pushing up, buoyed by its lower density, like a beach ball held under the waves.

The crust above buckles and splits as the magma lifts it into the air, peeling it from the mantle beneath. Mountains form, volcanoes burst, and earthquakes shudder. This process of delamination is the same mechanism driving the crackling of paint.

Oceanic mantle, which makes up the sea floor, isn't as permeable as continental crust. It doesn't allow the magma asthenosphere to push all the way up. Instead, it clings onto the crust above. The losing plate pulls the crust all the way under with it.

So that's the model: Delamination peels up crust on the continent, and subduction sinks it in the ocean. Seismic surveys haven't shown any evidence of subduction off the coast of Lisbon, and no delamination is occurring on the ground in Portugal.

A possible solution to a 300-year-old mystery

If you were to show the results of the recent study published in Nature Geoscience to a survivor of the 1755 Lisbon earthquake who had received a 21st-century geological education from a time traveler, they would most certainly be agog.

"Oceanic delamination?" they would exclaim, clutching one hand to their chest. "But surely such a thing cannot happen! The oceanic mantle is too solid to allow for it! There must be another explanation."

But oceanic delamination is exactly what the new paper proposes. The evidence:

1) There's a strange blob of magma traveling deep below the ground.

2) A number of earthquakes seem to originate from the same region, with no obvious subduction.

3) All those earthquakes started from deep below the surface.

The blob of magma, dramatically called the "southwest Iberia anomaly," indicates that the asthenosphere is straining against its boundaries. This, coupled with the earthquakes, suggests violent geological activity, even if no subduction is visible. And the deep origin of most of the earthquakes (at least 20km below the surface) means that the upper crust isn't directly connected to the mantle beneath. If it were, activity in one region would trigger activity in another.

All this points to delamination, a theory backed up by the team's simulations. It's possible that the strong presence of serpentinite off the coast of Portugal may play a role in this geological oddity. Even though delamination isn't supposed to occur on oceanic mantle, serpentinite is so slippery that it may be easier for the upper crust to peel off it.

So that's the Lisbon earthquake, 270 years later: still theologically troubling. But geologically, an answer may be near.

As light pollution threatens our view of the stars the world over, the annual Dark Sky photography contest is here to remind us what we stand to lose.

DarkSky is a non-profit that works to help preserve astronomical heritage and nighttime ecology. In their photography competition Capture the Dark, they reward not only photographs that capture the majesty of dark skies, but also host categories such as dark sky-friendly lighting, the impact of light pollution, and nocturnal flora and fauna. Thanks to funding from local governments, special prizes also go out to photographs shot in Utah and Tucson, Arizona.

Beauty in darkness

The overall prize this year goes out to a split-second photograph of red sprites over Australian tidal flats. Red sprites are a rare form of lightning seen during thunderstorms. Unlike the more common tropospheric lightning, which occurs at the base of the atmosphere, red sprites last only about 10 milliseconds. Their short duration makes them notoriously difficult to photograph.

Another winner in this category depicts a swathe of white snow beneath the southern Milky Way. A small cabin stands in stark, man-made dichotomy beside the peak of a volcano. On the ground, a trail of footsteps mirrors the glowing lights of the galaxy above.

International Dark Skies

Many entries in this competition tempt viewers into buying a plane ticket to New Zealand, but perhaps none so much as the winner of the International Dark Sky Places category. Officially inaugurated in 2012, the Aoraki Mackenzie International Dark Sky Reserve stretches across several national parks. The first-place winner of this category documents the entry to the park.

Another photograph showcasing the Aoraki Mackenzie International Dark Sky Reserve made it to the podium as well. Flowers dance beneath star trails, all against the backdrop of the Church of the Good Shepherd.

How to build for dark skies

There are many steps urban planners can take to reduce light pollution. The first place winner in the category Dark Sky Friendly Lighting and Design is a gentle cityscape of Paris in the hours before dawn. The City of Lights will never be a stargazer's dream. But Paris turns off the lights on many of its most prominent landmarks late at night, allowing some stars to peek out of the firmament.

Warmer, redder lights also help reduce light pollution. Because blue light scatters more easily off the atmosphere, it travels farther from its origin. Red light is also less energetic, so it leaves less of an imprint on your retina, allowing you to preserve night vision. And crucially for local ecology, red light attracts fewer insects and birds than other colors.

As a bonus, it gives any building a nice cyberpunky feel, as shown in the second-place winner in this category.

Light Pollution

The light pollution category is here to dispel any hopeful feelings you're having about humans' ability to diminish their natural impact. Fortunately, the prize winners in this category make light pollution as striking as dark skies.

First place goes to a mountainscape above Chamonix. Despite the glittering stars above, the lights from the town below travel up through the fog bank, glowing like a lamp.

Two photographs from major Chinese cities take second and third place, documenting very different aspects of light pollution. In the second-place photograph, the skyscrapers of Shanghai far outshine a few sparse star trails above.

The third-place winner, taken in Beijing, documents not the impact of the city but the constellations of satellites above. The Pinwheel Galaxy shines against a star-speckled sky crisscrossed by satellite trails.

Creatures of the night

Darkness serves a crucial ecological purpose. This category spotlights the flora and fauna that flourish at night, from fungi to insects and birds. Particularly striking is the third-place winner, a close-up portrait of an owl in the Sonoran Desert:

Deep-sky images

No astrophotography competition is complete without a deep-sky category. The first-place winner shows the Vela supernova remnant. Made from a whopping 109 hours of integrated observations, this photograph consists of different colors highlighting layers of oxygen, hydrogen, and silicon.

Visit Tucson Location Award

As a former resident of Tucson, Arizona, I'd be remiss to leave out my favorite from the Visit Tucson location award. Thanks to the City of Tucson for funding this charming photo entitled Two Lovers Watching the Moonrise:

Take a look at the other winners!

You can find out more about the importance of dark skies and how to preserve them here. The rest of the Capture the Dark 2025 winners are here.

In an unassuming farm field in Yorkshire, peat preserves secrets. Tens of thousands of fragments of wood, bone, antler, and stone pack into the mud beneath prim grass. Until 1948, they lay undisturbed, a time capsule from the Stone Age. Then an amateur archaeologist found remnants of habitation. Thus began a much-publicized excavation.

This is Star Carr, the most complete Mesolithic site in Britain. It paints a striking portrait of daily life just after the Ice Age, but the answers it doesn't give are even more intriguing. Why did the inhabitants construct elaborate headdresses made of deer antlers? What was carved into the oldest jewellery in Britain? And what did they do with their dead?

Treasure trove

At the time of Star Carr's discovery, the British Mesolithic (from about 15,000 to 5,000 years ago) lacked for evidence. The Neolithic that followed had Stonehenge, but the Mesolithic only had hints of stone knapping and some fragments of bone. Then came Star Carr, named for the modern farm below which lurked history.

Inhabited for at least 800 years at the end of the last Ice Age, Star Carr sat at the side of a lake that no longer exists. The long-gone Lake Flixton hosted at least 16 sites of human activity, including three on islands, but Star Carr was special.

The original excavations in the 1950s found evidence aplenty for stone working, hunting, and the now-iconic antler frontlets. Generally made from red deer antlers, the frontlets featured boreholes presumably used to fasten them onto heads. Some were only nubs of antler, lightweight and purposefully shorn. Others extended out to the side in dramatic branches. Their purpose remains unknown.

When archaeologists returned in the 2000s, they found that exposure to the modern climate had destroyed much of the early digs. What had been peat-logged bone decades before was now mere jelly. For over a decade, archaeologists raced to save the rest of the site. They found more antler frontlets, as well as the first known house in Britain and the first known artwork.

Stone Age capital

Star Carr offers a singular view of the technology of Mesolithic people in Britain. Post holes show where structures once stood, one as large as 3.5m in diameter. Split timber beams line the shores of the lake, the first known carpentry in the Isles. They may have been used for traversing the waterlogged shore, mooring boats, or both.

The other sites around Lake Flixton aren't anything like Star Carr. They feature remnants of habitation, including stone knapping, but Star Carr was a center of industry. Probably inhabited during the spring and summer, its cultural status survived at least one century-long dip in temperature.

Star Carr is so extensive that it has filled in many details of everyday life in the British Mesolithic. We know that they ate perch, pike, and even hedgehogs. We know that domesticated dogs played an important role in their community and were laid to rest on the shores of the lake. Also given special treatment in death was the red deer, whose antlers and bones became both tools and ritual objects. At least, archaeologists have to assume the antler frontlets were used in rituals.

Before the Isles were islands

When humans lived at Star Carr, the British Isles weren't Isles yet. A land bridge stretched from the coast of western Europe to what is now England. Called Doggerland, this real-life Atlantis was lost to rising sea levels at the end of the last glacial maximum.

Star Carr stands as a testament to this lost connection between the mainland and England. The only other known examples of antler frontlets are in Germany, where their purpose is also shadowy. Why were some cut down to the base of the antlers, while others extended out to the side? Why were they found deposited on the peaty lakebed? Who wore them, and why?

On this point, Star Carr offers no answers. Artifacts such as the antler frontlets hint at a rich cultural life but do not elaborate.

First art in the British Isles

In a similar category, the Star Carr pendant shines as the first example of art in the British Isles. Found by a student at the tail end of the excavations in 2015, the pendant is a small, triangular piece of shale with a borehole at one end. Engraved lines layer its surface. They bear a passing resemblance to those on Mesolithic pendants from mainland regions like Denmark. But mainland pendants were almost always made from amber, not shale.

The carved lines are enigmatic and obscure. In the discovery paper, the excavation team says that they showed various colleagues the pendant. Their interpretations "included a tree, a map, a leaf, tally marks, even a representation of the wooden platforms which have been found at Star Carr."

Many of the artifacts at Star Carr lie in giant piles. The archaeologist who led the 1950s excavation interpreted them as midden piles, but modern archaeologists disagree. Why would the inhabitants of Star Carr lay only arrowheads and axe heads to rest in the lake if they were disposing of them? Why not the whole arrow or axe? What is the meaning of those antler frontlets? And why bury red deer and dogs along with them, but no other animals?

"Radiocarbon dating of artifacts and animal bones has shown that the assemblage was generated over a very short period of time, perhaps in a single event," wrote team lead Nicky Milner of one of the most dramatic such piles.

Again, Star Carr taunts us with its eternal question: What did this mean to the people who made it?

Where are the dead of Star Carr?

Archaeologists have found the remains of many animals at Star Carr. Some, like the red deer and the dog, clearly played important roles in contemporary society. Others were food. But this site's Rosetta Stone, which cracks the code, has yet to be found.

Despite being inhabited for over 800 years, Star Carr does not have any human remains.

Negative evidence is always tricky in archaeology. But given the evidence for ritualistic burials of red deer and dogs, the lack of human bones anywhere in the excavations is striking. It's not just Star Carr, either. No sites around Lake Flixton feature any human graves.

Presumably, humans did die at Star Carr. That leaves two options: either their bodies were carried to the ocean for disposal, or they were destroyed in a way that left no archaeological trace.

"This may have included practices involving the disarticulation of human bodies through excarnation and dismemberment," writes the excavation team. "Equally, bodies may have been cremated."

These, then, are the people of Star Carr: not nomads, but seasonal dwellers. Hunters and fishermen, who used not just stone but also bone and antler to create their tools. Voracious omnivores who roasted hedgehogs in clay to remove the spines, just like Romani British would do millennia later. They made jewellery and elaborate antler headdresses, built docks, and loved their dogs.

Then they died and disappeared from the archaeological record.

Fast-than-light travel, instantaneous communication, terraforming. Science fiction relies on imaginative physics ideas to enrich its stories. Some of these are pure fiction, while others are closer to fact than you might expect. Which is which?

Faster-than-light travel probably won't work

Perhaps no concept is more foundational to modern space fiction than that of faster-than-light (FTL) travel. After all, exploring a galaxy even at lightspeed takes prohibitively long for any narrative. In the time it takes the Enterprise to travel to a new planet each episode, any characters not on the ship have aged and died.

The proposed mechanics of FTL vary across sci-fi properties, but many authors (George Lucas, Douglas Adams, Martha Wells, CJ Cherryh...) use the vocabulary of wormholes and hyperspace. Both of these refer to real, physical solutions to Einstein's equations.

In fact, many physicists suspect that if we fully understood gravity, these solutions would be impossible. Einstein's equations fail to describe gravity at the atomic scale, for example. A theory that encompasses quantum gravity as well as macroscopic gravity might make wormholes impossible.

Right now, though, Einstein's equations are the best we have. And while they allow wormholes, further calculations suggest that it's probably impossible to travel through them. This might be a good thing, considering the eldritch horror of getting stuck in hyperspace, as depicted in CJ Cherryh's haunting sci-fi novel Port Eternity, where a spaceship drifts forever through hyperspace darkness while unknown creatures knock on the walls.

But there is a property that uses an FTL mechanism closer to reality: Star Trek. In fact, physicist Miguel Alcubierre cited Star Trek in his seminal paper on an object now known as an Alcubierre drive. This shortens the space in front of a ship in the same way gravitational waves do. With an Alcubierre drive, a spaceship doesn't actually move faster than light, and so doesn't violate any laws of general relativity.

The catch? How to make a machine that can contract and expand spacetime. Alcubierre showed that it fits mathematically into Einstein's laws, but only if it uses matter with negative mass as fuel. Right now, most physicists suspect such peculiar matter does not exist.

Still, Star Trek gets closer to feasible FTL than most other sci-fi properties. Take that, Star Wars.

FTL communication is also a no-go

Very few pieces of space fiction depict worlds without faster-than-light travel. The first book in the peculiar Bobiverse novels, whose major characters are all clones of one human-turned-AI, does show its protagonist colonizing the universe without FTL, but the process takes centuries. In Cixin Liu's novel The Three Body Problem (now a Netflix series), humans buy precious time to prepare for an alien invasion thanks to the aliens' sub-light travel speed. And in the early Ender's Game novels, the eponymous Ender spends enough time on sub-light spaceships that he's still alive 2,000 years after the first book, thanks to time dilation — at which point he is universally reviled.

All of these authors, though, cave on the point of FTL communication. Despite the laws of physics being just as firm on superluminal Zoom as they are about superluminal spaceships, the allure of real-time conversations seems too much for science fiction authors not to take advantage of.

When authors try to work in FTL communication, they often appeal to the phenomenon of quantum entanglement -- where particles become linked together so that they share the same fate, no matter how far apart they are. Entanglement is so bizarre that Einstein, in the throes of his philosophical war on quantum mechanics, famously called it "spooky action at a distance."

Quantum mechanics predicts that two particles can be connected so that any measurement of one also tells you the state of the other. For instance, imagine an atom with zero intrinsic angular momentum, or spin, decays into two smaller particles. We measure one of them and find that it's spin points in the upward direction. Since we started with no spin, we know that the other particle's spin has to cancel this out. It must have a downward spin.

The pioneer of quantum photonics, John Stewart Bell, described entanglement in reference to a quirky coworker of his, Reinhold Bertlmann. "Dr. Bertlmann likes to wear two socks of different colors. Which color he will have on a given foot on a given day is quite unpredictable," wrote Bell, in an excellent and accessible essay on entanglement. But when you see, illustration below, that the first sock is pink, you can already be sure that the second sock is not pink."

Bertlmann's socks, of course, are simpler than quantum entanglement. If you turn around and give his socks a moment, they won't randomly switch color. Quantum systems, though, do. You can measure one decayed particle at 9 am, find that it has a downward spin, and then come back after lunch only to find its spin has switched direction. The one thing you know is that at each point, the other particle will have the opposite spin.

It's surprisingly easy to test this in a lab. Entangled photons and electrons are bizarre, but totally real. Physicists have even managed to entangle millimeter-sized diamonds.

If whatever happens to one particle affects the other, Einstein reasoned with skepticism, then wouldn't entanglement allow FTL communication? For instance, the pure act of measuring a quantum system collapses it into a classical system, without all the mucky probabilistic behaviors of quantum.

Say the Greek hero Theseus has one half of an entangled quantum system and gives the other to his father. They agree that if Theseus survives his fight against the Minotaur, he will measure his half of the system, thereby collapsing the half in the care of his father into a classical system as well. The transfer of information is instantaneous. Theseus enacts spooky action at a distance.

But there's a problem. In order to check whether his half of the entangled system has collapsed, Theseus' father has to measure it. Doing so would collapse it. His father has no way of knowing whether Theseus' observation or his own has changed the system. No matter what, it looks as though Theseus lives. This goes to show that if the ancient Greeks had only had quantum theory, everything would have turned out all right for Theseus' father.

Collapsing a quantum state is only one of many proposed mechanisms for FTL communication via entanglement. But the "no-signaling theorem," provable with relatively simple mathematics, outlaws all of them. The very act of measurement breaks the entanglement, and each half of the system joins its surrounding environment, independent of the other half. Trying to communicate across quantum entanglement is like sending a letter via a beautiful, fast carrier pigeon that happens to drop dead if you tie anything to its feet.

Terraforming is not instantaneous

In Star Trek II: The Wrath of Khan, the enigmatic antagonist searches for a terraforming mechanism called the Genesis Device, which remakes planets in minutes. No such device exists, and no serious physicists or biologists propose to make one.

But the idea of turning a lifeless planet into a life-bearing one does have legs. The core questions of astrobiology are: How does life form, and how rare is it? Research on these topics naturally leads to the suggestion, either as a thought experiment or a policy proposal, that we attempt to create it ourselves.

We've reported before on proposals to breed specialized microbes capable of surviving on Mars and eventually giving rise to algae. But perhaps the biggest barrier to Martian terraforming relies not on biologists but on physicists to solve it. Life on Earth only exists because of our planet's magnetic field, and Mars has none.

Every second, tens of thousands of dangerous particles pummel our atmosphere. Called cosmic rays, these particles -- primarily electrons and light atoms -- originate in the Sun, in the explosive deaths of stars, and even in distant black holes. Their births are violent. They accelerate to nearly the speed of light and shoot through anything in their way like a bullet.

That includes human cells. But fortunately, the Earth's magnetic field gently ushers cosmic rays to the Poles, where they either cascade down to Earth or join the solar wind. Unless you're a researcher at the Amundsen-Scott South Pole Station, you don't have to worry about cosmic rays.

But you would on Mars. So would any hopeful plant life trying to get a foothold on the red planet. Physicists, however, are already tackling the issue of an artificial Martian magnetic field. One team found that "the most feasible design is to encircle Mars with a superconducting wire with a loop radius of about 3,400 km" and running a current through it to create a magnetic field. Making this wire would only require mining 0.1% of Olympus Mons(!)

Both the microbial and the magnetic components of terraforming are potentially feasible. But neither one is the instant Genesis Device from Star Trek. Granting algae a toehold on Mars would take decades, and full-fledged forests would come centuries later. And no matter how we would create a magnetic field for a planet, it would take massive amounts of labor.

Real-life terraforming

Terraforming research has picked up in recent decades, as climate change looms ever-larger in the minds of many scientists. It's tempting to hear the phrase, "There is no Planet B," and ask: But what if there was?

There could be. But terraforming a new planet, while feasible, would be slow and painstaking.

In fact, terraforming is already occurring in small controlled experiments on Earth. Scientists have begun using salt-based aerosols to deflect sunlight. After successful tests, one team has even begun using them over the fragile, floundering Great Barrier Reef.

Experiments like these are deeply controversial but are gaining traction as the effects of climate change become more apparent.

Solar-deflection aerosol engines look like something out of the planet-creation scene in The Hitchhiker's Guide to the Galaxy. But they're real, and unlike in Hitchhiker's Guide, they're happening on the only Earth we have.

A week after the criminal sentencing of two men who cut down the iconic Sycamore Gap Tree, I hiked along Hadrian's Wall to the ruins of where the tree once stood. It was overcast. My through-walk had begun two days before in the sun, but by the time I swung away from the highway and tame agricultural land, the wind had swept in with force.

It was the perfect moody northern British day to stare mournfully at the treeless Gap, a monument to senseless vandalism. But that wasn't all I found.

An unexpected symbol

Sycamore Gap sits in the most well-traveled section of the Hadrian's Wall Path, a 135km through-walk that cuts from one coast of northern England to the other. Day trippers with picnic bags trek out to the Roman forts that cluster along the hillside. But the most iconic image of Hadrian's Wall, a 1,900-year-old structure built to defend Roman territorial conquests, was the arching tree that sat between two steep sections of the wall.

The tree, a 150-year-old non-native sycamore, featured in an evocative scene in the otherwise schlocky 1991 film Robin Hood: Prince of Thieves. Despite the all-American ridiculousness of Kevin Costner in the lead role, the association with Robin Hood bought the Sycamore Gap tree even more folkloric cachet than it had from its placement in the middle of Hadrian's Wall.

Sycamore Gap was the site of marriage proposals and ash-scattering, and was a natural foreground for landscape photography and astrophotography. In 2015, it won England's Tree of the Year competition and with it, £1,000 for a root health survey. Then, in 2023, someone cut it down.

A deliberate act of vandalism

"I can't believe they only got four years."

I heard that sentiment over and over again during my through-walk, sometimes from fellow walkers but more often from locals. The tree was in the news that week. One publican told me he had been hoping the two Cumbrian men who cut it down would get at least ten years. Instead, they were given four years and three months, of which they will serve at most 40%.

The trial denied a lot of people any sense of closure. The two convicts cited drunkenness and peer pressure, while the prosecutors argued spite and bravado. The tree had meant a lot to many people in life, but to its destroyers, its death meant nothing discernible.

The stump lives on

When you descend toward the Gap from the west, as I did, the stump of the tree is hidden until you're almost upon it. You head downhill alongside the remnants of Hadrian's Wall, clambering over ancient Roman steps until a boxy fence appears. The tips of leaves peek over the edge.

I approached. The stump was not as big as I expected. As stark a symbol of senseless anti-naturalism as it was, the surrounding foliage overshadowed it. Burnt red leaves jostled with shiny green ones for space. Purple clover thronged.

At length, a man joined me in gazing over the side of the fence. "Those are sycamore saplings sprouting up from the roots," he said, pointing out the glossy red and green leaves.

Coppicing, the practice of regrowing trees from their roots, stretches back to the Neolithic. It provides firewood and fosters ecological diversity, especially in densely canopied forests. But young, coppiced saplings are easy prey for passing rabbits or deer. The wooden fence protecting the nascent sycamore saplings might not keep humans out, but it would give a deer pause.

I took a few photos of the hopeful little shoots and pointed out how tall they were already. The man nodded. "They're in a race to see which one of them is going to be the next big tree."

For the last few weeks, the Schmidt Ocean Institute has been livestreaming submarine dives off the coast of Argentina. The livestreams feature close-ups of the seafloor and the specimen retrieval process, as well as the scientists' running commentary. Audiences have thronged to celebrate discoveries such as a plump starfish and a floppy sea cucumber.

Exploring a submarine canyon

The Schmidt Ocean Institute's remotely operated vehicle (ROV), nicknamed SuBastian, is prowling the bottom of the ocean off the coast of Argentina at a depth of about one kilometer. The target is the rich seafloor of the Mar del Plata Canyon, which sits at the confluence of two oceanic currents. The churning waters support copious life, including many undiscovered species that modern technology can now observe.

Under the leadership of Dr. Daniel Lauretta from the Museo Argentino de Ciencias Naturales Bernardino Rivadavia, the team directs the progress of SuBastian from a research vessel on the surface. An average snapshot of the sea floor includes spiny sea stars, determined aquatic plants, and little flecks of white worms. Even on the bottom of the ocean, the current is so strong that you can see sand flowing past the ROV at all times.

More exotic guests regularly make their appearance. On today's livestream -- the final trip in the expedition -- the team abducted a hapless fish with a net, vacuumed up a snail, and zoomed its high-definition camera in on coral oases.

Although the sea floor boasts more life than one might expect, it's around the vibrant red-orange coral that many of the most dramatic scenes occur. Live snails shelter in its folds, and dead ones rest on the seafloor around it. Fish throng. Urchins lurk in the protected inner sanctum. A coral, in the Mar del Plata Canyon, is a city plaza.

