||David R. Lide. CRC Handbook of Chemistry and Physics, 84th Edition. CRC Press 2003.
||1) Mohr, Peter J., Taylor, Barry N., CODATA Recommended Values of the Fundamental Physical Constants: 1998 J Phys Chem. Ref. Data 28, No. 6, 1999 pp. 1713-1853 p. 1808 table 23 (2) Rev. Mod. Phys. 72, No. 2, 2000.
||The speed of light is taken as constant in vaccum by Einstein's theory of relativity. It is the speed of not just visible light, but of all electromagnetic radiation, as well as gravitational waves and anything having zero rest mass. The speed of light decreases when it moves through other media, according to the refractive index. Exactly 299,792,458m/sec according to primary source (1)