From: Spike (spike66@comcast.net)
Date: Thu Jul 03 2003 - 21:12:02 MDT
-----Original Message-----
From: Alejandro Dubrovsky
Subject: RE: Solar sailing vs. laws of physics ?
On Fri, 2003-07-04 at 01:14, Spike wrote:
> --- Spike <spike66@comcast.net> wrote:
> >
> > Subject: Solar sailing vs. laws of physics ?
> >
> >> The reflected photon would have the same
> >> frequency as the pre-reflection photon
> >> only if the light source and the reflector
> >> are stationary with respect to each other.
but, spike, the dude doesn't claim that solar sails break the first law
of thermodynamics (energy conservation). he claims the second (getting
work done at 100% efficiency) would be broken. I don't know enough
physics to tell wether he's right or not, but his basic argument seems
to be: solar sail starts propulsing => solar sail gets hot => solar sail
stops working... alejandro
Ja, I saw that, but thought the argument too silly
to take seriously. A thin sheet of mylar in space
doesn't get very hot, even when reflecting sunlight
continuously. It doesn't reflect *all* the light
falling upon it of course, only about 90% or in the
high 80s.
The really high frequencies pass right thru. Some
of the energy is converted to heat, which is
radiated from the shade side into cold space.
So a solar sail isn't a perfect reflector, and no, it
doesn't get so hot it stops working, I can assure you,
nor does this violate the second law of thermodynamics.
I don't even understand the argument in light of the
fact that we have *plenty* of data on what happens to
reflective surfaces in space, plenty. In fact, Amara's
interplanetary dust is blown outta the solar system by
the same mechanism which Gold is questioning. Good
thing too, otherwise we would be choking on the stuff
by now.
Actually, Dr. Gold is smart enough to know all of this.
I don't know what his game is. He is intentionally
playing with our heads for some reason.
spike
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