Anderson, Carl David
ANDERSON, CARL DAVID
Anderson was awarded the Nobel Prize in Physics in 1936 for the discovery of antimatter, in particular the positive electron, or positron. Just one year later, he was promoted to associate professor of physics at the California Institute of Technology (Caltech), in Pasadena, California, and in 1939 he became a full professor.
Winning the Nobel Prize came as a considerable surprise to Anderson. Unbeknownst to him he had been nominated for it by Caltech’s chief administrative officer and unofficial president Robert A. Millikan (himself a physics laureate in 1923), and Anderson had to borrow $500 from Millikan just to be able to go to Stockholm and get his share of the award, which amounted to $20,000. He shared the prize with Victor Franz Hess of the University of Innsbruck, who was honored for his work in cosmic rays.
Anderson was a quiet, unassuming man. As a graduate student at Caltech, he signed up to take a course in quantum theory from the theoretical physicist J. Robert Oppenheimer, who was then dividing his time between the physics departments at Caltech and the University of California, Berkeley. About forty people were following the course. Oppenheimer, who was not yet the eloquent speaker he would later become, would mumble his way through lectures, writing a squiggle, or part of an equation, on whatever part of the board happened to be handy. It was all too much for Anderson, who went to see Oppenheimer to tell him he was dropping the course. Anderson later recalled the incident in his autobiography, reporting that Oppenheimer urged him to stay, promising that by the end of the term “everything will be all right” (Anderson, 1999, p. 18). When he asked why it was so important that he not drop the course, he was told it was because he was the only registered student.
Anderson was born in New York City in 1905, the only child of Carl David Anderson, a chef, and Emma Adolfina Ajaxson, both of whom grew up on farms near Stockholm and came to America around 1900, in their late teens. (Their son, Carl, learned Swedish at home, and was able to converse with the king of Sweden comfortably in that language when he accepted his Nobel Prize in Stockholm at the age of thirty-one.) In 1912 the family moved to Los Angeles, where Anderson attended grade school and Los Angeles Polytechnic High School, from which he graduated in 1923. By then his parents had separated and he continued to live at home with his mother for many years. In 1923 he enrolled at Caltech, hoping to become an electrical engineer, but in his sophomore year a course in modern physics with Ira Bowen turned him into physics major.
Discovery of the Positron. After receiving his BS in 1927, Anderson remained on campus as a graduate student, working under Millikan on the emission of electrons induced by bombarding various gases with x-rays. He received his PhD magna cum laude in 1930 and stayed on at Caltech as a research fellow, working with Millikan on cosmic rays. Initially, Millikan had urged him to go elsewhere to broaden his research experience, and, accordingly, Anderson had applied for and won a National Research Council fellowship to work under Arthur H. Compton at the University of Chicago. But Millikan then had a change of heart and convinced Anderson to stay on at Caltech, where Anderson spent his entire career.
Millikan’s newfound interest in the study of cosmic rays accounted for his sudden determination to hang on to the talented Anderson. Millikan was convinced (inaccurately, as it turned out) that cosmic rays, a term that he himself coined in 1925 for the penetrating radiation bombarding Earth from all directions, were the birth pangs of new elements being formed out in space. In order to prove this hypothesis, he needed accurate measurements of their energies. He established three research efforts at Caltech in the new field, each using a different type of detector: one under Victor Neher using electroscopes, one under William Pickering using Geiger counters, and one under Anderson using cloud chambers in a magnetic field. Anderson’s investigations paid off almost immediately, but not exactly as Millikan had foreseen.
