What if we were to reintroduce aristtelianism back into physics not the common sense notion of motion of bodies but teleology.
Category: physics – Page 3
Sean Carroll — Why Fine-tuning Seems Designed
Make a donation to Closer To Truth to help us continue exploring the world’s deepest questions without the need for paywalls: https://shorturl.at/OnyRq.
Watch all Closer To Truth interviews with Sean Carroll here: https://shorturl.at/qS047
If all is random and our universe is the only universe, the chance existence of human awareness would seem incredible. Because the laws of physics would have to be so carefully calibrated to enable stars and planets to form and life to emerge, it would seem to require some kind of design. But there are other explanations.
Get special subscriber-only exclusives by registering for a free membership: https://bit.ly/3He94Ns.
Sean Carroll is Homewood Professor of Natural Philosophy at Johns Hopkins University and fractal faculty at the Santa Fe Institute. His research focuses on fundamental physics and cosmology.
Droplet impacts reveal surprising physics in shear-thickening fluids
From ketchup to quicksand, non-Newtonian fluids have long fascinated and puzzled scientists. Unlike ordinary fluids, their flow properties change depending on how much force is applied, but the precise mechanics governing this behavior remain poorly understood—particularly under rapid deformation. Now, a team led by Xiang Cheng at the University of Minnesota has used droplet impacts to probe these dynamics in new detail, uncovering behaviors which have eluded physicists so far. Their findings appear in Physical Review Letters.
While ordinary Newtonian fluids maintain a constant viscosity regardless of the forces acting on them, non-Newtonian fluids behave very differently: with viscosities that can increase or decrease in response to stress. One classic example is a “shear-thickening” fluid, which can be made simply by mixing cornstarch into water. At high enough concentrations, these suspensions can jam almost completely solid under sudden impacts, even allowing a person to run across them without sinking.
In their study, Cheng’s team prepared cornstarch-water suspensions ranging from 30% to 43% cornstarch by volume, spanning regimes from mild to dramatic shear thickening. They then dropped millimeter-scale droplets of the fluids onto a metal plate at high speeds, producing particularly extreme shear thickening.
From ship wakes to soft tissues: Exploring fluid and solid surface-wave physics
A new study by scientists in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) shows that when a pressure disturbance moves across an ultrasoft elastic material, such as a gel or a biological tissue, it generates a V-shaped wake that’s strikingly similar to the waves that travel behind a boat.
Published in Physical Review Letters, the study offers a unified perspective, combining experiments and theory, on surface motion that spans fluids, solids, and the soft materials that lie between. It opens the door to new approaches to imaging and understanding the behavior of both natural and engineered soft materials.
The research was led by L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, Organismic and Evolutionary Biology, and Physics, in SEAS and FAS, and includes first author and former postdoctoral researcher Aditi Chakrabarti; postdoctoral researcher Divya Jaganathan, and SEAS research associate Robert Haussman.
Rapid method uncovers hidden structures in materials—including elusive quasicrystals
An international team of scientists, including researchers from Loughborough University, has developed a method to dramatically speed up the discovery and design of advanced materials. The study, published in Physical Review Letters, shows how the new approach can map complex phase diagrams in as little as a day—rather than weeks or months—and pinpoint where important structures, including crystals and quasicrystals, are likely to form.
The method will enable scientists to “scout ahead” and identify where promising structures are likely to form and the conditions needed to create them, rather than using a trial-and-error approach. It could help accelerate the development of advanced materials and technologies that harness the unique properties of quasicrystal structures.
“Our approach is a day’s work for an expert—it’s much faster,” said Professor Andrew Archer, an expert in applied mathematics and theoretical physics at Loughborough University and one of the paper’s authors.
How young galaxies grew magnetic fields faster than expected
How fast can a galaxy build ordered magnetic fields spanning thousands of light-years? Existing theories say several billion years, but observations of galaxies in our universe imply shorter timescales. In a study published in the Physical Review Letters and highlighted in the Physics magazine, scientists propose an explanation that resolves this contradiction. They say that the collapse of plasma clouds during the formation of galaxies could significantly accelerate the growth of these magnetic fields.
Almost all visible matter in our universe is in the form of plasma, which can be stirred by forces related to gravity, temperature gradients and rotation. If these lead to turbulent flow, the dynamo theory predicts that the existing magnetic fields in the plasma are amplified. The dynamo theory is our primary framework for understanding the origin of cosmic magnetic fields.
“However, dynamo theory has its limitations,” says Pallavi, an assistant professor at the International Centre for Theoretical Sciences (ICTS) and an author of the study. “In particular, it struggles to explain observations of young galaxies with robust magnetic fields across thousands of light-years.”
Astronomers discover Andromeda XXXVI, an ultra-faint dwarf satellite galaxy
By analyzing the data from the Pan-Andromeda Archaeological Survey (PandAS), European astronomers have discovered a new satellite of the Andromeda galaxy. The newfound object, which received the designation Andromeda XXXVI, appears to be an ultra-faint dwarf galaxy. The finding is reported in a paper published March 30 on the arXiv preprint server.
The so-called ultra-faint dwarf galaxies (UFDs) are the least luminous, most dark matter-dominated, and least chemically evolved galaxies known. Therefore, they are perceived by astronomers as the best candidate fossils from the universe at its early stages.
Now, a team of astronomers, led by Joanna D. Sakowska of the Institute of Astrophysics of Andalusia in Spain, reports the finding of a new UFD. Andromeda XXXVI was first spotted and classified as a candidate UFD by amateur astronomer Giuseppe Donatiello during a systematic, visual inspection search of public images from the full PAndAS footprint. Sakowska and her colleagues recently performed follow-up deep imaging of Andromeda XXXVI with the Roque de los Muchachos Observatory, which confirmed the UFD nature of this galaxy.
New AI video tool removes objects without breaking the laws of physics
When movie and TV directors want to tinker with their footage in post-production, they have an array of tools at their disposal to perfect a scene if it wasn’t shot exactly how they liked. That includes removing objects like stray equipment or unwanted background actors. But the tech has its limits when it comes to more complex physical interactions.
For example, if you want to remove an object that was bumping into or supporting something else, traditional tools often leave the remaining objects behaving in ways that defy the laws of physics, like a character hovering mid-air if the chair they were sitting on is deleted.