Hot water freezes faster than cold water

“Why hot water freezes faster that cold water” and “How long have dogs been our best friends?”

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26 March 2026

Today’s Visualized peers at a drone’s uniquely batty navigation system. But first, catch up on the latest science news, including why hot water freezes faster than cold water and just how long dogs have been our best friends.

Biology | News from Science

Polar algae get by with a little help from… giant viruses?!

Some forms of the single-cell, green algae called Chlamydomonas do just fine in polar waters despite the fierce cold, harsh UV radiation, and other extremes. Their success may stem in part from genes given them by so-called giant viruses.

Uncommonly large and complex, and often sporting unusual tendrils, giant viruses were first discovered in 2003. They most often infect algae or amoebae, but can invade more complex multicellular organisms, and are found throughout the world, including in marine, aquatic, and terrestrial habitats.

In Current Biology yesterday, a team reported that polar algae have hundreds of genes given to them by these viruses—roughly 5% of their genome. Further studies showed these genes, remnants of past infection, were active and made proteins that could help the algae—some of the genes encode ice-binding proteins, which help keep the algae from freezing in waters that can dip as low as –2°C. “ The amount of virus-derived DNA described here is remarkable ,” said virologist Jônatas Santos Abrahão, who wasn’t involved in the research. “The study really adds to the view that giant viruses can leave a deep and lasting imprint.”

Read the full story

Physics | News from Science

Unified theory explains paradox of freezing water

Throwing hot water into cold air to instantly create snow is a manifestation of the Mpemba effect. TOBIAS SCHWARZ/AFP VIA GETTY IMAGEs

Here’s an oddity of nature: Hot water seems to freeze faster than cold water. But it turns out that the phenomenon, called the Mpemba effect after a Tanzanian teenager who first noticed it in the 1960s, occurs in a variety of materials, from crystallizing polymers to magnets. More recently, the effects have turned up in the quantum realm, such as single ions suspended with lasers.

Now, a new theoretical framework, published yesterday in Physics Review X, stitches the assorted Mpemba effects together. It explains how, in each case, a system that’s pushed farther from equilibrium can find a quicker path back to a steady state. “ All these effects you might think of as completely different are actually sort of the same thing,” said physicist John Bechhoefer.

The shortcuts to equilibrium are not just curios of nature; if scientists can identify the initial conditions that give rise to Mpemba effects, they could optimize all kinds of processes. That could lead to more efficient cooling and heating schemes, and in the quantum realm, could help speed up quantum computers and the preparation of quantum states.

Read the full story

Ancient DNA | News from Science

World’s oldest dog identified at ancient hunter-gatherer site

Despite decades of study, dogs remain one of the greatest mysteries in archaeology. Scientists know that they descend from gray wolves, but exactly when this happened—and whether it happened more than once —has been unclear. Archaeologists have unearthed suspected dogs—animals whose shorter and wider skulls, for example, are a hallmark of changes that took place as wolves became domesticated—that are much older than the reigning 11,000-year-old genetically confirmed record. But they did not have the detailed genetic information needed to close the case—until now.

Ancient DNA analyses of suspected dogs revealed that the animals were indeed dogs and that our canine pals were widespread across Europe by 14,000 years ago. The oldest dog in the samples dates to about 15,800 years ago, making it the oldest genetically confirmed dog to date and pushing back the definitive origins of dogs nearly 5000 years.

The genomes of the animals are strikingly similar to one another, despite the vast geographical distances separating the sites—from the UK to Switzerland to Italy. As such, they may represent Europe’s ur-dogs, an ancient lineage that had yet to become specialized , said Greger Larson, an evolutionary biologist and co-author on both studies. Whereas later dogs were bred to perform a wide variety of tasks, these early dogs were more of a “Swiss Army knife,” explained Larson. “It’s almost as if this is a new, super-cool thing that everyone wants.”

Neither study answers the age-old question of exactly where and when dogs arose. More digging should help clarify that story, said Natalie Munro, an archaezoologist who was not involved with either study. “There’s a chance they will find more dogs,” she told ScienceAdviser. “And that’s super exciting.”

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Visualized

Duh-nuh-nuh-nuh-nuh-nuh-nuh-nuh, BATDRONE! Manoj Velmurugan

Bats can detect objects just a few millimeters across, track moving prey midair, and navigate at speed in total darkness, all using sound. Despite echolocation’s appeal to robotics, replicating that process has been a difficult engineering problem. A new study in Science Robotics reports a palm-sized drone that can fly through complex environments using ultrasound alone, matching the performance of camera- and lidar-based systems in conditions where optical sensing fails.

Inspired by the bumblebee bat, researchers built a wee drone, PeARBat160, that navigates using ultrasound. Instead of relying on single echoes, the system analyzes streams of returning signals over time using a neural network called Saranga (named for a mythological bow said to pierce any target), extracting structures in the environment from noisy data.

The system’s performance relies on two components. On the hardware side, a physical barrier reduces interference from the drone’s propellers, which can otherwise overwhelm faint echoes. On the software side, Saranga processes echo sequences over time, improving detection of small or low-reflectivity objects such as thin wires and transparent membranes.

In tests, PeARBat160 navigated cluttered indoor and outdoor environments using only onboard sensing, maintaining performance in fog, snow, and low light where optical systems typically fail. It also operated at milliwatt-scale power with no external infrastructure, making it viable for smoke-filled buildings, disaster zones, or underground tunnels.

In a related Focus, roboticists Xin Zhou and Fei Gao note that ultrasound has long been dismissed as too noisy and limited for real autonomy. They suggest that by choosing sensors based on which physical signals remain reliable in a given environment, modern computation could revive older sensing approaches.

REad the Science Robotics paper

Read the Focus

Et Cetera

PCASTing a narrow net

Donald Trump’s new President’s Council of Advisors on Science and Technology (PCAST) is heavily skewed toward artificial intelligence and quantum computing—topics his administration has emphasized. But unlike previous iterations, this council features some of the world’s wealthiest people and several of Trump’s biggest political supporters from high-tech industry—and only one academic scientist. “The unfortunate part of these choices is that it leaves out the ‘S’ in ‘S&T’ [science and technology],” said one higher ed lobbyist.

Read more at ScienceInsider

Egypt’s not-so-wicked stepmother

Queen Hatshepsut, a rare female pharaoh who ruled over ancient Egypt for nearly 20 years, has always been depicted as an evil stepmother whose stepson, Thutmose III, hated so much that he ordered the vicious destruction of her statues. But a new analysis suggests much of the damage came later, and that the queen’s statuary was treated no differently than that of other pharaohs after their deaths. The work “clearly demonstrates that individual statues were broken with different processes and therefore different intentions,” said one expert. “There is no one-size-fits-all explanation for this destruction, and personal animosity is the least likely explanation.”

Antiquity Paper | Read more at The New York Times

If AI development follows the path of previous major evolutionary transitions or “intelligence explosions,” our current step-change in computational intelligence will be plural, social, and deeply entangled with its forebears (us!).

EXPERT VOICES | 19 March 2026 | James Evans, Benjamin Bratton, and Blaise Agüera y Arcas

Last but not least

According to Albert Einstein, wisdom “is not a product of schooling but of the lifelong attempt to acquire it.” I can’t help but wonder whether the researchers that study wisdom will prove him wrong on its teachability.

Christie Wilcox, Editor, ScienceAdviser

With contributions from John Travis, Zack Savitsky, David Grimm, and Ana Georgescu

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