RE: The Cosmological constant (was Re: [asa] PredestinedFame:)

From: George Cooper <georgecooper@sbcglobal.net>
Date: Wed Jul 16 2008 - 15:59:05 EDT

You might enjoy seeing Lorentz's quote of Maxwell...

o give some indication of the historical setting in which the M&M experiment
was conducted I quote some sentences from the paper which H.A. Lorentz wrote
in 1895.

"As Maxwell first remarked and as follows from a very simple calculation,
the time required by a ray of light to travel from a point A to a point B
and back to A must vary when the two points together undergo a displacement
without carrying the aether with them..."

In other words, Maxwell recognized there should be a travel time difference
from A to B when comparing the trip time with the aether flow as compared to
the trip time across it, which is true of a fixed speed boat across a river
vs. downstream and back.

This insight, apparently, prompted the first experiment I mentioned.

There is more here: http://www.aquestionoftime.com/michmore.htm

Coope

-----Original Message-----
From: asa-owner@lists.calvin.edu [mailto:asa-owner@lists.calvin.edu] On
Behalf Of Alexanian, Moorad
Sent: Wednesday, July 16, 2008 2:20 PM
To: Ted Davis; ASA; George Murphy; Murray Hogg
Subject: RE: The Cosmological constant (was Re: [asa] PredestinedFame:)

When one derives the wave equation from Maxwell's four equations for the
vacuum, no mention is made of any particular reference system. Therefore, it
would seem from that that the speed of light in vacuum is invariant, viz.,
the same for all observers. Of course, this must imply that Maxwell's
equations may not be the same for an accelerated frame, that is to say, a
non inertial frame. I believe that an accelerated frame would see a
blackbody radiation, as I recall from somewhere, even in the vacuum. Someone
in general relativity can clear that up.

 
Moorad

________________________________

From: Ted Davis [mailto:TDavis@messiah.edu]
Sent: Wed 7/16/2008 3:07 PM
To: ASA; George Murphy; Murray Hogg; Alexanian, Moorad
Subject: RE: The Cosmological constant (was Re: [asa] PredestinedFame:)

Moorad asked:

I believe Einstein did know of the negative result of the Michelson-Morley
experiment before he wrote his seminal work on special relativity. Is there
any doubt about this?

***

Ted replies:
Yes, Moorad, there is considerable doubt about this. Let me say right away
that my knowledge of this is not really up to date, in terms of the
historical scholarship on the development of Einstein's theory, but when my
knowledge was up to date a quarter century ago, a good argument could be
made that he had not actually heard of the MM Expt at the time he wrote his
early papers on special relativity (pub 1905). There were several other
expts by others, trying to detect the earth's motion through the ether in
other ways, and he did know about some of those, but maybe not MM.

For a clear presentation of this argument, see Gerald Holton's essay,
"Einstein, Michelson, and the 'Crucial' Experiment," Isis 60 (1969): 133-97,
or as reprinted in Holton's book, "Thematic Origins of Scientific Thought."
Holton concludes, after surveying all of the evidence available to him, that
the primary sources (that is, what was actually said at the time) "tell a
story for which the secondary sources had not prepared us. It is a scenario
of which we cannot, in the nature of the case, be absolutely certain, but
one which is highly probable. Indeed, the role of the Michelson experiment
in the genesis of Einstein's theory appears to have been so small and
indirect that one may speculate that it would have made no difference to
Einstein's work if the experiment had never been made at all."

My own view is (and I caution people that I am no expert on Einstein) that
the crucial insights for Einstein were theoretical and conceptual, not
experimental. Consider for a moment the difference in how one explains what
happens in these two cases:

(1) hold a solenoid stationary (relative to you), and move a bar magnet
through it. A current is induced, but why? The magnetic field is
moving/changing, but the electric charges in the solenoid are not. The emf
comes from the changing magnetic field, not from the moving charges.

(2) hold a bar magnet stationary, and move the solenoid through it. A
current is induced, but why? The magnetic field is not changing, but the
charges are moving. The emf comes from the moving charges, not from a
changing magnetic field.

Einstein was committed to the view that the relative motion of the magnet
and the coil was the only factor that should matter, and he sought an
explanation that was symmetric to the two cases. You know a lot more
physics than I do, Moorad, so you can see more clearly than me where this is
going...

Ted

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Received on Wed Jul 16 15:59:25 2008

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