All posts tagged: physics

New form of friction arises purely from magnetic interactions – no contact required

New form of friction arises purely from magnetic interactions – no contact required

Published by Jenni Sidey

Friction usually announces itself through contact. A chair scraping across a floor, a tire gripping asphalt, a hand sliding over fabric. For centuries, the rule seemed simple: press harder, and resistance grows. That idea, formalized in Amontons’ law, has guided physics since the 17th century. Now a tabletop experiment suggests a very different picture can emerge when nothing touches at all. Researchers at the University of Konstanz have identified a form of friction that arises purely from magnetic interactions. No surfaces rub together. No material wears down. Yet resistance appears, peaks, and then fades again as conditions change. The familiar rule linking friction to load no longer holds in a straightforward way. Instead of steadily increasing, friction rises to a maximum and then drops, all because of how tiny magnetic elements struggle to agree with each other. Experimental set-up, total friction and order parameter. (CREDIT: Nature) When More Pressure Does Not Mean More Resistance Amontons’ law rests on a simple observation. Heavier objects press surfaces together, increasing microscopic contact points and boosting friction. That logic …

We’re solving the fundamental mystery of how reality is glued together

We’re solving the fundamental mystery of how reality is glued together

Published by skeptic

As you read this, every atom in your body is desperately trying to tear itself apart. In fact, that goes for every atom, everywhere, since the beginning of time. Thankfully, those efforts have failed. These self-destructive tendencies relate to the nucleus, a tiny knot of matter at the centre of every atom. Inside, protons are packed shoulder to shoulder, each one bristling with positive charge and frantic to get away from its companions. If atoms obeyed only electricity and magnetism, the universe would have been a brief, bright firework. Instead, something else intervenes, a force so strong it makes electromagnetism look feeble. This maintains the solid furniture of reality by keeping the building blocks of atoms glued together. But the deeper physicists have probed this force, the stranger it has seemed. The equations that describe it look disarmingly simple, yet follow them through and something puzzling happens: a theory built from weightless ingredients somehow produces particles that are unmistakably heavy. Sweeping away this inconsistency wouldn’t just tidy up our understanding of the force that binds …

Desktop particle accelerators are opening new frontiers in physics

Desktop particle accelerators are opening new frontiers in physics

Published by Jenni Sidey

A beam of electrons crossed just a few millimeters of plasma, then helped trigger an effect that usually belongs to massive research sites. In this case, the light produced fell in the extreme ultraviolet range, at wavelengths from 27 to 50 nanometers. The result points toward a future where some accelerator technology may shrink from building-sized systems to something much smaller. “Our work has made several substantial improvements over previous techniques, allowing us to achieve free-electron laser amplification at extreme ultraviolet wavelengths,” lead author Zhan Jin said. Proof-of-concept experimental setup used to generate an extreme ultraviolet (XUV) free-electron laser (FEL) driven by a laser wakefield acceleration (LWFA) electron beam. (CREDIT: University of Osaka) Taming a difficult accelerator Traditional particle accelerators, including radiofrequency linear accelerators and synchrotrons, have pushed physics forward for decades. They are also expensive, physically large, and limited in how strongly they can accelerate particles over a given distance. Laser wakefield acceleration offers a very different path. Instead of relying on long conventional structures, it sends a powerful laser through plasma, where it …

Gravitational waves may be responsible for dark matter in the universe

Gravitational waves may be responsible for dark matter in the universe

Published by Jenni Sidey

Dark matter is thought to exist everywhere, wrapping around galaxies and helping to shape the largest things in the universe. But nobody knows what it is made of. Now, a new theoretical study presents a surprisingly unique situation that could provide some of the missing puzzle pieces. Some of the dark matter may have originated from ancient gravitational waves. These waves travelled through the early universe before stars or galaxies had formed. This hypothesis is the product of collaboration between Professor Joachim Kopp from Johannes Gutenberg University Mainz and the PRISMA++ Cluster of Excellence. The work was also in collaboration with Dr. Azadeh Maleknejad from Swansea University. Furthermore, this work was published in Physical Review Letters. Visible matter makes up approximately 4% of our universe. It contains all the planets, stars, and living organisms which we can actually observe. Dark matter is estimated to represent around 23% of the universe. Although astronomers are aware of its existence due to its influence on the formation of galaxies and the structure of the universe as a whole, …

Light can travel for billions of years yet experience no time

Light can travel for billions of years yet experience no time

Published by Jenni Sidey

A photon emitted from a star a billion light-years away arrives at a telescope having experienced no time whatsoever. Not very little time. None. That result is not a loose approximation or a poetic way of speaking. It falls directly out of the mathematics of special relativity, and it points toward something genuinely strange about the structure of the universe: time is not a fixed backdrop against which events unfold. It is something that changes depending on how fast you move through space. Two Clocks, One Disagreement The cleanest entry point into this problem is a thought experiment, though it has since become a laboratory result. Imagine two identical atomic clocks, synchronized and placed side by side. One remains stationary. The other is carried aboard a fast-moving aircraft and brought back. When the traveling clock returns, it shows slightly less elapsed time than the one that stayed behind. This effect has been confirmed experimentally, most famously in a 1971 experiment by physicists Joseph Hafele and Richard Keating, who flew cesium clocks around the world and …