Big-butt starfish and 'sweet potato'

Two denizens of the deep, in particular, caught the audience's attention. The first is a starfish whose anatomy resembles Patrick from SpongeBob.

LiveScience theorized that the appearance of human glutes comes from gravity, since the starfish is stuck to an upright surface. Normally, starfish are radially symmetric, and their anus is actually in the center of their outside flesh.

The chat also nicknamed a sea cucumber batatita, or "little sweet potato." Unlike the big-butt starfish, this oblong creature found itself on a one-way trip to the surface. According to the team, it's currently thriving in its laboratory tank.

While the expedition is concluding, all the previous livestreams are posted on the Schmidt Ocean Institute's YouTube page. If you need a morale boost, check out the comment section, where thousands of subscribers cheer on the team. The Argentinian flag is a mainstay, as are cries of "viva la ciencia!"

Planetary scientists have published a detailed follow-up on the debris from their historic 2022 asteroid impact experiment in outer space. What they found challenges their understanding of the asteroid's behavior since the impact. Two tight clusters of boulders have veered off from the main zone of debris at very high velocities.

Those boulders have escaped the asteroid system and are now orbiting the Sun. It's unclear where on the asteroid they came from, why they're moving so differently from the rest of the debris, or what they mean for the long-term course of the asteroid.

A historic asteroid deflection test

In 2022, NASA live-streamed one of the most daring missions in its history. The Double Asteroid Redirection Test, or DART, sought to change the orbit of an asteroid by slamming into it with a spacecraft. The challenge was enormous. The size of the target asteroid -- named Dimorphos -- in the night sky is akin to a single atom held at arm's length.

The team behind DART knew they might be live-streaming their spacecraft missing the asteroid. But in an era of misinformation, conspiracy theories, and apocalyptic panic, they wanted the public to have transparency every step of the way.

Their gamble paid off. The DART spacecraft knocked smack into Dimorphos. NASA proved that in the event that a killer asteroid is heading towards Earth, we can knock it out of the way.

Strange boulders

DART was proof to the public that planetary scientists can keep them safe, but first and foremost, it was a scientific experiment. Simulating asteroid impacts on a computer doesn't compare to the real thing, especially when there are so many things about asteroids we don't know. They can be as chemically and topologically variable as terrestrial geology, and their tiny size makes observing them challenging.

So, to protect Earth from a hazardous asteroid, planetary scientists have mined every aspect of the DART mission for pieces of the puzzle. The new boulder tracking study, published this month in the Planetary Science Journal, uses images taken by an ESA spacecraft called LICIACube that accompanied DART.

The researchers found that two main groups of boulders veered off from Dimorphos in the minutes after impact. Many of them aren't following the main cloud of debris, and have such high velocities that they can escape the asteroid system.

The team's top theory is that these boulders are the fractured remnants of larger rock formations right next to the impact site. Since they were already loose, the spacecraft easily dislodged them before reducing them to smithereens.

Boulders mean orbital calculations might be off

None of these boulders is anywhere near large enough to threaten life on Earth. If they happened to head towards us, they would vaporize upon atmospheric entry, treating us to a spectacular meteor shower. But they are massive enough that, without accounting for them, planetary scientists may have been miscalculating Dimorphos' new orbit.

The theory of rubble and impacts has to catch up to the observations. How can we predict what kinds of debris will form from striking an asteroid? How much momentum do boulders account for? How do we figure out how boulder-prone an asteroid is before we get there? We need to understand all of this so we don't miscalculate how to strike an asteroid.

DART means that we get to figure this out now, rather than when the Earth is on the line.

The international team of astrophysicists behind the world's three gravitational wave detectors just submitted a paper analyzing a uniquely strong gravitational wave from 2023. Caused by merging black holes, this gravitational wave is unusual for more than just its strength. The team's best models suggest that at least one, if not both, of the black holes shouldn't exist.

The black hole "mass gap"

Most large black holes are created when massive stars jettison their outer layers. The iron core, no longer supported against gravity, collapses in on itself and forms a black hole. But this kind of supernova only works for stars up to about 130 times the mass of the Sun.

Above that, astronomers theorize that a new type of supernova takes over. The light the star generates in its core doesn't manage to exit the star itself. Instead, many of the photons are so energetic that they create extra particles when they hit atoms at the right angle. That means that the pressure of light holding up the star vanishes. With its only defense against gravity gone, the star begins to collapse, triggering a massive thermonuclear explosion that vaporizes it entirely. Nothing remains, not even a black hole.

Astronomers have yet to confirm this kind of "pair instability supernova" actually exists, although simulations suggest it does. There are also several candidate pair instability supernovae observations, but further study is needed to confirm them. On balance, though, pair instability supernovae are a well-supported theory of stellar evolution. They imply that stars can't create black holes above 64 times the mass of the Sun and below about 130 times the mass of the Sun. After that, a new kind of supernova takes over and can produce black holes once more.

But the best models of the 2023 gravitational wave predict two black holes of 103 and 137 times the mass of the sun. The error bars on these measurements are sizable, but still place the lighter black hole firmly in the mass gap, while the heavier one is either in or above it.

These are also the heaviest reliable black hole measurements to come out of the LIGO collaboration.

Spinning black holes create gravitational waves

Gravitational waves occur when massive objects accelerate, rippling spacetime in their path. Black holes spinning together in the final moments before their collision create the most powerful gravitational waves.

Earth-bound systems of lasers, able to detect changes in distance of only 1/10,000th the size of a proton, go after this class. The Laser Interferometer Gravitational-Wave Observatory (LIGO) detected its first gravitational wave in 2015, finally confirming their existence.

The many possibilities for formation

The research team found one other clue to the history of this strange black hole system. Each of the black holes is spinning much faster than usual. Any explanation for how this system formed has to explain that as well.

It's possible that there are toggles on stellar evolution, such as exact nuclear reaction rates at high densities, that change the range of the mass gap. But that doesn't explain the high spin rates. The theory of two stars combining to create each black hole has the same issue.

One explanation that accounts for the spin rates is that one or both of the black holes are the remnants of previous black hole mergers, rather than a collapsing star. Although this requires exotic star cluster conditions, the universe is filled with those. (The research team favors this explanation.)

The colliding objects could also be primordial black holes, a predicted population of black holes formed during the dense stages of the early universe. Primordial black holes don't have any mass gaps, but they are also far more theoretical than pair instability supernovae.

In 2035, the European Space Agency plans to launch the Laser Interferometer Space Antenna, or LISA. LISA will probe a different regime of gravitational waves from the Earth-based detectors like LIGO. In doing so, it will add a host of strange new black holes to the canon.

A team of genetics researchers has sequenced the genomes of Greenland sled dogs, or qimmeq (plural qimmit), both living and dead. Their results shed light on both the development of this breed and Greenland's murky human history.

Qimmit are the oldest dog breed, and the Greenland government takes their genetic conservation seriously: no other dogs are allowed above the Arctic Circle. But interbreeding is not the only threat to their survival.

Qimmit are tough, working dogs, and they regularly injure or even kill humans, particularly children. For a long time, their usefulness outweighed any danger; they were a vital part of Arctic travel, and their intense pack-bonding and high drive were a feature, not a bug. But snowmobiles have changed everything. In 2002, there were around 25,000 qimmit in Greenland. In 2020, there were only 13,000.

New research, published in the journal Science, began as a quest to preserve the genetic information of the qimmeq before it's too late.

Qimmeq DNA challenges timeline of Greenlandic settlement

Traditional scholarship places the Inuit settlement of Greenland at about 1200 CE. They would have joined the preexisting Dorset culture, which dropped out of the archaeological record several centuries later, as well as the Norse.

The Norse first ventured to Greenland in 985, when Erik the Red made contact with the "Skraelings" of the southeastern coast. They maintained a presence on the island until sometime in the 15th century. In the 18th century, Denmark embarked on a mission to recolonize Greenland, although first they had to find it again. Greenland has remained a Danish colony since.

By analyzing the remains of qimmit before Danish colonization, the team of geneticists challenged this narrative. Their models suggest that qimmit diverged from earlier species of sled dog 1,164 years ago -- over a hundred years before Erik the Red's arrival. In the centuries afterward, different regional variations diverged from one another within Greenland.

Either the qimmit were migrating on their own, or the Inuit arrived in Greenland much earlier than previously thought.

Where did the first Greenlandic Inuit come from?

Another interesting facet of the new research is the qimmeq's closest genetic relative. Rather than a modern husky or samoyed, qimmit shares the most DNA with the remnants of a dog from Alaska. Found near Teshekpuk Lake, this dog was alive about 3,700 years ago.

Finding the most similar genetics in Alaska rather than in Canada indicates that the ancestors of the Inuit moved rapidly from Alaska toward the eastern coast of Canada. The next closest relative of the qimmeq is a 4,000-year-old dog from Port-au-Choix in Newfoundland and Labrador.

The shadowy history of northeastern Greenland

The dogs' DNA also adds to the scant archaeological record of northeastern Greenland.

In 1823, an up-and-coming captain in the British Navy named Douglas Clavering received an assignment: to escort his friend, astronomer Edward Sabine, to the Arctic Circle. Sabine, a veteran of both the Ross and Parry Arctic expeditions, was engaged in a quest to measure the shape of the Earth using a pendulum. The period of a pendulum depends on gravity. Therefore, if the Earth bulges at the equator, the pendulum will have different periods at different latitudes.

But while engaged in his scientific ventures, Clavering twice encountered the same group of 12 Inuit. This was the last time any Inuit were confirmed to live in the northeast of Greenland before resettlement in the 19th century.

Oral history preserves stories of Inuit migration toward the southeastern coast of Greenland from the north over multiple centuries before Clavering's encounter. But the motives of this migration, along with when exactly the Inuit finally vacated the northeast, are unclear.

Clues from Qimmeq DNA

The new research places the first concrete estimate on the settlement of northeast Greenland: 1,146 years ago. This suggests that the Inuit settlers of Greenland moved from the northwest to the northeast within only a generation or two.

The pre-Danish northeastern qimmit is the most distinct regional population by far. Despite the rapid settlement of the northeast, once they were there, the northeastern Inuit didn't seem to intermingle with other communities in Greenland. Trade networks connected the whole west coast, but qimmit DNA suggests they did not venture east.

This supports one particular theory of the abandonment of the northeast: isolation. Archaeologists have suggested that among the many challenges faced by inhabitants of the northeast, the death knell may have been the nigh-insurmountable distance between their villages and any other communities. When the Little Ice Age struck in the early modern era, they would have had no allies. Migration may have been their only chance of survival.

A new tool for human history

In the absence of a historical record, the genetic analysis of companion animals can trace human migrations. Qimmit present a unique case because of their genetic preservation to the modern day.

Outside of Greenland, many dog breeds face serious genetic ailments because of inbreeding. Several breeds are now unable to give live birth. Meanwhile, the qimmeq has stayed healthy despite modern, artificial isolation and over a thousand years of natural isolation. This is a testament to the care with which its human companions have treated it for over a millennium.

A new competition dedicated to aerial photography has just released its winners. With a $5,000 cash prize for first place and publication of the top 101 images in a hardcover book, the International Aerial Photographer of the Year award attracted strong submissions from around the world.

The directors, who previously ran the International Landscape Photographer of the Year award, kept eligibility loose. Aerial photography can be taken from a drone, a mountaintop, or anything else (other than via AI).

Overall winner

Joanna Steidle, a New York-based drone photographer, took the inaugural first-place prize. Her work focuses on dramatic aerial seascapes and fauna interactions. With their recurring teals and silvers, the photographs she submitted to Aerial Photographer of the Year all feel like different pieces from the same overall work of art.

Icelandic volcanoes take second place

Daniel Vine Garcia of Spain brought home second place with his photographs of Icelandic volcanism. The color scheme of his work stands in stark contrast to Steidle's. Where in her photos, water smooths out the frame, Garcia's images feature stark contrasts between rock and magma.

Third place

While Steidle and Garcia both won for bodies of work focusing on the same landscape features, the third-place winner submitted more varied landscapes. American David Swindler's work ranges from ice encrusting a fractal plateau to...

...to wading birds in the shallows...

...to the swirl of algae and clouded water on a lake as flamingos fly by...

Individual aerials

Alongside the photographer winners, three individual photographs also won prizes. First place went to Igancio Palacios' image of a miraculously conical mountain in Argentina at dusk, below.

In second place, Talor Stone photographed a glacier splintering into a lake in Greenland. The streaks of melting ice mimic the branching of a tree.

Finally, Thomas Vijayan took home third place for his photograph of a glacier in Svalbard melting.

To see more, head on over to the competition website.

Yesterday, the ATLAS telescope identified a potential interstellar interloper. The memorably named A11pl3Z (kidding) is currently zooming toward the Sun. Right now, it's about the same distance from the Sun as Jupiter is. But the strange angle of its approach suggests it may be coming from interstellar space.

If confirmed, it would be only the third identified interstellar small body.

Small bodies encompass everything from dwarf planets like Eris to comets and asteroids. Only in the last decade have astronomers gotten good enough at tracking small bodies to find interstellar ones. Each new visitor tells us something about other solar systems, from the chemistry of their small bodies to their orbital conditions.

The first two interstellar visitors

In 2017, astronomers at the University of Hawaii found an asteroid that behaved oddly. It didn't come from any of the normal directions for asteroids or comets passing by the Sun. Moreover, it wasn't on a bound orbit at all. It was traveling so quickly that after half a loop around the Sun, it zoomed back off into interstellar space.

They called it 'Oumuamua, meaning "scout." It was the first known visitor from beyond our solar system. Planetary scientists jumped at the chance to study an asteroid from the great beyond. More excitable astronomers theorized it was actually a spaceship. 'Oumuamua entranced the world for a few months, stirred up controversy, and then disappeared into the blackness of space, beyond the reach of our telescopes.

Then, in 2019, an amateur astronomer and telescope-maker in the Crimea found a comet (a rocky body that contains large amounts of ice, unlike asteroids) on a similarly unusual trajectory. Like 'Oumuamua, Comet Borisov darted through our neighborhood only long enough to vaporize some of its ice in the heat of our Sun. Then it, too, was gone.

What we know about A11pl3Z

Astronomers have only just discovered A11pl3Z, and it's very faint. Since it doesn't generate its own light, we can only see it via reflected sunlight. At its current distance, that only gives it a brightness equivalent to that of galaxies about one billion light-years away.

This obfuscates exactly how fast A11pl3Z is traveling, and in what direction. While it's still possible that A11pl3Z is just a very odd object from our solar system, it looks very interstellar. Not only is it entering the solar system from a strange angle, it's also orbiting in the opposite direction from solar system bodies.

Right now, it seems less perturbed by the Sun's gravity than Oumuamua or Borisov. That means it came from outer space with a much higher velocity.

The study of small bodies moves very quickly. Every night, planetary scientists get a plethora of new information on interesting objects. Soon, we should know whether A11pl3Z is an unusual member of our own solar system or something from much further abroad.

About 30,000 years ago, humans arrived in Japan's southern Ryukyu Islands, 110km from Taiwan.

The archaeological record hasn't preserved any clues as to how these Paleolithic people made the crossing to this new land. But the obstacles to doing so seem, at first glance, insurmountable without modern technology and knowledge. So in 2013, a group of Japanese archaeologists set out to recreate the trip using only Paleolithic tools.

This week, they published the results of their experiments in the journal Science. 

A challenging crossing

Archaeologists find evidence of humans in the Japanese archipelago as early as 35,000 BCE. Judging from the dates at different archaeological sites, the earliest inhabitants of Japan seem to have migrated both northward from Taiwan and southward from Korea.

But from the Taiwanese coast, the low-lying islands of Ryukyu sit below the horizon. One of the strongest currents in the world, called Kuroshio ("Black Tide"), runs northward from Taiwan. It carries any lackadaisical drifters west of the Ryukyu Islands at a velocity of one meter per second. And a distance of 110km from Taiwan to the nearest Ryukyu island, Yonaguni, was no joke for people without metalworking or sails.

Yet they made it.

When the Japanese archaeologists set out to recreate this trip, they didn't have an easy time. They tried reed-bundle rafts and bamboo rafts, both of which floundered in the strong current. The bamboo also began to crack and fill with seawater, further weighing it down.

The beginning of the voyage

In July of 2019, the team attempted one final trip. They launched Sugime, a hand-made dugout canoe, from the coast of Taiwan in typical calm summer weather.

Construction of the dugout started in 2017. The team used replicas of stone axes found in Japanese Paleolithic sites to fell a one-meter-thick Japanese cedar tree. They peeled off the bark and carved a seating area in the center of the trunk. While dugout canoes from the Paleolithic haven't survived in Japanese archaeological sites, dugouts from the later Jōmon period (starting around 14,000 BCE) boast burn marks on the inside. In turn, the team polished the inside of their craft with fire.

The plan was simple: to row from Wushibi, on the eastern coast of Taiwan, across the strait to the small Ryukyu island of Yonaguni. A motorized ship with safety supplies would escort the Paleolithic reenactors.

Sugime's crew consisted of five paddlers, four men and one woman. For the first hour and a half of their journey, they skidded over a calm sea, with only wispy clouds on the horizon. Then the water depth dropped, and they hit the edge of the Kuroshio. The wind slammed into the current, giving rise to choppy water and an ever-present swell as high as the side of their boat. One of the crew had to pause paddling to bail out the dugout over and over again.

They kept rowing into the night. The wind dropped slightly, but the dugout kept threatening to capsize in the strong swell. There was no rest that night, and it was a constant fight to keep the nose of the dugout pointing northeastward. As the water approached a flow of 1 m/s, the dugout pivoted northward along with the current.

Just as steering the boat was a challenge, so too was figuring out where to steer it. Clouds obscured the stars, and GPS wasn't an option in the Paleolithic. Only the direction of the swell indicated which way was north.

As midnight approached, the wind dropped and stars appeared. The paddlers took turns resting. But in the early hours of the morning, clouds once again obstructed the stars. At 3:40 am, while the captain was taking his rest, one crew member thought she saw dawn on the horizon. The crew pointed the dugout accordingly.

Then the captain woke up. The dugout was traveling due north, dragging them off course from their destination. He realized that far from being dawn, the light on the horizon was from the northern cities of Japan and was reflecting off the clouds. Sugime turned eastward once more.

Exhaustion and triumph

The next day dawned bright. Still unable to see their destination, Yonaguni Island, the crew kept paddling east-southeast to combat the current of the Kuroshio. Unbeknownst to them, however, they had left the Kuroshio behind them. They were now heading due east, away from Yonaguni.

They had already exhausted all the water they had packed for the voyage. Tired and thirsty, they called in a resupply. At noon, finding themselves in calmer waters and realizing they had left the Kuroshio, the whole crew slept for half an hour.

As they paddled into the afternoon, Yonaguni still failed to appear. They steered the dugout this way and that, hoping it would peek above the horizon. It didn't. Moreover, the crew was exhausted. Some of them jumped into the ocean to rest in the cool water. But nothing prevented the onset of excruciating muscle cramps and, as evening drew close, hallucinations.

Then, just before the sun set, a bird flew overhead. Before this, the sea had been lifeless and isolated. Now, land was near, even if they couldn't see it.

The sun was so intense that the food they had brought with them began to rot. They obtained replacements from the escort ship and ate a dinner of rice balls and noodles. As night slid in, the crew rested while the boat drifted loose on the water.

The captain kept watch. He thought he saw the glint of a lighthouse on the horizon that he hoped was from Yonaguni. As it turned out, it was an optical illusion, but the swell carried the dugout gently northeastward. In the early hours of the morning, the actual light from Yonaguni's lighthouse appeared on the horizon.

When the crew awoke in the dark hours before dawn, they began the final stretch of their journey toward it.

It was not until just after dawn on the third day that the crew finally saw Yonaguni Island. They were 20km from shore and had been rowing for over 40 hours.

Five hours later, they reached land. Since their crew included Taiwanese paddlers, they had to follow immigration protocol and land Sugime at a predetermined beach. Paleolithic explorers, presumably, did not have this restriction.

Piecing together a Paleolithic voyage

The crew had made it. Dugout canoes, unlike reed and bamboo rafts, can cross the Kuroshio. But at various points during the trip, the crew's mistakes had worked in their favor. When they rested, the swell naturally carried them in the right direction. And the first hint they saw of Yonaguni was from a lighthouse, which does not feature in Stone Age archaeological sites. Was their success a fluke?

To test this, the team used the data from their paddling to simulate hundreds of dugout voyages starting from different points in Taiwan. They used both modern and Paleolithic oceanographic models to approximate the flow of the Kuroshio, varying the strength of the current between ebbs and peaks. As long as the virtual boats paddled in the right direction, they made the crossing, even when the Kuroshio was at its strongest.

But the voyage could not be completed by accident. The Kuroshio does not carry mariners from Taiwan comfortably to the shores of Yonaguni. Paleolithic humans had to identify the direction and strength of the Kuroshio and plan their voyage accordingly.

They also had to know Yonaguni was there. From the coast of Taiwan, it is not visible. Only when one climbs the mountains in the north does the little speck of island appear over the horizon. The summit of the highest of these mountains sits at nearly 4,000m.

This research in experimental archaeology shows that inhabitants of Taiwan 30,000 years ago did not drift aimlessly towards the Ryukyu Islands. They climbed mountains, they built sturdy boats, and they knew how to chart a course against one of the strongest currents in the world.

A team of astronomers in Australia searching for radio flashes from distant galaxies has found something a lot closer to home. The defunct communications satellite Relay 2, out of commission since 1965, is chirping at the Earth in radio frequencies.

A mysterious burst from nearby

The Australian Square Kilometer Array Pathfinder (ASKAP) searches the radio sky for sudden, unexpected flashes. These can come from supernovae or more exotic sources like rotating white dwarfs. But ASKAP is particularly talented at finding Fast Radio Bursts, brief outbursts of radio waves coming from galaxies millions or even billions of light years away.

In a preprint paper released this month, a team at ASKAP reported a signal that looked like a startlingly bright Fast Radio Burst. It lasted the same general amount of time (only 30 billionths of a second) and emitted a broad range of radio frequencies. But unlike Fast Radio Bursts, it seemed to come from right outside the Earth's ionosphere.

When radio waves travel from faraway galaxies, they interact with electrons floating around in interstellar space. Those electrons slow down low-frequency waves more than the high-frequency waves, causing them to arrive at the telescope after the high-frequency ones. Astronomers call this effect "dispersion," and it works as a rough proxy for distance. Since we know about how many free electrons there are in every direction, we can calculate how far radio waves must have traveled through those electrons to be delayed a certain amount.

But for the recent ASKAP burst, there was barely any delay between the high- and low-frequency parts of the wave. The burst came from our own neighborhood.

Radio astronomers have a touchy history with things that look like Fast Radio Bursts but come from nearby. For a long time, mysterious signals called perytons showed up all over the place, until a group realized it was actually the microwave oven in the observatory break room.

Needless to say, microwaves are now kept under strict control at radio telescopes. So what was this new signal?

Tracking down an undead satellite

Reasoning that the only things floating around in nearby space that might release radio waves are satellites, the ASKAP team started searching. They compared the point of origin of the burst to maps of satellites. But the only matching satellite, Relay 2, hasn't been in operation since 1965.

Relay 2 was a NASA telecommunications satellite with a handful of physics experiments onboard, all long since defunct. According to NASA reports, it's been more than 50 years since anyone has purposefully used Relay 2.

While it's possible NASA is using Relay 2 secretly, the ASKAP team doesn't think this is likely. The plans for the satellite are publicly available, and nothing onboard is capable of producing such a short, bright burst.

The explanation

The team proposes two possible explanations for this strange emission. In the first, solar winds slam into Relay 2, building up charge against one plate of the satellite like rocks by the ocean build up salt. When the charge becomes so strong that the scant gas molecules between one plate and another can't take it anymore, the gas ionizes, releasing a sudden burst of visible light and radio waves. This is called electrostatic discharge. It's like lightning for satellites.

