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Category: physics

Uranus and Neptune are hiding something big beneath the blue

Uranus and Neptune may not be the icy worlds we’ve long imagined. A new Swiss-led study uses innovative hybrid modeling to reveal that these planets could just as easily be dominated by rock as by water-rich ices. The findings also help explain their bizarre, multi-poled magnetic fields and open the door to a wider range of possible interior structures. But major uncertainties remain, and only future space missions will The Solar System is commonly grouped by planetary composition: four rocky terrestrial planets (Mercury, Venus, Earth and Mars), two massive gas giants (Jupiter and Saturn), and a pair of ice giants (Uranus and Neptune). However, new research from a scientific team at the University of Zurich (UZH) suggests that Uranus and Neptune may contain far more rock than previously assumed. The study does not argue that these planets must be either water-rich or rock-rich. Instead, it questions the long-standing idea that an ice-heavy interior is the only conclusion supported by available data. This broader interpretation also aligns with the finding that Pluto, a dwarf planet, is dominated by rock.

To better understand what lies inside Uranus and Neptune, the researchers created a specialized simulation technique. “The ice giant classification is oversimplified as Uranus and Neptune are still poorly understood,” says Luca Morf, PhD student at the University of Zurich and lead author of the work. “Models based on physics were too assumption-heavy, while empirical models are too simplistic. We combined both approaches to get interior models that are both “agnostic” or unbiased and yet, are physically consistent.”

The process begins with a randomly generated density profile representing the interior of each planet. The team then determines the gravitational field that would match observational measurements and uses that information to infer the possible composition. The cycle is repeated until the model best fits all available data.

Why a chiral magnet is a direction-dependent street for electrons

RIKEN physicists have discovered for the first time why the magnitude of the electron flow depends on direction in a special kind of magnet. This finding could help to realize future low-energy devices.

The work is published in the journal Science Advances.

In a normal magnet, all the spins of electrons point in the same direction. In a special class of magnets known as chiral magnets, the electron spins resemble a spiral staircase, having a helical organization.

The simulation hypothesis: Mathematical framework redefines what it means for one universe to simulate another

The simulation hypothesis—the idea that our universe might be an artificial construct running on some advanced alien computer—has long captured the public imagination. Yet most arguments about it rest on intuition rather than clear definitions, and few attempts have been made to formally spell out what “simulation” even means.

A new paper by SFI Professor David Wolpert aims to change that. In Journal of Physics: Complexity, Wolpert introduces the first mathematically precise framework for what it would mean for one universe to simulate another—and shows that several longstanding claims about simulations break down once the concept is defined rigorously.

His results point to a far stranger landscape than previous arguments suggest, including the possibility that a universe capable of simulating another could itself be perfectly reproduced inside that very simulation.

Measuring how materials hotter than the sun’s surface conduct electricity

Warm dense matter is a state of matter that forms at extreme temperatures and pressures, like those found at the center of most stars and many planets, including Earth. It also plays a role in the generation of Earth’s magnetic field and in the process of nuclear fusion.

Although warm dense matter is found all over the universe, researchers don’t have many good theories to describe the physics of materials under those conditions. Measurements of a material’s electrical conductivity would help test and refine models of warm dense matter. However, classic probes for such measurements require contact with the material. These can’t be used because materials in a warm dense matter state are very hot, often as hot or even hotter than the surface of the sun. Consequently, information about the electrical conductivity has so far been inferred indirectly.

In other words, without direct measurements, “there’s a lot of stuff in the universe happening that we as physicists are still struggling to understand,” said Ben Ofori-Okai, assistant professor at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University and a researcher at the Stanford PULSE Institute.

Hubble captures rare collision in nearby planetary system

In an unprecedented celestial event, NASA’s Hubble Space Telescope (HST) captured the dramatic aftermath of colliding space rocks within a nearby planetary system.

When astronomers initially spotted a bright object in the sky, they assumed it was a dust-covered exoplanet, reflecting starlight. But when the “exoplanet” disappeared and a new bright object appeared, the international team of astrophysicists—including Northwestern University’s Jason Wang—realized these were not planets at all. Instead, they were the illuminated remains of a cosmic fender bender.

Two distinct, violent collisions generated two luminous clouds of debris in the same planetary system. The discovery offers a unique real-time glimpse into the mechanisms of planet formation and the composition of materials that coalesce to form new worlds.

