Why cracking your knuckles can be so noisy

“Pop” goes the knuckle — but why? Scientists disagree over why cracking your knuckles makes noise. Now, a new mathematical explanation suggests the sound results from the partial collapse of tiny gas bubbles in the joints’ fluid. Most explanations of knuckle noise involve bubbles, which form under the low pressures induced by finger manipulations that […]

Comb jellies have a bizarre nervous system unlike any other animal

Shimmering, gelatinous comb jellies wouldn’t appear to have much to hide. But their mostly see-through bodies cloak a nervous system unlike that of any other known animal, researchers report in the April 21 Science. In the nervous systems of everything from anemones to aardvarks, electrical impulses pass between nerve cells, allowing for signals to move […]

Northern elephant seals sleep just two hours a day at sea

Northern elephant seals are the true masters of the power nap. On long trips out to sea, the seals snooze less than 20 minutes at a time, researchers report in the April 21 Science. The animals average just two hours of shut-eye per day while swimming offshore for months — rivaling African elephants for the […]

Cosmic antimatter hints at origins of huge bubbles in our galaxy’s center

MINNEAPOLIS — Bubbles of radiation billowing from the galactic center may have started as a stream of electrons and their antimatter counterparts, positrons, new observations suggest. An excess of positrons zipping past Earth suggests that the bubbles are the result of a burp from our galaxy’s supermassive black hole after a meal millions of years […]

Urchins are dying off across the Caribbean. Scientists now know why

Since early 2022, sea urchins have been mysteriously dying off across the Caribbean. Now scientists say they have identified the main culprit: a type of relatively large, single-celled marine microorganism called a scuticociliate. The discovery is a little surprising given that “ciliates are not normally seen as agents of mass mortality,” says Ian Hewson, a […]

The classic map of how the human brain manages movement gets an update

The classical view of how the human brain controls voluntary movement might not tell the whole story. That map of the primary motor cortex — the motor homunculus — shows how this brain region is divided into sections assigned to each body part that can be controlled voluntarily (SN: 6/16/15). It puts your toes next […]

A prehistoric method for tailoring clothes may be written in bone

An animal bone fragment full of human-made pits hints at how prehistoric people in Western Europe may have crafted clothing. The nearly 40,000-year-old artifact probably served as a punch board for leatherwork, researchers report April 12 in Science Advances. They suggest that the bone fragment rested beneath animal hide while an artisan pricked holes in […]

Methane may not warm the Earth quite as much as previously thought

Methane is a greenhouse gas with dual personalities. It heats Earth’s atmosphere 28 times as potently as carbon dioxide, gram for gram. But its absorption of the sun’s radiation high in the atmosphere also alters cloud patterns — casting a bit of shadow on its warming effect. So rather than adding even more thermal energy […]

Octopus, squid and cuttlefish arms evolved to ‘taste’ different compounds

People have different tastes. It turns out that octopuses, squid and cuttlefish do too. These soft-bodied cephalopods have proteins on suckers along their tentacles that allow them to “taste” by touching objects. But the species have evolved to detect different compounds, researchers report in two studies published in the April 13 Nature. And the differing […]

Saturn’s icy rings are probably heating its atmosphere, giving it an ultraviolet glow

The rings that make Saturn such a spectacle are probably heating its atmosphere and making it glow at ultraviolet wavelengths. Researchers detected an excess of ultraviolet emission in Saturn’s northern hemisphere that comes from hydrogen atoms. The emission, known as Lyman-alpha radiation, is probably the result of water ice, which contains hydrogen, falling into the […]