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From: lew@ihlpa.UUCP (Lew Mammel, Jr.)
Newsgroups: net.physics
Subject: Re: Experimental verification of General Relativity
Message-ID: <159@ihlpa.UUCP>
Date: Wed, 20-Mar-85 11:07:11 EST
Article-I.D.: ihlpa.159
Posted: Wed Mar 20 11:07:11 1985
Date-Received: Thu, 21-Mar-85 04:49:40 EST
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 19

I believe a group at Harvard demonstrated General Relativity circa 1970
by "dropping photons down the stairwell" of the physics building.
This experiment depended on the Mossbauer effect, which provides an
ultrafine resolution of gamma ray absorption.

The Mossbauer effect is the absorption of a gamma ray by a nucleus in
a crystal lattice where the lattice as a whole absorbs the recoil. This
is more technically known as the "zero phonon line" of the absorption
spectrum.  Because of the large mass of the macroscopic lattice the line
is VERY sharp.  Sorry I can't be quantitative, but you could look it up.

A preliminary experiment measured the velocity redshift with a sinusoidally
oscillating source. The velocities involved were a few cm/sec, but the
apparatus had no trouble resolving the redshift. They then proceeded to the
stairwell where they measured the GRAVITATIONAL redshift and found it
to be in agreement with the prediction of General Relativity (as well as
half a dozen rival theories no doubt.)

	Lew Mammel, Jr. ihnp4!ihlpa!lew