Hybrid excitons: Combining the best of both worlds

Faster, more efficient, and more versatile—these are the expectations for the technology that will produce our energy and handle information in the future. But how can these expectations be met? A major breakthrough in physics has now been made by an international team of researchers from the Universities of Göttingen, Marburg, the Berlin Humboldt in Germany, and Graz in Austria.

The scientists combined two highly promising types of material—organic semiconductors and two-dimensional semiconductors—and studied their combined response to light using photoelectron spectroscopy and many-body perturbation theory.

This enabled them to observe and describe fundamental microscopic processes, such as energy transfer, at the 2D-organic interface with ultrafast time resolution, meaning one quadrillionth of a second. The combination of these properties holds promise for developing new technology such as the next generation of solar cells. The results are published in Nature Physics.

A 3D-printed Christmas tree made entirely of ice

A team of physicists from the University of Amsterdam’s Institute of Physics has 3D-printed a Christmas tree made entirely of ice. Researchers Menno Demmenie, Stefan Kooij and Daniel Bonn used no freezing technology or refrigeration equipment—just water and a vacuum. In time-lapse videos, you can see how the Christmas tree is printed and how it melts again when the vacuum pump is turned off. The work is published on the arXiv preprint server.

The secret of the tree lies in so-called evaporative cooling. This is the same principle mammals use to regulate their body temperature.

In a low-pressure vacuum chamber, water evaporates rapidly at room temperature. As each water molecule evaporates, it takes with it a small amount of heat, causing the remaining water to become increasingly colder, eventually cooling to below 0°C. At that point, the water is still liquid, but supercooled. As soon as the ultra-thin stream (about as thin as a human hair: 16 micrometers) hits the already formed layer of ice, it freezes instantly.

The Psychedelic Scientist

The reality is Deamer and the psychedelics-inspired Damer may very well be right about the origin of life on Earth. They may never win over scientists like Nick Lane, an evolutionary biochemist at University College London, who argues life needed the singular mix of physics and chemistry in hydrothermal ocean vents to originate. As recently as 2024, Lane and chemist Joana C. Xavier of Imperial College London explained in Nature that the wet and dry cycles of hot springs, key to Deamer’s and Damer’s hypothesis, could not lead to “the network of hundreds of reactions that keeps all cells alive.”

However, biologist Jack Szostak, a Nobel laureate, whose lab at the University of Chicago focuses on the origin of life, told me it’s likely that life did begin in volcanically active regions or impact craters on Earth’s surface. “Deep sea hydrothermal vents are not a plausible site for the origin of life,” he said. “Geothermally active areas,” he added, “are attractive because they do provide the environmental fluctuations needed to drive the primordial cell cycle.” Synthetic biologist Kate Adamala, from the University of Minnesota, who builds artificial protocells to probe how life might have first taken shape, agreed. “I’m on Team Dave and Bruce,” she said.

Presented with either criticism or praise of his origin-of-life theory, Damer remained as sanguine as ever. “You’re never going to have a complete understanding of the origin of life on the early Earth, because we just can’t reproduce the exact conditions,” he said. Of course, he believed the hot springs hypothesis would stand the test of time.

Surprising optics breakthrough could transform our view of the Universe

FROSTI revolutionizes mirror control in gravitational-wave detectors, opening the door to a far deeper view of the cosmos. FROSTI is a new adaptive optics system that precisely corrects distortions in LIGO’s mirrors caused by extreme laser power. By using custom thermal patterns, it preserves mirror shape without introducing noise, allowing detectors to operate at higher sensitivities. This leap enables future observatories like Cosmic Explorer to see deeper into the cosmos. The technology lays the groundwork for vastly expanding gravitational-wave astronomy.

Gravitational-wave detectors may soon get a major performance boost, thanks to a new instrumentation advance led by physicist Jonathan Richardson of the University of California, Riverside. In a paper published in the journal Optica, Richardson and his colleagues describe FROSTI, a full-scale prototype that successfully controls laser wavefronts at extremely high power inside the Laser Interferometer Gravitational-Wave Observatory, or LIGO.

LIGO is an observatory that measures gravitational waves — tiny ripples in spacetime created by massive accelerating objects such as colliding black holes. It was the first facility to directly detect these waves, providing strong support for Einstein’s Theory of Relativity. Using two 4-km-long laser interferometers located in Washington and Louisiana, LIGO senses incredibly small disturbances, giving scientists a new way to study black holes, cosmology, and matter under extreme conditions.

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