Monday, November 15, 2010

Daemons and their powers...

I have just come across an article on New Scientist site, mentioning Maxwell daemon and its possible real-life implementation.

One thing that bothers me about it (don't I see the obvious?..):

Conceived by James Clerk Maxwell in 1867, the demon exploits the random thermal motions of the microworld. It might watch a tiny ball on a spiral staircase, waiting for it to randomly hop up a step and then slam in a barrier to stop the ball moving down again. If the demon keeps doing this the ball keeps climbing. The potential energy of the ball could then be used to drive an engine.
and regarding the implementation:
Finally, enter the demon, whose eye is a camera and brain a computer that controls the electric field. Whenever the rotor makes some progress in turning against the torque, the demon shifts the electric field so that the rotor suddenly finds itself nudged onto the top of that "step". This keeps happening, and the overall effect is to gradually climb the staircase.
As it does, the rotor gains energy. Crucially, though, the demon need pump no energy into the rotor, only information about the position of the rotor, which it uses to switch the field.

Doesn't shifting the field or slamming a barrier also mean that you make some work? You need to spend some energy to move that barrier and then to lift it again. These two movements cannot cancel each other in the real world because of friction (unless we operate in a real vacuum). Same about the shifting the electric field... Do they really mean that we can disregard friction-like effects in that case?

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