The other option is that micrometeoroids are slamming into the satellite, creating a cloud of dust and plasma right around the satellite. Then electrostatic discharge can happen even more easily.

It will be hard to tell which of these options is at play without observing Relay 2 over a long period of time. If the radio bursts happen at regular intervals, then they likely come from electrostatic discharge after a buildup. Micrometeoroids, on the other hand, wouldn't stick to a schedule.

Either way, observing short radio bursts from satellites may be a new way to probe the electric composition of space right outside the ionosphere.

In Chile, a monumental telescope has opened its eyes. The telescope at Vera C. Rubin Observatory is the largest digital camera ever built, with a resolution of 3200 megapixels. It will photograph the entire southern sky every three nights.

Today, the team behind this ambitious project released the telescope's first images of the sky, which astronomers call "first light."

Over 10 years, the Vera C. Rubin Observatory (VRO) will create a time-lapse movie of the changing universe. Explosions from massive stars in other galaxies, pulsating stars, and asteroids make up most of the VRO's targets. Objects like these, called transients, change on timescales observable to humans. By contrast, most things in space look the same today as they would a thousand years from now.

Unprecedented scale

The VRO will acquire astronomical data at an unprecedented scale. It will rapidly outpace the combined data of every single other telescope in history, both on Earth and in orbit. As a consequence, it will blow open the door on transient astronomy. Before the VRO, astronomers discovered thousands of supernovae every year. With it, they will discover thousands every night.

But the VRO won't just focus on the distant universe. The camera also picks up nearby objects like asteroids and comets darting across the field of view. Today, we know of about one million of these rocky bodies in our solar system. The VRO will find five million more, dramatically improving our understanding of the danger Earth faces from medium-sized asteroids.

More than 40 international organizations contributed to the telescope, which sits on the 2,682m summit of Cerro Pachón in Chile. The telescope's main mirror, which is the size of a small car, journeyed to Chile from the Mirror Lab at the University of Arizona.

At the press conference announcing the first light images, Chilean ambassador Juan Gabriel Valdes discussed the key role Chile plays in astronomy.

"Astronomy is part of our identity and our heritage," he said, noting that protecting their dark skies is crucial for the world's space science. "Today, more than 40% of the world's astronomical observations take place in Chile."

The mother of dark matter

Vera C. Rubin -- the woman, not the observatory -- made a name for herself in the mid-20th century as a determined scientist in the face of entrenched sexism. Rubin found the first evidence for dark matter when she observed that galaxies rotate faster than their visible matter explains. There must be, she reasoned, additional invisible matter holding them together.

Nowadays, dark matter is a household term, even if no one (including astronomers) knows what it is. But Rubin, like many other female scientists responsible for key discoveries, never received the Nobel Prize.

Although the bread and butter of the VRO is transients, it can also probe how light bends around distant galaxies. The amount it bends depends on how massive galaxies are -- another clue to how much dark matter exists in the universe.

Harriet Kung, director of science at the Department of Energy, summarized the questions on dark matter and dark energy that the VRO will help answer.

"How can we better understand the matter and energy that make up 95% of our universe? Why is our universe expanding quickly, and how does that change over time? What role does dark matter play in how our universe evolved?"

First light

"The movie is starting," announced Kenneth Wright, director of development for the Office of Science and Technology Policy. "The camera is running. And we're gonna see our universe unfold before us."

The first image revealed in today's press conference showed two Milky Way-like spirals whirling against a background of more distant, yellower galaxies. This image comprises only 2% of the telescope's full field of view.

Since the camera can photograph light from the near-ultraviolet to the near-infrared, the colors in this photograph are more dramatic than what the naked eye would see. Galaxies that look blue emit strongly in the ultraviolet, while reddish-yellow galaxies shine in the infrared.

Red galaxies tend to be older, made up of aging stars that don't spit out the violet ultraviolet radiation of young blue ones. They also lose their defined spiral arms, as in the large elliptical galaxy in the first light image below. Many of the galaxies here comprise the Virgo Supercluster, a massive family of galaxies about 65 million light years away.

Moving asteroids

In a sneak peek of the VRO's time-lapse power, the observatory's director released a video of asteroids moving against the static background of stars. Every asteroid in this video, shown with a turquoise dot, was previously unknown. None of them are on an interception course with Earth.

In just one week, the VRO found 2,100 previously unknown asteroids.

Unparalleled resolution

The final first light image released shows the nearby Trifid and Lagoon Nebulae, yet another strength of this versatile telescope. Dark streaks against clouds of glowing dust and gas show regions of high density where baby stars are forming. Because the telescope was designed to see things very far away, turning it on such close objects allows it to zoom in with the resolution of 400 ultra-high definition TVs stacked next to each other.

A new view on the universe

Maryam Modjaz, a professor of astronomy at the University of Virginia and a member of the VRO science collaboration, explains that the VRO will transform how she does research.

"I’m particularly interested in very young supernovae, right after the explosion," she says.

Right now, astronomers have to be lucky to find these objects. More often, they don't catch them until days after they've exploded, missing crucial early information. That won't be an issue with the VRO, says Modjaz. "We can study the stars that gave rise to those explosions in what I call a 'stellar forensics' investigation."

The VRO is open to more than just astronomers. The observatory has just released its Skyviewer app, where anyone around the world can explore this project, which it calls the Legacy Survey of Space and Time.

In recent years, we have shown many spectacular images from the James Webb Space Telescope. The difference between them is that the JWST looks at very fine detail, while the Vera Rubin Observatory focuses on the big picture. After the VRO finds something new, the JWST can follow up for a more precise study.

The California Academy of Sciences has announced the winners of its annual Big Picture photography competition. This year, the $5,000 Grand Prize went to a golden hour shot of a brown lemur jumping between limestone spires. The lemur leading the group makes the giant vault with her baby clinging to her back.

Aquatic Life winners

The judges also awarded prizes in different categories. In Aquatic Life, another mother and her young took home the gold. A Caribbean reef octopus curls around her children, her tentacles protecting the eggs. Inside each egg, a tiny octopus floats.

The Big Picture also released the finalists in each category, which you can peruse here. In the Aquatic Life category, this wide shot of a green sea turtle is particularly striking.

Terrestrial Life winners

The finalists in this category span the Arctic tundra to deserts and savannas. Highlights among the finalists include this shot in the Chilean mountains of a puma stalking similarly colored guanacos...

...and this dramatic photograph of an elephant and an eland herd in Zimbabwe during the dry season. Dust in the air creates those blood-red African sunsets.

But a pack of Arctic wolves on Ellesmere Island took the prize after curiously thronging the photographer. They were close enough that he could smell their breath.

Winged Life winners

Bats, birds, and bugs galore! But this category doesn't focus only on photos of winged creatures in flight. Finalists include this moth pupa...

...alongside this grey-headed flying fox soaring through the air with its pup.

The Honduran white bat took the prize in the Winged Life category. This mother plunges off a leaf to look for food, leaving behind her five pups clustered together like a bunch of berries.

Landscapes, Waterscapes, and Flora winners

This non-wildlife category rewards less dynamic shots than the typical wildlife show stopper. The winning photograph this year documents what looks like an eye but is actually the unfrozen center of a lake in Poland, crisscrossed by animal tracks.

A particularly striking finalist image documents a 2024 cyclone that flooded southeastern Morocco. Once-dry lake beds suddenly revitalized, destabilizing local ecosystems.

Art of Nature winners

This category rewards photographs for which the medium is the message. Unusual shutter speeds, instruments, and sensitivities all have their home here. The winner is this Turner-esque photo of waves off the coast of Germany. A slow shutter speed captured the motion of the water.

One of the finalists in this category also used a slow shutter speed and moving water to create an artistic image. The streaks that grant this starfish a sense of flight arise from the water flowing against the sand.

Human/Nature winners

Many of the finalists in this category emphasize species' vulnerability or suffering. But the winner shows humans risking their own safety to help an animal. The Kenyan Wildlife Service veterinary team, shown here, attempts to administer anesthesia to an endangered black rhino, an animal more than capable of killing a human even when sedated.

Work by the Kenyan Wildlife Service has gone a long way to protecting this creature, once hunted nearly to extinction.

Specialists at Australia's Square Kilometer Array (SKA) released a report this week showing Starlink's unexpected impact on radio astronomy. Despite national and international protections against radio emissions in certain bands, Starlink is clogging the skies with electromagnetic pollution.

A crowded spectrum

Light pollution stretches far beyond the hazy glow of a city on the horizon. Down in the radio portion of the electromagnetic spectrum, governments barter sections of light. Large portions of bandwidth stay reserved for the military, while others get auctioned off (sometimes literally) to communications companies. Squeezed in between these chunks of spectrum lie bands for public broadcasting, HAM radio, and science.

Governments, corporations, and private citizens are supposed to stay away from protected bands so that radio telescopes can observe in peace. When the Starlink satellites launched, SpaceX collaborated with key radio astronomy observatories to avoid broadcasting while transiting above telescopes. Strategies include turning off Starlink WiFi services completely in certain regions of the sky.

The resulting disruptions to Starlink operations are not insignificant. Spectrum management, especially in the United States, involves give-and-take on both sides. But American observatories have the benefit of observing at mid- to high-frequencies, at least by radio standards. Those frequency bands are less polluted than low frequencies, because emitting at low frequencies takes less energy and so costs less.

'Unintended electromagnetic radiation'

If corporations and the military ignored protected bands, it would cause serious problems for radio astronomy. But a new study by engineers at the SKA suggests unintended electromagnetic radiation, or UEMR, may be a bigger issue than intended radiation.

The SKA is still under construction. When completed, it will be the most powerful radio telescope in the world. The low-frequency part of the telescope (SKA-Low) is designed to go after trace echoes from when matter began to coalesce 13 billion years ago. SKA-Low looks odd even by the standards of radio telescopes. A thick forest of metallic Christmas trees in the Australian desert maximizes sensitivity to faint signals.

But the new era of radio telescopes is butting up against a new era of satellites. There are more satellites in orbit than ever before, including massive networks of related satellites called constellations. With 7,000 satellites in Low Earth Orbit, Starlink is the biggest constellation.

As they transit above SKA-Low, Starlink satellites release radio emissions through multiple protected bands. In a pre-print of their study, the SKA-Low team reports 112,534 intrusions of Starlink satellites in their radio images. Their month-long study showed that 30% of all Starlink satellites in the sky at the time appear in their data.

Most of this emission seems to be accidental. UEMR from Starlink interfering with radio astronomy isn't unprecedented. During the initial launch phase, radio astronomers found that the propulsion system on the satellites emitted at unexpectedly low frequencies, decreasing the quality of astronomical data in an already polluted band. But the satellites had all been launched at the time of this new study. So where is all this radio pollution coming from?

No answers, and no regulation

We don't know the various origins of the UEMR the SKA-Low team observed, except for one feature at 99.7 MHz. If that sounds like an FM radio band, it's no coincidence. Starlink satellites bounce FM radio shows back down to the Earth. For telescopes carefully located in radio-quiet zones, that's not ideal.

Fixing this issue is particularly crucial to the success of SKA-Low, which seeks to look further back in time than any telescopes in a similar radio band. Signals from the early universe are very faint, and Starlink satellites are not.

Unfortunately, the codes governing spectrum use only ban intended radio emission in protected bands. Consider a hyperbolic analogy: Imagine if murder were illegal, but manslaughter wasn't. Spectrum experts and regulators are currently discussing how to address this issue. For now, though, as long as Starlink is here, so are the unintended radio emissions.

Last week, the Trump administration released a presidential budget request that would cancel almost all NASA science missions in order to focus on putting humans on Mars. It's mainly a showy, we-can-do-it project.

Mere weeks before, the CEO of a small San Francisco non-profit argued in a new paper that we need to start seriously considering terraforming Mars. The priorities of the two groups could not be more different.

The lead author of the paper, Erika DeBenedictis, received the prestigious Astera Fellowship to found Pioneer Labs, a small startup dedicated to designing microbes for terraforming. In The Case for Mars Terraforming Research, published last month in Nature Astronomy, she and her co-authors explain why terraforming studies are important. They also address how little we still know about potentially terraforming Mars. The main takeaway: Mars is not ready for humans, and humans are not ready for Mars.

Why bother with all this, anyway?

For some readers, the question of colonizing Mars isn't why, but how. If that's you, feel free to skip ahead. But others might approach the matter with more skepticism.

Space colonization has become a political byword, but opposition is far from new. Perhaps most famously (at least among us science geeks), Gil Scott-Heron's 1970 poem Whitey on the Moon contrasted the poverty conditions of many Black Americans with the perceived excess of the Apollo missions.

"I can't pay no doctor bill (but Whitey's on the Moon)," he wrote. "Ten years from now, I'll be paying still (while Whitey's on the Moon)."

From this vantage point, is spending billions on terraforming research anything more than a nationalist vanity project? DeBenedictis and her team argue that it is important.

"Technologies developed for Mars habitation, such as desiccation-resistant crops...will probably benefit Earth," they write.

In an older interview with the Astera Institute, DeBenedictis summed up this aspect of the paper's argument.

"Researching the possibility of a green Mars involves an infinite number of steps, all of which are in the right direction. How do we make human presence net-positive for the surrounding environment, rather than net-negative?"

Unlike the Trump administration, the study doesn't advocate for current human spaceflight to Mars. Instead, it proposes taking the questions of colonization seriously, starting from first principles. Should we? How would we? What would the future of Mars look like?

Not just science fiction

You'd be forgiven for assuming terraforming is just science fiction. But unlike faster-than-light travel, this staple of space adventure has a real scientific basis behind it.

The new study lays out a timeline for terraforming Mars, and it's a lot more rapid than you might expect. They propose that careful bioengineering can accelerate the formation of an ecosystem. Instead of the billions of years it took Earth to turn green, Mars could achieve it in a few decades.

The key to this rapid progression would be the development of microbes that thrive on Mars. Bypassing the labyrinth of evolution, humans could combine traits of Earth-based microbes such as temperature tolerance (surface temperature on Mars swings from -150°C to +20°C), invulnerability to fierce radiation and toxic gas, and no preference for atmospheric pressure. Such species could lead to an algae-covered Mars within decades.

How scientists would prevent such hardy microbes from disrupting ecosystems on Earth, the team doesn't address.

The natural advantages of Mars

According to their estimates, if all the water ice on Mars melted, it could form 10,000,000 km² of ocean at a depth of 300m. That's far less than the amount of liquid water on Earth, but it's enough to support long-term life on Mars.

In turn, the melting of Martian ice caps, which include both water and carbon dioxide ice, would increase atmospheric pressure. A thicker atmosphere would lessen the dramatic temperature swings between Martian night and day, in turn allowing the proliferation of life.

Martian soil also includes the necessary components for agriculture. Science fiction author Andy Weir exploited this so his marooned protagonist could grow potatoes in the hit 2017 science-fiction novel The Martian.

Such calculations have led planetary scientists to scour Mars for evidence of past life, mostly through remote sensing. (Soil samples are notoriously difficult to return to Earth for testing.) So far, they haven't found any evidence of life, only evidence of conditions necessary for life at some point in the distant past.

So, are we missing something?

The big unknowns

This is where DeBenedictis and Pioneer Labs' vision of Mars colonization research differs most dramatically from that of Elon Musk and SpaceX. The gist of the new paper is not that terraforming should happen now, but that scientists from different disciplines need to consider terraforming when designing future projects.

In planetary science, for example, the paper argues for continued research on everything we don't know about Mars. For instance, ice covers one-third of the planet. What's under it? More ice? Networks of caves? Liquid water? The answer could portend wildly different visions of a bioactive Mars.

They also call for extensive simulations of dust storms, a notable feature of Martian weather. Right now, planetary scientists understand dust storms on Mars fairly well. But how would dust change the atmosphere in a warmer, wetter Mars? How would the new climate alter the strength of the dust storms?

But perhaps the biggest open question for terraforming is whether Mars has enough electron acceptors to support life. Electron acceptors are molecules capable of transferring electrons -- and thereby energy -- down a chemical chain. They include carbon dioxide and nitrates, and are vital not only for photosynthesis, but also for human respiration.

Where to go from here

Despite their affiliation with Pioneer Labs, which focuses on microbe engineering, the authors don't call for the scientific community to jump on the terraforming bandwagon.

"While the possibilities are exciting, anything as big as modification of a planetary climate has major consequences and would require careful thought," they write. "But until we do more research, we do not even know what is physically or biologically possible."

In other words: research now, decide later.

"Priorities include quantifying H₂O, N_2, and CO₂ reserves...soil sample return, test missions for proof of concept of warming methods, and climate feedback studies," they explain, linking various NASA science directives with terraforming questions.

Current NASA goals for Mars already support human exploration, they add. "No abrupt change of course is needed."

But an abrupt change of course is in store for NASA. The presidential budget request cancels all Mars research missions except for the Martian Moons eXploration, which is mostly funded by the Japan Aerospace Exploration Agency. It still wants to put colonists on Mars, but without laying the scientific groundwork first. If science takes up Mars terraforming research, it will be without the United States.

This week, a team of maritime archaeologists completed a detailed underwater study of the wreck of the SS Terra Nova. Their findings paint a vivid portrait of the famous ship's final hours, and of its fate in the 80 years since.

Launched in 1884, the Terra Nova lived a peaceful life as a whaler until she joined Robert Falcon Scott's ill-fated Antarctic expedition in 1910. Unlike Scott and the other members of the South Pole party, she survived the expedition but fell victim to pack ice during World War II and sank off the coast of Greenland.

There she rested until 2012, when marine survey technician Leighton Rolley proposed the general location of her sinking as a test project for new sonar equipment. The sonar scans detected various wreck-like features on the sea floor. One of them exactly matched the recorded length of the SS Terra Nova, 57m. After 70 long years, they had found the ship.

The survey team then lowered what was officially called the Simple High Resolution Imaging Package (SHRIMP), which was, in practice, simply an underwater camera and four flashlights attached to a cable. SHRIMP revealed the wooden skeleton of a wreck.

Terra Nova in detail

Now Leighton Rolley is back at the site of the wreck, this time with the equipment necessary for a full visual survey. The expedition vessel, MY Legend, is a high-tech yacht accustomed to polar cruises. Expert divers and a submarine have replaced SHRIMP, exposing details of the wreck.

Their survey confirmed the SS Terra Nova's identity. They also found that the bow had violently split in half. Remnants of gear still on the deck testified to the rapid evacuation of the ship in 1943.

"One of the most powerful moments was discovering the helm station near the stern — a symbolic and moving find," wrote submarine officer Aldo Kuhn. Photographs from the survey also show the ship's wheel, still intact after 80 years in the frigid water.

Still supporting life

But the team didn't only find the remnants of life. They found life is still there.

According to Kuhn, "a beautiful marine ecosystem is now thriving on the wreck, bringing new life to this historic site." Rolley wrote that the team saw corals, anemones, and fish living on the old oak whaler.

Shipwrecks often act as havens for marine life. Plants and corals grow well on wood in underwater environments, and small fish use the structures as shelter. Many oceanic organizations worldwide take special care to preserve the ecological role of shipwrecks.

Every year, elegant shots of gliding whales and prowling tigers wow the world. But one competition is brave enough to take a stand against the tyranny of animals looking impressive. The Comedy Wildlife Photography Awards platforms animals making stupid expressions, sitting in weird ways, and having bad hair days.

Entry into the 2025 competition is free, and open until June 30. But select entries were shared with Popular Science -- and with over 1,000 more already submitted, it's clear 2025 will be a great year for animals being silly.

You don't look as suave as you think

One subset of these photos features animals engaged in normal behavior, such as running and diving. But the timing of the photographs highlights the dorky positions in which we all find ourselves during routine moments. Especially when we're penguins.

What's that on your head?

Another staple of the Wildlife Comedy Awards is animals with things on their heads that definitely shouldn't be on their heads. From other animals hitching a ride to make-shift hats and hairdos, the new photos have got you covered.

Hey, leave that to humans...

Douglas Adams, author of Hitchhiker's Guide to the Galaxy, posited that there were at least two species on Earth more intelligent than humans (dolphins and -- well, the other is a spoiler). But some of the 2025 Wildlife Comedy photos suggest other species are working their way up the ladder as well...

That was my bad angle, can you retake it?

No collection of funny animal photos would be complete without this old classic. Sometimes animals look majestic right until you see the expression they were making when you snapped the photo.

Admittedly, mudskippers were probably never majestic in the first place.

For words from the competition's founder and the original photo captions, head on over to Popular Science.

After escaping the Nazis by minutes and then getting smuggled through spy-infested Stockholm, the bomb bay of a British fighter jet might have been a relief to physicist Niels Bohr. His approach to quantum mechanics held unsettling implications about the meaning of death, and now he had nearly escaped its shadow.

The Nazis had invaded his native Copenhagen in 1940. That was three years before the father of quantum mechanics found himself strapped to the felt-lined insides of a de Havilland Mosquito with only an ill-fitting helmet, a reading light, an oxygen mask, and a thin blanket for comfort. Bohr abhorred the Nazis, but had resisted every previous attempt by the British government to evacuate him. He had work to do in Copenhagen. He was busy shuffling Jewish scholars through his Institute of Theoretical Physics. During their visits, they were all offered very prestigious, very convenient fellowships to leave the Axis territories immediately.

Bohr did not worry as much about himself as he did about others. His mother might have been Jewish, but he didn't practice Judaism. Surely if he didn't consider himself Jewish, neither would the Nazis.

Then, in 1943, a tip-off from a Gestapo worker led to Bohr's narrow escape on a boat to Stockholm. And now the fighter jet, and a helmet that didn't fit right. The rip would last only two-and-a-half hours as they flew over the contested airways to England, where Bohr would finally be safe. Perhaps he felt as though the danger of his last week was finally over.

Blackout

Over the helmet's intercom, the pilot advised him to put on his oxygen mask, as the Mosquito was nearing 7,000m. But Bohr didn't hear the announcement through his badly fitting helmet. As the Mosquito climbed, Niels Bohr, whose discoveries in physics would lead to both quantum computing and the atom bomb, lost consciousness and drifted toward death.

Nearly a decade before, Niels Bohr's colleague Albert Einstein had co-authored a paper contending that the emerging theory of quantum mechanics was incomplete.

Einstein and Bohr had been tossing the matter back and forth for years. While Bohr was far from the only contributor to quantum theory, he was its earliest and most prominent advocate. Einstein agreed that quantum mechanics appeared to work, but he thought Bohr's interpretation of it made no sense at all.

The Copenhagen interpretation

It was called the Copenhagen interpretation, after Bohr's beloved city. If you have taken a physics class that covers quantum mechanics, this is almost certainly how you learned the subject. Bohr developed the Copenhagen interpretation in conjunction with Werner Heisenberg (who would go on to lead the Nazi effort to build an atom bomb) and Max Born (who would be among the first wave of Jewish academics to flee Germany in 1933).

Copenhagen posits that at the very small scale, such as individual atoms or electrons, the universe exists in a permanent juxtaposition of different possibilities. The exact position of a particle in a box, for instance, is not defined by default. It is not merely that we don't know where a particle is. Instead, the particle has no actual location, merely probabilities of being in different locations, until we try to observe where it actually is. Then all those probabilities coalesce into an actuality: The particle is here, not there, and moreover, it will stay there even when we stop observing. We can go make a cup of tea, do some dishes, and when we come back, it will be exactly where we left it. If we shake the box around, though, the position of the particle goes back to a fluffy cloud of probabilities.

For obvious reasons, this upset a lot of people. It agreed with experiments, and the math made sense, but nothing else did. It had some pretty bizarre implications regarding how events exist in space, too, which Einstein derided with the ever-quotable line, "spooky action at a distance."