A once-fantastical collider could answer physics’ biggest mysteries

A once-fantastical collider could answer physics’ biggest mysteries

Published by skeptic

When it comes to particle physics, Tova Holmes has been there, done that and got the T-shirt – in fact, she designed the T-shirt herself. It all started back in 2022, when she and a few colleagues arrived at a meeting of particle physicists determined to make the case for developing an entirely new kind of particle-smashing machine. They did so by sporting tops emblazoned with a motif representing a circular particle accelerator and a single word: BUILD. “We wanted to find a way for people to visibly show how excited they were about a muon collider,” says Holmes, who is based at the University of Tennessee, Knoxville. To its advocates, this newfangled collider would be exactly the shot in the arm that particle physics so desperately needs. The famous Large Hadron Collider (LHC) at the CERN particle physics laboratory near Geneva, Switzerland, wonderful as it is, simply hasn’t delivered any truly new discoveries in years. The answer, say Holmes and her ilk, isn’t to build ever-more powerful successors to the LHC, as some would …

Sneakers squeak on basketball courts. Physics explains why

Sneakers squeak on basketball courts. Physics explains why

Published by skeptic

air pressure: The force exerted by the weight of air molecules. frequency: The number of times some periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time. physicist: A scientist who studies the nature and properties of matter and energy. pitch: (in acoustics) The word musicians use for sound frequency. It describes how high or low a sound is, which will be determined by the vibrations that created that sound. pressure: Force applied uniformly over a surface, measured as force per unit of area. range: The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. silicone: Heat-resistant substances that can be used in many different ways, including the rubber-like materials that provide a waterproof seal around windows and in aquariums. Some silicones serve as grease-like lubricants in cars and trucks. Most silicones, a type of molecule known as a polymer, are built around long chains of silicon and oxygen atoms. sound …

The weird physics of plant-based milks is only just coming to light

The weird physics of plant-based milks is only just coming to light

Published by skeptic

Just a splash of the non-Newtonian, please Jack Andersen/Getty Images The physics of plant-based milks is strange. Researchers are only now beginning to understand it, and they hope that doing so could result in better beverages. Vivek Sharma at the University of Illinois Chicago and his colleagues found that most plant milks flow and drip in more complex and unusual ways than their animal counterparts. The team looked at eight different milks – cow, goat, pea, soy, oat, almond, coconut and rice – and studied their viscosity, or how difficult it is for them to flow. They found that all the plant-derived milks except for rice milk exhibited something called shear thinning, where the viscosity decreases with pressure. That means those milks are non-Newtonian liquids, physically more similar to ketchup or shampoo, which flow more easily when you apply pressure to the bottle than cow or goat milk, which have a constant viscosity. Sharma says this is because the plant milks contained very small amounts, often less than 0.1 per cent, of gums derived from …

The physics of no return: What actually happens if you get pulled into a black hole

The physics of no return: What actually happens if you get pulled into a black hole

Published by Jenni Sidey

In 1916, only a year after Albert Einstein had published his general theory of relativity, Karl Schwarzschild used mathematical calculations to show this: If sufficient mass could be placed into an extremely small volume, then this sufficiently dense mass would create a zone where gravity is so strong that nothing, including light, could escape from it. One hundred years later, scientists have actually imaged the shadow of such an object. They have also recorded the gravitational waves produced when two of these celestial bodies collide. However, the ultimate question (the ultimate unresolved question) in science about the fate of matter that crosses an event horizon of a black hole is still unanswered. The answer includes a long list of things: how atomic structure changes or gets stretched during the collapse of the star, spatial distortion due to relativistic time dilation, luminous rings of matter and debris surrounding the black hole, and the nature of the event horizon itself (which has no physical wall). It is simply becoming an irreversible relationship with the universe beyond the …

How Anthony Leggett pushed the boundaries of quantum physics

How Anthony Leggett pushed the boundaries of quantum physics

Published by skeptic

Sir Anthony Leggett was a giant in the field of quantum physics University of Illinois Urbana-Champaign/L. Brian Stauffer In my first year of graduate school, I briefly shared an office with a quiet, older graduate student. When we finally managed some chit-chat, I learned that he was “working on theory of glasses with Tony.” Two things became clear: cracking the physics of glasses was difficult, and I really ought to have known who Tony was. I met him soon enough. A polite British man in his 70s, he spoke with the cadence of a life-long teacher and an incontrovertible twinkle in his eyes. His full name was Anthony James Leggett: a Nobel laureate, a knight of the British Empire, winner of countless prizes, an expert on the ultracold denizens of the quantum world, and a theorist who co-developed an influential test for probing just where that world might end, a question he pursued for decades. He passed away on 8 March, survived not only by his family but by countless inspired researchers to whom he …