Sara Chodosh Archives | Popular Photography

Behold this giant spinning ice disk

Sara Chodosh — Tue, 15 Jan 2019 21:00:25 +0000

Tina Radel - City of Westbrook

The image above might suggest someone dropped a small planet in the middle of the Presumpscot River in Westbrook, Maine, but (shocker) that’s not the case. It’s actually a big disk made of ice that’s slowly rotating in place. It would be reasonable to think the river’s current is propelling that rotation, but research suggests the object may be spinning all on its own. Giant disks like this form not infrequently during the cold winter months, and in 2016 some physicists decided to get to the bottom of the phenomenon. The group created a miniature ice disk and floated it in a tank, where they determined that the rotational force was generated by a vortex that formed beneath the disk. Water, you see, is at its most dense at 4°C (that’s 39.2°F). As the ice of the disk cools down the fluid surrounding it, that water reaches the four-degree mark and sinks. It flows down and horizontally, creating a swirling vortex. And the larger the temperature gradient—meaning the warmer the river water is compared to the frozen disk—the faster the cooling water will sink. That means the disk spins faster, too. it’ll spin because the cooling water will sink faster.

That also means spinning disks like this wouldn’t necessarily happen in any body of water. Some lakes may already be at 39.2°F or colder when water starts freezing, which means the cooled water next to the ice wouldn’t sink at all, and thus there wouldn’t be a vortex to rotate the disk.

The same phenomenon also happens you place an ice disk on a solid surface, such as a plate of aluminum. If the plate is warmer than the ice, it melts and creates a miniature vortex inside the pooled water beneath.

We can all agree that the science behind this photo is the coolest thing about it, but that doesn’t mean we can’t enjoy watching this drone footage of the disk set to almost-over-the-top dramatic music.

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16 stunning photos of scientific phenomena in action

Sara Chodosh — Thu, 19 Dec 2019 20:34:47 +0000

The tentacles on this sea anemone are white because they’ve been bleached. Like coral, anemones can lose their color (along with their health) as oceans heat up. Researchers are still figuring out how that might affect the symbiotic relationship between anemones and clownfish like the young one pictured here. Morgan Bennett-Smith

The Royal Society Publishing Photography Competition champions images that depict scientific phenomena, as captured by scientists themselves. Out of hundreds of entries, judges narrowed it down to a single winner in each of five categories along with a few runner ups. This gallery rounds them all up for a truly stunning experience.

