Thermodinamics
Posted: 31 March 2008 05:37 AM   [ Ignore ]
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I was reading this:

http://rsc.anu.edu.au/~evans/papers/selectnewsreportsFT.pdf

I fail to recognize how it violates the second principle. As far as I understand it, it doens’t precludes that a few atoms or molecules could, during a short and arbitrary period of time, be in certaint order. Also, the laser needs energy to work, so I don’t see how it could be a closed system.

Any scientist over here?

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Posted: 31 March 2008 06:11 AM   [ Ignore ]   [ # 1 ]
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Hi Barto,

Ok, I am not quite a scientist (anymore downer ), but may I give it a try?

The main motivation for the article seems to be to investigate where the borders of thermodynamics are, which becomes important for nano machines, as some of them contain only a few thousands of molecules, instead of many billions. The article tries to quantify the border where thermodynamics cannot be applied anymore to nano machines:

[quote author=“from the article”]The truth of the second law is ... a statistical, not a mathematical, truth, for it depends on the fact that the bodies we deal with consist of millions of molecules… Hence the second law of thermodynamics is continually being violated, and that to a considerable extent,in any sufficiently small group of molecules belonging to a real body.

The header seems to be a little exaggerated for the article, but scientists (or scientific journals) must draw attention too! (Obviously that strategy worked for you..  wink )

It remembers me of an article in the “New Scientist”: “Quantum theory proven wrong”. In fact it was an article that showed that a layman explanation of the Heisenberg uncertainty principle (that photons push away particles, and so spoil the measurement) is wrong experimentally.

GdB

Edit:

Oh my G… I just looked it up in Wikipedia, the Heisenberg principle… They do not read the “New Scientist”!  big surprise

[quote author=“Wikipedia, Article Uncertainty principle”]Physically, the uncertainty principle requires that when the position of an atom is measured with a photon, the reflected photon will change the momentum of the atom by an uncertain amount inversely proportional to the accuracy of the position measurement. The amount of uncertainty can never be reduced below the limit set by the principle, regardless of the experimental setup.

[ Edited: 31 March 2008 06:29 AM by GdB ]
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Posted: 31 March 2008 06:58 AM   [ Ignore ]   [ # 2 ]
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Not sure as to your precise question, but it’s been known for quite some time that notions of time, space and causality break down at the microlevel, due to issues of quantum oddness.

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Posted: 31 March 2008 07:08 AM   [ Ignore ]   [ # 3 ]
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No, the issue has nothing to do with quantum mechanics. Statistical mechanics already existed before quantum mechanics. But the opposed is true: quantum mechanics does need statistical mechanics, at least in the Kopenhagen interpretation.

GdB

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Posted: 31 March 2008 07:22 AM   [ Ignore ]   [ # 4 ]
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Well, but I wasn’t talking about statistical mechanics in particular; I was talking about the second law of thermodynamics. The second law is a macroscopic law, that many believe is linked to the arrow of time. (Future = higher entropy).

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Posted: 31 March 2008 08:25 AM   [ Ignore ]   [ # 5 ]
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GdB - 31 March 2008 06:11 AM

The header seems to be a little exaggerated for the article, but scientists (or scientific journals) must draw attention too! (Obviously that strategy worked for you..  wink )

As I understand the article, I agree with you. Anyway, I don’t have a lot of confidence on my basic sciences education grin , so I didn’t dare to dismiss an article coming from a reputable source.

I knew that the thermodynamics needs a big amount of molecules because it is stadistical, so claiming that something composed of just a few molecules breaks the second law is what we could call ‘The PEARL Fallacy’ (take a statistical process, analyze small periods after the fact and draw the conclussion that there is an anomaly there because you have something diferent from the global trend).

On the other hand, am I missing something about the laser? As far as I see, the laser breaks the isolation of the system, at least it works as the maxwell’s devils, without using energy. grin

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