Patrick Maynard Stuart Blackett
Blackett, Patrick Maynard Stuart
BLACKETT, PATRICK MAYNARD STUART
(Baron Blackett of Chelsea)
(b. Kensington, London, 18 November 1897; d. London, 13 July 1974), nuclear physics, cosmic-ray physics, cloud-chamber physics, geomagnetism and geophysics, operational research.
Blackett was one of the most versatile experimental physicists of his generation. He received the Nobel Prize in Physics in 1948 for his development in the 1920s and 1930s of new methods for using C. T. R. Wilson ’s cloud chamber and for his discoveries which included pair production of electrons and positrons in cosmic radiation. During the 1950s, Blackett undertook magnetic research that provided evidence from paleomagnetism in sedimentary rocks for the much-debated theory of continental drift. Blackett pioneered operational research during the Second World War, and he was an influential voice in government circles from the 1930s to the 1970s on matters of science and technology policy, science education, nuclear armaments, and British technical aid to India.
Nuclear Physics and the Cloud Chamber. Blackett entered Osborne Royal Naval College in 1910 and matriculated with other cadets to Dartmouth Royal Naval College in 1912. At these two schools, Blackett received what was probably the most intensive physical science and engineering secondary education available in England at the time. When war broke out in August 1914, Blackett and his fellow students were immediately sent into action. He fought in the Battle of Falkland Islands in 1914 and the Battle of Jutland in 1916, emerging from the war with the rank of lieutenant. In January 1919, the Admiralty sent him to Cambridge along with other officers whose study had been interrupted in 1914. Once he had settled into Magdalene College and visited the Cavendish Laboratory at Cambridge, Blackett found the prospect of studying mathematics and physics so appealing that he resigned from the navy in February 1919.
After earning his undergraduate degree in 1921 and gaining election to a Bye-Fellowship at Magdalene College, Blackett became a research postgraduate student under Ernest Rutherford in the autumn of 1921 at the Cavendish Laboratory. Assigned by Rutherford to modify an automatic cloud chamber for the study of alpha particles bombarding targets, Blackett worked diligently to perfect the instrument in the face of Rutherford’s impatience for results. When the volume of a cloud chamber suddenly expands, the temperature decreases and water droplets form on charged particles in the chamber. Blackett perfected a spring action linking the sudden expansion to a camera shutter so that a photograph is taken just as the expansion is completed. Peter Kapitza collaborated with him briefly in developing a powerful magnetic field around the chamber. At last, in the summer of 1924, Blackett obtained eight tracks (from twenty-three thousand photographs) showing the capture of an incident alpha particle by a nitrogen nucleus, creating an isotope of oxygen, and the path of a hydrogen ion (proton) ejected from the recoiling oxygen nucleus. These photographs were widely reprinted after that, and they made Blackett’s reputation at the age of twenty-seven.
In March 1924, Blackett married Costanza Bayon, a student of modern languages at Newnham College, Cambridge. Their daughter Giovanna was briefly a photographer before her marriage and their son Nicolas followed a career in medical physics, studying the effect of radiation on biological cells. Patrick Blackett spent the 1924–1925 academic year with the physicist James Franck in Göttingen and returned to Germany in 1930 for a summer in Berlin. There he met Bruno Rossi, who was thinking of ways to use the Geiger-Müller counter to detect charged particles in cosmic radiation, and Rossi suggested that Giuseppe P. S. Occhialini join Blackett in Cambridge to learn cloud-chamber techniques.
Blackett and Occhialini soon devised a counter-controlled cloud chamber in which the passage of charged particles through the plane of the cloud chamber triggered expansion of the chamber. While they were accumulating data and discussing its theoretical implications with Cambridge theoretical physicist Paul Dirac in the autumn of 1932, Carl Anderson at the California Institute of Technology announced his discovery, using a cloud chamber, of a positively charged electron and characterized this particle’s production as a rare event. In contrast, Blackett and Occhialini in a paper in February 1933 used their data explicitly to link this antielectron, or positron, to Dirac’s relativistic electrodynamics, a theoretical insight that had not occurred to Anderson. Blackett and Occhialini also demonstrated the existence of showers of positive and negative electrons in cosmic radiation. This was called the phenomenon of pair production. They further confirmed the reverse process, or annihilation, of electrons and positrons upon their collision with one another, in confirmation of Dirac’s theory of the electron. British newspapers attributed a revolutionary discovery to the Cavendish physicists, dubbing the new, tiny positive particle a “googlie” electron because, like a cricket ball, it breaks the wrong way. Although Blackett and Occhialini immediately received nominations for a Nobel Prize, it was Anderson who received part of the Nobel Prize in Physics in 1936, for discovery of the positron, sharing the award with Viktor Hess who had established the existence of cosmic radiation.
