time reversal

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Superfluid Helium

September 15th, 2008 by william

In a class I am taking called Emergent States of Matter, we recently watched a video from the stone age that shows a lot of cool phenomena related to superfluidity. If you have a spare hour, you should watch the whole thing; if not, you should at least watch the first few minutes. The narrator does a good job of explaining what is going on, so even if you know nothing about physics, you will not be completely lost.

I will give one forewarning to the uninitiated. When water boils, there are random local thermal fluctuations in temperature all throughout whatever body of water is boiling. So parts are turning into water vapor and parts are still liquid, but when you observe water boiling, the bubbles only come from the surface of water (the top or usually the sides and bottom of whatever pot you boiling water in). Bubbles don’t form randomly within a boiling fluid because the surface tension of water is really high, and the edges make it much easier for bubbles to form.

In a superfluid, due to off-diagonal long range order (i.e. quantum mechanical awesomeness), the temperate is exactly the same everywhere within the superfluid and boiling isn’t possible. And you can watch this happen with your eyes!

http://guava.physics.uiuc.edu/~nigel/courses/569/video/

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