## torsdag 24 oktober 2019

### What is the Postulate of Einstein's Special Theory of Relativity?

As a follow up to the 2019 Nobel Prize in Physics, I have asked a panel of physicists which formulation of the Basic Postulate of Special Relativity SR is the correct one?

James Peebles received the Prize "for theoretical discoveries in physical cosmology", based on Einstein's relativity theory, which never was awarded any Nobel Prize, and so it is of interest to figure out why? Is relativity theory bogus? While Peebles' work is not?

Let us start by noting that all the confusion and the many paradoxes of SR can be traced back to the Basic Postulate of SR, which occurs in two different forms in the literature:

Version 1: (Einstein's formulation)
• Observations of the speed of light in all inertial systems give the same result = c independent of the motion of the source vs the inertial system.
Version 2: (In some books):
• Observations of the speed of light in all inertial systems give the same result = c independent of the motion of both the source and the observer vs the inertial system.
To be more exact, Version 1 is a condensation of the two postulates made in Einstein's 1905 article presenting SR, which take the following verbatim form:

Version 1A:
• The same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good.
• Light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.
Or alternatively from The Collected Papers, Vol. 2, 1989, p.143:
• Each ray of light moves in the coordinate system “at rest” with the definite velocity V independent of whether this ray of light is emitted by a body at rest or in motion.
The essential difference between Version 1 and 1A  is that the act of observation is present explicitly in Version 1, while it must be implicitly present in Version 1A, since some form of Observation by some Observer is necessary to give meaning to the concept of speed of propagation of light.

Version 2 allows both source and Observer to move with respect to the inertial system used.

Version 1 states that the source can move, but says nothing about the observer, which leaves room for confusion with the following alternatives concerning Observations in a given inertial system S:
1. Observers are assumed to be fixed in S.
2. Observers are allowed to move in S.
With alternative 2, we end up Version 2, while with 1 we get the following more precise version of Einstein's 1905 formulation:

Version 1B: (Possible Einstein formulation)
• Observations of the speed of light in all inertial systems give the same result = c independent of the motion of the source vs the inertial system. Observers are assumed to be stationary in the inertial system where observations are made.
The question is now which formulation of the Basic Postulate of SR is the correct one, if any?
Einstein's formulation as Version 1, 1A or 1B,  or the common text book formulation as Version 2.

In short:
• Is the Observer allowed to move in the inertial system in which light is assumed to propagate ("move") when making Observation of the speed of light?
Yes or No?  The panel of physicists does not seem eager to give an answer. Maybe the  question is too difficult. But maybe someone outside the panel has some idea to report?

The answer will show to have far-reaching consequences...watch out...

PS1 Unfortunately we cannot ask Einstein, but even if it was possible we would probably not get a clear answer, since Einstein was a master of cryptic answers...but the question is not cryptic...

PS2 Note the ambiguity in Version 1A with the role of Observer/Observation not spelled out, while the Observer has a completely central role in SR.