RE: Solar sailing vs. laws of physics ?

From: Alejandro Dubrovsky (s328940@student.uq.edu.au)
Date: Thu Jul 03 2003 - 10:05:57 MDT

  • Next message: scerir: "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. I understand why the first step happens but not why the second
    step is necessarily so (unless it gets hot enough for the beast to break
    up, which it would if it would reach the temperature of the photons
    hitting it)

    alejandro



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