[Phys-L] Re: Quotation

[jbellina <jbellina@SAINTMARYS.EDU>]

Perhaps one way to think about the difference is that in the
macroscopic world there are many ways in which objects can lose
energy..it is unavoidable when objects move relative to their
environment this are friction losses for example.
However in the atomic world where the discreteness of energy become
apparent , unless there is some good coupling between one atomic
system and another, there is no way to lose or gain energy, so things
just keep going.
A cross-over region might be conducting solids where there are so
many states in the bands that it is almost continuous, so in normal
metals, electrons can lose energy easily...the wire gets warm, as the
current decays.  Things change when the metal is cooled and the loss
mechanism goes away...you have a superconductor.
So the core idea is, I think, that when you get down to energy
differences where quanta are important, energy transfer is less easy
then when you have energy differences are so large that quantum
effects are not observable.  Then there are many channels for energy
transfer and so energy is transferred from macroscopic motion and
objects stop.

So the statement is indeed true enough.

does that help?  Anyone got a better spin?

joe

Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556

On Dec 22, 2005, at 8:23 AM, Carl Gaither wrote:

> Hello to the group--
>
> I came across a very interesting quotation:
>
> "Physics proves to us the impossibility of perpetual motion among
> visible,
> tangible bodies, at the same time that it reveals to us a world where
> perpetual motion is the rule--the world of molecules and atoms."
> Burroughs, John
> The Breath of Life
> Chapter IX (p. 190)
>
> I was just wondering how one would go about explaining why this
> statement
> must be false.
>
> Carl Gaither
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