Items in sci.space.policy

Subject:Re: Solar sailing DOESN"T break laws of physics'
Date:Sat, 5 Jul 2003 09:53:21 -0700
From:"Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com>
Newsgroups:sci.physics,sci.space.policy

"David M. Palmer" <dmpalmer@email.com> wrote in message
news:040720031618552800%dmpalmer@email.com...
> In article <be4g3k$ob6$1@slb9.atl.mindspring.net>, Steve
Harris
> <sbharris@ix.RETICULATEDOBJECTcom.com> wrote:
>
> > Come on. You're like the guy who says: when I heat up an
> > object, its weight doesn't change (to first order).
> > Therefore the equivalence of mass and energy is
violated.
> > Duh.
> >
> > There is no energy cost to move the stationary sail *to
> > first order.* Carnot's law is broken to exactly the
degree
> > that you simplify the problem with approximation. But
don't
> > confuse your approximation with violation of physical
law.
>
> There is no energy cost to move the stationary sail to
first order.
> There is no change in photon energy to first order
>
> There is an energy cost to move the stationary sail to
second order.
> There is an equal change in photon energy to second order.
>
> There is no breaking of Carnot's law to any order.



If there's no change in photon energy to first order, then
obviously that's a breaking of Carnot's law to first order,
since Carnot requires an decrease in photon temperature
(photon energy) for work to be extracted. Carnot requires
two thermal baths of different temperatures for kinetic
energy to be gained.

But it's okay, because in any inertial frame where work is
being done on the sail, you see two populations of photons
(those coming and those leaving), and these two DO have two
different temperatures. That's it.

SBH