# Zero point energy

Discussion in 'Physics & Math' started by ScRaMbLe, Jan 4, 2004.

1. ### ScRaMbLeChaos Inc.Registered Senior Member

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666
Ok, I read it but couldn't get my around the math. Does what they're saying make sense? If so, has Wang, Evans had a chance to refute their claims? I would be interested to see if they stand by their results. National universities generally try to maintain solid credibility, so I wouldn't have thought they would make such huge claims prematurely.

Last edited: Jan 6, 2004

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3. ### CrispGone 4everRegistered Senior Member

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As a huge fan of the second law, I can only say it does make sense

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I do not have the original Wang & Evans article anywhere near me at the moment, but if I remember the explanation that I read correctly, they measure the work done by their laser trap. Sometimes it turns out that the particle does work on the trap and not the other way around (which would be the "good" way). From the fact that the particle does work on the trap, they conclude that entropy decreases through a chain of reasoning (but I forgot exactly how). I believe that they do the experiment quasistatic, so that the first law of thermodynamics becomes

dU = dQ + dW = T dS + dW.

From the work dW and the knowledge of temperature T and internal energy U, you can determine the change in entropy dS. I suppose they say that it is a closed system, so dU is a constant. Hence if dW > 0 (particle does work) then dS < 0, entropy decreases or something.

The first article explains how the second law is statistical in nature. The second article explains that when you take the average work done by the trap, you find that it is positive (i.e. even though the particle might do work on the trap, it is not lickely because on the average everything is ok).

Furthermore they explain how the situations where work is done by the particle are really just fluctuations of the thermal equilibrium that the particle is in at each instant (everything is quasistatic meaning always in equilibrium).

In other words: the Wang and Evans result is perfectly consistent with the second law, and even a confirmation of it

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Bye!

Crisp

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5. ### ScRaMbLeChaos Inc.Registered Senior Member

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Well that sucks!!

Cheers for your input crisp

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I'm goin away for a couple of weeks, so this'll be my last post for a while. Feel free to carry on without me tho

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I'll drag this thread up when I get back and catch up with any further posts...

See y'all...

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