Rudolf Clausius, Polish-German physicist and mathematician (died 1888)

Rudolf Julius Emanuel Clausius was a German physicist and mathematician and is considered one of the central founding fathers of the science of thermodynamics. By his restatement of Sadi Carnot's principle known as the Carnot cycle, he gave the theory of heat a truer and sounder basis. His most important paper, "On the Moving Force of Heat", published in 1850, first stated the basic ideas of the second law of thermodynamics. In 1865 he introduced the concept of entropy. In 1870 he introduced the virial theorem, which applied to heat.

January 2 is the second day of the year in the Gregorian calendar; 363 days remain until the end of the year.