The Special Theory of Relativity (SR) is a theory invented in 1905 by Einstein to explain several experimental results. Since then it has been found to explain a wide range of experimental results. SR is not a mathematical game or just a hypothesis. SR is a physical theory that has been well tested many times. A detailed account of the early history of SRT is given in: Arthur L. Miller, Albert Einstein's Special Theory of Relativity: Emergence and early interpretation, Addison Wesley, 1981, ISBN 0-201-04680-6.