The National Institute of Standards and Technology’s new cesium fountain clock is one of the most precise atomic clocks ever created.
Category: physics – Page 28
Are wormholes possible?
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Would a musical triangle of any other shape sound as sweet?
The triangle is a small instrument made of a metal rod bent into a triangle shape that is open at one corner. While small, its sound is distinct, with multiple overtones and nonharmonic resonance. But what causes the surprisingly powerful sound?
“The triangle instrument produces enchanting and beautiful tones, raising deep and profound questions about the connection between music and physics,” author Risako Tanigawa said. “Optical sound measurement has only been applied to limited subjects until now. By observing the sound field of a triangle for the first time, we captured phenomena not previously explored through microphone observations.”
In a paper published in JASA Express Letters, Tanigawa and colleagues at NTT Corporation and Waseda University in Japan captured sound fields around musical triangles.
Manta ray group formations reveal how collective swimming affects propulsion efficiency
From bird flocking to fish schooling, many biological systems exhibit some type of collective motion, often to improve performance and conserve energy. Compared to other swimmers, manta rays are particularly efficient, and their large aspect ratio is useful for creating large lift compared to drag. These properties make their collective motion especially relevant to complex underwater operations.
To understand how their group dynamics affect their propulsion, researchers from Northwestern Polytechnical University (NPU) and the Ningbo Institute of NPU, in China, modeled the motions of groups of manta rays, which they present in Physics of Fluids.
“As underwater operation tasks become more complex and often require multiple underwater vehicles to carry out group operations, it is necessary to take inspiration from the group swimming of organisms to guide formations of underwater vehicles,” said author Pengcheng Gao. “Both the shape of manta rays and their propulsive performance are of great value for biomimicry.”
Discovery of extended slip bands reshapes understanding of material deformation under stress
University of California, Irvine scientists have expanded on a longstanding model governing the mechanics behind slip banding, a process that produces strain marks in metals under compression, gaining a new understanding of the behavior of advanced materials critical to energy systems, space exploration and nuclear applications.
In a paper published recently in Nature Communications, researchers in UC Irvine’s Samueli School of Engineering report the discovery of extended slip bands—a finding that challenges the classic model developed in the 1950s by physicists Charles Frank and Thornton Read.
While the Frank–Read theory attributes slip band formation to continuous dislocation multiplication at active sources, the UC Irvine team found that extended slip bands emerge from source deactivation followed by the dynamic activation of new dislocation sources.
Text-to-video AI blossoms with new metamorphic video capabilities
While text-to-video artificial intelligence models like OpenAI’s Sora are rapidly metamorphosing in front of our eyes, they have struggled to produce metamorphic videos. Simulating a tree sprouting or a flower blooming is harder for AI systems than generating other types of videos because it requires the knowledge of the physical world and can vary widely.
But now, these models have taken an evolutionary step.
Computer scientists at the University of Rochester, Peking University, University of California, Santa Cruz, and National University of Singapore developed a new AI text-to-video model that learns real-world physics knowledge from time-lapse videos. The team outlines their model, MagicTime, in a paper published in IEEE Transactions on Pattern Analysis and Machine Intelligence.
A snapshot of relativistic motion: Special relativity made visible
When an object moves extremely fast—close to the speed of light—certain basic assumptions that we take for granted no longer apply. This is the central consequence of Albert Einstein’s special theory of relativity. The object then has a different length than when it is at rest, and time passes differently for the object than it does in the laboratory. All this has been repeatedly confirmed in experiments.
However, one interesting consequence of relativity has not yet been observed—the so-called Terrell-Penrose effect. In 1959, physicists James Terrell and Roger Penrose (Nobel laureate in 2020) independently concluded that fast-moving objects should appear rotated. However, this effect has never been demonstrated.
Now, a collaboration between TU Wien (Vienna) and the University of Vienna has succeeded for the first time in reproducing the effect using laser pulses and precision cameras—at an effective speed of light of 2 meters per second. The research is published in the journal Communications Physics.
Peter Gustav Lejeune Dirichlet
It inspired further work — mathematicians like Sophie Germain had previously contributed techniques (notably the “Sophie Germain trick” for special primes), and Dirichlet’s work continued the trend of applying novel number-theoretic tools.
( ; [ 1 ] German: [ləˈʒœn diʁiˈkleː] ; [ 2 ] 13 February 1805 – 5 May 1859) was a German mathematician. In number theory, he proved special cases of Fermat’s last theorem and created analytic number theory. In analysis, he advanced the theory of Fourier series and was one of the first to give the modern formal definition of a function. In mathematical physics, he studied potential theory, boundary-value problems, and heat diffusion, and hydrodynamics.
Although his surname is Lejeune Dirichlet, he is commonly referred to by his mononym Dirichlet, in particular for results named after him.