Re: What was original in Einsteins SR theory ?

In article <1128407331.040336.266700@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
blackboab <blackboab@xxxxxxxxx> wrote:
>the two postulates of SR
>
>1. That the speed of light is a constant in all reference frames was
>actally the work of Maxwell where the quantity c appears as a constant
>independent of frame of reference.
>
>2. All inertial reference frames are similar was actually the work of
>Galileo.
>
>the gamma correction was the work of Lorentz and Fitgerald
>
>Poincare and Fizeau also added ideas
>
>what EXACTLY did Einstein add ?
>
>what in SR is uniquely Einsteins ?
>

In earlier work, it was thought that the speed of light is constant in the
same way that the speed of a sound wave in air is constant-- it has a
particular speed through the medium, but it still transforms under boosts
as c+v. The gamma factor of Lorentz represented a physical change in
dimensions of objects moving relative to the aether, and it was not
theoretically motivated but was just what term was required to remove a
dependence of velocity through the aether from electromagnetism while
preserving the assumption of c+v.

Related to the assumption of c'=c+v, Maxwell's equations as given in the
textbooks would be for the rest frame of the aether. Under a boost they
would pick up velocity-dependent terms. The assumption was basically that
Newton's mechanics were correct, and electromagnetism had to be fixed up.

Lorent'z aether theory, which matched experiment, was specifically a
theory of electromagnetism. It didn't say much about gravity under
transformations, and the nuclear forces hadn't been discovered yet.

Einstein postulated that c is not just a characteristic speed of a wave in
a medium, but an invariant. That is, it transforms under boosts as c'=c.
He postulated that the principle of relativity applies to all fundamental
physics, including Maxwell's equations. Since electromagnetism had been
tested at high speeds while Newtonian mechanics had not, he assumed
Maxwell's equations were correct and that mechanics had to be fixed up.

This messed around with the conceptions of space and time. The gamma
factor can be derived from those postulates without reference to Maxwell's
equations or particular experiments, and it became geometrical rather than
physical. That is, the Lorentz transformations now applied to everything,
not just electromagnetism. One of the consequences is that a magnetic
force and electromagnetic radiation follows from special relativity and
Coulomb's law. In fact, Maxwell's equations themselves could be derived
from special relativity and Coulomb's law, and the assumption that the
Coulomb force is velocity-independent. Another consequence, since the new
relativistic mechanics is universal, is that gravity also must have
analogs to magnetism and electromagnetic radiation. In fact, all forces
must, including the nuclear forces-- to suppose otherwise would produce a
logical contradiction with the theory.

The fact that the strong and weak nuclear forces, not yet discovered in
1905, seem well described by the standard model, a relativistic theory,
gives a nice suggestion that Einstein had a good idea. If the Lorentz
transformations were not universal, it could have been the case, e.g.,
that particle decays mediated by the electromagnetic force would go as
t'=t/sqrt(1-v^2/c^2) while those mediated by the strong force would go as
t'=t. But that's not what we see.

--
"The main, if not the only, function of the word aether has been to
furnish a nominative case to the verb 'to undulate'."
-- the Earl of Salisbury, 1894
.

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