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Scientists are watching while Heat is moving through & # 39; Lead Pencil & # 39; at Sound Speed



Scientists see something astonishing that is happening inside the graphite, the objects of your pencil are made: The heat moves to waves at the speed of sound.

That's pretty cool for some reason: The heat should not move like a wave – it usually diffuses and bounces off jiggling molecules in every direction; If the heat can travel as a wave, it can move in one direction en masse away from its source, the type of zapping energy simultaneously from one thing. In a few days, this heat transfer graphite behavior can be used to cool microelectronics in a snap. That is, if they can get it to work a reasonable temperature (they work at bone-chilling temperatures of minus 240 degrees Fahrenheit, or minus 1

51 degrees Celsius).

"If it makes room temperature in some materials, then there will be prospects for some applications," study researcher Keith Nelson, a MIT pharmacy, told Live Science , and added that it was the highest temperature anyone saw that this behavior occurred. [The 18 Biggest Unsolved Mysteries in Physics]

Researchers describe the "normal" heat movement with a heated kettle – After turning off the burner, the heat energy hitches a ride on the air molecules, which override one and pass the heat in the process. These molecules fall in every direction; some of these molecules are scattered back into the kettle. Over time, the water of the kettle and its surroundings reaches the equilibrium at the same temperature.

In solids, the molecules do not move because the atoms are locked in position. "The move can sound," said Nelson, who talked to Live Science with co-author Gang Chen, a mechanical engineer at MIT.

Instead, heat hops in phonons, or small packets of sound vibration; phonons can bounce and scatter, bringing heat types such as air molecules from the kettle. [What’s That Noise? 11 Strange and Mysterious Sounds on Earth]

That's not what happened in the new experiment.

Previous theoretical work by Chen predicted that heat can travel like a wave when moving through graphite or graphene. To test this, MIT researchers crossed two laser beams over their graphite, creating a so-called interference pattern with parallel lines of light and no light. It has the same pattern of heated and unheated regions over the graphite. Then, they aim for another laser beam to setup to see what happened at the moment of touching the graphite.

"Usually, the heat gradually spreads from heated regions to unheated regions, until the temperature is washed," says Nelson. "Instead, the heat flows from the heated up to the unheated regions, and keeps flowing even though the temperature is equal everywhere, so the unheated regions are actually hotter than those previously heated region. " The heated region, meanwhile, has become cooler than the unheated regions. And all this has happened breathing fast – at about the same speed that sounds normal traveling in graphite. [8 Ways You Can See Einstein’s Theory of Relativity in Real Life]

"The heat flows faster as it moves in a wave-like fashion without scattering," said Nelson Live Science.

How they get the odd behavior, called by the scientists "second sound," "Because of a basic point of view, it's not just ordinary behavior. Secondary sound is measured only by a small material , at any temperature. Anything we observe far beyond the common challenges we understand and explain it, "Nelson said.

Here's what they are thinking of happening: The graphite, or 3D material, has a layered structure where thin layers of carbon do not know if one is there, and they're the kind of acting like graphene, which is a 2D material. Because of what Nelson calls "low dimensions," phonons that carry heat in a layer of graphite are more likely to bounce and scatter the other layers. Also, phonons that can make up the graphite have wavelengths that are usually large to reflect backwards after the crashing of the atoms in the trellis, a phenomenon known as backscatter. Small packs of sound are scattered a little, but travel in most one direction, meaning that in general, they can travel a bigger distance more quickly.

Their research was published today (March 14) in the journal Science.

Editor's Note: This article has been updated to clarify some of the experimental methods and the fact that heat travels about the same speed that sounds is traveling through graphite, not turned , as previously stated. (Var rect = document.getElementById ("comments") {if (document.getElementById ("comments")) {var listener = function () "). getBoundingClientRect (); if (rect.top <window.innerHeight) {loadAPI (); window.removeEventListener (" scroll " ("script"); js.src = "http://connect.facebook.net/en_US/ sdk.js # xfbml = 1 & appId = 131734303545872 & version = v2.4"; document.body.appendChild (js) }
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