Schrodinger's cat

When Einstein and two co-authors published their famous rebuttal of the Copenhagen interpretation in 1935, fellow Copenhagen critic Erwin Schrodinger wrote to him in support. To illustrate how ridiculous the Copenhagen interpretation was, Schrodinger described a hypothetical scenario in which the fate of a cat in a box depended on whether or not a particular quantum process (in this case, the nuclear decay of an atom) had occurred. If the atom decays, a mechanism in the box releases poison, killing the cat. If the atom doesn't decay, the cat is fine. Schrodinger wrote how in this quantum system, the cat is alive and dead at the same time, "mixed or spread out in equal parts."

Ridiculous though it was, the Copenhagen interpretation agreed. If there exists some quantum process in the brain that makes the difference between life and death during oxygen deprivation, then for two-and-a-half hours, the bomb bay of the de Havilland Mosquito contained both the living (but unconscious) and the dead bodies of Niels Bohr, father of quantum mechanics.

The many-worlds theory

For such an odd theory of the universe, the Copenhagen interpretation has surprising tenacity. It has vanquished every other approach to quantum mechanics in popularity if not in evidence. Why?

Part of it is that, as the first explanation, it has priority. Part of it has to do with the fact that its rivals are even more mathematically complicated (pilot wave theory), spiritually troubling (conscious measurement theory), or far out there (many-worlds). 

In the pilot wave theory, the mathematics that predict probabilities in the Copenhagen interpretation instead describe a background field along which particles travel, much like an electric field. Particles have a real position, the cat is either alive or dead, but if we try to find out specifics, then we disturb the system. We will never know if the cat was alive just before we opened the box.

Conscious measurement theory runs far in the opposite direction. Possibility only collapses into reality when it interacts with a conscious observer. It is not enough to be seen on camera, someone has to be controlling the camera and attempting to process its information. The nature of death is about the only thing that isn't unsettling about this theory: A conscious observer collapses the probabilities, so the cat (or Niels Bohr) is either alive or dead, not both.

When everywhere becomes somewhere

But as bizarre as the Copenhagen interpretation of death might be, the many-worlds theory of quantum mechanics rivals it. It began with Hugh Everett III, a PhD student studying under John Wheeler, one of Niels Bohr's former students. Everett grew troubled by the Copenhagen interpretation, which seemed unnecessarily complicated. Why mess around with this business of something that was everywhere suddenly being somewhere when observed? After all, that implies the universe rearranges itself instantaneously. If nothing moves faster than the speed of light, how is that possible?

Easy, said Everett. It isn't. Nothing rearranges itself. Instead, the different probabilities predicted by quantum mechanics don't relate to whether the particle is actually at point A rather than B. Rather, they describe the chance that we are in a particular universe where the particle is at A instead of B. When we open the box, all we do is check which universe we are in.

This all sounds rather abstract. Nonetheless, Everett's PhD advisor, John Wheeler, recognized that in many ways, it's the simplest interpretation of the probability-based math required by quantum experiments. Wheeler encouraged Everett to publish it as his thesis, including a mathematical formulation for branching universes.

In 1959, Wheeler made the mistake of sending his protégé off to Copenhagen to meet the grandmasters of quantum mechanics. The meeting did not go well. Everett later described it as "hell" and "doomed from the start." One of the physicists he met, Leon Rosenfeld, detailed his impression of Everett in a letter: "He was indescribably stupid and could not understand the simplest things in quantum mechanics."

Everett promptly left academia for defense work.

Quantum immortality

Many-worlds lay dormant for a decade. Then, in 1970, a small circle of physicists rediscovered it and coaxed Everett into elucidating his ideas. Everett never returned fully to physics, but he stayed engaged with the small community of many-worlds enthusiasts.

One of the oddest features of many-worlds is the nature of death. In the Copenhagen interpretation, the probability of Schrodinger's cat being alive when we open the box is vanishingly small, the longer the experiment goes on. So small, in fact, that it approaches zero very quickly. In many-worlds, however, there is always a universe where one version of the cat survives.

This is very nice for the surviving cat in that just-right universe and not at all nice for the different versions of it that died. Hugh Everett had a solution to this, although even he did not dare publish it. Privately, he believed that his consciousness would always stay in the universe in which it continued to exist.

Everett died of a heart attack in 1982. He was 51 years old. His daughter committed suicide fourteen years later and wrote in her last letter that she was going to join her father in a parallel universe.

The fate of Niels Bohr

When the British army opened the bomb bay of the Mosquito, they found Niels Bohr unconscious but alive. Death by oxygen deprivation is not truly a quantum mechanical process, so our analogy notwithstanding, his survival says nothing about quantum mechanics.

Bohr went on to participate in the British arm of the Manhattan Project until his morals got in the way. He believed that the atom bomb would alter the world forever, and to develop it in secret was unforgivable. Hinting at the project in letters to Russian colleagues, he found an ally in Robert Oppenheimer. With Oppenheimer's help, Bohr met with Franklin D. Roosevelt, whom he tried to convince to make the project public. Roosevelt declined. By all accounts, though, he was more sympathetic to Bohr than Winston Churchill, who wrote, "It seems to me Bohr ought to be confined or at any rate made to see that he is very near the edge of mortal crimes."

Churchill kept Bohr under close watch in England. Not until the United States bombed Hiroshima and Nagasaki was Bohr finally permitted to return to his native Copenhagen, where he dedicated much of the rest of his career to nuclear non-proliferation. He passed away in 1962, three years after meeting with a hot-headed young physicist named Hugh Everett III, who believed neither would ever truly die.

A three-penguin race on Galindez Island, site of the Ukrainian Antarctic Expedition, concluded on Tuesday. The victory went to a newcomer to the racing scene, Unidentified Penguin #2. Unfortunately, no penguin equivalent of FastestKnownTime.com exists, but we encourage the penguin-loving community to create one.

Not professional racers

Penguin racing often flies under the radar. Averse to social media, many champion FPT-setters also have day jobs as penguins, doing penguin things like diving for fish. Fortunately, the Ukrainian Antarctic Expedition (UAE) filmed the first half of the Galindez Island race.

"This video is for those who still doubt that penguins are surprisingly fast creatures," wrote the UAE on Facebook.

In the video, the eventual winner races neck and neck with two other penguins. The three-penguin lead pack jostles for space. A large part of penguin racing appears to be strategy: when to waddle like a weird little windup toy versus coast on one's belly like a sled? Penguins can accelerate to 6kph on their bellies, but navigating difficult ground requires a combination of the two modes of transport.

Penguins are even faster in water, reaching speeds of 36kph.

The purpose of the race remains unclear

While setting the FPT on Galindez Island is a worthy goal, the exact nature of this race has not been confirmed.

"This trio must have had extremely important things to do," the UAE suggested. "Was it krill again at a discount, or did they bring a truckload of pebbles from a neighboring island?"

Penguins are very social birds, nesting in large groups and often mating for life. A penguin in veterinary care at the Perth Zoo made headlines in 2021 for its investment in watching episodes of Pingu on an iPad. And in Japan's Tobu Zoo, a penguin captured the internet's heart by apparently falling in love with a cardboard cutout of an anime character.

Still, documented evidence of racing on land is a rare treat.

Last week, my friend Dana finished law school. To celebrate, I proposed a two-day trip to the Monongahela National Forest in West Virginia, two hours from our home of Charlottesville and less than four hours from Washington, DC, where Dana spent a sizable chunk of her time as a lawyer-in-training.

Dana agreed, and the plan was made. The day after she finished finals, I would drive her around and show her the radio astronomy observatory, the old railway station, and the countryside. It would be a nice getaway between three years of law school and a summer of studying for the Nevada bar.

Right before we were set to leave, Dana told me she'd mentioned the trip to a friend. "They say there's no cell reception at all out there."

I could not believe I had neglected this detail. After all, the no cell service, no Wi-Fi shtick was the appeal of the thing. And in the modern United States, it's a crucial piece of information for any travel plans. "I promise I'm not trying to lure you into the woods out of cell service to axe murder you," I told her.

But Dana was thrilled. She sent off a flurry of emails to everyone who might want to contact her, and on Thursday, the two of us set off in my battered 2007 Toyota Corolla toward the offline, disconnected world of the National Radio Quiet Zone.

Here's my guide to doing the same.

The road to the Quiet Zone

Part of the appeal of any backcountry is that it's off the grid. But for anyone who wants to check out some museums, see a little bit of history, and eat local cuisine, tourism in the United States comes with connectivity. The exception is the National Radio Quiet Zone, a massive square of land in the Appalachian Mountains blanketing over 30,000 square kilometers of rolling woodland. At the heart of the Quiet Zone sits the Monongahela National Forest of West Virginia.

Historically, the United States government has made a sport of neglecting key infrastructure in Appalachia. But the Quiet Zone, established in 1958, was not the child of that neglect. Rather, the trappings of contemporary life, even in the 1950s, were causing an uptick in Radio Frequency Interference, or RFI. That didn't bode well for the nascent Green Bank Observatory, set to become a behemoth of American astronomy, or for the military radar experiments in nearby Sugar Grove, West Virginia.

Flash forward to the present day, and the Quiet Zone defends against a lot more than home radios and satellite TV. As you pass westward from the frantic world of Central and Northern Virginia, cell service flickers out.

A curious name

But this isn't the backcountry. Historical monuments line the one-lane highway to Green Bank, including the bafflingly named Confederate Breast Works. Nestled at the top of a mountain, this scenic overlook and conversation starter features a pleasant one-mile loop hike, perfectly situated for stretching one's legs on the way to the heartland of the Quiet Zone.

Of course, there's no cell reception to Google any key definitions. Dana and I faithfully read every sign at the place, none of which specify exactly what Confederate Breast Works are, or why they needed to happen right here.

After about an hour of driving without reception, VA-250 spits you out in the bustling city of Monterey, Virginia (pop. 172). This is the last time you will have reception on the road to the Monongahela National Forest.

Last chance Wi-Fi

While there are multiple places to eat in Monterey, I beg you to try the Curly Maple. Doubling as a brunch spot and a store for local goods, it boasts an impressive selection of maple syrup and cider (tested and approved by yours truly).

If you're looking for something fresh, wander down the street to the Highland Roots Market. With produce sourced exclusively from local farmers, the shelves change with the seasons. If you catch them in the fall, the fresh apple cider is to die for.

But the shining gem of Monterey is an unobtrusive building labelled the Charles Pinckney Jones Museum. This beautifully restored, 19th-century townhouse is free to enter. It boasts two floors of old furniture, photographs, and fashion. While named for Charles Pinckney Jones, a Confederate soldier and later Rector of the University of Virginia, the museum focuses mostly on the material history of upper-class rural Virginia. We left knowing a lot more about early indoor plumbing than Jones or his family.

Dana and I spent a long time hovering over one wall in particular, where the restoration had uncovered pencil markings under the flaking wallpaper. Union soldiers boarded there during the war. Although their handwriting is a bit too nice to be modern, their signatures look like they could have been written yesterday.

The joy of the Quiet Zone

As soon as you exit Monterey, you head up and away from the thick maple groves of Virginia and up into more rarefied air. Pine trees begin to appear among the maple and beech.

I was thankful to head out of the cell service zone once more. As soon as I had arrived in Monterey, my phone began buzzing with an hour and a half's worth of missed messages. Someone needed me to urgently sign a form, and someone else wanted to know whether I had tested a new algorithm yet. The world, in short, was falling apart without me.

I spent a frantic 15 minutes on the phone in Monterey, feeling wretched and guilty. The online world seemed to have its claws more firmly stuck in me than in Dana, whose job it was to be up-to-date, tapped in, connected. I had planned this trip for her, but after two intense years of work for my Master's degree, perhaps I needed it just as much as she did.

So I asked someone else to handle the form, since I couldn't do anything about it from Monterey, and turned off my phone.

The pine trees engulfed us. The rest of the world dropped away.

And there, ensconced in the heart of the National Radio Quiet Zone, waited Green Bank Observatory.

A trip to the telescopes

When I talk to astronomers from other countries, they're always surprised at how open our telescopes are. Visiting most foreign sites requires background checks and waivers. At Green Bank Observatory, the site of the largest steerable telescope in the world, anyone can just wander up.

Schools around West Virginia send field trips to the Green Bank Science Center, a charming astronomy museum guarded by a large statue of a fish (the Bicentennial Trout). For the adults, outside stands the first ever purpose-built radio telescope, the Reber Dish.

Only film photography allowed

Only diesel vehicles are permitted within the zone around the crown jewel telescope, a 300-foot behemoth with a support structure like an industrial crane. Digital cameras are banned; you must use old-fashioned film cameras.

You can take a bus tour from the science center, but I recommend the walk. It's a neat three-mile loop that takes you past a purgatory of radio telescopes. Most haven't been operational in years, and one has a nuclear bunker under it.

Radio telescopes are undemanding of their audience. They tap into something in the hind brain, some human impulse that appreciates gothic cathedrals and pyramids. The brain says: That's big. Wow. It doesn't matter how many times I go to Green Bank, my first thought is always: Oh, I forgot how big these things are. Wow. 

Where to eat and sleep in Pocahontas County

It's good form to take Trader Joe's orders before heading out to the food deserts of West Virginia, where Dollar General is often the only place to buy food. Dana and I bought one night's lodging at a friend's house with tofu, coconut milk, and onions. But for anyone checking out the Monongahela for the first time, there are a variety of campsites and Airbnbs. I recommend avoiding anything in Snowshoe -- the upscale ski resort might as well be another planet from everything else in Pocahontas County. If you're looking for something on the swankier side, the town of Marlinton features several local inns.

As for food, I had been hyping up Dean's Den in Frost, about 20 minutes from Green Bank, for the last week. Dana was starting to get a bit sick of it. "Can I check the menu online?" she kept asking me. "No," I said, since nothing in the Monongahela has an online menu. "You'll like it."

She liked it. Everyone likes Dean's Den. It's a shack by the side of the road, valiantly restored from the time a semitruck plowed into it last year, that serves West Virginia's customary mix of country barbecue and Italian, plus a smattering of whatever else the chef feels like cooking that week. My last time in the Monongahela, I had a surprisingly good plate of General Tso's Chicken. I've joked about Dean's Den being the best restaurant in America, or at least I claim it's a joke. My partner, meanwhile, has actually dreamed about their cheese fries.

Power outages

If the power is out, as it often is in the Monongahela, then Dean's Den will be tragically closed. While it will be hard, I recommend you don't commit yourself straightaway to suicide. In Marlinton, Mim's Kitchen offers casual, fresh food (and very good cheesecake). If you're in the mood for some live music with your dinner, especially roots and bluegrass, check out Old Mountain Tavern.

Oh, and be sure to stop by Mountain State Cakes Bakery in Dunmore for freshly made pepperoni rolls, a West Virginia classic. No, they're not pizza rolls. Watch it.

The steamy history of Cass

By the next morning, I had been out of cell service and Wi Fi for maybe 18 hours. Everything felt slower. Without the ability to check our phones, Dana and I had both started new books and sunk deeper into conversation than usual. I had wished my partner goodnight on the landline like it was 1985 (apologies to anyone to whom 1985 doesn't feel that long ago).

We bade goodbye to my friend and their cats and headed out the door for a hike behind the observatory.

Then we set off to Cass for lunch. There's something deeply eerie about Cass, and it's not the hulking specter of a derelict mill by the river. You don't spend long in West Virginia without becoming desensitized to the signs of a region that the country has failed. Rather, the unsettling thing about Cass is exactly what it prides itself on: rows and rows of white pillbox houses from its days as a logging company town.

The houses remain cheerfully inhabited and beautifully maintained. A tiny City Hall building lurks over a black iron door labelled JAIL that looks as though it should be restraining a train robber.

And speaking of trains, there's the station. The Cass Scenic Railroad State Park offers hours-long tours through the surrounding landscape. You can even take it up to the ghost logging town of Spruce. Your vehicle: a genuine, century-old steam train running on the old Chesapeake & Ohio line.

Inside the old company store, you can grab a bite to eat at Shay's Restaurant and poke your head into the railroad and logging museum. Alongside copious local foods and keepsakes, there's also a recreation of the old Cass pharmacy, operational during its logging years.

Back into the world

I resurfaced in Monterey 24 hours after I had left it, feeling refreshed. I had missed 80 messages, most of them about some guy called Robert Prevost, and a host of emails. It had only been a day. How was it moral for anyone to receive that many emails in a day?

Living within a nice weekend trip's distance of the Quiet Zone is a privilege. But being able to exit it is more so. When I brought my mother out for her birthday last year, a violent storm swept across the Monongahela. One of my mother's three pedigree Australian Shepherds decided that it was the night that her body was going to shut down. With a pet's unerring eye for inconvenience, she crawled under the bed, whimpering, and wouldn't stop, no matter what my mother tried.

There were no emergency vets in Pocahontas County. There were no emergency vets in nearby Highland County, where Monterey is, or in the county beyond that. In fact, the nearest emergency vet was in Staunton, a full two hours away in the best of weather.

Not to be deterred, my mother woke me at 2 in the morning to let me know she was setting off with her shivery dog into the storm. Once she left, I had no way to contact her.

A fallen tree

She came back three hours later, having made it just past Monterey, where a tree had fallen across the one-lane highway connecting the Quiet Zone with the rest of the world. In the dead of night, with a sick dog and no way of calling for help, she stared at it and wondered if she could move it herself. But she was utterly alone, and there was nothing she could do. She turned around.

As it happened, her dog had -- has -- a nasty form of cancer. As soon as we returned to Charlottesville, she got surgery. They took a lump out of her intestine the size of a fist. (Miraculously, she's still happily chugging along a year later.)

Nothing like that happened on my trip with Dana. But with the lack of veterinary and medical services, fresh food, and infrastructure, it's not hard for people outside the Quiet Zone to question why anyone lives there.

Head out for a weekend, if you're in the DC area. You'll see.

Eighteen bold letters, preserved in a clearing, sight a dark room's view of brave surfers reeling.

From dry ruin's gate to solar's tall mast, chart a historic cross -- the start of one's path.

These are the first lines of a rhyming riddle, posted two days ago on r/sanfrancisco, that kicked off a city-wide treasure hunt.

"We always figured treasure hunting would feature more heavily in life," the anonymous authors announced. "Right alongside quicksand and tattered rope brides."

So they made it happen themselves. To their astonishment, though, San Francisco harbors extremely efficient treasure hunters. Within 12 hours, the treasure had been found.

An ominous riddle led treasure hunters to Sutro Baths

"Omg I totally could have gotten the clues to Sutro Baths if I had seen this!" I texted my editor after skimming the riddle for the first time. As a San Francisco native who grew up with a copy of the famous Sutro Baths painting on my father's wall, I put high stock in my ability to parse clues leading towards it.

To trace the true route, venture only at night: to be certain of bearing, you'll need pack a light.

In the steadfast basin, where feet part and agree, dig a shovel's depth down-- you'll find the treasure you seek.

A basin, swimmers, the idea of dry ruins: All of it seemed to lead to the abandoned wreckage of Sutro Baths, which burned down in 1966.

The post on r/sanfrancisco went viral hours after its premiere. Other San Franciscans came to the same conclusion I did and swarmed the ruins of Sutro Baths.

Meanwhile, 9km away...

Three friends and their dog thought differently. The men, who all work in tech, and the dog, who presumably doesn't, decided to work carefully through the whole riddle.

" We figured that the reference to Sutro Baths was probably a red herring, both because it's too difficult to conceal digging and it's also too highly trafficked," said TJ Lee, one of the three men, in an interview with NPR.

Other treasure hunters had ignored the opening line eighteen bold letters, preserved in a clearing. Instead, this group made the connection to the India Park Basin. There, the remnants of a large concrete sign lie disused. Eighteen concrete letters in a bold face.

As it happens, near the letters sits a strange San Francisco landmark. A vintage-colored building overlooks the surf, and its brave surfers reeling: the Camera Obscura, or dark room. 

Underneath the Camera Obscura sits the ruin of another historical saltwater pool. Like Sutro Baths, years of neglect doomed Fleishhacker Pool long before its official demise, in this case due to a storm.

So the crumbling entrance to Fleishhacker gave dry ruin's gate. "For those looking at Sutro Baths, we'd note that those ruins are still quite wet," wrote the treasure hunt authors in their solution manual.

Onward to the treasure

The Point of Infinity sundial sculpture on Treasure Island, visible from the coast, slotted neatly into place as solar's tall mast. Then the riddle instructed the hunters to chart a historic cross -- the start of one's path. 

The four locations above formed the points of this historic cross. And at their center, X marked the spot. The three friends and their dog dug a shovel's depth down on the coastal West Ridge Trail before hitting something hard.

Only 12 hours had passed since the start of the hunt, and the treasure had been found. Within it: $10,000 worth of historical San Francisco artifacts, gold ingots, and historical currency.

"It's validating to be like, 'I know San Francisco well enough' that we were able to find this in the first spot we checked," team member Austin Theriault told NPR.

As for the hunt's organizers? They're staying anonymous, since they aren't sure if what they did was entirely legal. But according to NPR, they aren't the kind of rich tech bros for whom the city is infamous.

"It was a non-insignificant amount of savings," they admitted.

The city loved them for it.

Back in the prehistoric days of theoretical astrophysics (1985), in a mystical and exotic corner of planet Earth (Fresno, California), a man sat in the back of a car and tried to break the spacetime continuum. His name was Kip Thorne: future scientific consultant on the movie Interstellar, future Nobel Prize winner, and all-around geek.

While he was a respected and innovative theoretical physicist, Thorne had not yet garnered a reputation as the mathematical mind behind some of science fiction's trickiest plot points. He was, instead, known for his deft familiarity with Einstein's equations of general relativity, a flexible set of conditions for how space and time interact. His friend Carl Sagan had called him up for help in solving a problem in his in-progress novel Contact, about radio astronomers who connect with interstellar beings.

Sagan, a science communicator by trade but an astrobiologist by training, needed Thorne's expert eye for the finer points of general relativity. He needed his heroine to get from the Earth to Vega, a journey of 26 light-years. And he needed her to get there fast.

Hyperspace

His initial treatment featured her plunging into a black hole, which carried her on a shortcut through hyperspace to Vega. Hyperspace isn't just a convenient term for hand-wavy science fiction authors. It's a real geometric concept describing space that occupies more than three dimensions. In short, Sagan's protagonist might travel through a fourth dimension, along a route where the distance from Earth to Vega is much less than 26 light-years.

Thorne wasn't having it. After all, all the matter and light that crossed the event horizon of the black hole would congregate at the singularity, accelerated to ultrarelativistic speeds.

"The calculations were unequivocal," Thorne wrote in Black Holes and Time Warps. "Any vehicle for hyperspace travel gets destroyed by the explosive 'rain' before the trip can be launched. Carl's novel had to be changed."

He proposed something even spacier than black holes: wormholes.

The temptation of wormholes

"If this FTL drive isn't fixed soon, we're dead!"

That's Captain Lee Adama on Battlestar Galactica, and as much as they reference it, the show never explained exactly how their faster-than-lightspeed (FTL) drive actually worked. They're not the only ones. Most science fiction properties lean on an implication of hyperspace tunnels, or wormholes.

In Hitchhiker's Guide to the Galaxy, most ships travel via hyperspace expressways. In Martha Wells' Murderbot series, the sardonic main character hitches rides through wormholes, although how these wormholes form or operate is left up to the imagination. Other authors, like CJ Cherryh, try to throw in a bit more of a theoretical physics vibe, with phrases like "Einstein-Rosen bridge." That's just a fancy name for a wormhole.

The truth is that although FTL travel is the backbone of science fiction, no one has figured out how it might actually work. Kip Thorne's proposition of wormholes, though, shaped the genre for decades.

The tempting thing about wormholes is that they are, in fact, a mathematically sound solution to Einstein's equations. It is absolutely possible for a tunnel to exist between two points in space such that the distance inside the tunnel is shorter than outside. What's not so clear is how such an object could form, or how it could stay open if it did.

The problem with wormholes, Part I

What Thorne struggled with in the backseat of a car in 1985, trying to fix Carl Sagan's plot, is that wormholes don't want to be used for interstellar travel. Previous physicists found that they have a fatal flaw. All the matter that passes through a wormhole causes it to gravitationally contract. Right after forming, it closes. Nothing gets all the way through.