Blackett was a Fellow of King’s College from 1923 until 1933, when he moved to Birkbeck College in London to head the physics department and his own laboratory. In 1937, he succeeded William Lawrence Bragg in the physics chair at Manchester, a position that previously had been held by Rutherford. During the mid and late 1930s, Blackett’s research groups gathered additional evidence for
the cosmic-ray cascade or shower effect. Lively debate occurred in the mid-1930s over the identity of a particle that Anderson and Seth Neddermeyer called a mesotron or heavy electron, which Robert Serber and Robert Oppenheimer suggested was the theoretical particle predicted by Hideki Yukawa in 1935, even though the mesotron’s mass was lower than Yukawa’s prediction. Blackett initially questioned the interpretation of the mesotron, which later was renamed the mu-meson and eventually often shortened to muon. In 1947, Cecil Powell and his colleagues at Bristol found Yukawa’s particle and demonstrated that it (the pi-meson) decays into the mu-meson and a single neutral particle which they soon hypothesized to be a neutrino. In the same year, at Blackett’s laboratory in Manchester, George Rochester and Clifford Butler announced discovery of another new particle, evidenced by a V-shaped track, which they followed Blackett in interpreting as the product of decay of a heavy neutral (“strange”) particle.
The Second World War and Operational Research. In late 1934, Harry Wimperis, who was director of Scientific Research in the Air Ministry, joined others in setting up a Committee for the Scientific Survey of Air Defense, chaired by the chemist and rector of Imperial College, Henry T. Tizard. Blackett joined the committee, which advised the Air Ministry to give high priority to the development of radar for defense against future air attack. This argument prevailed over the objections of Oxford physics professor Frederick A. Lindemann (Lord Cherwell), who favored other kinds of defense technologies and who was to become Winston Churchill’s scientific advisor in 1939.
At the outbreak of the war in 1940, Blackett joined the instrument section of the Royal Aircraft Establishment, where he worked with Henry John James Braddick on the design of the Mark 14 bombsight, which eliminated the need for a level bombing run at the time of bomb release. In August 1940, Blackett became scientific advisor to General Frederick A. Pile in the Army’s antiaircraft command, organizing a group of scientists to study the operational use of radar sets, guns, and mechanical calculators for antiaircraft fire. Joining the Royal Air Force’s Coastal Command in March 1941, Blackett headed a group that recalculated the depth settings for antisubmarine explosives and applied mathematical techniques, such as the Poisson distribution, to settle tactical and strategic arguments within the command. At the Admiralty, from January 1942 to the summer of 1945, Blackett and “Blackett’s circus,” as it became known, brought about significant improvement in the use of airborne radar for finding German submarines that were sinking merchant ships in the Atlantic. This work often is credited as a turning point in the war during the summer of 1943, so that U.S. supplies and troops could reach England for the invasion of Europe.
Two reports that Blackett drafted in 1941 on the organization and methodology of operational research enjoyed broad circulation in Great Britain and the United States, earning Blackett the reputation as a founder of operational research. However, by the late 1950s, Blackett was expressing misgivings about the teaching of operational research as an academic specialty divorced from intimate everyday contact with military officers. He considered nuclear-war game theory inadequate on practical grounds and reprehensible on moral grounds. In addition, and more controversially, Blackett made public at the war’s end the arguments against saturation bombing of German cities that he had pressed in government circles during wartime. These arguments brought him into conflict during wartime and afterwards with Churchill’s scientific advisor Frederick Lindemann, who had favored large-scale bombing of German cities as a means of undermining German morale, although John Desmond Bernal and other scientists had data disputing the claim that British citizens’ morale was undermined following the Germans’ bombing of Hull and Birmingham.
