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Sir Harold Jeffreys (22 April 1891 – 18 March 1989) was a mathematician, statistician, geophysicist, and astronomer.

He was born in Fatfield, County Durham, England. He studied at Armstrong College in Newcastle upon Tyne, then part of the University of Durham but later to become the University of Newcastle. He then went to St John's College, Cambridge and became a fellow in 1914. At Cambridge University he taught mathematics, then geophysics and finally became the Plumian Professor of Astronomy.

He married another mathematician and physicist, Bertha Swirles (1903-1999), in 1940 and together they wrote Methods of Mathematical Physics.

Among his other contributions was a Bayesian approach to probability (also see Jeffreys prior), and the idea that the Earth's planetary core was liquid. He was knighted in 1953.

Jeffreys received the Gold Medal of the Royal Astronomical Society in 1937.

He should not be confused with William H. Jefferys who is also both an astronomer and a Bayesian.

References

• David Howie, "Interpreting Probability: Controversies and Developments in the Early Twentieth Century" (Cambridge University Press, 2002)
• Maria Carla Galavotti. "Harold Jeffreys' Probabilistic Epistemology: Between Logicism And Subjectivism". British Journal for the Philosophy of Science, 54(1):43-57 (March 2003). (A review of Jeffreys' approach to probability; includes remarks on R.A. Fisher, Frank P. Ramsey, and Bruno de Finetti. Also online: [1])
• Bertha Swirles, Reminiscences and Discoveries: Harold Jeffreys from 1891 to 1940, Notes and Records of the Royal Society of London, Vol. 46, No. 2, pp. 301-308 (1992). [2]