This is called pinching, and Thorne needed to avoid it for Carl Sagan's sake. He calculated that the only way around pinching is to coat the inside of the wormhole with "exotic matter." Exotic matter has a negative energy density from the perspective of light passing through the wormhole.

When traveling at light speed, Einstein's equations result in strange effects, and one of those is that negative energy density isn't technically forbidden.

Thorne's conjectures inspired a flurry of papers on exotic matter and whether it could coat a wormhole. The results, to this day, are inconclusive. We do know that exotic matter actually exists, at least near black holes, where the event horizon disrupts energy fluctuations in a way that favors negative energy density. The same occurs when two uncharged plates approach one another. But we don't know whether such matter would stay exotic on the inside of a wormhole.

For Contact, Thorne was content to skip over the finer details of how the Vega aliens coat their wormhole with exotic matter. But academically, he and his collaborators were only getting started.

The problem with wormholes, Part II

Say we have exotic matter. Say we can use it to coat the insides of a wormhole so that the sides repel each other and stay open. How do we go about finding a wormhole?

As bizarre as black holes seem, they have a perfectly reasonable origin story. When massive stars get very heavy and can no longer hold themselves up against their own gravity, they collapse into an infinitesimally small point. That's a black hole.

But there's no similar mechanism for the formation of wormholes. At least, not for those large enough to allow travel. At the quantum level, Kip Thorne's graduate advisor, John Wheeler, laid the groundwork for wormhole formation back in the 1960s. He predicted that at very, very small scales, all spacetime should froth and bubble. Based on a fundamental theorem of quantum physics called the Heisenberg Uncertainty Principle, this "quantum foam" might form very small wormholes every second and annihilate them the next.

So can one forcibly enlarge a wormhole from the quantum to the classical regime? The answer lies in the realm of quantum gravity -- an enduring and unobtained Holy Grail in theoretical physics.

That's a no-go.

How wormholes imply time travel

Let us create a wormhole through unspecified quantum mechanical processes. Despite its immaculate conception, free of the bizarre time effects plaguing other proposed creation mechanisms, it will still succumb to the temptation of time travel.

The classic example, first conceptualized by Kip Thorne shortly after his contact with Contact, banks on an effect called time dilation. When objects move very close to the speed of light, the time that the object experiences flows more slowly than the time of a stationary observer. Think of Ender's Game, in which the protagonist skips forward 2000 years between the first two books because of how much time he's spent on very fast spaceships.

If Ender takes one end of a wormhole with him on his spaceship and leaves the other end on Earth with his sister Valentine, the wormhole will connect his sister to his time frame. Say he spends 10 months on a round-trip voyage and winds up back on Earth where he started. Then 10 months after his departure, Valentine can look through the wormhole and see him back on Earth.

But say that thanks to time dilation, from Valentine's perspective on Earth, Ender's trip takes 10 years. When he finally returns to Earth, entering his side of the wormhole will return her to her side, 9 years and 2 months before.

More paradoxes

This is where all sorts of paradoxes come into play. What if, for instance, Ender uses this setup to journey 50 years into the past and kill his own grandfather? The world misses out on one very enjoyable novel and quite a number of mediocre ones (sorry, Speaker for the Dead fans). Then no Ender would exist to go kill his grandfather, so his grandfather would live, and Ender would be born once more.

Bizarrely, that scenario actually makes perfect sense in a quantum mechanical world. The laws of quantum mechanics don't predict outcomes, just the probability of different outcomes. Attempting to understand what that actually means is an entire branch of physics called quantum foundations. It leads to elegant but unsettling theories such as Hugh Everett's "many-worlds" theory of splitting timelines. Each time a quantum mechanical system is tested, Everett proposes, the universe settles into one of many possible timelines, branching constantly.

This fits in nicely with the grandfather paradox. There is some probability that a man arrives out of nowhere and murders Grandfather Wiggin in his youth. There exists some other probability that Grandfather Wiggin carries on happily, eventually allowing Ender to be born and travel backward in time. When the moment comes for him to die, the universe makes a choice. We lift the lid and peer in on Schrodinger's grandfather: either he's alive or dead, but a second ago, he was both.

Why time travel (probably) can't exist

So, as far as we can tell, under the basic principles of quantum mechanics, time travel isn't as obviously a no-go as one might assume.

Yet we know of at least one mechanism by which any wormhole acting as a time machine might destroy itself. Kip Thorne, his graduate student Sung-Won Kim, and Stephen Hawking calculated that the same kind of quantum foam present in all space might build up inside a wormhole, destroying everything inside it and causing it to pinch shut.

The keyword here is might. We don't know enough about quantum gravity to say whether it would.

Hawking hypothesized that the universe would protect itself from time travel to avoid the manifestation of quantum phenomena on a human scale. More importantly, he wrote, this would "make the universe safe for historians."

He tested his theory in 2008 by hosting a party for time travelers. The day after the party, he sent out the invitations. No one showed up.

A majority of physicists agree with his conjecture. But to this day, no one can conclusively resolve it. That would require a working theory of quantum gravity. We're a long way away from that -- unless anyone from the future wants to help us out.

How do you speed up something that only interacts regularly with itself?

That's the question gripping astrophysicists at the Cubic Kilometer Neutrino Telescope (KM3NeT). In 2023, before the telescope was even completed, a high-energy neutrino shot through the Earth's atmosphere and into the detection zone of KM3NeT. Since KM3NeT looks for neutrinos, finding one wasn't a huge surprise. But this was the most energetic neutrino ever detected. So energetic, in fact, that it crashed their computer.

Where did it come from?

A telescope at the bottom of the ocean

KM3NeT looks about as much like a traditional telescope as, say, a rhinoceros does. It consists of indented spheres of metal standing guard over smaller glass spheres hanging from strings. The whole contraption sits 3,500m underwater at the bottom of the Mediterranean Sea.

Its strange design comes from its purpose: to hunt some of the most elusive particles in the universe. Neutrinos are omnipresent, with over a billion of them flowing through each square centimeter of space every second. But they barely interact with matter, and not at all with light or magnetic fields.

Still, some dramatic events create ultrarelativistic neutrinos that move at almost the speed of light. Both cosmic rays hitting the upper atmosphere and supernovae create neutrinos observable from Earth. Astrophysicists try to detect these energetic neutrinos.

But detecting something that doesn't interact with light, magnetism, or most matter is mildly challenging, to say the least. The most famous neutrino detector in the world, IceCube, uses the Antarctic ice sheet to do so. KM3NeT opts for the salty waters of the Mediterranean Sea.

In water, light travels at only 75% of its speed in air, but neutrinos keep speeding along at the same velocity they always have. But even for a weakly interacting particle, 3,500m of water is a lot of water. Very occasionally, neutrinos collide with a proton or electron in the water with exactly the right angle and momentum to interact via the weak nuclear force.

These interactions can produce charged particles, including muons, which are more susceptible to interactions with matter. When the muons hit water molecules at velocities higher than the speed of light in water, they create a shock wave akin to a sonic boom. That, in turn, releases blue light called Cherenkov radiation.

The suspended spheres of glass and metal in KM3NeT are optical detectors searching for this Cherenkov glow. When they detect it, they use its strength and direction to trace back where the muon-molecule collision happened and what the muon's energy was. From there, they can work out the energy of its parent neutrino.

The neutrino that crashed the computer

Lowering precious optical devices to the sea floor takes a lot of time. By February 13, 2023, only 6% of KM3NeT detectors were in place. They had been detecting a few neutrinos here and there, but that day, something strange came in.

"When I first tried looking at this event, my program crashed,” KM3NeT physicist Paschal Coyle told New Scientist.

It was a neutrino unlike anything seen before. Hundreds of times more energetic than the previous record-holder, it defied traditional astrophysical origins like supernovae, gamma ray bursts, or black hole accretion.

When they looked in the region of the sky from which the neutrino came, they found nothing. No signs of supernovae, energetic distant galaxies, or stellar collisions. Just empty space.

Empty space does have its own background field of neutrinos, but high-energy neutrinos are exceedingly rare.

The team's paper on the event came out earlier this year in Nature. In it, they calculate the rate at which we should be observing such neutrinos and find that about one should show up every 70 years. The chances that such a neutrino would show up one year into the run of a telescope that was only 6% completed are stunningly low.

The KM3NeT team has another hypothesis. Particle physicists have long theorized that high-energy cosmic rays (protons and electrons traveling near the speed of light) could interact with the background light of the universe and produce massively energetic neutrinos. This event would be exceedingly rare and has never previously been observed.

At least, as far as we know. It's possible that KM3NeT observed it in 2023. But astrophysicists have a lot of work to do before the identity of the mysterious neutrino is anywhere close to resolved.

At 23, Kyle Parker paddled all 682km of the Wisconsin River in a blur of muscle fatigue and no sleep. Coming in at 5 days, 19 hours, and 22 minutes, he set the fastest known time for the route in a solo canoe.

Parker wants to take his time for his new project, which will begin in just under a month.

"Today, we travel by all sorts of modes, often opting for the easiest and fastest we can find," he writes on his blog. "I am looking forward to slowing down to just a few miles an hour and really getting under the skin of the country."

The U.S. from 'tip to tip'

Parker's big dream is to traverse the country from northwestern Washington to southeastern Florida. He expects the trip to take six to eight months.

The route encompasses the frigid, deep waters of Puget Sound, hundreds of kilometers of rivers across the continental United States, the warm waves of the Gulf of Mexico, and even a few days on the western seaboard of the Atlantic Ocean.

He will have to contend with more than just choppy water and fierce currents. Usual canoe routes feature regular portages over dams when the interruption of the river requires carrying the canoe. But Parker will have to portage hundreds of miles over highways and, on one occasion, the continental divide.

"But it’s not just about the scenery or the wildlife, or even the excitement of being absolutely miserable," Parker writes. "It’s also about the people I’ll meet and the stories I’ll uncover. I want to connect with locals...and experience the culture of each place I visit."

Carrying on Stachovak's legacy

This kind of expedition is unusual but not unheard of. In 2009, Parker's fellow Great Lakes native Jake Stachovak completed the 9,237km Great Loop by kayak. The Great Loop starts in Portage, Wisconsin, and ends in Portage, Wisconsin, with a brief detour to the Gulf of Mexico. In 2022, Stachovak passed away to cancer at the age of 46.

Now his widow has supplied 24-year-old Kyle Parker with a portage cart, water bag, radio, and a pink cup holder that all belonged to Stachovak.

Parker has support from local paddling stores, too. Ethan Scheiwe, the manager of Madison's Rutabaga Paddlesports and one of Parker's sponsors, told the Wisconsin State Journal, "It’s a very daunting trip, but Kyle is the right person for it. If he does this, it will be the National Geographic adventure of the year. It’s that kind of trip.”

Parker sets out on May 1. You can follow the adventure on his blog.

The year is 2021. On Earth, COVID-19 rages. NASA is finally about to launch the James Webb Space Telescope (JWST), prophesied to usher in a new era of astrophysics. And a Cambridge professor named Nikku Madhusudhan writes the unobtrusive first entry in his to-be trilogy of papers on nearby exoplanet K2-18b.

Madhusudhan and his two collaborators propose a new category of planet, which they dub a "Hycean" world. Much larger than Earth but smaller than Neptune, Hycean worlds would boast water oceans under a hydrogen-rich atmosphere. In terms of habitability, they would be more flexible than rocky worlds like Earth. Their atmospheres would keep their temperatures stable. They might even have plentiful aquatic life.

Flash forward to 2025, and astronomers have yet to confirm the existence of Hycean planets. But last week, Madhusudhan's team at Cambridge claimed the discovery of potential biosignatures on K2-18b, one of their candidate Hycean worlds. The biosignature in question is the molecule dimethyl sulfide, largely produced on Earth by phytoplankton.

Headlines around the world have run rampant with this sign that we might not be alone. However, what many outlets leave out is the history of the claims in question and the concerns raised by a host of astronomers, many of whom are deeply enthusiastic about the search for extraterrestrial life. The first "hints" of possible life, reported by the Cambridge team in 2023, met with widespread derision among the astronomical community. The same is true for this new evidence in 2025.

That's not to say that the new results are obviously false, or even that aliens are definitively not involved. But the story of dimethyl sulfide on K2-18b isn't a simple one.

JWST is the best in the game, but the game is a hard one

Sitting at 1.5 million kilometers from Earth, JWST is the premier instrument in the solar system for observing exoplanetary atmospheres.

Under irradiation from their host star, atoms and molecules tense up, absorbing light at specific wavelengths. When they relax again, they emit that light. Observing patterns of missing or surplus light allows astronomers to identify the chemistry of the universe.

Much of the field of astrochemistry focuses on either the diffuse gas in interstellar space or the dusty rings around protostars. While not simple, these systems don't hold a candle to the complexity of exoplanet atmospheres. Planets have so much gas, such turbulent atmospheres, and are so irradiated by their host star that their light signatures are a blurry mess. Different atoms and molecules all jockey with one another for space. If astrochemists typically deal with barcodes, exoplanet atmospheres are like identifiers from the 17th century, stored in a damp warehouse, half-eaten by moths.

Oh, and if you want to take a photo of it, you have to do it while it's on the hood of a car with its brights on. The light from stars overwhelms anything from the planet. Astronomers use JWST to analyze the light coming from the star while the planet is in front of it, and compare that to the light coming from the star while the planet is behind it. This technique, called transit spectroscopy, separates the light from the star and the light from the planet. It's also very, very difficult.

'Possible' biological activity

In October of 2023, Nikku Madhusudhan and his team published the results of their JWST observations of K2-18b. Their paper, entitled Carbon-bearing Molecules in a Possible Hycean Atmosphere, drew less attention for its carbon-bearing molecules and more for its discussion of dimethyl sulfide.

Unlike many other kinds of spectra, astronomers can only parse exoplanet spectra using complex models. These models run through different options -- more methane, less methane, more ammonia, less ammonia but at a higher temperature, etc. -- to find the best fit. But the models require educated guesses on what molecules might be in the atmosphere. The chosen molecules can greatly affect the model's conclusions.

So when the Cambridge team ran their models on their JWST spectra of K2-18b, they limited the options to typical molecules found in exoplanet atmospheres: water, methane, carbon dioxide, and so on. And then, building off their 2021 work on Hycean worlds, they added five molecules they identified as biosignatures. These included dimethyl sulfide.

The best-fit model incorporated dimethyl sulfide at low confidence. According to their model, there was a 66% chance they had detected dimethyl sulfide, and a 33% chance it was random noise. Further muddying the issue was the fact that the JWST instrument used has a gap in the region where dimethyl sulfide is strongest.

The authors theorized that the dimethyl sulfide might originate from an ocean filled with algae-like life, despite the lack of other chemical byproducts associated with phytoplankton. They admitted, however, that future observations were required.

Follow-up observations on dimethyl sulfide

“This is a revolutionary moment,” Nikku Madhusudhan told The New York Times in an article published last Thursday. His new results were soon to be published in The Astrophysical Journal Letters. A deluge of comments on the NYT piece asked to read the actual paper, to no avail until the following day, when the press embargo lifted before the actual paper came out. “It’s the first time humanity has seen potential biosignatures on a habitable planet,” the author enthused.

The Cambridge team's new paper reports on follow-up observations using a different instrument on JWST, this time without a gap in the region of interest. Their models came back with higher confidence this time. They also returned a hit for dimethyl disulfide, a relative of dimethyl sulfide and another potential biosignature.

Many astronomers noted the results were tentative, including Madhusudhan himself. "It is in no one’s interest to claim prematurely that we have detected life," he told The New York Times. But that didn't temper his enthusiasm. “Given everything we know about this planet, a Hycean world with an ocean that is teeming with life is the scenario that best fits the data we have."

The pushback

Not everyone is as thrilled as Madusudhan.

ExplorersWeb spoke with Anthony Remijan, an astrochemist and interim director of Green Bank Observatory.

"There are probably dozens of molecules that can fit the extremely low resolution, low sensitivity of the 'features' seen in the JWST spectrum," said Remijan. "To claim they can be attributed to a singular, unique molecule such as DMS [dimethyl sulfide] is an extraordinary claim. As such, it should be reinforced by extraordinary data, which is not what we have here."

In fact, the new paper doesn't address a recent reanalysis of the 2023 data by a separate team that didn't find any evidence of DMS or even that K2-18b actually has an ocean. Some work has suggested K2-18b might be covered in magma rather than water, and therefore not a prime candidate for phytoplankton. Perhaps most crushingly, several recent papers show that dimethyl sulfide doesn't even need life to exist. It's also found on comets, which are not notable hotbeds of algae.

Remijan is particularly concerned about the validity of dimethyl sulfide as a biomarker.

"Over the past decade, interstellar urea was confirmed in the [interstellar medium] where at one point, urea was thought only to be formed by biological processes," he pointed out. Urea is the main component of urine. "Obviously, this is not the case in the [interstellar medium]."

'Practitioner vs commentator'

The Cambridge team acknowledges the uncertainties, but stand by their conclusions. When an interviewer brought up the biosignature issue on BBC Radio 4, Madhusudhan said, "This is the difference between a practitioner and a commentator. From a practitioner's point of view, this is as good as it gets in science, and you just have to recognize it. But for that, you have to be in the field, not outside."

As it happened, the interviewer questioning him was Chris Lintott, a published exoplanet astronomer.

In the press, too, some skeptical voices have tempered the hope for aliens. A scathing article in The Atlantic noted that "the word possible is doing load-bearing — if not Atlas-like work -- in these headlines."

Scientific American, meanwhile, interviewed Chris Lintott before his conversation with Madhusudhan on BBC Radio 4. "Dimethyl sulfide should exist in a chemical network," he told them. "If it’s produced by biology, it should break down, and the raw materials such as H₂S [hydrogen sulfide] used to make it should be visible in the spectrum, too. They aren’t."

A blind search for life

The day after the Cambridge team's press release, Nikku Madhusudhan's former graduate advisor, MIT astrophysicist Sara Seager, published a paper of her own. Along with her collaborators, she analyzed the sensitivity and precision of JWST's instruments in relation to exoplanet atmospheres. What she found wasn't hopeful.

In a world racked by insecurity, political strife, and environmental degradation, it's no surprise that so many of us want to believe in life on another planet. But according to Seager, we'll have to wait.

She writes, "With JWST, we may never be able to definitively claim the discovery of a biosignature gas in an exoplanet atmosphere."

And Anthony Remijan adds:

"To invoke a biological origin suggests there is no abiologic way to form these molecules, which is simply not the case. We are just beginning to scratch the surface on how molecules can form in these extreme environments, where [it was] once believed that no molecule should ever exist in space, except for hydrogen. So even if DMS was found in space, there is likely an abiogenic process we haven't thought of yet that formed it."

Everything that falls into a black hole falls in at the same time. Perhaps in the distant past, some unfortunate alien astronaut was sent past the event horizon to explore what lies beyond. From our perspective, he is still falling across the threshold. He has been since he first fell in, back before his civilization crumbled, before his home planet tumbled into its sun, and that sun collapsed into a white dwarf.

From his perspective, he only just crossed it. What will he find on the other side? As of right now, physics only has guesses. In this week's Great Mystery of Outer Space, we cover the uncertain insides of black holes.

Black holes might be mysterious, but they're real

Albert Einstein believed black holes to be a grand mistake. They were a natural extension of his theory of general relativity, a set of otherwise airtight formulations of how gravity and light behave, but they could not possibly be real. After all, how could anything have mass if it was infinitely small? How could it trap light within it, thereby removing information from the universe?

He set out to disprove their existence in a 1939 paper, and while his conclusions were correct, he started from a set of assumptions that were not.

Unfortunately for Einstein, the existence of black holes has now been proven over and over again. First, by strange X-rays from a star being shredded apart by something massive. Then came the ultra-bright radio emission in the center of galaxies from disks of matter orbiting an invisible center. Strange orbits, things lurking at the heart of supernovae remnants, and huge jets of plasma in distant galaxies all added evidence.

In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves from a pair of distant black holes colliding. And finally, in 2019, the Event Horizon Telescope (EHT) succeeded in directly imaging the center of nearby galaxy M87. Black holes don't emit light, and the shadow they leave is visible against the bright plasma around them. The EHT images of M87's black hole shadow are the closest we can get to photos of a black hole itself.

The anatomy of a black hole

Hear me out: black holes are the simplest objects in the universe. No, really, I promise. They only have two features of note.

The first is the event horizon, which isn't technically part of the black hole itself. Instead, it's the distance from the black hole where gravity becomes so strong that nothing, not even light, can escape the inexorable pull toward the center. Material caught in the black hole's orbit circles around the event horizon, disrupted by the strong gravity and by colliding with other matter. This is what causes the bright rings known as accretion disks and the flares called, in various different circumstances, quasars or active galactic nuclei.

Right at the event horizon is where things get very, very strange, but it's a known kind of strange. The laws of general relativity predict that everything that crosses the event horizon crosses it at the same time, and to an outside observer, things crossing it freeze. In fact, before physicist John Wheeler coined the term "black holes," most physicists referred to them as "frozen stars." (Personally, I find the original name much more evocative.)

Far below, at the center, lurks the singularity. It is an infinitely small point or, in certain peculiar cases, an infinitely thin ring. It can weigh up to 10¹¹ times the mass of the Sun. It has no dimensions, no volume, no time. But it has a lot of mass.

Just what is a singularity?

In the clumsiest terms, a singularity is a place that's very weird compared to everything else around it. The usual laws don't seem to behave so well around singularities; that's what makes them so singular. The idea of a point with infinite density makes sense on paper. It falls right out of Einstein's equations, much to the consternation of Einstein himself. But elsewhere in physics, the presence of singularities tends to indicate the theoretical models are missing a few components.

That's what many physicists believe is happening with the black hole singularity. The infinitely small point might not physically exist, but general relativity can't quite grapple with the true nature of black holes.

If the singularity is quite small but not infinitely so, then it's the purview of the theory known as quantum gravity. Unfortunately, quantum gravity barely exists.

The world of physics needs a mathematical formulation of how gravity behaves at small scales. It needs something revelatory and revolutionary, the quantum gravity equivalent of general relativity. That's a hard ask. The only widely popular framework to attempt it is string theory, an astoundingly beautiful theory of nature that, after more than 60 years of development, has yet to predict anything testable.

So the nature of the singularity remains, for now, a mystery.

Okay, but what would the 'singularity' actually do?

We don't know what a singularity is. Do we know what it does?

The answer is maybe. General relativity is a set of laws, not a recipe. Mathematically, there are many recipes for how space works that obey the laws of general relativity. Among these recipes (obscurely called "metrics" in physics lingo), several are more pertinent to our lived reality than the others.

The Schwarzschild metric, for instance, describes spacetime around spherically symmetric points, black holes included, as long as those points aren't spinning. The Kerr metric takes it a step further and describes spacetime around points that are spinning, which adds in a slew of bizarre effects with intimidating names like "frame dragging."

Buried in some of these distinct metrics are places where Einstein's equations give out. With well-understood metrics there as guide rails, physicists can fill in some of the blanks.

Currently, common thought is that the unknowable singularity at the center of a black hole probably devolves into three marginally more knowable ones as the black hole ages.

Singularities to watch out for

Three singularities in particular might haunt the insides of an aging black hole. We'll start with the worst news first: the BKL singularity. Formally named the Belinski–Khalatnikov–Lifshitz singularity after its discoverers, the BKL singularity is also known as the chaotic or oscillatory singularity. That's because as an observer approaches it, their body is subject to increasingly violent tidal forces that alternately stretch and compress them. If anything in a black hole is most out to get humans, it's the BKL singularity.

Then there's the ingoing singularity. All of the matter and light that falls into the black hole gathers together, falling for infinity. The gravity of this region can be so strong that it forms its own singularity. Good news, though: the region where matter congregates might be so thin that other objects can actually pass through it undeterred.

Similarly, the outgoing singularity arises from the light that bounces off things inside the event horizon and then travels backward, colliding with the ingoing singularity. What happens then is unclear, but once again, it might be avoidable.

