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Very Fundamental Question on Special Relativity?
Einstein's Special Relativity, and its all consequences was derived from (or I suppose you might say, amounts to), two postulates:
(i) The Principle of Relativity
(ii) The Principle of Invariant Light Speed
How is it so that the second postulate is not superfluous and redundant and simply a specific instance of the first postulate? By this I mean, the first postulate states, essentially (please correct me if I am over-simplifying this), that the laws of physics are the same for any observer in an inertial reference frame.
Can we not say that c, the speed of light, is one such law?
If this is the case, then why is the second postulate necessary at all; in this case, does not the second postulate derive logically from the first? i.e., if the laws of physics are independent of one's inertial frame, and if the speed of light is assumed to be one such law of physics, then should it not be naturally expected that the speed of light is invariant??
Thanks. Let me elaborate my thought process!
I figured that if the Laws of Physics are unaffected by one's frame, then the speed of light should appear as c to any hypothetical individual regardless of the velocity of his/her frame relative to the light source.
So, syllogistically, like this:
1. c is a law of physics
2. The Principle of Relativity states that the laws of physics are independent of relative motion, and hence are the same irrespective of one's frame relative to other frames
3. Therefore, c is c is c whatever the frame of the observer relative to the frame of the light source.
Where does this thinking fail?
2 Answers
- Anonymous1 decade agoFavourite answer
The principle of relativity states, "In physics, the principle of relativity is the requirement that the equations, describing the laws of physics, have the same form in all admissible frames of reference."
How does that statement imply that the speed of light is invariant?
The special theory of relativity reconciles those two statements mathematically.
- troutfisherLv 51 decade ago
A flaw in your reasoning is that the speed of light is not a law it is a quantity to be measured. When the Michaelson-Morely expt was done there was the hypothesis that the law for light propogation iwas that light waves must have a medium - the aether and light propogates at a constant velocity in that medium, but not at a constant velocity for observers moving relative to the aether. The experiment showed this was wrong and led to your (ii).
