American physicist (1882–1961)

Bridgman, the son of a journalist, was born in Cambridge, Massachusetts, and educated at Harvard where he obtained his PhD in 1908. He immediately joined the faculty, leaving only on his retirement in 1954 after serving as professor of physics from 1919 to 1926, professor of mathematics and natural philosophy from 1926 to 1950, and as Huggins Professor from 1950 to 1954.

Most of Bridgman's research has been in the field of high-pressure physics. When he began he found it necessary to design and build virtually all his own equipment and instruments. In 1909 he introduced the self-tightening joint and with the appearance of high tensile steels he could aim for pressures well beyond the scope of earlier workers. At the beginning of the century Emile Amagat and Louis Cailletet had attained pressures of some 3000 kilograms per square centimeter; Bridgman increased this enormously, regularly attaining pressures of 100,000 kg/cm².

Bridgman used such pressures to explore the properties of numerous liquids and solids. In the course of this work he discovered two new forms of ice, freezing at temperatures above 0°C. He also, in 1955, transformed graphite into synthetic diamond. Bridgman was awarded the 1946 Nobel Prize for physics for his work on extremely high-pressures.

He was also widely known as a philosopher of science and in his book The Logic of Modern Physics (1927) formulated his theory of ‘operationalism’ in which he argued that a concept is simply a set of operations. In his 70s Bridgman developed Paget's disease, which gave him considerable pain and little prospect of relief. He committed suicide in 1961.

The American experimental physicist Percy Williams Bridgman (1882-1961) was a pioneer in investigating the effects of enormous pressures on the behavior of matter - solid, liquid, and gas.

Percy Bridgman was born in Cambridge, Mass., on April 21, 1882, the son of Raymond Landon and Mary Ann Maria Williams Bridgman. At high school in Newton, Mass., he was led into the field of science by the influence of one of his teachers.

Bridgman received his doctorate from Harvard University in 1908 and remained there as a research fellow in physics. He married Olive Ware in 1912, with whom he had a daughter and a son. By 1919 he rose to a full professorship, and 7 years later the university appointed him Hollis professor of mathematics and natural philosophy.

In 1946 Bridgman received the Nobel Prize in physics. He was a fellow of the American Academy of Arts and Sciences and at one time served as president of the American Physical Society. He continued to work at Harvard several years after his official retirement, until he died on Aug. 20, 1961.

Bridgman's major work dealt with the building of apparatus for the investigation of the effects of high pressures, apparatus that would not burst under pressures never reached before. Quite by accident he discovered that a packed plug automatically became tighter as more pressure was applied. This proved a key to his further experimentation. Using the steel alloy Carboloy and new methods of construction and immersing the vessel itself in a fluid maintained at a pressure of approximately 450,000 pounds per square inch (psi), which Bridgman later increased to more than 1,500,000 psi, he reached, inside the vessel, 6,000,000 psi by 1950. To measure such hitherto unattainable pressures, Bridgman invented new measuring methods.

The most striking effect of these enormous pressures was the change in the melting point of many substances. Bridgman also found different crystalline forms of matter which are stable under very high pressure but unstable under low pressure. Ordinary ice, for example, becomes unstable at pressures above about 29,000 psi and is replaced by stable forms. One of these forms is stable under a pressure of 290,000 psi at a temperature as high as 180°F. This "hot ice" is more dense than ordinary ice and sinks completely in water.

In 1955 the General Electric Company announced the production of synthetic diamonds, which their scientists, working on methods and information derived from Bridgman's work, had produced from ordinary carbon subjected to extremely high pressures and temperatures.

Further Reading

Reflections of a Physicist (1950; 2d ed. 1955) is a collection of Bridgman's nontechnical writings on science. A detailed biography of Bridgman is in National Academy of Sciences, Biographical Memoirs, vol. 41 (1970). Niels H. de V. Heathcote, Nobel Prize Winners in Physics: 1901-1950 (1954), contains a chapter on Bridgman. He is included in Royal Society, Biographical Memoirs of Fellows of the Royal Society, vol. 8 (1962), and in National Academy of Sciences, Biographical Memoirs, vol. 12 (1970).

Additional Sources

Walter, Maila L., Science and cultural crisis: an intellectual biography of Percy Williams Bridgman (1882-1961), Stanford, Calif.: Stanford University Press, 1990.

Bridgman, Percy William (1882-1962) American physicist and Nobel prizewinner (1946). Bridgman wrote extensively on the philosophical implications of modern physics. He is inseparably linked with operationalism, or the view that each scientific concept is defined in terms of a set of empirical operations. However, he later modified this stark, and some say stifling, doctrine by allowing indirect connections between concepts and experience. Works include The Logic of Modern Physics (1927) and The Nature of Physical Theory (1936).

1882–1961, American physicist, b. Cambridge, Mass., grad. Harvard (B.A., 1904; Ph.D., 1908). From 1910 he taught at Harvard, as professor from 1919. He won the 1946 Nobel Prize in Physics for his work on the physics of high pressures. He is known also for his studies of electrical conduction in metals and properties of crystals and for his writings on the philosophy of modern science. His works include The Logic of Modern Physics (1927), The Nature of Physical Theory (1936), and Nature of Thermodynamics (1941).

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