Monday, February 3

Tag: physics

The Quest to Map the Inside of the Proton
14Apr By adminNo Comments
Technology

The Quest to Map the Inside of the Proton

“How are matter and energy distributed?” asked Peter Schweitzer, a theoretical physicist at the University of Connecticut. “We don’t know.”Schweitzer has spent most of his career thinking about the gravitational side of the proton. Specifically, he’s interested in a matrix of properties of the proton called the energy-momentum tensor. “The energy-momentum tensor knows everything there is to be known about the particle,” he said.In Albert Einstein’s theory of general relativity, which casts gravitational attraction as objects following curves in space-time, the energy-momentum tensor tells space-time how to bend. It describes, for instance, the arrangement of energy (or, equivalently, mass)—the source of the lion’s share of space-time twisting. It also tracks information about how momentum...
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Can You Really Run on Top of a Train, Like in the Movies?
12Apr By adminNo Comments
Technology

Can You Really Run on Top of a Train, Like in the Movies?

Just because you see something done in a movie, that doesn't mean you should try it yourself. Take, for example, a human running on top of a moving train. For starters, you can't be sure it's real. In early Westerns, they used moving backdrops to make fake trains look like they were in motion. Now there's CGI. Or they might speed the film up to make a real train look faster than it really is.So here's a question for you: Is it possible to run on a train roof and leap from one car to the next? Or will the train zoom ahead of you while you're in the air, so that you land behind where you took off? Or worse, would you end up falling between the cars because the gap is moving forward, lengthening the distance you have to traverse? This, my friend, is why stunt actors study physics.Framing the...
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School of Rock: The Physics of Waves on Guitar Strings
16Dec By adminNo Comments
Technology

School of Rock: The Physics of Waves on Guitar Strings

The rubber band example does indeed have two nodes—they are at the ends of the rubber band where your fingers hold it. We only have half a wavelength in the standing wave, but there is indeed a relationship between the length of the rubber band and the size of the wavelength.Guitar StringsIt's time to put all these ideas together and look at a guitar string. Once you hit that string, it's going to create a standing wave with an antinode in the middle and two nodes on the ends. This is called the first harmonic wave.It's possible to also produce a second harmonic wave (with a node in the middle) and even higher harmonics. However, because of drag forces on the string, these higher frequencies die out fairly quickly so that you are just left with a standing wave that has a wavelength equal ...
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An Invisible ‘Demon’ Lurks in an Odd Superconductor
4Dec By adminNo Comments
Technology

An Invisible ‘Demon’ Lurks in an Odd Superconductor

A few years ago, the researchers decided to put a superconducting metal called strontium ruthenate in their crosshairs. Its structure is similar to that of a mysterious class of copper-based “cuprate” superconductors, but it can be manufactured in a more pristine way. While the team didn’t learn the secrets of the cuprates, the material responded in a way that Ali Husain, who had refined the technique as part of his doctorate, didn’t understand.Husain found that ricocheting electrons were sapped of their energy and momentum, which indicated that they were setting off energy-draining ripples in the strontium ruthenate. But the waves defied his expectations: They moved 100 times too quickly to be sound waves (which ripple through atomic nuclei) and 1,000 times too slowly to be charge waves ...
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Magnetic Minerals May Have Given Life Its Molecular Asymmetry
16Oct By adminNo Comments
Technology

Magnetic Minerals May Have Given Life Its Molecular Asymmetry

Naaman and his team discovered that chiral molecules filter electrons based on the direction of their spin. Electrons with one spin orientation will move more efficiently across a chiral molecule in one direction than the other. Electrons with the opposite spin move more freely the other way.To understand why, imagine throwing a Frisbee that glances off the wall of a hallway. If the Frisbee hits the right-hand wall, it will bounce forward only if it’s rotating clockwise; otherwise, it will bounce backward. The opposite will happen if you hit the Frisbee off the left-hand wall. Similarly, chiral molecules “scatter the electrons according to their direction of rotation,” Naaman said. He and his team named this phenomenon the chiral-induced spin selectivity (CISS) effect.Because of that scat...
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A New Proof Moves the Needle on a Sticky Geometry Problem
17Sep By adminNo Comments
Technology

A New Proof Moves the Needle on a Sticky Geometry Problem

The original version of this story appeared in Quanta Magazine.In 1917, the Japanese mathematician Sōichi Kakeya posed what at first seemed like nothing more than a fun exercise in geometry. Lay an infinitely thin, inch-long needle on a flat surface, then rotate it so that it points in every direction in turn. What’s the smallest area the needle can sweep out?If you simply spin it around its center, you’ll get a circle. But it’s possible to move the needle in inventive ways, so that you carve out a much smaller amount of space. Mathematicians have since posed a related version of this question, called the Kakeya conjecture. In their attempts to solve it, they have uncovered surprising connections to harmonic analysis, number theory, and even physics.“Somehow, this geometry of lines pointi...
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