Alternate Name

Baron Blackett of Chelsea

Born London, England, 18 November 1897

Died London, England, 13 July 1974

British experimental physicist Patrick Blackett received the 1948 Nobel Prize in Physics for the discovery among cosmic-ray secondaries of the particle now called the muon, confirmation of the positron (discovered by Carl Anderson ), and for the instrument development that made these possible. Blackett received his early education at Osborne and Dartmouth Naval Colleges and was commissioned as a midshipman at the outbreak of World War I, though he had not yet completed his education. He participated in the battles of the Falkland Islands and Jutland, rising to the rank of lieutenant. Blackett had decided by the end of the war to resign his commission and briefly visited the laboratory of James Franck at Göttingen, but the Navy sent him and about 400 other young officers up to Cambridge University for a 6-month course to complete their formal education, and within a few weeks, he decided to remain at Cambridge, completing first degrees in mathematics (part I of the tripos in 1919) and physics (part II of the tripos in natural sciences in 1921).

Ernest Rutherford had then just arrived in Cambridge, and Blackett began work with him on the study of collision processes using a Wilson cloud chamber as a detector, obtaining unambiguous evidence both for the disintegration of atomic nuclei and for the buildup of a heavy nucleus from the lighter ones. G. P. S. (Beppo) Occhialini (a student of Enrico Fermi) then arrived in Cambridge, also for a short visit that extended for many years. Together they modified the cloud-chamber technique to improve by a very large factor its efficiency for detection of cosmic-ray particles. Cloud chambers have a very low duty cycle, and the early ones, fired at random, often caught not even one cosmic-ray secondary particle. The improvement was a coincidence counter, above the chamber, which told the gas to expand, cool, and reveal particle tracks only when a particle had been seen coming.

In 1933, Blackett became professor of physics at Birkbeck College, London, where the discovery of the particle with the same charge as an electron, but much larger mass (the muon), occurred. In 1937, he was appointed to the Langworthy Professorship at the University of Manchester, following William L. Bragg. As war approached, Blackett joined the Tizard committee, endorsing the majority report that Britain should develop Watson-Watt’s radar for defense against enemy aircraft, and, later, the Maud committee, from which his minority report urged Britain to join with the United States in the development of atomic weapons as was eventually done rather than proceeding alone. He moved quickly through a variety of wartime positions, finally becoming director of Naval Operations Research (1942–1945), supervising work on bombsights, radar, antisubmarine measures, and much else, including convoy sizes (which he concluded should be as large as possible, rather than being limited to 60 vessels at most).

Blackett returned to Manchester in 1945 and implemented a large increase in the size of his department. He encouraged Bernard Lovell to set up trailers of ex-military radar equipment at Jodrell Bank, near Manchester, and made radio astronomy one of the subjects to be studied in his department. Later, he helped Lovell with plans for the construction of the 250-ft. steerable paraboloid and helped him through subsequent financial and political difficulties.

In 1947, Blackett suggested that the Earth’s magnetic field was a fundamental property of a rotating body and further suggested that the magnetic fields of rotating bodies (the Earth, the Sun, and the star 78 Virginis, the strong magnetic field of which had just been measured by Horace Babcock ) were roughly proportional to their angular momenta. A critical test of the idea was the measurement of very weak magnetic fields suitable in rotating laboratory objects, and Blackett was able to show that the suggested relationship was wrong. He then turned to the measurement of very weak magnetic fields in igneous rock (remanent fields) beginning in 1951. These paleomagnetic fields preserve the direction that the rocks had relative to the Earth’s magnetic field when they solidified. Blackett’s work showed that both the latitude of England and the orientation of the land had changed over the past 100 million years and so provided some of the early evidence in favor of plate tectonics and continental drift.

Blackett continued work in paleomagnetism as professor of physics at Imperial College, London, from 1953, in particular encouraging the work of Keith Runcorn and providing support for a critical conference in London in 1964 in which supporters and opponents of ideas about paleomagneticism and plate tectonics presented their opposing views, and more believers left the conference than had arrived. His own work continued, for instance, to reveal the correlations between ancient climates and ancient latitudes determined from rock magnetic measurement.

Blackett officially retired in 1965, being very soon thereafter elected president of the Royal Society (London) and appointed advisor to the new Ministry of Technology. Blackett received more than 20 honorary degrees and academy fellowships and prizes in addition to the Nobel Prize. He was invested with the British Order of Merit in 1967 and created a Life Peer (as Barson Blackett of Chelsea) in 1969.