Anderson built his magnetic cloud chamber (designed entirely by him) in the Guggenheim Aeronautical Laboratory on the Caltech campus, where the generator that powered the wind tunnel provided enough electricity to handle 600 kilowatts. The giant magnet, which took Anderson many months to build, consisted of eight hundred turns of copper tubing laboriously wound into two coils welded together to carry electrical current and cooling water. In a cloud chamber, a supersaturated vapor is caused, by a sudden change in pressure, to form visible droplets on the track left behind by a fast moving charged particle. A handmade camera inserted in a square hole at one end of the magnetic pole piece allowed Anderson to record the curved tracks of condensation left by an electron or any other charged particle. Incoming cosmic-ray particles entering the field would curve to the left if they were negatively charged or to the right if they were positive. In the very first experiments in 1931 and 1932, Anderson saw the deflected tracks of as many positive as negative cosmic-ray particles. At this time, scientists had identified two elementary particles of matter: negatively charged electrons, and positively charged nuclei. Anderson and Millikan initially disagreed over whether the vivid tracks they observed in Anderson’s much-improved cloud chamber were actually negative charges moving downward (Millikan’s view) or positives moving upward (Anderson’s view), but Anderson finally settled the question by placing a lead plate in the path of the particles. They would have more energy and therefore less curvature before passing through the plate than after, when they would be slower and therefore curve more. On 2 August 1932, these efforts were rewarded by a clear track left by a particle moving upward through the plate and curving to the left, meaning it was positively charged, but with a degree of ionization in the cloud chamber gas that indicated that the particle had the mass of an electron. This event marked the entirely unexpected discovery of the positive electron.
One month later, pushed by Millikan to establish the priority of his findings quickly, Anderson published a brief report on “The Apparent Existence of Easily Deflectable Positives,” in Science; the definitive results and famous photograph (“it’s got to be a positive electron,” Anderson later recalled thinking) appeared in Physical Review in 1933. The physics world expressed skepticism. However, a relativistic theory by the Cambridge University theorist Paul A. M. Dirac, published in 1930, had predicted the existence of a positive electron, and the evidence on Anderson’s photographic plate was unimpeachable. Anderson’s result was soon confirmed by Dirac’s Cambridge colleagues Paul M. S. Blackett and Giuseppe P. S. Occhialini, who in a March 1933 paper in the Proceedings of the Royal Society reported similar results and proposed the mechanism of pair production to account for their existence. They postulated that when an energetic gamma ray was converted into matter, it would emit a negatively charged electron, balanced by Dirac’s positively charged positron (as the positive electron came to be called). Asked once by an interviewer if Dirac’s theory had influenced the direction of his research, Anderson replied, “I don’t know whether the existence of Dirac’s work had any effect at all on the work I was doing. I was looking at the cloud chamber data and going by that.”
James Chadwick reported the discovery of the neutron in 1932. With the neutron and the positron as two new fundamental particles of matter, the physics world suddenly looked considerably more complicated than it had previously seemed, a trend that has continued to the present day.
Mu-Meson Research. Anderson, together with his first graduate student, Seth Henry Neddermeyer, went on to discover two more elementary particles, which came to be called the positive and negative mu-mesons, or muons. Unlike his discovery of the positron, these discoveries were not due to mere chance, but were rather the result of much hard work, a great deal of it carried out at the summit of Pikes Peak in Colorado, where the cosmic-ray flux was considerably stronger than at sea level. The research also had to be done on a shoestring budget. It was the height of the Depression and funds were scarce. Anderson and Neddermeyer started by buying a 1930 flatbed truck for $400. They mounted the cloud chamber on it and transported it with great difficulty to the top of Pikes Peak (in point of fact they had to be towed up the mountain— the ancient truck just could not make it). They also brought along a Cadillac motor generator, but it would not produce adequate power at 4,300 meters (14,000 feet). When they took the generator to Colorado Springs to be fixed, the old truck broke down.
Fortunately, at this dismal point in the story, a savior appeared in the form of a General Motors vice president accompanying the test-drive of a new truck to the top of Pikes Peak. Hearing the two scientists’ tale of woe, he kindly arranged for their truck to be towed back up the mountain, and had the engine replaced. That did not end their difficulties, but it was certainly a timely intervention.
