An erg (short for ergon ’έργον a Greek word meaning "work/task") is a unit of energy and mechanical work equal to 10−7 joules. It originated in the centimetre–gram–second (CGS) system of units, symbol "erg". It is not an SI unit.
An erg is the amount of work done by a force of one dyne exerted for a distance of one centimeter. In the CGS base units, it is equal to one gram centimeter-squared per second-squared (g·cm2/s2). It is thus equal to 10−7 joules or 100 nanojoules (nJ) in SI units. An erg is approximately the amount of work done (or energy consumed) by one common house fly performing one "push up", the leg-bending dip that brings its mouth to the surface on which it stands and back up.
1 erg = 10−10sn·m = 100 psn·m = 100 picosthène-metres
1 erg = 624.15 GeV = 6.2415×1011 eV
1 erg = 1 dyne cm = 1 g·cm2/s2
In 1864, Rudolf Clausius proposed the Greek word (ἐργον) ergon for the unit of energy, work and heat. In 1873, a committee of the British Association for the Advancement of Science, including British physicists James Clerk Maxwell and William Thomson defined the C.G.S. System of Units, and recommended the name erg or ergon for the C.G.S. unit of energy.
- Lumen second, for the lumerg and lumberg units
- Metre–tonne–second system of units
- Foe (unit), relative measure for energy released by a supernova
- Oxford English Dictionary
- Filippenko, Alex, Understanding the Universe (of The Great Courses, on DVD), Lecture 44, time 24:30, The Teaching Company, Chantilly, VA, USA, 2007
- Clausius, Rudolf (1867). "Appendices to Sixth Memoir . Appendix A. On Terminology.". In Hirst, T. Archer. The Mechanical Theory of Heat, With Its Applications to the Steam-engine and to the Physical Properties of Bodies. London: J. Van Voorst. p. 253. Retrieved 2014-03-17.
- Howard, Irmgard K. (2001). "S is for Entropy. U is for Energy. What Was Clausius Thinking?" (PDF). Journal of Chemical Education 78 (4): 505. Bibcode:2001JChEd..78..505H. doi:10.1021/ed078p505. Retrieved 2014-03-17.
- Thomson, Sir W; Foster, Professor GC; Maxwell, Professor JC; Stoney, Mr GJ; Jenkin, Professor Fleeming; Siemens, Dr; Bramwell, Mr FJ (September 1873). Everett, Professor, ed. First Report of the Committee for the Selection and Nomenclature of Dynamical and Electrical Units. Forty-third Meeting of the British Association for the Advancement of Science. Bradford: John Murray. p. 224. Retrieved 2014-03-17.