Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American physicist who received the Nobel Prize in Physics in 1939 for his invention of the cyclotron. He is known for his work on uranium-isotope separation for the Manhattan Project, as well as for founding the Lawrence Berkeley National Laboratory and the Lawrence Livermore National Laboratory.
A graduate of the University of South Dakota and University of Minnesota, Lawrence obtained a PhD in physics at Yale in 1925. In 1928, he was hired as an associate professor of physics at the University of California, Berkeley, becoming the youngest full professor there two years later. In its library one evening, Lawrence was intrigued by a diagram of an accelerator that produced high-energy particles. He contemplated how it could be made compact, and came up with an idea for a circular accelerating chamber between the poles of an electromagnet. The result was the first cyclotron.
Lawrence went on to build a series of ever larger and more expensive cyclotrons. His Radiation Laboratory became an official department of the University of California in 1936, with Lawrence as its director. In addition to the use of the cyclotron for physics, Lawrence also supported its use in research into medical uses of radioisotopes. During World War II, Lawrence developed electromagnetic isotope separation at the Radiation Laboratory. It used devices known as calutrons, a hybrid of the standard laboratory mass spectrometer and cyclotron. A huge electromagnetic separation plant was built at Oak Ridge, Tennessee, which came to be called Y-12. The process was inefficient, but it worked.
After the war, Lawrence campaigned extensively for government sponsorship of large scientific programs, and was a forceful advocate of "Big Science", with its requirements for big machines and big money. Lawrence strongly backed Edward Teller's campaign for a second nuclear weapons laboratory, which Lawrence located in Livermore, California. After his death, the Regents of the University of California renamed the Lawrence Livermore National Laboratory and Lawrence Berkeley National Laboratory after him. Chemical element number 103 was named lawrencium in his honor after its discovery at Berkeley in 1961.
Ernest Orlando Lawrence was born on August 8, 1901 in Canton, South Dakota. His parents, Carl Gustavus (1871–1954) and Gunda Regina Jacobson (1874–1959), were both the offspring of Norwegian immigrants who had met while teaching at the high school in Canton, where his father was also the superintendent of schools. He had a younger brother, John H. Lawrence, who would become a physician, and was a pioneer in the field of nuclear medicine. Growing up, his best friend was Merle Tuve, who would also go on to become a highly accomplished physicist.
Lawrence attended the public schools of Canton and Pierre, then enrolled at St. Olaf College in Northfield, Minnesota, but transferred after a year to the University of South Dakota in Vermillion. He completed his bachelor's degree in chemistry in 1922, and his M.A. in Physics from the University of Minnesota in 1923 under the supervision of William Francis Gray Swann. For his master's thesis, Lawrence built an experimental apparatus that rotated an ellipsoid through a magnetic field.
Lawrence followed Swann to the University of Chicago, and then to Yale University in New Haven, Connecticut, where Lawrence completed his Ph.D. in Physics in 1925 as a National Research Fellow, writing his doctoral thesis on the photoelectric effect in potassium vapor. He was elected a member of Sigma Xi, and, on Swann's recommendation, received a National Research Council fellowship. Instead of using it to travel to Europe, as was customary at the time, he remained at Yale University with Swann as a researcher.
With Jesse Beams from the University of Virginia, Lawrence continued to research the photoelectric effect. They showed that photoelectrons appeared within 2 × 10−9 seconds of the photons striking the photoelectric surface—close to the limit of measurement at the time. Reducing the emission time by switching the light source on and off rapidly made the spectrum of energy emitted broader, in conformance with Werner Heisenberg's uncertainty principle.
In 1926 and 1927, Lawrence received offers of assistant professorships from the University of Washington in Seattle and the University of California at a salary of $3,500 per annum (equivalent to $64,900 in 2025). Yale promptly matched the offer of the assistant professorship, but at a salary of $3,000. Lawrence chose to stay at the more prestigious Yale, but because he had never been an instructor, the appointment was resented by some of his fellow faculty, and in the eyes of many it still did not compensate for his South Dakota immigrant background.
Lawrence was hired as an associate professor of physics at the University of California in 1928. He became a full professor two years later, becoming the university's youngest professor. Based on Frédéric and Irène Joliot-Curie's 1934 published work on artificial radioactivity, Lawrence discovered the nitrogen-13 isotope by firing high-energy protons into a carbon-13 element in his laboratory. He and his team including Martin Kamen and Samuel Ruben accidentally discovered the carbon-14 isotope by bombarding graphite with high-energy protons. Robert Gordon Sproul, who became university president the day after Lawrence became a professor, was a member of the Bohemian Club, and he sponsored Lawrence's membership in 1932. Through this club, Lawrence met William Henry Crocker, Edwin Pauley, and John Francis Neylan. They were influential men who helped him obtain money for his energetic nuclear particle investigations. There was great hope for medical uses to come from the development of particle physics, and this led to much of the early funding that Lawrence was able to obtain for research.
While at Yale, Lawrence met Mary Kimberly (Molly) Blumer, the eldest of four daughters of George Blumer, the dean of the Yale School of Medicine. They first met in 1926 and became engaged in 1931, and were married on May 14, 1932, at Trinity Church on the Green in New Haven, Connecticut. They had six children: Eric, Margaret, Mary, Robert, Barbara, and Susan. Lawrence named his son Robert after theoretical physicist Robert Oppenheimer, his closest friend in Berkeley. In 1941, Molly's sister Elsie married Edwin McMillan, who would go on to win the Nobel Prize in Chemistry in 1951 with Glenn T. Seaborg.
The invention that brought Lawrence to international fame started out as a sketch on a scrap of a paper napkin. While sitting in the library one evening in 1929, Lawrence glanced over a journal article by Rolf Widerøe, and was intrigued by one of the diagrams. This depicted a device that produced high-energy particles by means of a succession of small "pushes". The device depicted was laid out in a straight line using increasingly longer electrodes. At the time, physicists were beginning to explore the atomic nucleus. In 1919, the New Zealand physicist Ernest Rutherford had fired alpha particles into nitrogen and had succeeded in knocking protons out of some of the nuclei. But nuclei have a positive charge that repels other positively charged nuclei, and they are bound together tightly by a force that physicists were only just beginning to understand. To break them up, to disintegrate them, would require much higher energies, of the order of millions of volts.
Lawrence saw that such a particle accelerator would soon become too long and unwieldy for his university laboratory. In pondering a way to make the accelerator more compact, Lawrence decided to set a circular accelerating chamber between the poles of an electromagnet. The magnetic field would hold the charged protons in a spiral path as they were accelerated between just two semicircular electrodes connected to an alternating potential. After a hundred turns or so, the protons would impact the target as a beam of high-energy particles. Lawrence excitedly told his colleagues that he had discovered a method for obtaining particles of very high energy without the use of any high voltage. He initially worked with Niels Edlefsen. Their first cyclotron was made out of brass, wire, and sealing wax and was only four inches (10 cm) in diameter—it could be held in one hand, and probably cost a total of $25 (equivalent to $600 in 2025).