Relativitatea speciala a lui Einstein postuleaza ca-s egale. E o conventie care usureaza calculele dar nu ceva demonstrat.
https://www.fourmilab.ch/etexts/einstein/specrel/www/
"But
it is not possible without further assumption to compare, in respect of time, an event at A with an event at B. We have so far defined only an “A time” and a “B time.” We have not defined a common “time” for A and B, for
the latter cannot be defined at all unless we establish by definition that the “time” required by light to travel from A to B equals the “time” it requires to travel from B to A."