Lunar halos like this one, captured in Mogilev, Belarus, appear only when there’s substantial numbers of ice crystals in the atmosphere. Most often they’re from very thin cirrus clouds hovering at or above 20,000 feet. All those hanging bits of moisture refract light from the moon (or the sun, in a solar halo), making it appear as if there’s a halo around it.
If you live in the Northern Hemisphere, you might not be familiar with the Magellanic Clouds—they’re a set of two dwarf galaxies 150,000 lightyears away that only inhabit the southern skies. This photo shows them alongside the Milky Way over Mount Taranaki, a stratovolcano on New Zealand’s North Island.
This year we had three supermoons in quick succession, but this one aligned with the equinox which made it more special for some folks. Supermoons are only 14 percent bigger than normal, which is too small to really be able to tell with the naked eye—but it sure makes for some beautiful photos. This one comes from Quadra Island in British Columbia, looking out across the Georgia Strait.
These fish might look like they’re belting out opera, but they’re actually fighting with each other. Blue spotted mudskippers are territorial and end up in frequent tiffs with their neighbors. As they emerge from the water they’re making these funny faces, captured perfectly in their home amongst the mangroves in the Mai Po wetlands in Hong Kong.
Like clownfish hiding in anemones, juvenile fish like this blue trevally sometimes hide inside jellyfish tentacles for protection. The jelly gets some extra defense in exchange, and the fish lives to see adulthood.
Food is scarce in the Bulgarian winter, so these Northern Nutcrackers fight over the stashes they’ve stored the previous fall. They have to start breeding before the snow event melts. These two are arguing over one particular cache.
This funnel cloud shows the way most tornadoes start to form, though this particular one never made contact with the ground and therefore wasn’t an actual twister. They’re created when low-pressure areas produce a rotating column of air, and made visible by the moisture in the cloud.
These bubbles come from volcanic seeps on the ocean floor that release carbon dioxide into the warm waters. Researchers are using areas like this to study how sea life might fare as climate change progresses, since they mimic the higher temperatures and acidities we’re going to see in the near future.
When cold air rushes down and collides with rising warm air, you get mammatus clouds. These formed during summer in Jackson, Wyoming and were lit up fiery red by the setting sun.
More than 400 people died in the tsunami resulting from Krakatoa’s eruption in December 2018, but this photo captures it at the very beginning of its eruptive phase in August of that year. One side of the volcano would eventually collapse from all this activity, which is what triggered the tsunami.
The tentacles on this sea anemone are white because they’ve been bleached. Like coral, anemones can lose their color (along with their health) as oceans heat up. Researchers are still figuring out how that might affect the symbiotic relationship between anemones and clownfish like the young one pictured here.
Ropalidia marginata paper wasps have no real protection against their main predator, so instead females like this one have to stand guard and sound the alarm against intruders. That way at least their fellow nestmates can flee in time.
These swirling colors aren’t paint—they’re pigments from microscopic algae and cyanobacteria, which are forming that white film on the water. The organisms are taking advantage of rotting water lily stems in the Ľuboreč water reservoir in Slovenia, a welcome food source.
These droplets of silicon are moving much like quantum particles, making them behave like quantum waves. That might not seem significant, but it’s experimental proof that helps confirm theoretical work on hydrodynamic quantum analogs, which is a jargon-y way of saying it would help us understand more about quantum mechanics.
You’ve probably seen ferrofluids like this before, but that doesn’t make it less beautiful. The colloidal suspensions of minuscule ferromagnetic particles behave wildly under the influence of magnets as they try to compromise between the pulling magnetic force and the pressure to minimize surface area.
You might think this is something microscopic, but it’s actually a piece of surgical thread as seen under a scanning electron microscope. This particular knot was used to stitch a head wound, and the little bits of debris you can see are bits of skin.

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Watch meerkats engage in a fiercely adorable war dance

Sara Chodosh — Wed, 18 Dec 2019 20:41:57 +0000

A fearsome meerkat war dance. Robert Sutcliffe, Kalahari Meerkat Project

If you were a meerkat, this photo would be terrifying. Sure, those itsy bitsy paws are adorable to us. But this is serious business to a meerkat—this is a war dance.

Yes, the real-life Timons in this image are aggressively fending off another group of meerkats by erecting their tails and puffing out their fur, both of which are apparently quite intimidating if you’re a small carnivore. So says a study about intergroup aggression in meerkats published in Royal Society Proceedings B this week. The researchers spent more than a decade observing 422 separate interactions involving 36 meerkat groups living in the Kalahari desert in South Africa.

Though you might think of them as timid and cute, these little guys are actually quite territorial. They leave feces and anal scent markers to mark their burrows, and when one group wins a fight against another, they expand their land boundaries accordingly—like tiny feudal lords.

Two meerkats fighting Dominic Cram, Kalahari Meerkat Project

The researchers found that nearly a third of potential interactions resolved when one group simply avoided the other entirely. But when things did escalated into a feud, the meerkats generally displayed some kind of chasing or dancing behavior as a prelude to the actual violence. The Jets and the Sharks could learn a thing or two: A meerkat war dance is quite effective at deterring a battle. Some 86 percent of all aggressive interactions ended before the fighting ever began. Meerkats didn’t kill one another most of the time, but at least one death occurred in 13 cases, adding up to 22 total fatalities. Most upsetting of all, 20 of those were pups.

Larger groups with more pups were more likely to win these battles, which the researchers think could be for a variety of reasons. Maybe groups with pups have more to gain from expanding their territory, or perhaps they’re more worried about losing those pups if they have to retreat in battle. It may even be that adult meerkats have some instinctive response triggered by the presence of their pups that makes them put more effort into the fight.

Whatever the reason, meerkat wars are serious business… but they’re pretty cute, too.

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