Anderson and Neddermeyer subsequently took thousands of pictures and discovered among them the clear tracks of both positively and negatively charged particles that were too heavy to be electrons and too light to be protons. In fact they had found the mu-meson, whose discovery was first presented by Anderson at a physics colloquium at Caltech on 12 November 1936, followed by a short note in
Science (“we hemmed and hawed about it in the ’36 publication,” Anderson told an interviewer in 1966). In the absence of a theoretical framework that could explain the existence of two new elementary particles of intermediate mass, Anderson and Neddermeyer adopted a cautious and conservative approach. The formal announcement followed in the 15 May 1937 issue of Physical Review, but only after Anderson and Neddermeyer had taken an additional six thousand photographs of cosmic-ray particles in Anderson’s cloud chamber as additional proof that the pair of new particles really existed. Anderson later recalled that he provided the first reference in the physics literature to the new particles in the closing line of his 12 December 1936 Nobel lecture in Stockholm, where he said, “These highly penetrating particles, although not free positive and negative electrons, will provide interesting material for future study.” Unfortunately, the world of physics had no place for these new particles, and their precise nature and significance remained a mystery until after World War II.
World War II ushered in a change in Anderson’s activities. According to Anderson’s autobiography, when Arthur H. Compton approached him informally in May 1942 concerning his possible availability to head the Manhattan Project—which produced the atomic bomb— Anderson replied that he did not wish to be considered, largely because he could not afford to support two households, one for his ailing mother in Pasadena, and another for himself in a distant city. In February 1943, that job went to his former teacher, Oppenheimer, while Anderson joined the solid-propellant rocket project headed by Charles C. Lauritsen, another Caltech professor. In 1941 Caltech had contracted with President Franklin Roosevelt’s new National Defense Research Committee for the development and testing of land and aircraft rocket projectiles for the U.S. Navy. In particular, Anderson worked on how to fire various types of Caltech artillery rockets from military aircraft, and he was successful enough to be flown to Europe in June 1944 to supervise the installation of rockets on Allied fighter planes.
When the war came to an end, so did Anderson’s bachelorhood. In 1946 he married Lorraine Bergman, who had been married once before and had a three-year-old son, Marshall David, whom Anderson adopted. The couple settled in San Marino, not far from Caltech, and had a son, David Anderson, born in 1949.
With the war over, Anderson resumed his studies of cosmic rays. His research group included Robert Leighton and Eugene Cowan, both of whom would become Caltech professors, and Donald Glaser, who would win the Nobel Prize in 1960 for his 1952 invention of the bubble chamber, a novel type of particle detector. The team’s work turned up a variety of baffling new elementary particles, which would collectively be dubbed the “strange” particles by Anderson’s Caltech colleague Murray Gell-Mann, but by the late 1950s particle accelerators had begun to replace cosmic rays as the preferred source of these high energy phenomena, and Anderson moved increasingly into administrative work. In 1962 he became head of Caltech’s Division of Physics, Mathematics, and Astronomy, a job he held until 1970. During his chairmanship, two Caltech faculty won Nobel Prizes in physics: Richard Feynman in 1965, and Gell-Mann in 1969. Anderson himself won numerous honors in addition to his Nobel, including the Gold Medal of the American Institute of the City of New York (1935), the Presidential Certificate of Merit (1945), the Elliott Cresson Medal of the Franklin Institute (1937), and the John Ericsson Medal of the American Society of Swedish Engineers (1960).
In 1979, Anderson recorded an oral history for the Caltech archives. Asked about his research activities in later life, Anderson replied, “I did try to do some research, even after retiring as division chairman … under some difficulties because I was near enough at that time to retirement so I could not expect to take on graduate students…;. So I did some minor work that had nothing to do with particle physics, but it did have to do with things that I had thought about for many, many years but were less important than what I was doing at that time, namely working with cosmic rays and particles.” These last experiments, he added, did not provide the same psychic enjoyment as his earlier work and he stopped doing research completely in 1976 when he became Board of Trustees Professor of Physics, Emeritus. A fan of auto racing and automobiles from a very early age, Anderson drove a sporty convertible long after he retired. He was also a ham radio operator (call sign W6KGR), dabbled in real estate, and belonged to the Twilight Club, an exclusive private club to which Millikan and other prominent Pasadena men belonged. Anderson was nearly 80 when he started to write an account of his life. The manuscript, finished in 1991, shortly before his death, was published in 1999, eight years later.
