Rudolf Julius Emmanuel Clausius
Clausius, Rudolf Julius Emmanuel (1822-1888), a German physicist, was one of the founders of thermodynamics and helped establish that field as a science. His great skill lay in the interpretation and mathematical analysis of other scientists' work.
Clausius studied mathematics and physics at the University of Berlin. In 1847, he received a Ph.D. degree from the University of Halle. In 1850, he became professor of physics at the Royal Artillery and Engineering School in Berlin. That year he rejected the caloric theory—that a weightless, invisible fluid in matter determined its thermal state—in favor of the equivalence of heat and work. He published a paper that laid the foundation for modern thermodynamics, in which he stated that heat cannot of itself pass from a colder body to a warmer one. That concept has become known as the second law of thermodynamics. In his studies, Clausius also introduced the concept of entropy. He helped develop the kinetic theory of gases and also formulated a theory of electrolysis, which anticipated the work of Swedish chemist Svante August Arrhenius .
Clausius moved to Switzerland in 1855 to become professor of mathematical physics at the newly founded Zurich Polytechnic. He stayed in Zurich for 12 years before returning to Germany to become professor of physics at the University of Würzburg. In the late 1870's, he became chair of physics at the University of Bonn, a post he held until his death.
During the Franco-Prussian War (1870-1871), Clausius led a voluntary student ambulance service and sustained a wound that caused him continual pain. In 1879, he received the Royal Society's Copley Medal in recognition of his achievements. In 1885, his first wife, Adelheid Rimpau, died, leaving him to care for their six children. Clausius married Sophie Sack in 1886, and the couple had one daughter.