Re: Teaching logic is urgent (the only reasonable transformations)

[Stephen Speicher <sjs@COMPBIO.CALTECH.EDU>]

On Fri, 6 Jun 2003, Spagna Jr., George wrote:

> Stephen Speicher wrote:
>
> > The Michelson-Morley experiment failed to detect a
> > _stationary_ ether, but did not alone rule out a partial
> > dragging theory, such as that advocated by George Stokes,
> > where there is full drag at the Earth's surface, tapering off
> > to zero at some distance.  The authors even acknowledged
> > Stokes' theory in the conclusion of their 1887 paper.
>
> By itself the Michelson-Morley results cannot rule out ether
> dragging, but the aberration of starlight (first measured
> in 1729 by James Bradley) is incompatible with ether drag.

Please note that I referred to Stokes' theory as a PARTIAL
dragging theory, which, in fact, is not ruled out by the
existence of aberration.  Stokes focused primarily on mechanisms
rather than underlying causes, and his thinking evolved somewhat
over time, in part due to his own expanding knowledge, and in
part due to experiments by himself and others.  Early (circa
1845),  he put forth a perspective to differ with Fresnel's in
explaining Arago's experiment on aberration:

   "I shall suppose that the earth and the planets carry a
    portion of the ether along with them so that the ether
    close to their surfaces is at rest relatively to their
    surfaces while its velocity alters as we recede from
    the surface till, at no great distance, it is at rest
    in space."[1]

Stokes thought mainly in terms (as Whittaker points out[2]) of an
ether which is condensed upon entering a body, and rarefied upon
exit. By analyzing the motion of a "mass" of this ether, Stokes
arrived at the exact same drag coefficient formula as did
Fresnel, which of course was experimentally verified in Fitzeau's
experiment in 1851.  This was the "aether-drag hypothesis" which
Stokes used to explain aberration "without the startling
assumption that the earth in its motion round the sun offers no
resistence to the ether."[3]

Note also that Michelson was well-aware of Stokes' theory -- in
fact, Michelson supported that theory until he experimentally
disproved it in 1925 -- and of the fact that a
partially-entrained ether was not ruled out by aberration.

[1] George G. Stokes, "On the Aberration of Light,"
_Philosophical Magazine_, 3rd ser 27: p. 9, July 1845.

[2] Sir Edmund Whittaker, "A History of the Theories of Aether &
Electricity," _Dover_, 1951/1989.

[3] George G. Stokes, "On the Constitution of the Luminiferous
Aether Viewed with Reference to the Phenomenon of the Aberration
of Light," _Philosophical Magazine_, 3rd ser 29: p. 6, July 1846.

--
Stephen
sjs@compbio.caltech.edu

Ignorance is just a placeholder for knowledge.

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