(1907-1980) British Geophysicist
Sir Edward Bullard was one of the giants of geophysics. Even though he started out as a physicist, carefully experimenting on electron scattering in groundbreaking research, he quickly realized that his true calling was in geophysics. His work set the stage for modern methods in geophysics in four areas: heat flow, generation of Earth’s magnetic field, and gravity and seismic refraction methods. Bullard devised the methods that are currently used for heat flow surveying shortly after World War II. He devised methods to measure thermal conductivity, which unless incorporated into heat flow analysis leads to erroneous results. He used thermal gradients in South African gold mines, as well as British coal mines, in addition to numerous borehole measurements to show that thermal conductivity greatly affects the actual temperatures that are measured at various depths. He established the first reliable average heat flux value for the continents. Perhaps even more impressive were his methods to measure heat flow on the ocean floor. He invented a device that was driven into the ocean floor to obtain temperatures of the underlying rock. He then tested it on deep-sea cruises with ROGER REVELLE and others at the Scripps Institution of Oceanography, California. The result was the identification of elevated heat flow at the mid-ocean ridges, which later served as an important piece of evidence for plate tectonics.
His interest in designing new practical, portable equipment to measure geophysical quantities also spread to gravity and seismic refraction techniques. His earliest geophysical work was to redesign a pendulum apparatus for measuring gravity and then to conduct a field study with it over the East African Rift System, which earned him a Smithson Fellowship from the Royal Society. He designed a portable short period seismograph (to take a sonogram-like picture of the Earth) which he used to measure the depth to basement in a field survey in southeast England. Although these pieces of equipment were later redesigned, his success in carrying out field geophysical surveys set the stage for modern geophysical work.
After his extensive work in magnetics during World War II, Sir Edward Bullard investigated how motions in the Earth’s core might induce the main magnetic field. He measured secular (short-term) changes in the magnetic field, like the rate of westward drift of the poles, and then used mathematical models to obtain numerical solutions for fluid mechanical problems in the Earth’s core. He was the first to model the core as a self-exciting dynamo using primitive computers, thus setting the stage for later more appropriate studies. Bullard even got involved with the plate tectonic revolution. He was the first to apply Euler’s theorem to determine poles of rotation to better fit the dispersed continents back together into the supercontinent of Pangea. Clearly, Sir Edward Bullard was one of the most influential Earth scientists of the 20th century.
Edward Crisp Bullard was born on September 21, 1907, in Norwich, England. His family produced Bullard’s Ales. He attended Cambridge University to study natural sciences but switched to physics and graduated with his doctoral degree in 1932. In 1931, he married Margaret Ellen Thomas. They had four daughters and the marriage ended in divorce in 1974. That same year, he accepted a position as demonstrator in the Department of Geodesy and Geophysics, where he was the second member. Later Sir Harold Jeffreys would join the department. When World War II broke out, Bullard became an experimental officer attached to the HMS Vernon in 1939. The Germans had developed a very effective magnetic mine that could be dropped from airplanes. They sank 60 ships in three months. With his knowledge of magnetics, Bullard developed mine sweepers that drastically reduced the threat. He even anticipated German advances in trigger mechanisms for mines, developing sweepers before the mines even came into use. He became assistant director of Naval Operational Research and oversaw projects on mine development and submarine warfare. He returned to Cambridge University after the war, but in 1948 he accepted the position of chair of the Department of Physics at the University of Toronto, Canada. After spending several months at Scripps Oceanographic Institute in La Jolla, California, in 1949, Bullard returned to England as the director of the National Physical Laboratory, where he remained until 1955. He returned to Cambridge University as the chair of the Department of Geodesy and Geophysics where he remained for the rest of his preretirement career. He retired to professor emeritus in 1974 with his health beginning to fail. He married Ursula Cooke Curnow that year and returned to Scripps Oceanographic Institute, where he remained for the rest of his life. Sir Edward Bullard died in his sleep on April 3, 1980.
It is difficult to overestimate the impact of Sir Edward Bullard’s career on the profession. Many of his papers are true milestones in geophysics (magnetics, seismic refraction, and heat flow) and especially in marine geophysics. In recognition of his contributions to the profession, Bullard received numerous honors and awards. In addition to having been knighted for his work at the National Physical Laboratory he was a Fellow of the Royal Society. He was a member of the U.S. National Academy of Sciences and the American Academy of Arts and Sciences. He received the Hughes Medal and the Royal Medal from the Royal Society (England), the Bowie Medal and the Maurice Ewing Medal from the American Geophysical Union, the Chree Medal from the Physics Society (England), the Arthur L. Day Medal from the Geological Society of America, the Gold Medal from the Royal Astronomical Society (England), the Wollaston Medal from the Geological Society of London, and the Vetlesen Prize from the Vetlesen Foundation of Columbia University.
Bullard also performed great service to the public and the profession. Among others, he was an adviser to the British government on nuclear disarmament, chair of the Anglo-American Ballistic Missile Commission and the chair of the Committee for British Space Research. He was active in industry as well, including as the director of IBM, U.K., and various positions in the family brewing business.