The Archives of the California Institute of Technology holds a selection of Anderson’s papers, including lecture and technical notes, plates and prints of cloud-chamber photographs, and portions of the apparatus used by Anderson in his discoveries of the positron and the mu-meson. The Archives also contains a 1979 oral history interview in eight sessions with Anderson by Harriett Lyle and a transcript of a more technically focused interview by Charles Weiner in 1966.
WORKS BY ANDERSON
“The Apparent Existence of Easily Deflectable Positives.” Science 76, no. 1967 (1932): 238–239.
With Robert Andrews Millikan. “Cosmic-Ray Energies and Their Bearing on the Photon and Neutron Hypotheses.” Physical Review 40 (1932): 325–328.
“The Positive Electron.” Physical Review43 (1933): 491–494.
“The Production and Properties of Positrons.” In Les Prix Nobel, vol. 9, Les Prix Nobel en 1936. Stockholm: Imprimerie Royale, 1937.
With Seth H. Neddermeyer. “Nature of Cosmic-Ray Particles.”Reviews of Modern Physics 11 (1939): 191–207.
“Early Work on the Positron and Muon.” American Journal of Physics 29 (1961): 825–830.
The Discovery of Anti-Matter: The Autobiography of Carl DavidAnderson, the Youngest Man to Win the Nobel Prize. Edited by Richard J. Weiss. Singapore: World Scientific, 1999.
Brown, Laurie M. “Nuclear Forces, Mesons, and Isospin Symmetry.” In Twentieth Century Physics, vol. 1, edited by Laurie M. Brown, Abraham Pais, and Brian Pippard. Bristol, U.K., and Philadelphia: Institute of Physics Publishing; New York: American Institute of Physics, 1995.
Brown, Laurie M., and Lillian Hoddeson, eds. The Birth of Particle Physics. Cambridge, U.K.: Cambridge University Press, 1983.
Goodstein, Judith R. Millikan’s School: A History of the California Institute of Technology. New York: W. W. Norton, 1991.
Kevles, Daniel J. The Physicists: The History of a ScientificCommunity in Modern America. Cambridge, MA: Harvard University Press, 1995. First issued in 1978 and still a very readable account of Anderson’s research program.
New York Times. “Carl Anderson, 85, Nobelist, Dies; Discovered the Positive Electron.” 12 January 1991.
Schwarz, John. “Fifty Years of Antimatter.” Engineering & Science 46, no. 2 (1982): 24–25. A special issue of the Caltech magazine on the fiftieth anniversary of the discovery of the positron.
Stuewer, Roger H., ed. Nuclear Physics in Retrospect: Proceedings of a Symposium on the 1930s. Minneapolis: University of Minnesota Press, 1979.
David L. Goodstein
Judith R. Goodstein
Anderson, Carl David
The American physicist Carl David Anderson opened up the entire field of particle physics, the study of the atom, the smallest unit of matter. Because of his discoveries of the positron (positive electron) and the meson (similar to the negative electron), two particles that make up the atom, Anderson was awarded the Nobel Prize in Physics in 1936.
Childhood and education
On September 3, 1905, Carl David Anderson was born in New York, New York. He was the only child of Swedish parents, Carl and Emma Anderson. When he was a child Anderson wanted a career in athletics, as a high jumper. The Anderson family moved to Los Angeles, where Carl David attended Los Angeles Polytechnic High School and first became interested in science. In 1924 he entered the California Institute of Technology (Cal Tech), with which he would remain associated throughout his life. In 1927 Anderson received his bachelor's degree. He then continued his education in graduate school on a research grant, centering his graduate work on physics and mathematics.
