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Physics: Quantum jitter lets heat travel across a vacuum

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A new experiment shows that quantum fluctuations permit heat to bridge empty space

Science News said:
For the first time, scientists have measured the heat transferred by the quantum effervescence of empty space.

Two tiny, vibrating membranes reached the same temperature despite being separated by a vacuum, physicists report in the Dec. 12 Nature. The result is the first experimental demonstration of a predicted but elusive type of heat transfer.

Normally, a vacuum prevents most types of heat transfer — that helps a vacuum-sealed thermos keep coffee piping hot. But “quantum mechanics gives you a new way for heat to go through” a vacuum, says coauthor King Yan Fong, a physicist who worked on the study while at the University of California, Berkeley. For distances on the scale of nanometers, heat can be transferred through a vacuum via quantum fluctuations, a kind of churning of transient particles and fields that occurs even in empty space (SN: 11/13/16).

Made of gold-coated silicon nitride, the two membranes each measured about 300 micrometers across. The researchers cooled one membrane and heated the other, to a temperature difference of about 25 degrees Celsius. That heat translated into a drumheadlike motion of the membranes — the warmer the membrane, the more vigorously it vibrated. When the membranes were brought within a few hundred nanometers of one another, separated by nothing but empty space, their temperatures equalized, indicating that heat had transferred between them.

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Bacchus

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I am presumably overlooking something completely obvious to the most vapid and irreflective quantum physicist, but doesn't heat travel across a vacuum by radiation? At a very basic level, this would be an awfully cold planet if heat didn't radiate from the sun?

on the other hand:-
"That heat translated into a drumheadlike motion of the membranes — the warmer the membrane, the more vigorously it vibrated" - quantum drum 'n' bass -- like it (c:
 

onesecondglance

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I'm no physicist, but it's light that travels from the sun, not its heat. The light then causes heat when it interacts with Earth's atmosphere. I think?
 

Biffington

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I've only got a bachelor's, and I hate quantum physics, but here's one way to think about how electromagnetic radiation works.

Sunlight is a great example of electromagnetic radiation, and that's what Bacchus is thinking of.

The sun sends out tons of photons. Some of these we see as light, while others we don't even think of as light. For instance, it spits out higher-energy photons that we call radio waves all the time. In fact, sometimes it spits out so many radio waves, it messes up radio communication. (Sunspots that strong are rare. In the 1800's a powerful sunspot started fires along a telegraph line and shock operators. I can't find records of one anywhere near that strong since.) Gamma rays and x-rays are also different levels of high-energy photons, and the sun pumps those out, too.

Anyway, many of these photons hit Earth or its atmosphere and deposit some of their energy. This is what heats the Earth's surface, and that's what we think of as electromagnetic radiation. (On a side note, everything releases EMR. Mostly. That lets you do cool things like laser cooling.)

Please note that electromagnetic radiation is different from nuclear radiation. Nuclear radiation can have plenty of EMR but also electrons, neutrons, and weird little particles that don't last very long.

So there you go. In order to transfer something via radiation, you still need photons to go between one object and another.

This experiment, which I haven't read up on, apparently didn't have any EMR at all. It makes use of a quantum mechanical phenomenon called the Casimir affect, which I'm definitely not an expert on.
 
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