Gibbs, Josiah Willard (1839-1903), was an American mathematical physicist who contributed to the basic theories of thermodynamics and statistical mechanics. Thermodynamics is the study of various forms of energy, such as heat and work, and of the conversion of energy from one form into another. Statistical mechanics is the study of temperature, pressure, and related phenomena by a mathematical analysis of movements of molecules that are assumed to obey the laws of mechanics. Gibbs published Elementary Principles in Statistical Mechanics (1902), a pioneering textbook on the subject. Gibbs also developed the phase rule, which explains physical relationships among the solid, liquid, and gaseous phases (states) of matter.
Gibbs was born in New Haven, Conn. He received a Ph.D. degree from Yale University in 1863 and taught mathematical physics there from 1871 until his death. He won many distinguished science awards, including the Rumford Medal from the American Academy of Arts and Sciences in 1880 and the Copley Medal from the Royal Society in England in 1901.