In 1948, Blackett published the book The Military and Political Consequences of Atomic Energy, which appeared in slightly revised form in 1949 in the United States as a book-club choice under the title Fear, War and the Bomb. In this book Blackett criticized Lindemann’s strategy which, Blackett noted, had escalated from the incendiary bombing of Hamburg and Dresden to the nuclear bombing of Hiroshima and Nagasaki. He further debunked claims that bombs and the air force alone can win a war, whether with traditional bombs or nuclear bombs. Blackett also offered the then novel interpretation that the decision to use nuclear bombs in Japan owed more to fears in the United States of Soviet ambitions in Asia and Europe than to conviction that Japan would not otherwise surrender. He opposed the development of atomic weapons in Great Britain, bringing him into conflict with the policy of his own Labour Party under Clement Attlee. These views led some of Blackett’s opponents to characterize him as a Soviet sympathizer and communist fellow traveler.
The Earth’s Magnetism and Continental Drift. After the war, new fields of study opened up for Blackett and his collaborators in the Manchester physics department. With Blackett’s support, Bernard Lovell located a radar facility at Jodrell Bank, twenty miles south of Manchester, and turned it into an observatory for radio astronomy that would become world famous. While some of his Manchester colleagues, including Rochester and Butler, continued cosmic-ray studies, Blackett became enthusiastic for a program of research that revived the hypothesis that the magnetic fields of the Sun, stars, and the Earth are fundamental properties of their rotating masses. His presentation at the Royal Society in May 1947 of a simple equation, including Newton’s constant of universal gravitation and the speed of light, led journalists to compare his new work with Einstein’s theory of relativity.
In 1952, in a tour-de-force paper titled “A Negative Experiment Relating to Magnetism and the Earth’s Rotation,” Blackett announced that he had failed to confirm this rotational theory of magnetism, following a series of experiments using a magnetometer which he had designed to detect minuscule magnetic effects in a rotating cylinder. He noted the suitability of his magnetometer for investigating remanent magnetism (paleomagnetism) in sedimentary rocks, a research program that resulted in a new kind of evidence for Alfred Wegener’s 1912 hypothesis of continental drift, which had largely languished in the previous few decades. Stanley Keith Runcorn, Edward A. Irving, and John A. Clegg were among those who subsequently worked with Blackett’s magnetometer or its successor instruments to gather data that converged in the 1960s with evidence leading to a theory of plate tectonics for explaining the continents’ past and present motions. Blackett’s work was important in convincing many skeptics that continental drift was a conjecture that could be tested. His group’s researches on paleomagnetism, along with his enthusiastic support of empirical studies of pale-olatitudes (or the locations of the latitudes of land masses in ancient times) and paleoclimates, played a huge role in the revival of the theory.
Leadership and Politics. In 1954, Blackett left Manchester for Imperial College in London, where he implemented a new strategy of a multiprofessorial department as he aimed to create an urban scientific educational and research institution that would equal the old universities of Cambridge and Oxford. In that year he declined to be a candidate to succeed Bragg as director of the Cavendish Laboratory. Throughout the 1940s and 1950s, Blackett was a forceful advocate of university expansion and government funding of research and development as a member of the Barlow Committee (1945–1946), the council and the research-grants committee of the Department of Scientific and Industrial Research (1956–1960), and the National Research and Development Corporation (1949–1964). He was dean of the Faculty of Science (1948–1950) and pro-vice-chancellor (1950–1952) at Manchester; and then dean of the Royal College of Science (1955–1960) and pro-rector (1961–1964) in London. Formally retiring from Imperial College and the University of London in September 1965, he served as president of the Royal Society from 1965 to 1970.
Blackett had Fabian and socialist political allegiances dating from his undergraduate years, and he was strongly associated publicly with the views of J. D. Bernal and others who advocated the social responsibility of the scientist and strong government support of science, although Blackett was himself not a Marxist. He was an active member and president (1943–1946) of the trade unionist British Association of Scientific Workers. From 1953 to 1963, he met with a group of scientists, including Bernal and Charles Percy Snow, that advised Hugh Gaitskell, when Gaitskell was leader of the Labour Party, and then advised the future prime minister Harold Wilson and his Shadow Minister for Education Richard H. S. Crossman. Under Wilson’s Labour Party government, Blackett was science advisor in the Ministry of Technology from 1964 to 1969.
Blackett’s maternal grandfather Charles Maynard had served in India at the time of the Indian mutiny in 1857, and his uncle William Maynard had been a tea planter in India. After Blackett first traveled to India in 1947, he became increasingly concerned with the gap between rich and poor and with the need to improve conditions in poorer countries through applications of science and technology. Blackett stirred up considerable protest when he put forward these ideas in his presidential address at the Dublin meeting of the British Association for the Advancement of Science in 1957. Blackett was a close friend of the Cambridge-educated Indian physicist Homi Bhabha, and he became a military and scientific advisor to Jawaharlal Nehru’s Indian government.
