Message-Id: <l03102800b16878d4cbee@[209.142.17.170]>
Date: Sun, 26 Apr 1998 00:17:30 -0700
To: pinhole@exploratorium.edu
From: Ron Wong <ronwong@inreach.com>
Subject: re Michelson-Morley experiment
Paul said:
>....
>If there were a medium, the aether, through which light travelled then you
>would get interference of the two light beams in the michelson-morely
>experiment.
>
> However there is no interference and this means there is no medium, no
>aether.
Actually, you will see interference fringes when you look through a
Michelson interferometer whether there is a lumeniferous ether or not. The
fringes come about because of the fact that any light source is extended in
space and, as a result, light rays fall on the mirrors at slightly
different angles of incidence as they arrive from different points of the
light source.
The evidence for the existance of a light-bearing medium comes about when
the apparatus is rotated through 90 degrees from its initial position. If
there is a medium, the original interference pattern would shift by a
measurable amount.
It didn't.
If I recall correctly, the equipment for this famous experiment was placed
on a very large, square block of concrete which sat on a disk that floated
on a pool of mercury. The block was then set in motion and a series of
measurements were made as it went round and round. A shift in the
interference pattern would have allowed us to measure our speed through the
ether.
In the latter part of the nineteenth century, with the acceptance of
Maxwell's electromagnetic wave theory, any investigation that would have
established the existance of the e-m wave's ether was considered to be the
ultimate achievement in the name of Newtonian physics. With this ether
(considered by all to be a solid), we would have had an absolute frame of
reference from which all motion could be measured.
Oh well. Back to the drawing boards.
ron