Take the 2-minute tour ×  In Einstein's papers, he used light
speed as a reference speed. What if we use a greater finite
speed and do the same calculations. Won't this greater speed
then be the limit.  share|improve this question OP's suggestion
seems equivalent to giving the photon a (rest) mass, cf.
physics.stackexchange.com/q/4700/2451 –  Qmechanic Dec 30 '11 at
14:28  2 Answers 2  The speed of light isn't the reference speed
because Einstein picked it---which would imply that you could
pick something else---but because the laws of physics seem to be
invariant on Lorentz boosts with $c=\text{the speed of light in
a vacuum}$.  When Einstein was doing the work the clearest
experimental evidence came from the form of Maxwell's Equations
and results of Michelson and Morley's interferometry
experiments. These days we have other evidence, including direct
evidence such as the behavior of very energetic particles in
accelerators.  That is, the special place of the speed of light
is an experimental fact.  share|i