Blackett never took a PhD. He held twenty honorary degrees and was an member of academic or other institutions in eleven countries, including the Soviet Union and China. In 1956, he was appointed to the Order of the Companions of Honour and in 1967 to the Order of Merit. In 1969, while President of the Royal Society, he received a life peerage, an honor that he had declined five years earlier. In an obituary essay in Nature, Sir Edward Bullard recalled Blackett’s quip that, at any rate, he had remained Mr. Blackett until after he retired. Tall and slim, always described as handsome, Blackett was said to be both formidable and charming. The grandson of a vicar on his father’s side, Blackett respected religious observances that were established social customs, but described himself as agnostic or atheist.
In the official presentation speech of the Nobel Prize in Physics to Blackett in 1948, the experimental physicist Gustaf Ising noted that the prize may be awarded for discovery or invention and that the award to Blackett was motivated on both grounds. At the Nobel banquet in 1948, Gustaf Hellström spoke of Blackett’s active part in two world wars and of his dedication to scientific discovery following each war. Blackett replied by discussing the paradoxes faced by scientists who pursue pure science, only to find that their discoveries make possible terrible catastrophes. Faithful to the principles that he maintained throughout his scientific career, Blackett challenged his Stockholm audience to recognize that it is the task of scientists and citizens to insure that scientific knowledge is used for the good of humanity and not its destruction. After becoming Baron Blackett of Chelsea in 1969, Blackett spoke four times in the House of Lords, using this new forum to warn against the widening gap between rich and poor. Frail in the last two years of life, Blackett died in hospital in July 1974.
WORK BY BLACKETT
With Giuseppe P. S. Occhialini. “The Ejection of Protons from Nitrogen Nuclei, Photographed by the Wilson Method.”Proceedings of the Royal Society, Series A, 107 (1925): 349–360.
“Some Photographs of the Tracks of Penetrating Radiation.”Proceedings of the Royal Society, Series A, 139 (1933): 699–726.
“The Craft of Experimental Physics.” In University Studies, edited by Harold Wright. London: I. Nicholson & Watson, 1933.
The Military and Political Consequences of Atomic Energy.London: Turnstile Press, 1948. Revised as Fear, War and the Bomb: Military and Political Consequences of Atomic Energy.
“A Negative Experiment Relating to Magnetism and the Earth’s Rotation.” Philosophical Transactions of the Royal Society, series A, 245 (1952): 309–370.
“Comparison of Ancient Climates with the Ancient Latitudes Deduced from Rock Magnetic Data.” Proceedings of the Royal Society, Series A, 263 (1961): 1–30.
Studies of War: Nuclear and Conventional. Edinburgh: Oliver and Boyd, 1962.
Bullard, Sir Edward C. “Patrick Blackett …; An Appreciation.” Nature 250 (1974): 370.
Bustamante, Martha Cecilia. “Blackett’s Experimental Researches on the Energy of Cosmic Rays.” Archives Internationales d’Histoire des Sciences, 47 (1997): 108-141.
Butler, Clifford. “Recollections of Patrick Blackett, 1945–1970.” Notes and Records of the Royal Society of London 53 (1999): 143-156.
Hore, Peter, ed. P. M. S. Blackett: Sailor, Scientist, Socialist.London: Frank Cass, 2003.
Lovell, [Sir] Bernard. “Patrick Maynard Stuart Blackett, Baron Blackett, of Chelsea.” Biographical Memoirs of Fellows of the Royal Society 21 (1975): 1-113. Includes bibliography of Blackett’s publications. “The Nobel Prize in Physics 1948.” Available from http://nobelprize.org/physics Includes presentation and banquet remarks.
Nye, Mary Jo. Blackett: Physics, War, and Politics in the Twentieth Century. Cambridge, MA: Harvard University Press, 2004.
Rau, Erik P. “Technological Systems, Expertise, and Policy Making: The British Origins of Operational Research.” In Technologies of Power: Essays in Honor of Thomas Park Hughes and Agatha Chipley Hughes, edited by Michael Thad Allen and Gabrielle Hecht. Cambridge, MA: MIT Press, 2001: 215-252.
Mary Jo Nye