Hidden Stages, Missing Fossils, Misread Stars

Physicists have long treated one feature of turbulence as fixed: energy moves between scales in only one direction, and the number of dimensions decides which. A team at the University of Pittsburgh led by engineer Lei Fang reports that in a two-dimensional flow, a small obstacle set at the right angle can push the energy cascade the other way. "The geometry matters," Fang said.

The rule being rewritten

In 1922 Lewis Fry Richardson, the founder of modern weather forecasting, described how turbulence works in three dimensions. Large eddies hand their kinetic energy to smaller ones, which hand it to smaller ones still, until viscosity takes over and the energy is lost as heat. Starting in the 1940s, Andrey Kolmogorov gave this picture a rigorous mathematical footing.

In the late 1960s, Robert Kraichnan and George Batchelor showed that two-dimensional turbulence runs in reverse. Energy flows from small eddies up into large ones. Jupiter's Great Red Spot is an example: smaller vortices around its edge feed the giant storm at the center. According to the article, physicists spent the following decades without seriously asking whether that direction could change.

Where sea monkeys come in

Fang's lab studies active matter, meaning things that move on their own and put energy into their surroundings, such as bacteria or tiny robots. Around 2021, graduate student Xinyu Si began studying brine shrimp, the "sea monkeys" once sold through comic-book ads. These animals are about 10 millimeters long and swim upside down. The team's hypothesis was that turbulence stirred up by billions of tiny organisms plays an underappreciated role in mixing natural waters. That work led them to the finding about energy direction.

Some old, metal-poor stars in the Milky Way's halo have element ratios that ordinary stellar deaths seemed unable to produce. Astronomers proposed hypernovas, an extra-energetic kind of supernova, as their source. These stars were among the evidence that hypernovas exist. A new study in the September Monthly Notices of the Royal Astronomical Society argues that ordinary supernovas and other fairly common stellar explosions could have done the job.

"The evidence for [hypernovas] is now very seriously challenged," says Ralph Schönrich of University College London, who did the work with UCL colleague Anmol Aggarwal.

How stellar ancestry is read, and where it can go wrong

When a star dies, it releases elements into space. That material mixes with gas that may later form new stars. Different kinds of explosion leave different chemical patterns, so the relative amounts of elements in a star act as a record of what came before it.

Reading that record depends on knowing how the ejected material spreads. Models have often assumed it mixes evenly into the gas that forms the next stars. But observations and simulations show that supernovas eject material asymmetrically. A clump of oxygen might go mostly one way and nickel another. Schönrich says interstellar mixing doesn't smooth these excesses out, especially in the earliest stellar generations, which had few heavy elements to dilute the new material. Two stars forming on opposite sides of the same supernova could therefore have different compositions.

The oldest generally accepted animal fossils are about 574 million years old and date to the Ediacaran period. A study published Oct. 2 in Science Advances argues that the first animals may have lived up to 200 million years before that, between about 800 million and 700 million years ago. The authors are careful about how much they claim. "This analysis does not prove that animals existed 800 million years ago," says first author Orin Lole Durbin.

Absent fossils, present animals

The case starts with an argument about what an empty rock can tell you. The Weng'an Biota in China is about 590 million years old. It preserves microscopic organisms in rare detail but contains no definite animals. Because of that, researchers have sometimes treated it as an upper limit: if animals had existed by then, the reasoning goes, Weng'an would have kept them.

To test that reasoning, Ross Anderson of the University of Oxford and colleagues examined more than 140 samples from the Kheseen Biota in Mongolia, which is over 40 million years younger than Weng'an. Scanning electron microscopy showed microfossils preserved in similarly fine detail, including spherical organisms and embryo-like structures with internal cells. None could be identified as an animal, yet animals were already living elsewhere on Earth when these rocks formed. "The Kheseen Biota breaks the argument," Anderson says. A well-preserved deposit with no animals in it does not show that animals were absent at the time.

Recalibrating the clock

The chytrid fungus Batrachochytrium dendrobatidis, or Bd, spreads mainly through water. A field study of Yosemite toads suggests it may do its worst damage somewhere drier: inside the burrows where young toads spend their first winter. The work was published September 23 in Functional Ecology.

Why this fungus matters

Bd infects amphibian skin and stops electrolytes and fluids from getting into the body. The result is often heart failure. A 2019 estimate tied the fungus to declines in at least 500 species and about 90 possible extinctions. Bd is one reason the Yosemite toad (Anaxyrus canorus) is listed as threatened under the U.S. Endangered Species Act.

These toads live high in California's Sierra Nevada and spend most of their time on dry land. Adults go to shallow pools only to breed. Because the winters are so long at that elevation, the toads spend roughly half of each year in brumation, a hibernation-like state, in burrows under several feet of snow. UCLA ecologist David Daversa wanted to know how a waterborne pathogen survives through all that time underground.

What the team measured

Daversa and colleagues caught Yosemite toads of every age in the park and swabbed their skin to test for Bd. For the youngest toads, they took samples both before the animals went into their burrows and after they came out.

The results:

• About 23% of juveniles, on average, tested positive before their first brumation.

About 12% of new cancers diagnosed worldwide in 2024, roughly 2.3 million cases, were caused by viruses, bacteria or parasites. That is the estimate from a study published Sept. 28 in The Lancet Oncology, which mapped how much cancer 12 known cancer-causing pathogens produce worldwide.

How the estimate was built

The researchers began with the Global Cancer Observatory's GLOBOCAN database. It pools cancer registries and estimates about 20 million new cancer diagnoses in 2024. They paired those counts with published data on how common each infection is among people with specific cancers. From that, they worked out how many cases of each cancer can be attributed to each pathogen. The result is a model built on existing data, not a direct count. The authors say the registries behind it cover only about 19% of the world's population and just 2% of Africa's, so the real burden may be larger.

Four pathogens account for about 92% of infection-driven cancers:

• Helicobacter pylori, a gut bacterium: 760,000 cases, mostly stomach cancer
• HPV: 750,000 cases, including cervical, penile, throat and mouth cancers
• Hepatitis B: 360,000 cases, mainly liver cancer
• Epstein-Barr virus (EBV): 260,000 cases, including throat cancers, some lymphomas and stomach cancers

Low- and middle-income countries carry 77% of the infection-related burden, and about 81% of HPV-linked cancers.

What prevention can do, and where it stalls

The HPV vaccine shows what is possible. Rebecca Perkins of Tufts University says cervical cancer is "starting to disappear" in countries that quickly vaccinated more than 80% of girls. Studies in Australia, England and Finland found zero HPV-related cancers or deaths among young adults vaccinated by age 13. Yet only 31% of eligible adolescent girls worldwide got even one dose in 2024, against a WHO target of 90%. Perkins argues that moving from two doses to one, an approach backed by recent trials, would cut costs and remove the need to track people for a second shot.