The predictions above have serious mathematical credentials, but at the end of the day, the nature of the singularities are still unknown. So, too, is the state of matter inside a black hole. Can matter survive the event horizon? Where is it located? Is it converted to light or even gravitational waves?

We can only hope that a new theory of quantum gravity will illuminate the insides of a black hole.

In the summer of 1950, four men sat down for lunch together at Los Alamos. It was, at the time, the center of American physics, and these men were respected contributors to their field. Among them was Enrico Fermi, a giant in the fields of quantum mechanics and thermodynamics.

But the men were relaxing over lunch, and the conversation was not erudite. Nuclear physicist Emil Konopinski brought up a cartoon he had recently seen in The New Yorker, explaining why public trash cans were disappearing from the streets of New York City. The cartoon showed what was evidently a flying saucer with little green men filing toward it with the spirited-away trash cans.

Well, Fermi pointed out, this was a very logical hypothesis. It explained both the regularity of UFO sightings and the strange disappearance of New York trash cans.

The group laughed and moved on. They finished lunch. Then, out of nowhere, Fermi exclaimed, "But where is everybody?"

He was talking about extraterrestrial life, and everyone at the table knew it. They tossed about some ideas but largely treated the matter as a joke.

"As far as our galaxy is concerned, we are living somewhere in the sticks, far removed from the metropolitan area of the galactic center," said physicist Edward Teller.

But the question stuck. It became known as Fermi's Paradox: if the Earth isn't special, and the Universe is so very big with so many stars, where is everybody?

The search for alien life begins

A decade passed. The Cold War kicked into high gear, driving scientific competition. Radio astronomy historian Rebecca Charbonneau told ExplorersWeb that the Cold War's technological advances spurred the search for extraterrestrial life.

"The launch of Sputnik in 1957 and the subsequent proliferation of artificial satellites — including early signals-intelligence platforms — made detecting non-human technosignatures suddenly plausible," she explained.

The thought of aliens began to captivate a fringe group of astronomers, notably Frank Drake. He convened a meeting on the subject at the National Radio Astronomy Observatory site in Green Bank, West Virginia.

"Drake had invited everyone he could think of with an interest in the scientific search for E.T. — all 12 of them — to the meeting," wrote Nadia Drake, his daughter.

The Drake Equation

In order to guide the discussion, Frank Drake sat down and estimated the number of civilizations in the galaxy with whom Earth could communicate. It was a very simple estimation. The number of civilizations would be equal to the rate of star formation, times the fraction of stars with planets, times the number of habitable planets per solar system, times the fraction of habitable planets that actually lead to life, times the fraction of life-bearing planets with intelligent life, times the fraction of intelligent civilizations that develop a means to communicate in outer space, times how long those civilizations actually release signals.

At the time, astronomers had begun to understand the rate of star formation in the Milky Way. Everything else in the equation was a complete mystery.

When Drake formulated his estimate, astronomers had no confirmation that planets even existed around other stars. All logic suggested they would, but they were far too faint to detect with contemporary telescopes. So the field theorized, argued, and waited.

Astronomers took another two decades to confirm that extrasolar planets, or exoplanets, existed. That confirmation didn't come from any of the famous modern methods of exoplanet detection, such as light fluctuations or watching a star wobble back and forth. Instead, it came from a previous candidate for extraterrestrial communication: the strange dead stars known as pulsars.

Little Green Man 1

The discovery of pulsars dates back to 1967 when graduate student Jocelyn Bell Burnell noticed a strange repeating radio signal in her telescope data. She had no idea what to make of it and dubbed it "Little Green Man 1."

Unfortunately for the little green men, it eventually became clear that the signal came from a rapidly rotating object known as a neutron star. Neutron stars are incredibly dense and incredibly small, with a mass greater than that of the Sun but a radius the size of San Francisco. Every time they spin around, their off-kilter magnetic fields fling out regular radio emissions.

Jocelyn Bell Burnell had discovered the first example of one of the most exotic objects in the known Universe. (The Nobel Prize, of course, went to her advisor.)

The study of pulsars blossomed into a flourishing subfield. In general, pulsars are near-perfect clocks. While different pulsars have different periods, every radio pulse arrives at the Earth perfectly on time.

Not so for the pulsar that Aleksander Wolszczan and Dale Frail observed in 1992. The arrival time of each pulse wobbled up and down: now just before expected, now just after.

First step: finding exoplanets

Wolszczan and Frail tried modeling the noise as a companion star to the pulsar. It didn't work. Every time they succeeded in getting rid of one part of the wobble, another part stepped forward to dominate.

They began thinking outside the box. The best solution was for not one but two companions to the pulsar: planets just a little bit more massive than the Earth. The varying pulse time of arrival came from the pulsar moving back and forth very slightly in its orbit such that each pulse had to travel a subtly different distance to reach the Earth.

Exoplanets existed. Grappling with the first two terms in the Drake Equation was suddenly far more tractable. Onto the next step: How many of the planetary systems out there had habitable planets?

Exoplanets were no longer the domain of the theorists. As the 21st century rolled ahead, new high-sensitivity telescopes allowed the detection of exoplanets around all kinds of stars. Today, we know of almost 6,000.

It took until 2014 for the Kepler satellite telescope to detect anything that looked like Earth. The first such exoplanet is the memorably named Kepler-186f, an Earth-sized planet orbiting at a habitable distance from a red dwarf star. The atmosphere and climate of Kepler-186f differs dramatically from that of Earth, but it's not a stretch to imagine other lifeforms might thrive there.

Nowadays, terrestrial-style exoplanets are so numerous that they comprise an entire subfield. The NASA Exoplanet Encyclopedia tracks all of them, including their mass and how habitable they seem. Statistics of exoplanet habitability are no longer a mystery.

So where's the life?

When Drake formulated his equation in 1961, astronomers had only pinned a value on the first term. Now, the first three are well-understood and understood to be high. In short, there are a lot of stars out there, a lot of those stars have planets, and a lot of those planets are habitable. So where's the life?

For the fourth term (the regularity with which life emerges on habitable planets), astronomers must turn to theoretical estimates by paleobiologists and geochemists. For the fifth (the fraction of intelligent life), evolutionary biologists. The sixth and seventh terms are the realm of theorists doing work that is important but so fringe that they don't have a field to call their own.

The fact remains that, as far as we know, we have never been contacted by any extraterrestrial species. So one of those terms must be exceedingly low, or else something stranger is going on.

Possible answers

Perhaps the simplest way to answer the Fermi Paradox is that life rarely forms in the universe. With the fourth term in the Drake Equation close to zero, humans could expect never to get a call from any nearby neighbors. The nearest extraterrestrial life might be across the Milky Way or in another galaxy entirely. This was the interpretation favored by paleobiologist Stephen J. Gould.

Other biologists posit that the fifth term is the blockade. In this scenario, life abounds nearby, but we're the smartest kids on the block. Astrobiologist Charles Lineweaver points out, "Dolphins have had about 20 million years to build a radio telescope and have not done so."

It's also possible that the sixth term is practically zero. Other intelligent life might exist, but can't communicate with us. Still on about dolphins, Lineweaver adds, "If you live underwater and have no hands, no matter how high your E.Q., you may not be able to build, or be interested in building, a radio telescope."

Those three solutions posit a universe where humans are special. They are also the happiest possibilities. Another common hypothesis is that the seventh term in the Drake Equation -- the length of time for which civilizations communicate -- is very short because natural catastrophes regularly cause the extinction of intelligent life. Asteroids, gamma-ray bursts, and volcanoes are all potential culprits.

A darker theory

The darker version of that theory is that intelligent life inevitably eradicates itself through nuclear war, climate change, or other disasters. Carl Sagan argued that self-destruction was common, but civilizations that avoided it would endure for eons.

"Perhaps there is a waiting time before contact is considered appropriate," he wrote, "so as to give us a fair opportunity to destroy ourselves first, if we are so inclined."

The Dark Forest Theory, named after the book by science fiction writer Cixin Liu, posits that intelligent life wouldn't destroy itself but others. Other science fiction writers such as Dennis Taylor have also flirted with this idea, painting a galaxy in which one species of alien has eradicated most other intelligent life. Stephen Webb suggested that since humans are superpredators, successful alien life would be as well.

It's also possible intelligent alien life exists, but we can't begin to comprehend it. It might not appear as life to us, or as intelligent. It might choose not to communicate for reasons that would baffle us. It might not want to leave its homeworld.

It might, in other words, be alien.

A 22-year-old climber died on Saturday in a fall from Scotland's highest mountain. His climbing partner, 30, is in the hospital with significant but not life-threatening injuries. Both men are believed to hail from England.

A rescue and a tragedy

Around 5 pm on Saturday evening, Police Scotland received reports of two injured climbers below the Moonlight Gully, a popular beginner's ski route.

Late Saturday night, the Lochaber Mountain Rescue Team (LMRT) located one injured but alive climber who had managed to move downhill. They evacuated him to Raigmore Hospital in Inverness. Strong winds and snow then forced them to pause the search.

The next morning, they found the body of the second climber, who was deceased. Scottish police have not disclosed the cause of death nor released the names of either climber. The families, however, have been notified.

Both men fell about 60 meters during the accident.

Fickle weather

At 1,345m, Ben Nevis is the tallest mountain in the UK and draws more than 125,000 visitors per year, according to Scotland's tourist board. The weather around Ben Nevis last week alternated between sun and rain. On Saturday, heavy storms caused the closure of surrounding trails due to flooding. Snow was also falling.

This kind of weather is typical in the Highlands. It impedes rescue efforts and has led to deaths before. More than 100 people have died on the mountain since records started in 1849.

The UK's busiest mountain rescue team

This was the fourth rescue for the LMRT this week. The number of rescues rises every year as more tourists flock to the Highlands and to Ben Nevis in particular.

"As an entirely voluntary team, responding to calls and attending training is a huge demand on time, and it is unnerving to see these numbers rise so quickly," said the LMRT website. "Taking the lead in a team like this requires extraordinary fortitude, resilience, and a remarkable ability to survive on little sleep and lots of chocolate bars."

You can donate to the LMRT here.

In the dying years of the Roman Empire, a vassal king in the distant territory of Wales rallied his forces to shake off Roman rule. When the Saxons, too, turned their eye on his kingdom, that Welsh king joined with his northern confreres to beat them back. Eventually, he founded a model kingdom 800 years ahead of its time, complete with knights, metal armor, and even an early form of parliament.

His name was King Arthur, and unfortunately he did not exist, at least in a recognizable way. But the late medieval writers who crafted his legend would have had cause to rejoice this week. Digital archivists at the Cambridge University Library have just recovered a new fragment of their work, hidden in plain sight for centuries. It had been used as the binding for an Elizabeth property register.

How a 13th-century story became the cover of a 16th-century book

Stories of King Arthur were all the rage in the 1200s. After the self-described historian Geoffrey of Monmouth popularized Arthur's legend in the 11th century, the setting of the Round Table spread across the Channel. What had once lived in the realm of pseudo-historical tracts and Welsh oral tradition reached the courts of France.

The defining stories of early French Arthuriana were poems. Marie de France, one of the most famous female French authors in history, wrote short, often satirical verse set in Arthur's court. At the same time, the daughter of Eleonore of Aquitaine, Marie de Champagne, commissioned the first stories of Sir Lancelot and Queen Guinevere's forbidden love and of the Grail Quest.

These stories captured the imagination of the French and English nobility, culturally bound from the Norman conquest of England in 1066. In about 1200, an anonymous coalition of authors adapted them into what may be the first European fantasy blockbuster: the five-book series known as the Vulgate Cycle.

The Vulgate Cycle

Novels were a new concept in Europe. But the magical quests, epic sagas of family strife, and heart-rending character arcs of the Vulgate Cycle were so successful that they endure even today. If you've heard of the Lady of the Lake, of Lancelot and Guinevere's affair triggering the downfall of Camelot, of the Holy Grail being the cup that caught Christ's blood on the cross, then that's the Vulgate Cycle at work.

By the 16th century, though, stories of the Round Table were passé, especially in England. In the same way that a 21st-century scrapbooker might dismember an old novel, Elizabeth bookbinders yanked out a handful of pages from a copy of a Vulgate book. The copy they used dated to about 1300. They needed to bind a register of property deeds, and parchment was precious. So they folded up the Vulgate pages and sewed them into a new cover. There, the pages sat for half a millennium.

Recovering the story

In 2019, archivists at Cambridge University were sorting through the records of an estate in Suffolk when they realized that the cover of the property register contained fragments of a much older text. But it would be impossible to unfold the fragments without damaging the cover it comprised, an important historical artifact itself. More advanced methods would be needed to read the cover text, and in 2023, Cambridge began a new program to do so.

Just this week, the Cambridge Digital Library released the first results from this project. Archivists used multispectral imaging (MSI) to scan the whole text without unfolding the cover. MSI breaks images down into color categories, allowing conservationists to deblur old writing or even recover the traces of erased text.

CT scans probed through the folded layers of parchment. Finally, new techniques in digital image manipulation allowed the team to "unfold" the text and read it.

The wizard Merlin greeted them.

Merlin's magical shenanigans

Nowadays, images of Merlin are dominated by two pop culture phenomena. Either he's a spry old wizard in a blue hat who ages backward (as portrayed in TH White's The Once and Future King and its Disney adaptation, The Sword in the Stone), or he's Arthur's 20-something best friend, as in the BBC TV show Merlin.

The medieval Merlin was a lot stranger. He was born speaking like an adult, the child of a human woman and a demon. He could disguise himself however he wished and was prone to prophesying the downfall of those around him. (Personally, if my wizard advisor handed me a sword inscribed with the words, "With this sword, Sir Lancelot shall kill the man he loves most, and that man shall be Sir Gawain," I wouldn't let anyone named Lancelot or Gawain anywhere near my peaceful Round Table.)

On one occasion, Merlin arrived at Camelot disguised as a blind harpist: "While they were rejoicing in the feast, and Kay the seneschal brought the first dish to King Arthur and Queen Guinevere, there arrived the most handsome man ever seen in Christian lands. He was wearing a silk tunic girded by a silk harness woven with gold and precious stones, which glittered with such brightness that it illuminated the whole room."

This is the excerpt that made up one of the two pages sewn into the cover. So far, the Cambridge Digital Library has only released the above passage, which agrees with other copies of the Vulgate Cycle. They are currently working to produce an annotated version of the whole text. Medieval scribes often edited or even rewrote the stories they copied, so it's possible this text could differ substantially from other manuscripts.

A medieval action hero

Although nowadays Arthur and Merlin are probably the most famous characters from the Arthurian canon, medieval readers had a favorite knight, and it wasn't Lancelot. It was Arthur's hot-headed, charismatic nephew Gawain.

Arthur has a relatively idyllic childhood in the Vulgate Cycle. A kindly knight raises him alongside his own son. But the children of his elder sister Morgause are less lucky. From a very young age, they fight alongside their father in wars against the Saxons. In addition to the Merlin episode, the property register cover text also includes a scene from this plot arc, in which Morgause's eldest son Gawain rides his beloved horse Gringolet into battle.

This is one of the final snapshots of Gawain as a teenager in the Vulgate Cycle. Soon after, one of Arthur's knights kills his father in battle. The young Gawain vows revenge, and although he later joins the Round Table, his vendetta against his father's killer spirals into a vicious blood feud that contributes to the fall of Camelot.

Of course, that's the version in other manuscripts. In the property register folio, none of that ever happens. Merlin dazzles Arthur's court, and Gawain rides victorious into battle. The rest is left to the reader.

Li Dongju made headlines recently for her cross-continental biking adventures. Between misadventures with border guards in Bosnia, reporting a budding wildfire in Australia, and camping out in cemeteries, there's enough peculiar adventure to fill any travel influencer's Instagram or YouTube page.

But Li Dongju isn't a content creator selling a lifestyle to millennials or Gen Z. She's 66, has a scant social media presence, and gets by on a meager pension from her time in a textile factory.

A silver tourism sweetheart

Li Dongju is the apotheosis of "silver tourism," a term describing the phenomenon of engaged, active senior travelers. For months every year, Li bikes the backroads, visiting towns on two wheels that most tourists never see on four.

It's a far cry from her earlier assumptions about where her life would go. In 2000, like many others in China, Li fell victim to mass national layoffs and lost her job at a textile factory. She was left with a slim pension of $414 a month. Shortly after, her life shifted once again. A female colleague of her husband's called her out of the blue and told her the two of them were having an affair.

The marriage went downhill rapidly.

"I will never forget how shocked I was when my husband asked for a divorce," she told China Daily. "Despite how simple and dull our daily lives were, I never thought we would go through that kind of change."

As soon as they separated, he remarried another woman.

Li spiraled into depression, exacerbated by bipolar disorder. She tried burying herself in video games and then in volunteer work. Nothing seemed to help, and she eventually wound up in a psychiatric ward.

Salvation through cycling

In 2013, amid rising concerns from her family about her mental state, a group of cyclists tore past Li on the street. The image grabbed her, but she couldn't afford a bicycle on her pension.

Sensing something important in her sudden desire, her son gifted her a mountain bike. It would have cost more than two months of her pension, and Li was thrilled. She wanted to bike through the high-altitude vistas of Tibet and see the "roof of the world."

But with only $23.50 in savings, that dream seemed far away. For a year, she worked as a house cleaner, saving her salary and biking around her hometown of Zhengzhou every day.

Then, in 2014, she set out on her first real venture: a trip to Vietnam with a group of other Chinese cyclists. Within a week, she accidentally became separated from her companions. She was lost and had knowledge of Vietnamese. Li eventually returned home, determined to get more practice in her own country before trying any more foreign trips.

She started by biking to 20 cities across China. This time, she took her poodle Xili with her. He rode in the basket as she biked from her native Zhengzhou to far-flung Hainan and Xinjiang. Life began to look up.

A new way of living for Li

With some real road time under her belt, Li set off once more for Southeast Asia with two other cyclists. A month of poor weather and punctured tires left the other two dispirited. By the time they arrived in Nha Trang, Vietnam, they were ready to turn back.

Li was not. After the group split up, a Chinese teenager living in Nha Trang offered her a room to stay and then cycled alongside her for the next leg of her journey.

After another month, she was back in Zhengzhou. But she wouldn't stay put for long. Her biggest venture came in 2019 when she set out across Europe armed with only her bike and Google Translate.

Then came Australia, where she alerted local authorities about a wildfire, and New Zealand.

And then, COVID-19.

Disease and death

COVID halted Li's travels as China initiated its zero-tolerance policy. Confined to her house, she began live-streaming and garnered significant media attention.

Her ex-husband came down with cerebral thrombosis. His wife left him. Li Dongju, who had "no hate" in her anymore after years of cycling, returned to Zhengzhou to remarry him and act as his caretaker. He was paralyzed and had no one else in his life but her.

To top it all off, her poodle died.

Back on the road

Li has recovered from the blows dealt to her during COVID and her ex-husband's illness, and she's ready to be cycling again.

She recently gave an interview on CNN in which she highlighted the kindness shown to her around the world. From the teenager in Nha Trang to trekkers in Australia who hugged her when she was covered in grease, the generosity of strangers has deeply inspired her.

"Every time I see her [photo], it brings tears to my eyes,” she told CNN, referring to a woman in Australia who offered her water and pomegranates on a brutally hot day.

Her next trip will pass through Kazakhstan and end in the United Arab Emirates. When Li sets out, she will do so with the eyes of the world on her.

Why Li Dongju?

The story above is the version that has made its way to the English-language press. Li Dongju cuts a different figure in China. In several Chinese-language stories about her, the scorned wife became a nagging harpy whose mental illness alienated those around her. A story of personal salvation became one of redemption as she relinquished her hatred of her husband and returned, penitent, to his bedside.

Part of the popularity of Li Dongju's story stems from how effectively it travels across cultural boundaries. For Western media, steeped in American individualism and an obsession with physical fitness, she's a strong-minded woman who forged a new, fulfilling life while working out in her old age.

For Chinese platforms, in a landscape dominated by family loyalty and respect for old age, she serves both as a redemption story and an inspiration to a rapidly aging population. (It's worth noting that there was plenty of pushback on the Chinese internet to the narrative of Li as a prodigal wife, just not on high-profile outlets.)

But despite their differences, both of these narratives share an obsession with Li's age. The word 奶奶 (grandmother) is ubiquitous across Chinese sources, a term that carries a level of fondness and respect not present in the English translation. In a culture that values old age, this focus makes sense.

English-language sources refer to her as a "Chinese grandma," "gung-ho grandma," and "Chinese grandmother."

The implicit suggestion in English-language headlines is that traveling the world, particularly in a manner as grueling as cycling, is a pastime for the young or middle-aged. A 66-year-old woman setting out so proactively to enjoy life, these articles imply, is unusual.

The rise of 'silver tourism'

Silver tourism is an economics term linked to the idea of active aging, which the World Health Organization somewhat stiffly defines as "the process of optimizing opportunities for health, participation, and security in order to enhance quality of life as people age."

For many seniors, participating in desired activities comes with limitations. Their mobility may be diminished. They may require easy access to healthcare providers, eliminating exotic, isolated locales. They may struggle to find travel information online.

In short, if tourism companies are to profit from this sector, the services they provide must differ from traditional models.

China has risen to meet the challenge. The government recently commissioned a host of new cross-country trains designed for the needs of senior citizens, with cushy berths, handrails, ready supplies of oxygen, and help staff on call. Part of the funding is allocated toward integrating the trains into local tourism services.

Some Chinese B&Bs target the senior population, featuring slow-paced travel plans and in-house physiotherapy. Hotels are introducing quiet floors and safety measures for those with decreased mobility.

“Senior citizens prefer to use offline travel agents with whom they can communicate face to face,” Wang Yonggang, a professor of tourism, told Sixth Tone, an English-language online publication. “Travel agency chains with branches in residential areas are a great channel for older generations to access information.”

Shanghai even boasts the University for the Senior, whose offerings include tourism courses. Speaking to Sixth Tone, 64-year-old tourism student Ying Limin said, "As long as I am able to walk, I hope to seize the opportunity to explore as many foreign countries as I can before it’s too late."

What about the West?

Li Dongju does not fall into the marketing profile of the silver tourist. She uses the internet to find cycling companions, makes copious use of Google Translate, and is as self-reliant a traveler as one could hope for.

Perhaps it's no surprise, then, that her story has caught on in American news sources. After all, the budding support system for mobility-impaired senior tourists in China is alien to American infrastructure.

I recently found myself on an Amtrak train from Charlottesville, Virginia to Huntington, West Virginia. By car, it's a drive of about four hours, or five hours if you drive like I do. On Amtrak, it took 10 hours. Two of those hours were spent on an incomprehensible stop in the middle of the Monongahela National Forest. We were already traveling at a speed any "gung-ho grandma" cyclist could beat when we slowly dwindled to a halt in a sea of kudzu and maples. No loudspeaker announcement elucidated the situation.

The internet had been down the whole trip, despite Amtrak's promises to the contrary, and the AC was paltry. This deep in the National Radio Quiet Zone, there was no cell service. I sat curled in my tiny seat with only a copy of Annapurna for companionship, feeling rather that Maurice Herzog had gotten off easy. At least he never had to experience the American train system.

For me, this baffling delay was an irritation. But for many senior travelers, Amtrak's tendency to fail on its already meager promises represents a serious barrier to travel. It's no wonder that cruises dominate American silver tourism. If you don't want to drive, it's easier to cross the ocean than to travel from one state to another.

In Europe, meanwhile, EU-funded companies such as Euromontana offer training courses in silver tourism. "The training is especially important for frontline service employees. They currently don't have the knowledge and experience needed to interact with people living with certain health conditions," tourism and health professor Jun Wen told Phys.org.

Still, silver tourism in Europe lags behind its Asian counterparts. "Asian consumers in the 'silver' age group are well-integrated into active social lives due to a culture that values longevity," a recent article in the journal Population and Economics noted.

