Percy Williams Bridgman (21.04.1882-20.08.1961) was an American physicist and a member of the National Academy of Sciences. He was born in Cambridge (USA). He graduated from Harvard University (1905), with which the whole of his subsequent work was connected (in 1926—54 as professor).
His main research concerned the physics of ultra-high pressures. He developed methods and instruments for producing ultra-high pressures, which enabled him to extend the range available for quantitative physical research from 3,000 to 425,000 atmospheres. He carried out extensive studies of compressibility, phase transformations, viscosity and other properties of matter under these conditions. In particular, he proved experimentally that there is no critical point on the melting curve, found a large number of polymorphic transformations (including the irreversible transition of yellow phosphorus into black), and discovered a particular kind of failure of materials at high pressures. He was the first to observe the metal — insulator transition under pressure (in tellurium and black phosphorus) and a phase transition in cerium at a pressure of 7000 atm and room temperature, caused by the passage of electrons from one band to another, as well as a transition in cerium at a pressure of 40 000 atm associated with the electron transition from the 6s to the 5d state. He established two reference points for calibrating high-pressure gauges (manganin gauges) and developed (1953) a method of detecting them. For his work in the field of high-pressure physics and the discoveries connected with it, in particular for building apparatus capable of reaching pressures of the order of hundreds of thousands of atmospheres, he was awarded the Nobel Prize in 1946. His work led to the creation of synthetic diamonds (1955). He studied the electrical conductivity of metals and the properties of crystals.
His work was also in philosophy, where he took an idealist position; he was the founder of operationalism. A member of a number of academies of sciences. The B. Rumford Medal. President of the American Physical Society (1942).