On 13/01/2016 18:29, Quadibloc wrote:
On Wednesday, January 13, 2016 at 6:45:12 AM UTC-7, Sam Wormley wrote:
Maxwell's demon as a self-contained, information-powered refrigerator
http://phys.org/news/2016-01-maxwell...rigerator.html


In 1867, Scottish physicist James Clerk Maxwell challenged the second
law of thermodynamics according to which entropy in a closed system
must always increase. In his thought experiment, Maxwell took a
closed gas container, divided it into two parts with an inner wall
and provided the wall with a small trap door. By opening and closing
the door, the creature - 'demon' - controlling it could separate slow
cold and fast warm particles to their respective sides, thus creating
a temperature difference in contravention of the laws of
thermodynamics.

On theoretical level, the thought experiment has been an object of
consideration for nearly 150 years, but testing it experimentally has
been impossible until the last few years. Making use of
nanotechnology, scientists from Aalto University have now succeeded
in constructing an autonomous Maxwell's demon that makes it possible
to analyse the microscopic changes in thermodynamics. The research
results were recently published in Physical Review Letters. The work
is part of the forthcoming PhD thesis of MSc Jonne Koski at Aalto
University.

The snag is your demon has to do a lot of work moving the trapdoor no
matter how small you make it. Entropy always wins in the end.

On this general subject...

I had thought that since self-winding watches are powered by the random motion
of the person wearing them -

Not a random motion of the person wearing them - the pendulum motion of
the arm as they walk along. If you have such a watch and do not wear it
every day you may need to own a "watch winder" to keep it going!

and Brownian motion is visible from placing small, but visible, objects in
liquids, so those objects are much larger than a molecule,

Brownian motion is still random so you can't derive useful power from it
although you can see pollen grains bouncing around.

it would seem as though one could make tiny electrical power generators that
broadcast power by radio that used a self-winding watch mechanism... to convert
heat directly into useful work, in violation of the laws of thermodynamics.

You can try but the second law of thermodynamics will be working against
you. Put simply you can't win and you can only break even under
exceptional circumstances that almost never occur in practice.

That is why most patent offices have stopped considering bogus patents
for any kind of perpetual motion machine (even the USPTO).

--
Regards,
Martin Brown