That, I think, is why Li Dongju inspires Western audiences as much as she does Chinese ones. Her success isn't contingent on infrastructure only available in Asian markets. Anyone with the money for a mountain bike and decent physical fitness can aspire to become like her. Li offers a positive vision of aging in a Western culture that valorizes youth.

Before it shut down in 2022, a telescope in Chile captured one final gift for the world that has just been released: the universe's baby photos, just 380,000 years after the Big Bang.

These freckled photos of the early universe, at an instant known as the Cosmic Microwave Background (CMB), are the farthest back in time we can look. Observing the Big Bang or immediately after is not possible, and not just because of technical limitations.

Before the epoch shown in these images, the universe was so dense with plasma that light couldn't travel for more than a fraction of a millimeter without scattering off a proton or an electron. Everything just looked like a dense fog. Then the universe cooled enough to allow those charged particles to fuse into hydrogen and helium. Space opened up and became visible. The last photons from those first visible moments were preserved.

The photons set off through space. All of them were stretched by the expansion of space around them. Some became further stretched out by gravitational wells around galaxy clusters. Others received an energy boost. The patterns of the evolving universe imprinted themselves on these ancient photons.

Almost 14 billion years after their liberation, some of them hit the smooth white surface of a radio telescope located in the Atacama Desert of northern Chile.

Last observations

The Atacama Cosmology Telescope (ACT) is now closed for business. After 15 years of productive data releases, it saw its final light in 2022. However, the ACT team only recently released the polished versions of the telescope's last observations.

These images not only show the most precise, high-resolution observations of the Cosmic Microwave Background but they also cover more of the sky than ever before. The red and blue speckles represent regions of over- and under-densities -- places where, 14 billion years ago, the universe had just a little more or less plasma.

The new images confirm previous observations that the structure in the early universe maps onto its modern structure. Where there were slightly more photons in the primordial plasma now sit the most massive galaxy clusters. Fewer, and there's empty space.

So far, general relativity holds up

Einstein's theory of general relativity, which predicts how matter and light interact with one another at large scales, is one of the best substantiated theories in modern physics. It also causes problems.

There appear to be four fundamental forces in nature: gravity, electromagnetism, weak, and strong. One set of physical laws known as the Standard model cohesively describes electromagnetism, the strong force, and the weak force. Gravity, though, has proven hard to mesh with the others.

Discovering that general relativity isn't quite accurate is the grand hope of those searching for one theory of physics that unites all four forces. Perhaps then, a new model of gravity will appear out of the cracks, one that slots nicely into the Standard model.

But general relativity has triumphed repeatedly so far, and the latest images from the ACT are no exception.

"The amount by which light bends around dark matter structures is just as predicted by Einstein’s theory of gravity," cosmologist Mathew Madhavacheril told Penn Today.

How polarized light fits in the early universe

Perhaps the most important part of these new observations is the detailed polarimetry. Polarimetry describes the measurement not just of how much light there is, or how much energy that light has, but in what direction the light is vibrating. Natural light is unpolarized, meaning that light waves traveling toward us may vibrate in any direction perpendicular to the line of travel.

It's easy to change that by sticking a thin grating in front of the light, only allowing one vibrational direction through. That's how polarized sunglasses work.

The polarization signal in the CMB sits at barely detectable thresholds. But ACT's new observations push past that threshold, and unlike the handful of other telescopes in the polarization game, they cover most of the sky.

Polarization goes beyond the effects of gravity from massive structures like galaxies. Microscopic quantum density fluctuations can alter the polarization of light.

Einstein's formulation of general relativity does not describe the quantum world. In fact, Einstein was uncomfortable with quantum mechanics and encouraged its proponents to better address its many peculiarities. While this leaves room for future physicists to etch their name in history, it would be a lot simpler if Einstein had just figured out everything for us.

He didn't. General relativity on the quantum (read: atomic) scale continues to confound us, not least because testing it in the lab is fiendishly difficult.

Fortunately, the new ACT data release is precise enough to contain clues about quantum gravity in its polarimetry. We just have to decode them.

The camera pans up a minimalist landscape of snow and stone. Jagged spires stab into the air, their dramatic profiles accentuated by the sharp drone of a male voice singing wordlessly. It might be the beginning of Meru -- until the throat singing cuts out, and the narrator says, "My bad, little something in my throat."

The Crystal Towers: a Yukon Climbing Story is one of three projects funded by the Yukon government for its 125th anniversary. This elegant short documentary is part climbing film, part lighthearted travelogue, and part advertisement for the sparse beauty of Yukon.

Radelet Peak

One hundred and twenty kilometers south of Whitehorse, Radelet Peak lurks above a small lake, still mostly frozen in July when the documentary was filmed. Only one of the team, self-professed flamingo fan Zach Clanton, had made the trip before. Clanton conceived of a new route up the knife-edge arete on the mountain's east side.

But bolting a new route would take hardware, and getting hardware to Radelet Peak would take a helicopter. Where might a "quintessential climbing dirtbag," in the words of his climbing partner Rob Cohen, acquire many thousands of dollars for such a flight?

The government, as it turned out. With support from the Yukon125 fund, four climbers set out with a drone, a carton of Metamucil, and (almost) enough gear to bolt a new route.

The route

The Crystal Towers starts gently as its protagonists tackle the ridge à cheval. The slope isn't steep, but we are frequently informed that it's wickedly sharp, and they would rather it weren't so sharp, thank you very much.

Then the first headwall flaunts up above them, and the documentary comes into its own. Climber and filming lead John Serjeantson effectively uses his drone for striking panoramas. One features Dave Benton nestled in a massive maw of rock just under the subsidiary peak.

Most of the route is crack climbing. Both finger cracks and hand cracks snake up seemingly impassible granite walls. Unfortunately, most of this climbing didn't make it to camera.

It's in close quarters that The Crystal Towers struggles: only a few short sections of GoPro footage supplement the wide shots, and the team largely did not record leads from below.

The lack of footage confuses the narrative. One climber taps out of summit day, referencing difficulties on the route never shown onscreen or explained to the audience.

But while it's clear that these are more climbers than documentarians, that doesn't stop them from creating a lovely film. The shots are clean, showcasing the splendor of the landscape, and the narration brings the audience along on the most exciting pitches. It's always a good sign when a video leaves you wanting more instead of less.

The film meets its goals

As for whether the team sends the route, you'll have to watch and see. But the bolting they carried out will allow a new generation of climbers to explore this region. Said Zach Clanton, "Our goal was to create somewhere that people can walk in with just a rack and a rope and have a super good time, and explore a part of the Yukon they never knew existed."

And as a promo for the beauty of Yukon, well, halfway through, I was already googling plane tickets.

It came from the Oort Cloud, a giant web of floating miniature planets lying just beyond the edges of the solar system. It dazzled the skies above Chile for a handful of weeks. Now it's gone for the next 600,000 years.

The Oort Cloud

The Oort Cloud, technically, isn't a confirmed place. It's a theoretical location. Some comets orbit the Sun over hundreds of thousands or even millions of years. They must, therefore, call somewhere home. That place is the Oort Cloud, a massive reservoir of icy comets lying outside the boundary of the solar wind, too far for telescopes to see.

Many famous comets return within a generation. Halley's Comet, for instance, will visit again in 2061. But when comets head in from the Oort Cloud, they won't be back anytime soon.

Early observations of the comet

Way back in April of 2024, observers at a small telescope in Chile reported a very faint speck hurtling toward the Sun. It was a comet, the icy siblings of asteroids, and it was 655 million kilometers away but approaching rapidly.

It took the name of the observatory that discovered it -- ATLAS. And as 2024 turned to 2025, amateur astronomers started reporting that ATLAS was visible with the naked eye at night. Instead of a little dot barely visible with a telescope, it was now as bright as Polaris, the North Star.

This sudden increase in brightness was caused by the disintegration of the comet's surface. As the comet sped towards the Sun, the temperature increase evaporated large chunks of ice from its surface, feeding its outgassing tail and the hazy glow around its nucleus. But in early January of 2025, it hadn't yet reached its full glory.

The Great Comet of 2025

On January 13, ATLAS entered an exclusive club: the list of comets within the last century that were visible to the naked eye during the day. At the time, it was passing through perihelion, the closest approach to the Sun. It was brighter than anything else in the southern sky, including the planets.

Astrophotographers snapped stunning photos of its tails, one comprised of heavy particles and the other of light gases. An astronaut on the ISS snapped a photo of it through the space station windows. And NASA used a telescope device called a coronagraph to block out the Sun's light, allowing sensitive cameras to observe the comet without being blinded.

Goodbye, ATLAS

ATLAS is heading away from us, but not unscathed. On January 19, the bright little speck of its nucleus vanished, suggesting that the comet fragmented after its passage around the Sun. What's left is a ghost: tails still streaming across the sky in the wake of debris that soon may disintegrate entirely. We'll have to wait half a million years to see if any part of it survived its vacation to the center of the solar system.

Last week, the world was obsessed with an asteroid that had a 3% probability of hitting us in 2032. Now NASA says it doesn't have a chance in 50,000. What happened?

How are impact probabilities calculated?

I wrote last year about how potentially hazardous asteroids are detected. One aspect I neglected is what that "impact probability" actually means. In the wake of the news about 2024 YR4 and its rapid upgrading and downgrading of threat, I've gotten a lot of questions about how reliable our asteroid observations actually are.

The answer: very. When asteroid hunters first detect that little moving dot against a stationary sky, they have only a handful of data points. Uncertainty will mar any measurements they make of the asteroid's position and velocity.

It's that uncertainty that defines impact probability. Astronomers calculate the trajectory of the observed asteroid, allowing room for error. If that trajectory passes anywhere near the Earth, then as long as the error bars are substantial, the impact probability is as well.

Why did the impact probability go up first?

Once asteroid hunters spot a potentially hazardous asteroid, telescopes around the world jump to observe it, reducing the uncertainty about its trajectory.

But if the asteroid is still heading anywhere near the Earth, the smaller error bars increase the probability of an impact. That's what brought YR4 into the public eye.

This is a pattern with asteroid impact probabilities. An asteroid starts with a moderate possibility of impact. Astronomers jump to observe it, decreasing the uncertainty but not yet ruling out a collision with the Earth. The impact probability jumps up.

Then the error bars on the orbit shrink even further, and suddenly they no longer encompass the Earth. The impact probability drops to pretty much zero.

Asteroid 2024 YR4 hasn't suddenly started behaving less chaotically. We just understand it better, and know exactly where it's going to go. And that's not the Earth.

In northwestern New Mexico lie the architectural remnants of the Chaco Culture. Starting in the 9th century AD, these ancestors of the Pueblo built multi-storied houses, long-distance trade networks, and broad roads carved straight into limestone.

When the U.S. government first started mapping the ruins in the 1980s, they assumed the Chaco roads were merely for transport. Today, archaeologists disagree. The recent discovery of a six-kilometer-long Chaco road that aligns, Stonehenge-like, with the winter solstice highlights how far our understanding of these roads has come.

Astronomical symbolism

The most famous site in the Chaco Culture is Chaco Canyon. This metropolitan sprawl features massive stone mansions known as Great Houses, more modest dwellings, temples, and burial grounds. The Chaco elites nibbled chocolate from Mesoamerica and kept macaws as pets. When they died, they were buried beside their ancestors in multi-generational crypts, evidence of some of the earliest known class divisions in America.

Chaco Canyon also records celestial symbolism. Astronomers often cite a strange painting of a fiery star as a record of the supernova of 1054 -- an interpretation many archaeologists and modern-day Pueblo dispute. Many buildings aligned with the cycles of the Sun and Moon. And one of the most famous sites, known as the Sun Dagger, manipulates the light of the summer solstice to illuminate an elaborate carving.

Broad roads

Elaborate three-meter-wide roads extend out from most major Chaco settlements. Early surveyors for the U.S. Bureau of Land Management assumed these roads served the same purpose that modern American roads do: to move people and goods from one settlement to another. But while most of the roads start at a settlement, many end seemingly in the middle of the desert.

In recent years, archaeologists have started investigating the road networks with a more open mind. The field also became a more hospitable place for Pueblo and Diné scholars. They contributed to our present understanding that many Chaco roads led to herraduras, horseshoe-shaped buildings thought to be roadside shrines. But are the shrines there because of the roads or are the roads there because of the shrines?

We certainly don't know everything about Chacoan architecture, but a paper published last month in Antiquity gave us another clue. Archaeologists used LiDAR to map a small, oft-forgotten ruin 70km from Chaco Canyon called the Gasco site. The Gasco site had the largest herradura of all, and archaeologists had also previously identified about 75 meters of road.

The new LiDAR mapping showed that the road was actually six kilometers long. And it wasn't one road but two, running parallel beside each other.

Sunrise over Mount Taylor

Both roads point straight at Mount Taylor, also known as Tsoodził in Navajo. The gentle slopes of this volcano rise to the east of the Gasco site. Uranium mining in the 20th century has left them riddled with rusting fences and radioactive debris. In 2009, though, an alliance of five tribes succeeded in protecting Mount Taylor from further mining due to its importance in local belief.

When the authors of the new paper saw the roads led to Mount Taylor, they carefully noted its orientation relative to the sky. They found that it aligns with the path of the Sun through the sky during the winter solstice.

On a hunch, they returned to the site during the 2022 winter solstice. As expected, the Sun breached the horizon right above Mount Taylor, casting the landscape in gold against the deep blue sky.

Roads, the solstice, and water

"One of the really exciting things about the work we've been doing with Chacoan roads is that they're forcing us to reconceptualize what a road might be, what a road might mean," lead author Robert Weiner told Live Science.

In fact, the roads don't just point at Mount Taylor. They start and end at water sources: a spring and the head of a canyon river. River pebbles have been found at the Gasco herradura, too, linking the roads to their shrine.

Archaeologists need more time to understand the exact relationship between these roads, the herradura, and the local villages around the Gasco site. That's something it's not clear they're going to get. Local tribal nations are at war with the federal government over drilling projects that could disrupt both the environment and the history of northwestern Mexico.

One thing is for certain: The 1980s interpretation of those roads as merely utilitarian was wrong. And it wasn't just the Chaco Culture that placed a deeper meaning in the construction of elaborate, elegant roads in the American Southwest. What's the deal with Route 66, anyway?

Archaeologists exploring a neglected corner of the Valley of Kings in Egypt have identified the tomb of an Egyptian pharaoh of the New Kingdom. This marks the first such tomb found since 1922 when the discovery of 19-year-old pharaoh Tutankhamun's burial chambers enraptured the world.

The inhabitant of this tomb has a lower profile. Pharaoh Thutmose II ruled for only five years until his death at age 30, when he fell victim to a disease that left him scarred and shriveled. His half-sister and widow, Hatshepsut, assumed the throne as his regent. As Egypt's second-known female pharaoh and an influential stateswoman, her legacy far outshone his.

Now Thutmose II is back in the spotlight.

A hidden tomb

In 2022, a joint Egyptian-British expedition found traces of a staircase leading into the stony depths below a monumental cliff. After months of excavation, they cleared the passageway of rocky debris and emerged into a stark, empty tomb.

There was no sarcophagus or any of the offerings traditional to Egyptian burial sites. Instead, huge limestone chunks clogged the hallways, just like the staircase. But above it all, the ceiling shone with painted stars, and the walls showed scenes from the book of Amduat, reserved for the burials of kings. This had been the tomb of a pharaoh.

So where was he?

Fragments of the old tomb

Scattered among the limestone debris, a few broken fragments of alabaster memorialized the name of the tomb's inhabitant: Thutmose II. Others bore the name of his widow, Hatshepsut.

The debris everywhere didn't align with grave robbers, the common reason for empty tombs. This looked like an orderly evacuation following some sort of disaster. The team concluded waterfalls had pummeled the base of the cliff and flooded the tomb, probably only five or six years after the burial.

But whoever had moved Thutmose II's remains hadn't done so immaculately.

"And thank goodness they did actually break one or two things," commented Dr. Piers Litherland, the lead archaeologist on the team, "because that’s how we found out whose tomb it was.”

Where was Thutmose II moved?

Egyptologists have known where Thutmose II's body was since 1881. Entombed alongside other royals in the Royal Cache at Deir el-Bahri, Thutmose II had been moved to this communal crypt about 500 years after his death, along with those whose own tombs had also disintegrated.

The French Egyptologist who unwrapped Thutmose II's mummy wrote, "He resembles [Thutmose I, his father], but his features are not so marked and are characterized by greater gentleness. He had scarcely reached the age of thirty when he fell victim to a disease of which the process of embalming could not remove the traces."

But if a flood destroyed his tomb a handful of years after his death, a second tomb would have had to house his remains and burial gifts for the intervening 500 years before his body wound up in that communal site. If archaeologists can find it, the artifacts within might cast more light on Thutmose II's brief and poorly documented reign.

Hatshepsut, his more famous widow, also stands to benefit should Thutmose II's second tomb be located. Her successor, Thutmose III -- son of Thutmose II by a minor consort -- set to erasing every record of her reign following her death. His motivation was likely revenge over her long reign, which prevented him from taking the throne.

Thutmose II's burial artifacts may contain information on both his reign and the early life of one of Egypt's most iconic but mysterious pharaohs.

Around 13.7 billion years ago, something collapsed. It fell outward into the nothingness that stretched in every direction, leaving something behind. A dense plasma, made of fundamental particles called quarks and gluons. For one tiny moment, the plasma collapsed outward unimaginably fast. Then, reigned in by the quarks coalescing into matter, the collapse began to coast.

The universe cooled. Small clumps of matter, set by random chance in the first moments of its existence, attracted more matter through gravity. They became gas clouds, and then galaxies. Galaxies formed galaxy clusters. And empty space continued to expand.

This was the Big Bang, and it set off the expansion of the universe. Today, we'll look at the strange forces that drive the acceleration of its expansion, as well as one of the most tantalizing open questions in modern astronomy: Exactly how fast is it expanding today? And why can't we figure that out?

The expanding universe

In 1929, an astronomer named Edwin Hubble found that every single galaxy outside of the Local Group -- our neighbors -- was speeding away from us. Galaxies like Andromeda, our nearest large neighbor, had stars that looked more or less the same color as the ones in the Milky Way. But beyond that, every galaxy looked red.

This, Hubble reasoned, was because of the Doppler effect. When a fire truck is driving away, its siren sounds like a decrescendo because the outgoing velocity stretches out the sound waves. The chances of every galaxy outside our local sphere of the universe being naturally red were small. Hubble concluded the simplest explanation was that every galaxy was moving away from us.

At first glance, this implies there is something special about the Earth. But one of the principles of cosmology, the study of the birth, death, and overall structure of the universe, is that there are no special locations. Any galaxy perceives all distant galaxies as moving away. This is because the space in between galaxies is expanding with every passing second.

In 1998, a team of cosmologists observed the recession velocities of distant galaxies and noticed something strange. At very high distances, galaxies were even further away than they should have been if the velocity was constant. That meant the universe hadn't expanded at a constant rate.

Instead, it's accelerating over time.

Introducing dark energy

According to Newton's first law, objects in motion will stay in motion unless acted on by an outside force. Once galaxies were moving apart from one another due to the Big Bang, therefore, it made sense for them to continue on their trajectories. But for the universe to be accelerating meant that a force was driving that acceleration.

Astronomers dubbed this new factor dark energy, because they didn't know what it was. It's still perplexing, but in the decades since, dark energy has become accepted as part of the universe's source code. Mass attracts mass, like-magnets repel one another, and empty space naturally expands.

Dark energy says: you can't have a true vacuum. Seemingly empty space actually has natural energy, and it wants to get out. It expands -- and if it's already expanding, that expansion accelerates.

The Hubble Tension

So if the expansion velocity of the universe isn't always the same, what is its present value?

For modern cosmologists, the answer to that question is a Holy Grail. It's not that we have no idea. We have too many ideas. Over and over again, the same two values keep cropping up: 67 km/s and 73 km/s.

In the past, astronomers like Edwin Hubble didn't realize the expansion was accelerating because their observations didn't reach far enough, and when they did, they weren't very precise. But over the last two decades, astronomers have developed very sophisticated techniques for measuring the expansion of the universe. About half of those techniques give a modern expansion velocity of 67 km/s, and the other half give 73 km/s.

At first, cosmologists assumed the values differed because the measurements weren't precise enough. The error bars covered the whole range of values between the two limits, so there was nothing to worry about.

Then the measurements got better and better, the error bars shrank, and still the two values stayed separate. Why?

Cosmic Microwave Background

The further away we look, the further back in time we look. That's because light takes time to travel toward us, so the light from very distant parts of the universe reaches us billions of years after it was emitted. As we look back, we see modern galaxies, then middle-aged ones, and then the strange clumpy squiggles of very ancient galaxies. Then we see the wall.

It's not a physical wall. Instead, it's the image of a time when everything in the universe was on fire. It's called the Cosmic Microwave Background, or CMB. It formed when protons and electrons merged into atoms, suddenly releasing the photons from ricocheting around the primordial plasma. Those photons have been traveling ever since, and are reaching us every day. Part of the static on any radio station or television screen comes from the earliest observable light in the universe.

The CMB isn't perfectly identical in every direction. It has clumps and divots, and those ancient clumps and divots laid the blueprint for the distribution of galaxies in the modern universe.

Cosmologists plug the attributes of those clumps into a general relativity model of the universe starting at the Big Bang. When the clock reaches the present day, the universe is expanding at about 67 km/s.

Wobbling Cepheids

So far, general relativity has withstood every test that's come its way. Why is it, then, that its predictions for the current expansion velocity from the CMB don't match our observations from galaxies?

Figuring out the current velocity from galaxies requires knowing how far away those galaxies actually are. Astronomers use something called the cosmic distance ladder to connect observations within our own galaxy to observations in other galaxies.

First, they observe nearby stars called Cepheids. Cepheids don't have a constant brightness. Instead, they get periodically dimmer before brightening again. The brighter a Cepheid is, the faster its light fluctuates. By observing how fast they fluctuate, astronomers can calculate how bright a Cepheid in another galaxy really is, instead of just how bright it looks when viewed from far away. That gives the distance to the galaxy.

Every so often, two orbiting white dwarfs in these galaxies collide, leading to a massive explosion called a Type 1a supernova (supernova astronomers are infamous for their opaque naming conventions).

Using the known distance of the galaxies, astronomers figured out that the peak brightness of these supernovae controls how fast the light fades. So if a Type 1a supernova goes off in a distant galaxy, we know from the light decay speed how bright it should appear. Once again, we can extrapolate the distance of the galaxy based off how bright its most exotic stars actually appear.

Finally, the Doppler effect allows us to calculate recession velocity of those galaxies. It's always about 73 km/s.

What causes the Hubble Tension?

The discrepancy between these two measurements is called the Hubble Tension, and it doesn't seem to be going away. Other methods of calculating distance from galaxies -- microwave lasers and neutron star mergers, for instance -- give the same result as the supernovae of 73 km/s. Meanwhile, no matter what methods are used to calculate the expansion velocity from the CMB, they all give 67 km/s. A handful of measurements fall somewhere in between, but the vast majority pick a side and stick to it even as their error bars shrink.

It's not clear what's going on. The universe can't be expanding at both 67 km/s and 73 km/s at the same time, so we're going wrong somewhere. Is there some recurring error in how astronomers are calculating distance of galaxies? Are the CMB measurements not as accurate as we think?

Why don't observations in the recent, galaxy-inhabited universe give us the same answers as observations from the very beginnings of the universe. And which of the answers is correct?

Anyone who can answer that question is practically guaranteed a Nobel Prize. But right now, cosmologists have no idea.

The dominant theory is that dark energy was stronger in the early universe in a way the models don't take into account. That would mean that no matter how precise our CMB measurements are, our models aren't correctly extrapolating that information to the present day. But if that were the case, why would dark energy change over time? Isn't it supposed to be a constant of the universe?

There are other, more outlandish theories involving strange "dark" photons that have pushed the modern universe into an increased expansion velocity. But the most disconcerting prospect is not the existence of yet another strange physical substance with "dark" in its name: it's the idea that our model of gravity itself is somehow fundamentally flawed. If so, the story of the universe will have to be rewritten.