As a teacher Anderson obtained a doctorate degree with honors in 1930 under the physicist R. A. Millikan (1868–1953), who was awarded the Nobel Prize in 1923 for his work in physics. After working with Millikan at Cal Tech as a researcher for three years, Anderson was promoted to assistant professor in 1933. He eventually worked his way to chairman of the Division of Physics, Mathematics, and Astronomy in 1962.
Discovery of the positron
In the years immediately after Anderson received his degree, he discovered the positron, or positive electron—a revolutionary discovery, because the positron became the first known antiparticle (the oppositely charged particles of an atom) and the first known positively charged particle other than the proton. Anderson made his discovery during his and Millikan's quest to determine the nature of cosmic rays (positive particles from outer space) by allowing the rays to pass through a Wilson cloud chamber (a device used to detect elementary particles) in a strong magnetic field. By 1931 he had found evidence indicating that the rays produced charged particles whose tracks were very similar to those produced by ordinary electrons, except that they were bent by the magnetic field in the opposite direction. His famous photograph taken on August 2, 1932, clearly displayed a positron crossing a lead plate placed in the cloud chamber.
The following spring P. M. S. Blackett (1897–1974) and G. P. S. Occhialini were working independently at the Cavendish Laboratory in England. They produced a number of cloud chamber photographs indicating that a gamma-ray photon (electromagnetic energy) interacting with the intense electromagnetic field surrounding a nucleus, the center part of an atom, can create a positron-electron pair—that is, matter (anything that has mass and occupies space). They also recognized, as Anderson at the time had not, that Anderson's positron was the same particle that had been predicted by P. A. M. Dirac's (1902–1984) 1928 relativistic quantum-mechanical theory of the electron, a theory that described the structure of the atom. (Many physicists had believed Dirac's theory to be imperfect because it used the yet-undiscovered positron.) Work by Anderson and others established beyond doubt the proper experimental conditions for the creation and destruction of positrons.
In 1936 Anderson made a second important experimental discovery: the existence of a charged particle in cosmic radiation (rays from the sun) with a mass (an amount of matter) of about 200 electron masses, or of about one-tenth the mass of a proton. Anderson named these particles mesotrons (later shortened to mesons). He believed them to be identical to the nuclear particle H. Yukawa (1907–1981) had theoretically predicted less than two years earlier. It was later realized, however, that Anderson's meson is actually the mu meson (or muon), and Yukawa's meson is actually the pi meson (or pion). After World War II (1939–45) Anderson continued to develop the field of particle physics, which his groundbreaking 1932 discovery had opened up for research.
Anderson received many honors, beginning at just thirty-one years of age with the Nobel Prize for Physics in 1936, which he shared with V. F. Hess (1883–1964). Anderson received several honorary doctoral degrees and became a member of the National Academy of Sciences.
In 1946 he married Lorraine Elvira Bergman. The Andersons had two sons, Marshall and David. Anderson maintained his research and teaching activities until his retirement in 1976. He died in San Marino, California on January 11, 1991, at the age of eighty-five.
For More Information
Heathcote, Niels H. de V. Nobel Prize Winners in Physics, 1901–1950. New York: H. Schuman, 1953.
Weiss, Richard J., ed. The Discovery of Anti-Matter: The Autobiography of Carl David Anderson, the Youngest Man to Win the Nobel Prize. River Edge, NJ: World Scientific Pub. Co, 1999.
Carl David Anderson
Carl David Anderson
The American physicist Carl David Anderson (1905-1991) opened up the whole field of particle physics for research by his discoveries of the first known antiparticle, the positron, and of the meson.
