Speed of light

The speed of light in a vacuum is defined to be 299,792,458 metres per second (1,079,252,848.8 km/h, which is approximately 186,282.4 miles per second, or 670,616,629.38 miles per hour). The speed of light is denoted by the letter c, reputedly from the Latin celeritas, "speed", and also known as Einstein's constant. Note that this speed is a definition, not a measurement; in fact, the fundamental SI unit of distance, the metre, is defined in terms of the speed of light and the second. The speed of light through a transparent medium (that is, not in vacuum) is less than c; the ratio of c to this speed is called the refractive index of the medium. "Speed of light" is sometimes abbreviated SOL.

References

Historical references

• Ole Rømer. "Démonstration touchant le mouvement de la lumière", Journal des Sçavans, 7 Décembre 1676, pp. 223-236. Translated as "A Demonstration concerning the Motion of Light", Philosophical Transactions of the Royal Society no. 136, pp. 893-894; June 25, 1677. (Rømer's 1676 paper, in English and French, as bitmap images: http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Roemer-1677/Roemer-1677.html, and in French as plain text: http://astro.campus.ecp.fr/histoire/roemer.html)
• Edmund Halley. "Monsieur Cassini, his New and Exact Tables for the Eclipses of the First Satellite of Jupiter, reduced to the Julian Stile and Meridian of London", Philosophical Transactions XVIII, No. 214, pp 237–256, Nov.–Dec., 1694.
• H.L. Fizeau. "Sur une experience relative a la vitesse de propogation de la lumiere", Comptes Rendus 29, 90–92, 132, 1849.
• J.L. Foucault. "Determination experimentale de la vitesse de la lumiere: parallaxe du Soleil", Comptes Rendus 55, 501–503, 792–796, 1862.
• A.A. Michelson. "Experimental Determination of the Velocity of Light", Proceedings of the American Association for the Advancement of Science 27, 71–77, 1878.
• Simon Newcomb. "The Velocity of Light", Nature, pp 29–32, May 13, 1886.
• Joseph Perrotin. "Sur la vitesse de la lumiere", Comptes Rendus 131, 731–734, 1900.
• A.A. Michelson, F.G. Pease, and F. Pearson. "Measurement Of The Velocity Of Light In A Partial Vacuum", Astrophysical Journal 82, 26–61, 1935.

Modern references

• Léon Brillouin. Wave propagation and group velocity. Academic Press Inc., 1960.
• John David Jackson. Classical electrodynamics. John Wiley & Sons, 2nd edition, 1975; 3rd edition, 1998. ISBN 047130932X
• Subhash Kak. The Speed of Light and Purāṇic Cosmology. In T.R.N. Rao and S. Kak, Computing Science in Ancient India, pages 80–90. USL Press, Lafayette, 1998. Available as e-print physics/9804020 on the arXiv.
• R.J. MacKay and R.W. Oldford. "Scientific Method, Statistical Method and the Speed of Light", Statistical Science 15(3):254–278, 2000. (Also available on line: http://www.stats.uwaterloo.ca/~rwoldfor/papers/sci-method/paperrev)