From: Spike Jones (spike66@ibm.net)
Date: Sun Mar 26 2000 - 14:00:39 MST
> Robert J. Bradbury... raises an
> interesting point, if the photons are always going light speed,
> and they are transfering momentum to the light sail, then, *shouldn't*
> the photon being reflected back be of a lower frequency (to allow
> for conservation of energy)? Hmmmmm...
Roger that Robert. It works both ways: if a light sail is coming
towards you and you shine a light on it to slow it down, then the
reflected photon picks up momentum with respect to you and
you would see it slightly blue shifted. Its actually momentum
that is conserved. Photons are kind of a special case: its energy
is hn where f is the frequency of the photon, and the momentum
is hn/c, where h is a constant.
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