Re: Photon, Momentum, Mass


"PD" <TheDraperFamily@xxxxxxxxx> wrote in message news:1177697402.688190.82020@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Apr 27, 12:36 pm, John Kennaugh
<J...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


"All that had been shown in 1905 was that the speed of light is constant
if source and detector are both stationary in the same
inertial FoR." I can only assume that it is a while since you read it
and you are under some delusion that it says something which it does
not. All the preamble is in justification of the first postulate. The
second is conjured out of thin air. His only introduction to the second
postulate is as follows:

"We will raise this conjecture (the purport of which will hereafter be
called the 'Principle of Relativity') to the status of a postulate, and
also introduce another postulate, which is only apparently
irreconcilable with the former,.....".

No justification for it, or even for source independence. Why? The first
postulate had been established experimentally. Contrary to everyone's
expectations experiments which were expected to give different results
in different inertial FoR didn't (MMX etc.). It had been assumed that
they would which is why the principle of relativity as stated by
Gallilao and restated by Newton could be brought out of mothballs. He
hardly needed to justify the first postulate. The second postulate is
the one which needs justifying. If there is an aether one would expect
the speed of light to be affected by the speed of the observer. If there
isn't there is nothing to stop it being affected by the speed of the
source.


Point of order. A *postulate* by definition is a statement that is
assumed for sake of argument to be true without justification.

Thus the PoR is a postulate, Einsteins's second and third "postulates"
are not. Point of order.




Scientific justification of a postulate is based on experimental
confrontation with the *implications* of the postulate, not
necessarily the postulate itself, and this is precisely what was done.

Now, perhaps you are asking what possible train of thought led
Einstein to even think that such a postulate was even worth proposing.
Here the answer is pretty clear. You are right that the first
postulate had been verified pretty thoroughly for the laws of
mechanics. However, it had not been verified for the laws of
electrodynamics, and in fact there was a glaring frame-independent
velocity exhibited in Maxwell's equations, which is the profoundly
different than the case for the laws of mechanics. This left two
choices: either the first postulate holds for the laws of
electrodynamics AND the second postulate holds, or there is no good
physical reason for either to hold. That is, if a frame-independent
velocity in Maxwell's equations isn't really frame-independent, then
neither are Maxwell's equations frame independent.

"It is known that Maxwell's electrodynamics--as usually understood at the present time--when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. " -- Einstein





Einstein had full right to *suppose* both postulates (even without
justification), and then work out the implications to the point where
they could be experimentally tested. The rest is history.

You have full right to be a fuckhead. The rest is history.




PD



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