Einstein used V in his original German-language papers on special relativity in 1905, but in 1907 he switched to c, which by then had become the standard symbol for the speed of light.
En 1905, Einstein utilizou V nos seus artigos orixinais en alemán sobre a relatividade especial, pero en 1907 pasouse a c, que entón se converteu xa no símbolo estándar para a velocidade da luz.