Tuesday, November 30, 2010

Maxwell's Demon experiment

Somehow, there has been very little exposure on the net about a really nice experiment that is an attempt at an actual realisation of a Maxwell's Demon scenario that we all learn in our undergrad years, and how to extract energy from the system using information about it.

A popular exposition is here where I first noticed it. The original Nature article is here (subscription required). If you don't have a subscription to Nature, look at the free arXiv version here.

You might want to see this Abstruse Goose :-)

8 comments:

gaddeswarup said...

There is also this piece
http://www.damtp.cam.ac.uk/user/jono/uncertainty-nonlocality.html
which was discussed in several blogs and which I would like to understand a little better.

vbalki said...

The topic is certainly a perennial one in physics. Whole books have been written on Maxwell demonology! The blog you have pointed to is a very clear and simple exposition of certain aspects of the problem.

What slips the mind ever so often is that the Second Law is a statistical one, and that fluctuations ride on top of mean values. If the system is sufficiently small, the relative fluctuation can show up dramatically, and in a direction that is opposite the one to which we are conditioned by the "intuition"
ingrained in us by the law of large numbers. This is not to belittle all the recent work on fluctuation theorems and the like, but merely to say (perhaps superfluously) that no fundamental principles of physics are violated by these results...

AmOK said...

OLO! Did not a man Fine-man from his famous lectern make all clear with a toothed wheel? Perhaps Nature should be renamed Nostalgia. Once I read the free article I may eat my demonic words with energy from those bits of information but this is highly unlikely....

Anant said...

Maybe off topic...but just as I was wondering whatever happened to AmOK...welcome back...

AmOK said...

Anant: Thanks. I was on vacation. I visit OLO's column only under extreme duress and upon the onset of ennui during the work week. :)
Oops - I didn't mean it EXACTLY like that, Sire!

vbalki said...

To AmOK: Just seen your comment on Feynman. Presumably you're referring to the discussion of the ratchet and pawl in the Feynman Lectures. Turns out that discussion is flawed (a rarity in the Feynman Lectures, of course). I forget the exact details right now, but he didn't take a crucial factor into account--I think it was the jiggling of the axis of the toothed wheel due to thermal fluctuations, if I recall correctly. So the graet man actually missed the point, for once.

AmOK said...

@vbalki: Yessir - that is what I meant. You say he was wrong but if he was wrong what was he wrong about? I mean he didn't take into account the jiggling of many other things but in science these are called modeling assumptions and you say the assumptions destroy.. what conclusions? Kindly quote a reference when you call Feynman wrong. I mean, maybe it is just a fluctation, not really WRONG? OLO your ruling please.

Gamma said...

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