Re: [Phys-l] Temperture profile in a graviational field

[John Denker <jsd@av8n.com>]

On 01/17/2012 03:46 PM, Christopher M. Gould wrote:
> mass transport equilibrium .... Here, with an imposed
> gravitational potential, air at the top of a column will be colder than
> at the bottom.

<hypothesis>
  Let's explore that idea.

  To make it more interesting, set up a copper rod next to the 
  air column.  There will be no mass transport in the copper,
  just thermal conductivity, so it will be isothermal.

  The rod and the air column have the same temperature at the
  bottom, since they are both in contact with the heat bath
  at that point.

  If they have a different temperature at the top, you can
  run a heat engine using the difference.  Voilà!  Perpetual
  motion machine.
</hypothesis>

I'm sticking with thermal equilibrium being isothermal,
even for a gas in the presence of the gravitational field.