that is the way the Universe works!
The physics of vector equations, in four dimensions will get to the heart of ‘Einsteinian’ physics, the real physics, the relativistic correct physics.
No, that is the way the theory works! If we understood how the universe works, there would be no need for theories!
The 4D interpretation is due to Minkowski, not Einstein.
'The Meaning of Relativity', Albert Einstein, 1956:
"The experiences of an individual appear to us arranged in a series of events; in this series the single events which we remember appear to be ordered according to the criteria of "earlier" and "later", which cannot be analysed further. There exists, therefore, for the individual, an I-time, or subjective time."
"The non-divisibility of the four-dimensional continuum of events does not at all, however, involve the equivalence of the space coordinates with the time coordinate."
"Finally, with Minkowski, we introduce in place of the real time co-ordinate l=ct, the imaginary time co-ordinate..."
I previously cited references to relative light speeds in the SR theory.
The light clock is a simple example of relative light speed <c. If it wasn't there would be no time dilation and light speed would add as vectors just as object speeds do.
In the train example, the observer A moving at train speed v measures the relative walking speed u of the passenger B. Since A is in motion u will be too large resulting from the clock sync convention (assigning the time of reflection). That requires a correction via the composition formula.
The light transit time from A to B is independent of A speed but depends on B speed.
The light transit time from B to A is independent of B speed but depends on A speed.
The formula is therefore reciprocal and each measures the same speed for the other.
Edited by sluggo, 06 February 2017 - 01:58 PM.