Sir Fred Hoyle (1915–2001)
Received 2001 November 12; accepted 2001 November 12
Sir Fred Hoyle, who was the cause and catalyst for the development of cosmology as a quantitative science, died on 2001 August 20. Sir Fred spent his scientific career wrestling with questions both large and fundamental.
Fig. 1.— Sir Fred Hoyle in 1967 February on the Caltech campus between Sloan Laboratory and West Bridge Laboratory. Hoyle had just invited Fowler, Wagoner, and Clayton to come to the opening of the new Institute for Theoretical Astronomy in Cambridge, England. Photograph is courtesy of Don Clayton from his picture archive World Wide Web site.
Sir Fred was born in Bingley, Yorkshire, England, in 1915. He was educated at Emmanuel College of the University of Cambridge, and he worked for the British Admiralty during the Second World War on the design of radar systems. He returned to Cambridge after the war, where he was a lecturer in mathematics (1945–1956), Plumian Professor of astronomy and experimental philosophy (1958–1972), and founder and first director of the Institute for Theoretical Astronomy (1966–1972). He was knighted in 1972.
Fig. 2.— Margaret Burbidge, Geoff Burbidge, Willy Fowler, and Fred Hoyle in July 1971, taken 14 years after the publication of their famous joint paper (B2FH) in Reviews of Modern Physics. They are shown with a steam train presented to Fowler at a conference in honor of his 60th birthday. This picture is also courtesy of Don Clayton.
In 1946 he asked whether the observed elements could be produced by known physical processes. He suggested that the answer could be found in a combination of equilibrium and nonequilibrium thermonuclear reactions. The equilibrium process gave a good account of the relatively high abundance of iron and required extreme densities and temperatures. The nonequilibrium processes required rapid cooling to produce their part of the observed abundances. He proposed that the supernova explosions identified by Walter Baade and Fritz Zwicky would fit both requirements, a view now amply confirmed. His association of the explosion with a rotating gravitational collapse of the stellar core may be the best explanation of the observed connection of gamma‐ray bursts and supernovae and of the spectacular image from the Chandra X‐Ray Observatory of the supernova core in the Crab Nebula.
Were all the elements synthesized in stars from primordial hydrogen? This question leads to the need to determine the conditions in stars with some accuracy. The defining equations are so nonlinear that the solution required the use of the newly developing electronic computer. More accurate thermonuclear reaction rates were needed as well. Willy Fowler, who became a lifetime collaborator with Hoyle, loved to tell the story of this brash younger Brit who, on the basis of stellar evolutionary theory and astronomical observation, predicted the existence of a new level in the carbon‐12 compound nucleus. Fowler, a leader of the nuclear experimental group, was not about to let such an outrage go untested. To his surprise and delight, the level was found.
The idea that the observed helium (more than a quarter of all observable matter) came from stellar burning of hydrogen was flawed. Sir Fred and Roger Tayler found that such extensive burning would have produced 10 times more stellar light than the observations allowed. Apparently hydrogen and most helium was primordial. In a landmark paper, Bob Wagoner, Willy Fowler, and Sir Fred numerically integrated by computer the nonequilibrium process of cosmological nucleosynthesis in an exploding context. They found that the big bang produced not only hydrogen but also deuterium, both isotopes of helium, and some lithium. This big bang nucleosynthesis is now a fundamental result of all serious cosmology.
Are the main features of the universe due to arbitrary fiat or consequences of the laws of physics? The big bang cosmology, which Sir Fred named, seemed to him to be arbitrary in that it depended on initial conditions, which had to be assumed. “Unless…all are coincidences, we are obliged to suppose that the laws of physics as we know them today are substantially incomplete, and that so far unperceived connections must exist between the physics of the ultrasmall and the physics of the ultralarge.” Particle astrophysics as well as inflationary cosmologies may be seen as a more recent attempt to deal with this issue. Sir Fred chose to build on the framework of the steady state cosmology of Hermann Bondi and Tommy Gold. This had the advantage that the present observable universe was independent of the starting conditions. However, was it correct? In the attempt to answer this question, cosmology became a quantitative science. To quote Sir Fred, “the stakes are high, and win or lose, worth playing for.”
Sir Fred received numerous prizes and awards for his work, including the Kalinga Prize (UNESCO, 1967), the Gold Medal of the Royal Astronomical Society (1968), the Jansky Prize (NRAO, 1969), the Bruce Medal of the Astronomical Society of the Pacific (1970), the Henry Norris Russell Lectureship of the American Astronomical Society (1971), the Royal Medal of the Royal Society (1974), the Karl Schwarzschild Medal (Astronomische Gesellschaft, 1992), the Balzan Prize (International Balzan Foundation, 1994), and the Crafoord Prize (Royal Swedish Academy of Sciences, 1997).
Exceptional people come in many varieties. Sir Fred did not have the verbal and mathematical magic of Richard Feynman nor the sheer power of Hans Bethe. He was relatively quiet for one who did not shy from controversy. However, his originality was striking. He could take a seemingly worn out topic and present it in a new light. This lucidity comes through in his writing and contributed to his extraordinary success in communicating science to nonspecialists and nonscientists. His book Frontiers in Astronomy inspired a generation of astrophysicists in their high school years. His autobiography Home Is Where the Wind Blows is beautifully done. He loved hiking, particularly in the Munros (Scottish peaks over 3000 feet in elevation), and he left younger men panting with his slow but steady gait. We will miss him.