The [[Michelson-Morley experiment]] proved that the speed of light (and everything else that is massless) will always be measured by an observer to be the same, in every frame of reference, no matter how fast the source or the observer are moving, this gives rise to the [[theory of relativity]]. | The [[Michelson-Morley experiment]] proved that the speed of light (and everything else that is massless) will always be measured by an observer to be the same, in every frame of reference, no matter how fast the source or the observer are moving, this gives rise to the [[theory of relativity]]. |