On the Universal Speed in Relativity

The Michelson-Morley experiment has been considered as a verification of the validity of Einstein’s postulate of the universal speed of light in vacuum. However, it has been shown that the special theory of relativity can be developed by applying only the principle of relativity without the need to postulate the universal speed of light and, as a consequence, this raises the question of what role the Michelson-Morley experiment would play in special relativity. In this work we show that the Michelson-Morley experiment not only can be used to confirm that the speed of light is not universal as postulated in Einstein’s special relativity but in fact can also be used to verify that a global universal speed has the value of √3 c.