Paleontologists have found the first complete skull of a controversial prehistoric bird. Known as Vegavis iaai, the bird thrived in late-Cretaceous Antarctica, then a tropical paradise. About a million years before the asteroid that wiped out 75% of life on Earth, it went extinct.

Its fossilized skull, first discovered in 2011, has finally been analyzed. It fills in gaps in ornithologists' understanding of Vegavis iaai -- and highlights the striking ecological diversity of early birds.

A controversial bird

The fossil's discoverers said it was a waterfowl, a broad order encompassing everything from geese to loons. That's where the controversy began.

Most of the time, when fossils are controversial among paleontologists, it's due to questions about their authenticity. One of the most controversial fossils in history was the Piltdown Man. In 1912, an amateur archaeologist combined an orangutan mandible with the skull of a human and claimed he had found it in prehistoric English gravel beds. And in an example of a genuine mistake rather than fraud, the infamous tooth of the Nebraska man turned out not to be from a prehistoric North American ape as originally proposed, but from a peccary.

But ornithologists never doubted that Vegavis iaai was some sort of dinosaur. Instead, they couldn't decide what kind of dinosaur it was. Dinosaurs included birds, but not all birds were dinosaurs. Was this the ancestor of a duck? A chicken? Or was it a completely different kind of dinosaur that just happened to look like a modern bird?

The lifestyle of Vegavis iaai

Although its exact identity was puzzling, the fossil of Vegavis iaai provided important clues about its lifestyle. It had flat feet to propel it underwater. A fast metabolism allowed it to thrive at high latitudes but kept it hungry for food. And it could sing.

In fact, Vegavis iaai wasn't just an early singing creature. As far as we know, it was the earliest. Most dinosaurs couldn't sing, and although avian dinosaurs -- birds -- lived prior to Vegavis iaai, they lived in silence.

But did Vegavis iaai evolve into a modern species, or was it peculiar to the late Cretaceous? To answer that question, paleontologists needed the missing link -- a skull.

Shedding light on prehistoric Antarctica

A paper published in Nature last week reports, for the first time, the 2011 discovery of a complete Vegavis iaai skull. Over the course of 14 years, the authors carefully analyzed the skull, including the use of X-ray microscopy to create a 3D model.

Its features don't slot neatly into any modern bird family. Vegavis iaai had the flat feet of ducks but a sharp, narrow beak like a loon. Thick muscles supported its jaw against water pressure, allowing it to bite underwater. Its skull, though, lacked the bony spurs at the base of the beak common to most modern birds.

It was a waterfowl, but it wasn't anything as familiar as a duck or a goose. In fact, the authors show that the closest relative to Vegavis iaai was another prehistoric Antarctic bird, Conflicto antarcticus. The kicker: unlike Vegavis iaai, Conflicto antarcticus dates from after the Chicxulub meteor killed all non-bird dinosaurs.

We know that birds survived the impact event because they existed before and, evidently, they exist today. But the new findings on Vegavis iaai make it the one lineage we can tentatively trace from immediately before the impact to immediately after.

Albert Einstein predicted in 1912 that massive objects should bend light as it passes through their gravitational field. He published his theory of general relativity four years later, and the curvature of light seemed a minor point at the time.

When Russian physicist Orest Khvolson posited that in rare cases, the bending of light would create a halo effect, Einstein acknowledged this but wrote, "Of course, there is no hope of observing this phenomenon directly."

Einstein, for once, was wrong. This week, a team from the European Space Agency's dark energy survey telescope Euclid published a high-resolution photo of a halo effect called an Einstein ring. And unlike previously observed Einstein rings, this one is from a nearby galaxy.

Einstein rings show distant galaxies

While the math of Einstein's theory of general relativity may be complex, the core principle is not. Gravity, Einstein argues, is best described as the warping of space around massive objects. There's a common analogy demonstrated in science museums, where guests can roll a penny (or other undesired coinage) down the sides of a funnel and watch as it orbits inexorably downwards. Planets perform the same dance in space distorted by the Sun's gravity.

In this framework, light bending around massive objects is a logical outcome. The space around those objects warps like a funnel, and light curves in an arc around the center.

This effect is called gravitational lensing. Einstein rings appear when the lensed image lies right behind the object that's doing the lensing. Because nothing on Earth or even in the Milky Way is massive enough, all the Einstein rings we observe are formed when the light from distant galaxies contorts around more nearby galaxies.

A uniquely nearby Einstein ring

The Einstein ring imaged by Euclid is one of the closest to home ever found. The lensing galaxy is only 590 million light-years away, or just over 200 times as distant as the Milky Way's nearest galactic neighbor Andromeda. In fact, astronomers have known of this galaxy's existence since 1884, before they even knew that galaxies lay outside the Milky Way. Meanwhile, the galaxy that's being lensed is a lot further -- a whopping 4.42 billion light-years away.

The clues hidden in Einstein rings

Previously, Einstein rings have given cosmologists -- astronomers who study the evolution of the universe -- key information on early galaxies. Our telescopes have a long way to go before they can detect the earliest galaxies whose light is reaching us. But when that light passes through a gravitational lens, more of it focuses on us. If we're an ant on the sidewalk, then the lensing galaxy is a kid with a magnifying glass.

That means that our only direct observations of very early galaxies come from lenses like Einstein rings. Cosmologists use them to understand what kind of stars existed in the early universe.

But Einstein rings also provide a lot of information about the galaxy doing the lensing. How massive are they? How is that mass distributed? And how much of it comes from dark matter versus ordinary stars and gas?

In this case, the Euclid team found that the lensing galaxy has more massive stars at its center than the Milky Way does. Massive stars are the rarest, numbering 1 for every 25,000 Sun-like stars. Astronomers still don't understand all the factors that lead galaxies to form certain types of stars. This Einstein ring adds another piece to the puzzle.

We know more about the universe than many people think.

Space mysteries are usually quite mundane to all but obsessive researchers. The most compelling open question in astrochemistry, for instance, is how often molecules are recycled during star formation before depositing onto the surface of planets. It's a key gap in our understanding of outer space environments, but it's not going to intrigue any first dates.

But there are a few tantalizing questions that are so big we can't even tackle them head-on. Questions that most astronomers hope against hope will be answered in our lifetime -- but deep down don't believe ever will be.

In this new series, we'll cover some open questions in astronomy, starting relatively small and working our way up. This week: the mysterious, sometimes-repeating extragalactic signals known as Fast Radio Bursts.

An accidental discovery

In 2007, a grad student at West Virginia University -- arguably the center of American radio astronomy -- found a strange whooping signal in old telescope observations. It started at high radio frequencies and, over the course of half a second, swept down to low. Then it disappeared.

The high-to-low-frequency aspect wasn't a mystery. That sweeping pattern appears all over radio astronomy because the free electrons floating around interstellar space slow down low-frequency light more than high-frequency light. Since it gets delayed more, it shows up at the telescope a moment after the high-frequency parts of the signal.

We see this all the time in radio signals from within the Milky Way. We know about how many free electrons there are floating around in our galaxy and how much they delay different frequencies of light. Therefore, the degree of delay from electrons is often used as a rough measure of the distance of an object.

The signal that grad student Ash Narkevic had just found was so delayed that it could only have come from another galaxy.

The Lorimer Burst

Narkevic's advisor was an up-and-coming professor of transient radio astronomy named Duncan Lorimer. He and Narkevic wrote a paper about their discovery, submitted it to the prestigious journal Science, and were soundly rejected.

They resubmitted. This time, their paper was accepted. The world of radio astronomy collectively lost its mind and began pouring over archival data, searching for similar bursts.

They found nothing. In fact, they found worse than nothing. In 2011, after four years of radio silence, a graduate student at WVU named Sarah Burke-Spolaor found a signal that looked uncannily like Lorimer's burst. She called it a peryton. The trouble was, it was so bright that it could only have been produced on Earth. Had the Lorimer burst, fainter though it was, also been created on Earth?

Furbies

The mystery remained for another two years until a PhD student at the University of Manchester named Dan Thornton turned his eye to a set of data with very precise time information. His search found four more bursts just like Lorimer's. The bursts were real, and at the suggestion of the Manchester team, they earned a name: fast radio bursts, or FRBs.

There was some early discussion on whether this should be pronounced "furbies," but the consensus was that this would make radio astronomers look silly. And FRBs are very serious indeed.

Microwave oven?

With new advances in observing using very precise time-processing software, the FRBs started pouring in. The one found by Ash Narkevic in 2007 hadn't traveled far compared to some of the new FRBs. One of them seemed to have been created 7 billion years ago.

But a specter hung over FRBs. The too-bright peryton signal found by Sarah Burke-Spolaor still lurked in the backs of everyone's mind, taunting them with the question: If these things look so similar, and some of them are definitely terrestrial, are all of them?

Then, in 2015, an experiment at the Murriyang radio telescope in Australia vindicated FRBs. Swinburne University graduate student Emily Petroff, long obsessed by the puzzle of perytons and FRBs, published the solution in probably the funniest non-joke paper ever written in radio astronomy.

The existence of obviously terrestrial perytons "had previously cast a shadow over the interpretation of [FRBs], which otherwise appear to be of extragalactic origin," she wrote. "We have identified strong out-of-band emission at 2.3–2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely, and the telescope is at an appropriate relative angle."

FRBs had nothing to fear: "We furthermore demonstrate that the microwave ovens on site could not have caused [the Lorimer Burst]."

The identity of perytons is a continued point of amusement among radio astronomers, and was even parodied in an xkcd panel.

The clues

For once, xkcd made a science mistake. In the comic strip, they describe the origin of FRBs as "stellar-sized objects." We know this can't be true. The time between the start and the end of many bursts is so short that light could only travel a distance of ten or so kilometers during them. Since light is the fastest thing in the universe, points not connected by light wouldn't know to emit at the same time. The bursts, therefore, are created within roughly the distance from Everest to Makalu.

Stars are a lot bigger than that.

Another clue in the FRB toolbox, discovered in 2015: Some of them repeat. The pulses look different every time, but they're very clearly coming from the same location and the same distance. Many more have only ever been seen once. So unless there is more than one mechanism creating FRBs, they aren't produced by one-off events like supernovae or two stars merging.

The magnetar explanation

And then there's the final clue. In 2020, independent teams at Caltech and at the CHIME telescope in Canada both found what looked like an FRB coming from an exotic object within the Milky Way called a magnetar. It was 30 times fainter than the faintest FRB but offered a tantalizing explanation.

Magnetars (Lead image) are the corpses of stars that can no longer support their own weight. Gravity crushes them until their protons and electrons squeeze together to form neutrons. They have massive magnetic fields and regularly send out brilliant flashes of gamma rays and X-rays -- high-energy photons that often go hand in hand with radio waves. In fact, the Caltech team found that the magnetar released X-rays at the same time as the FRB-lite.

The mystery

So magnetars produce FRBs somewhere on their surface via hijinks in their magnetic fields. Mystery solved.

Except that picture doesn't explain many extragalactic FRBs. Gamma-ray and X-ray bursts from magnetars are very rare, so how could so many FRBs repeat monthly or even weekly? And why do some FRBs come from galaxies where we don't expect to find any magnetars? After all, magnetars are all born early in a galaxy's life span. They only stay magnetized for about 10,000 years. Meanwhile, an FRB reported just this month came from a galaxy that's been around for 11 billion years.

At this point, astronomers know only one thing for sure: FRBs aren't coming from microwave ovens.

Anymore.

Two thousand kilometers from the southern tip of South America sits the island of South Georgia, a Yosemite-sized piece of polar tundra boasting thriving communities of king penguins, elephant seals, and fur seals. Alongside this charismatic fauna, native birds like the South Georgia pintail duck and Antarctica's only songbird, the South Georgia pipit, coexist. And here, in 2021, Belgian nature photographer Yves Adams caught a striking yellow-gold penguin on camera.

Where normal penguins had black feathers, this one had neon yellow. The effect was probably caused by leucism, a genetic mutation that results in depigmentation. Because the penguin was never studied closely, though, it could also have been albino.

Mission yellow penguin

Yves Adams returned to South Georgia this year as an expedition guide, hoping to find his golden penguin once more. It was nowhere to be found.

But his expedition leader tipped him off to something even more extraordinary, Adams told IFLScience. Adams kept his eyes open, and his patience was eventually rewarded. In a flock of its peers stood a jet-black king penguin.

Besides the video above, Adams snapped a set of glamor shots of the penguin: standing solo, frolicking in the snow, and inspecting the ground with neck-elongating intensity.

Adam's black penguin is striking, but beyond that, it's also amazingly rare. In 2019, a National Geographic photographer snapped a shot of another black king penguin, this one with splashes of white on his wing. Partial melanism, when animals are mostly but not entirely black, is more common than complete melanism. Even for the 2019 penguin, an ornithologist made the journalist who contacted him swear an oath that the black penguin was real.

But Adams' new penguin isn't mostly black -- it's entirely black.

#blackoutpenguin

Up close, Adams said, the penguin's belly feathers have a greenish tint. He seemed healthy and fit in with the rest of the flock.

On Instagram, he wrote, "This one is for the penguin addicts!" In case the penguin addicts needed some help from the algorithm, he tagged the photos #gothicpenguin, #formalpenguin, and #blackoutpenguin.

The prize for his best hashtag, though, stays with his original golden penguin: #yellowpenguinlove. Well, just look at it -- it's yellow, and hard not to love.

In 1863, a Russian paleontologist and mining engineer made his way through the Eocene strata of the Caucasus to the shores of the Caspian Sea. His name was Hermann Vil’gel’movich Abikh, and he had heard tell of ghost islands and strange fireballs over the water. As an expert on petroleum and natural gas, this had caught his attention.

Sitting in the rich blue waters off the coast of Azerbaijan was an island the size of a basketball court. By Abikh's measure, it stood 3.6m above the water-- higher than the elevation of Amsterdam. And yet on maps of the shoreline from the previous year, the island -- called Kumani -- sat a full 2.4m lower in the water.

What had happened? And did it have anything to do with the ever-burning flames seen on nearby Dashly Island?

Two centuries later, NASA geologists reviewing satellite footage of the Caspian Sea found themselves asking the same questions.

The same island

Landsat 8 and 9 orbit the Earth at a distance of about 700km. Designed for geological survey work, it's no surprise that their engineers pay careful attention to the seismologically excitable Caspian Sea. And in 2023, that attention was rewarded. Where before only empty water had sat, suddenly a speck of dirt jutted above the water line, trailed by a shallow sand bank.This was the same intermittent island that Abikh had recorded in the 1860s. By 2024, Kumani Island was almost gone again.

The reappearance of Kumani came a year after a massive explosion on nearby Dashly Island. Oil rig workers caught the fireball on camera. It made international news, especially given the strategic location of the Caspian Sea.

At the time, Kumani Island still sat under the water 10km away. But the same geological process driving the explosion at Dashly was ready to make its move at Kumani as well.

Not to be outdone by the Gulf of Mexico, there was a massive explosion in the Caspian Sea pic.twitter.com/JgxMkAmzUW

— philip lewis (@Phil_Lewis_) July 4, 2021

Kumani's short life

Abikh, the geologist who painstakingly charted the islands of the Caspian Sea, also solved the riddle of their existence. He found that irregular outflows of mud sporadically changed the underwater topology. They often erupted explosively above the surface of the water, and so they were called mud volcanoes.

He wasn't the first to describe them, but he was the first to realize that they clustered along fault lines in the tectonic plates below the water. The mud volcanoes and the dramatic flames that sometimes accompanied them sprang from subterranean friction that forced natural gas, mud, and water to the surface. Soft rock, the world's largest inland bodies of water, and plentiful natural gas explain why Azerbaijan is home to over half the world's mud volcanoes.

It's not clear how exactly some of them explode, but with natural gas involved, it's no wonder that the government keeps them under strict surveillance.

Mud volcanoes may exist on other planets

Mud volcanoes result in flashy explosions on Earth, but on Mars, they hint at a possible history of life on the Red Planet. Mounds of mud in the northern lowlands resemble terrestrial mud volcanoes. If that is what they are, then the material near their craters would be drawn from deeper under the ground than normal surface rock.

Given that the Martian surface seems utterly devoid of life, underground is one of the last places left to look for microbes, past or present.

When Yellowstone erupts again, as it certainly will, it won't matter whether people live in Bozeman, Montana or Cody, Wyoming -- they'll be just as dead. But new seismological research has finally nailed down where exactly the eruption will breach the ground. If you want to die by magma instead of ash, the northeast of the park is the place to be.

Hikers need not worry. A team from the United States Geological Survey (USGS), publishing last week in Nature Geoscience also measured the percentage of rock in Yellowstone magma reservoirs that's actually melted. They found that none of it is near levels where an eruption is imminent.

Yellowstone magma close to the surface

When Mount Saint Helens erupted in 1980, most of the upper part of the mountain broke off and slid down the slopes in a massive avalanche. What was left behind was a caldera. This crater-like divot in the rock isn't fed by a narrow vent like typical volcanoes. Instead, a large magma pool sits right below a shallow surface rock layer.

That's what lurks beneath the surface at Yellowstone National Park. But unlike Mount Saint Helens, the Yellowstone caldera doesn't just have one magma reservoir underneath it. It has four.

The Yellowstone caldera has a long history. It erupted at least three times before, mostly recently 70,000 years ago. Previous eruptions have left the northeast relatively untouched, but that will change when the next eruption comes.

To locate magma, the USGS team used a network of stations that measured the conductivity of material deep into the ground. This method, called magnetotellurics, relies on the fact that solid rock is very resistant to electric currents. As soon as rock starts melting, however, electric currents can flow through it. So magma appears on the magnetotellurics measurements as pockets of high subterranean conductivity.

These magma hotspots aren't really underground pools like aquifers but rather a honeycomb mix of solid and melted rock. As long as the melt percentage stays below 40%, the different pockets in the honeycomb can't gather enough pressure to erupt out of the ground. The largest melt fraction found in the new research is only 18%, and that won't increase much within the next few decades.

Where the magma runs deep

Although the USGS identified pockets of melted rhyolite rock under all of Yellowstone, channels of magma connect the northeast rhyolite melt pockets to deeper reservoirs of molten basalt. Magma made of rhyolite produces characteristic volcanic ash, but basalt is the real driver of eruptions because it flows more easily. That means it can circulate heat from deep within the Earth, pushing molten rhyolite to the surface.

Right now, the volume of magma under Yellowstone is larger than in any of the previous eruptions. It's hard to know how much of that will still be there when the caldera finally blows.

President Biden is using his last months in office to bolster his environmental legacy. First came a ban on offshore drilling, then two new national monuments in California, and now a loosening of filming restrictions in national parks.

Until Biden signed the EXPLORE Act on January 4, professional photographers filming in national parks had to apply for permits from the National Parks Service (NPS). The permit applications could cost hundreds of dollars, and rejections were common. Now most photographers won't have to bother submitting anything at all before heading out to the backcountry with their cameras.

Restrictions designed to protect public land instead made it less public

A crew filming a Hollywood blockbuster, an indie documentary maker, and a YouTuber eking out a handful of dollars a month from ad revenue -- until the new law, all of them had to apply for a filming permit in national parks. The previous law applied to all photographers who might profit from their work in the parks. Although it was passed to protect national parks from Hollywood studios, it was just as limiting to small, independent photographers.

Now that law is gone. Any crew under six people can stroll into a national park and record as they please for fun or profit, as long as they follow park rules. It's also now legal to record commercial footage of large events in national parks.

The EXPLORE Act does a lot more than just legalize professional filming, though. It requires the NPS to identify 10 potential new long-distance bike trails and to establish 27 new campsites. It also recommended that the NPS reopen all closed campsites within the next month.

A Grand Teton speed record triggered the new law

The EXPLORE Act stands for the Expanding Public Lands Outdoor Recreation Experiences Act. (Who comes up with these acronyms?) It came into being in response to a lawsuit from two photographers who teamed up with the Foundation for Individual Rights and Expression (FIRE), a free speech protection group.

Alex Rienzie and Connor Burkesmith set out to film Michelino Sunseri take on the Grand Teton speed record of 2 hours 53 min 2 sec, set by NPS ranger Andy Anderson in 2012. The project didn't start auspiciously. Their permit application was rejected on the grounds that filming would make the event too "competitive." The application fee was $325, non-refundable.

Not to be deterred, they filmed Sunseri's run anyway. To keep up with him over 26km of technical terrain, they had to travel light. They brought less equipment to the Grand Teton than most visitors.

Resolves the photographers' lawsuit

Sunseri finished the climb with a record time of 2h 50m 50s. That was where the trouble really started.

For his part, Sunseri faced controversy over the route he took. The records website Fastest Known Time rejected Sunseri's accomplishment because he had shaved half a mile off the route by cutting across a switchback.

As for Rienzie and Burkesmith, they had to handle the fallout from their illegal filming. The NPS released a vague statement that no charges would currently be pressed. If they tried selling the footage, however, they might wind up in legal hot water.

Rienzie and Burkesmith had had enough. On December 18, FIRE submitted a lawsuit against the NPS on their behalf. The filming restrictions, the lawsuit claimed, were a violation of First Amendment rights.

The lawsuit did its job without ever making it to court. It came to the attention of the Senate, which immediately passed the EXPLORE Act. Biden signed it into law this week, officially putting it on the books. But Sunseri's legal problems aren't quite over. He is facing a $5,000 fine or six months of jail time over his deviation from the trail.

The Mars weather report is in, and we're seeing harsh conditions for the first few months of the new year.

For the first time in two Earth years, it's spring on the Red Planet's northern hemisphere, and high-resolution space cameras have caught sight of dramatic landscape shifts all across the disintegrating ice fields. Between avalanches, geysers, and katabatic winds, the Martian spring has been packing all the worst weather events into its small northern ice cap.

Ice avalanches are common in Martian spring

November 12 marked the new year on Mars, counted from trips around the Sun since a dust storm raged across the planet's surface in 1955. Because Mars' orbit is much more elliptical than the Earth's, seasons are more extreme. On top of that, the thin carbon dioxide atmosphere offers little protection from extreme temperature shifts.

While some of the ice coating its north pole is water ice, much of it is carbon dioxide. Even on Earth, carbon dioxide never passes through a liquid state but sublimates directly into gas. Since Mars' weak atmosphere doesn't provide enough pressure to maintain liquid water, that gas doesn't just bubble up through melted ponds, it destabilizes entire glacial structures.

So far, NASA's Mars Reconnaissance Orbiter (MRO) hasn't caught any avalanches mid-fall this year. But in 2015, the MRO snapped a photo of a six-meter cornice in freefall over a scarp. It appears above as our lead image.

Geyers erupt across the Planum Boreum

If sublimated carbon dioxide can't escape through cracks in the ice, it builds up. When the pressure exceeds the weight of the ice, the gas jettisons everything above it and escapes into the atmosphere as a geyser. But the Planum Boreum, or northern polar plain, isn't just covered in ice. The frost is mixed in with sand and dust. That creates dramatic images like this recent one from the MRO, where geysers leave darkened fans across the frosty surface.

Melting ice reshapes the landscape

In Antarctica, glacial retreat driven by global warming has revealed permanent troughs in the ice. The legacy of long-ago ice erosion, these pale in comparison to the troughs spiraling across the northern ice cap of Mars. Every spring, the sublimated carbon dioxide forms winds, which gain speed as they propel their way down the labyrinthine corridors. They also rocket up in temperature, melting the walls of the troughs a little further each year.

On Earth, winds like these mainly occur as cold air flows down icy slopes, such as in Antarctica and Greenland. They're called katabatic winds. On Mars, they have thousands of kilometers of spiral troughs in which to gather power. They blast the sandy surface of the surrounding plains with enough force to shift entire sand dunes. These dunes are especially vulnerable in the spring because their frost layer has melted, as captured by the MRO on camera.

Come autumn, when the carbon dioxide frost starts to settle on the ice fields once more, the new progress of the glacial canyons and dunes will freeze in place. Mars then waits for the next thaw.