Percy Williams Bridgman

Percy Williams Bridgman was an American physicist who won the Nobel Prize in Physics in 1946 for his research into the behavior of matter under extreme pressure. He also published widely on the philosophy of science and the scientific method. Several concepts and materials bear his name, including the Bridgman effect, the Bridgman–Stockbarger technique, and the high-pressure mineral bridgmanite.

Born in Cambridge, Massachusetts, Bridgman grew up in nearby Auburndale. His father, a newspaper reporter covering state politics, was described as deeply religious and idealistic, while his mother was seen as more conventional, lively, and competitive. He attended local schools, where he did well in academic and athletic contests as well as chess. Shy and proud, his home life included family music, card games, and chores. The family was devoutly religious, reading the Bible daily and attending a Congregational Church, though Bridgman later became an atheist. He entered Harvard in 1900, earning his bachelor’s degree in 1904, a master’s in 1905, and a doctorate in 1908.

Bridgman taught at Harvard from 1910 until his retirement, becoming a full professor in 1919. He began studying high-pressure physics in 1905. After a machinery breakdown, he redesigned his pressure apparatus, creating a new sealing device that eventually allowed him to reach pressures over 100,000 kgf/cm²—a vast improvement over the previous limit of 3,000 kgf/cm². This equipment enabled him to investigate the compressibility, electrical and thermal conductivity, tensile strength, and viscosity of more than 100 substances. He also studied electrical conduction in metals and the properties of crystals. He developed the Bridgman seal, and his thermodynamic equations are named after him. Over the years, he made many refinements to his high-pressure apparatus and tried repeatedly, without success, to synthesize diamond. His high-pressure torsion device later became important in the field of severe plastic deformation.

His 1927 book *The Logic of Modern Physics* promoted operationalism and introduced the term "operational definition." In 1938, he served on the international committee organizing the International Congresses for the Unity of Science, and he was one of eleven signatories to the Russell–Einstein Manifesto. J. Robert Oppenheimer, later director of the Manhattan Project, was one of Bridgman’s undergraduate students. Oppenheimer called him a wonderful teacher who never fully accepted things as they were and always thought them through.

Bridgman married Olive Ware in 1912; her father was the founder and first president of Atlanta University. The couple had two children and lived most of their nearly 50-year marriage in Cambridge, also owning a summer home in Randolph, New Hampshire, where Bridgman was an accomplished mountain climber. He was described as a penetrating analytical thinker with a fertile mechanical imagination and exceptional manual dexterity. A skilled plumber and carpenter, he avoided hiring professionals for such work. He also enjoyed playing the piano and took pride in his flower and vegetable gardens.

After suffering from metastatic cancer, Bridgman died by suicide with a gun. His two-sentence note read: "It isn't decent for society to make a man do this thing himself. Probably this is the last day I will be able to do it myself." His words have been frequently cited in debates about assisted suicide.

His home in Massachusetts was designated a U.S. National Historic Landmark in 1975. In 2014, the mineral bridgmanite—a perovskite-structured form of (Mg,Fe)SiO₃ and the most abundant mineral on Earth—was named in his honor.