On September 3, 1905, Carl Daveid Anderson was born in New York City of Swedish ancestry. He attended Los Angeles Polytechnic High School and in 1924 entered the California Institute of Technology, with which he would be associated throughout his life. In 1927 Anderson received his bachelor's degree, and then continuing in graduate school as a Coffin research fellow and next as a teaching fellow, he obtained a doctorate magna cum laude in 1930 under the physicist and Nobel laureate R. A. Millikan. After working with Millikan at Cal Tech as a research fellow for 3 years, Anderson was promoted to assistant professor in 1933, to associate professor in 1937, to full professor in 1939, and to chairman of the Division of Physics, Mathematics, and Astronomy in 1962.
In 1946 he married Lorraine Elvira Bergman. The Andersons had two sons, Marshall and David.
Discovery of the Positron
In the years immediately after receiving his doctorate Anderson discovered the positron, or positive electron—a revolutionary discovery because the positron became the first known antiparticle and the first known positively charged particle other than the ordinary proton. Anderson made his discovery during his and Millikan's quest to determine the nature of cosmic rays by allowing them to pass through a Wilson cloud chamber immersed in a strong magnetic field. By 1931 he had found evidence indicating that the rays produced charged particles whose tracks are very similar to those produced by ordinary electrons, except that they are bent by the magnetic field in the opposite direction.
Several explanations of these oppositely bent tracks were possible: that they were due to low-energy protons; that they were due to ordinary electrons moving backward; or that they were due to positive electrons. Although the last hypothesis was the most logical, it was also the most radical, and only after Anderson (with the help of S. Neddermeyer) was able to eliminate definitely the first two did he feel compelled to accept the third. His famous photograph taken on August 2, 1932 unambiguously displayed a positron traversing a lead plate placed in the cloud chamber.
By the following spring, P. M. S. Blackett and G. P. S. Occhialini, working independently at the Cavendish Laboratory in England, produced a number of cloud chamber photographs indicating that a positron-electron pair—that is, matter—can be created by a gamma-ray photon (electromagnetic energy) interacting with the intense electromagnetic field surrounding a nucleus. They also recognized, as Anderson at the time had not, that Anderson's positron was the same particle that had been predicted by P. A. M. Dirac's 1928 relativistic quantum-mechanical theory of the electron. (Many physicists had believed Dirac's theory to be imperfect because it entailed the yet unobserved positron!) Subsequent work by Anderson and others established beyond doubt the proper experimental conditions for the materialization and annihilation of positrons.
In 1936 Anderson, again aided by Neddermeyer, made a second important experimental discovery: the existence in cosmic radiation of a very penetrating charged particle with a mass of about 200 electron masses, or of about one-tenth the mass of a proton. Anderson named these intermediate-mass particles mesotrons (later shortened to mesons) and believed them to be identical to the nuclear particle H. Yukawa had theoretically predicted less than 2 years earlier. It was later realized, however, that Anderson's meson is actually the mu meson (or muon), and Yukawa's meson is actually the pi meson (or pion). After World War II Anderson continued to cultivate the field of particle physics, which his momentous 1932 discovery had opened up for research.
Anderson received many honors, beginning, at just 31 years of age, with the Nobel Prize for Physics in 1936, which he shared with V. F. Hess. Anderson's contributions to the war effort earned him the Presidential Certificate of Merit in 1945. He received several honorary doctoral degrees and became a member of the National Academy of Sciences.
Anderson maintained his research and teaching activities until his retirement in 1976 with the title professor emeritus. He died in San Marino, California on January 11, 1991, at the age of 85.
There is a brief biography of Anderson as well as his own description of his prize-winning work in a Nobel Foundation publication, Nobel Lectures Including Presentation Speeches and Laureates' Biographies: Physics, 1922-1941 (1965). Niels H. de V. Heathcote, Nobel Prize Winners in Physics, 1901-1950 (1953), contains a short biography of Anderson. A historical-philosophical treatment of Anderson's discovery is in Norwood R. Hanson, The Concept of the Positron (1963). □