Hoyle, Fred (1915-1999)

English astronomer

A prolific and talented author in both science fact and fiction, Fred Hoyle is best known for publicizing the controversial steady state theory of the creation of the universe. Hoyle also helped develop radar and advance the understanding of the nuclear processes that power the stars. He has taught at both Cambridge and Cornell universities, received numerous awards and honors, and was knighted in 1972.

Born in Bingley, Yorkshire, England, Hoyle was the son of Benjamin Hoyle and Mabel (Picard) Hoyle. He attended Bingley Grammar School and went on to Emmanuel College at Cambridge, where he studied mathematics and astronomy, receiving his master of arts degree in 1939. On December 28, 1939, Hoyle married Barbara Clark and the couple eventually had two children.

During World War II, Hoyle served in the Admiralty at London, where he helped the British Navy develop radar (radio detection and ranging) technology. The Royal Air Force's victory in the Battle of Britain has been credited to the navy's improvement of radar during this period. After the war, numerous radar dishes were acquired by fledgling radio astronomers and converted into radio telescopes. These amateurs' discoveries in the 1960s ultimately helped to refute the theories Hoyle developed in the 1940s and 1950s.

During the early 1940s, Hoyle focused his attention on an issue that arose through the work of physicist Hans Bethe: energy production in stars. In 1938, Bethe had suggested a sequence of nuclear reactions that fuel the stars: Four hydrogen atoms were fused into a single atom of helium, resulting in a minute amount of mass being converted into energy. While this process of nuclear fusion was consistent with the predicted amounts of stellar energy observed, Bethe's theory did not account for the production of elements heavier than helium—heavy elements that exist within other stars and that are also abundant on Earth.

Hoyle expanded Bethe's findings. Elaborating on gravitational, electrical and nuclear fields, he determined what would happen to elements at ever increasing temperatures. He theorized that when a star has nearly exhausted its supply of hydrogen, nuclear fusion halts, and the outward radiation pressure generated by the fusion reaction also comes to a halt. Without this outward flow, the star begins to collapse because of gravitation. This causes the core of the star to heat up and reach a temperature great enough to fuse helium into carbon. The collapse of the star is then halted by the outward pressure of this new fusion radiation, and the star becomes stable. Hoyle's investigation into the nature of the carbon atom had the added benefit of helping scientists understand the origin of the atoms within the human body.

As the fusion cycle of stellar evolution continues, oxygen, magnesium, sulfur and heavier elements build up until the element iron is formed. At this point, no more fusion reactions can occur, and the star collapses catastrophically, becoming a white dwarf (a star dimmer than the Sun but much more dense). During this implosion, the star's outer layers ignite to become a supernova (an explosion whose luminosity is many times greater than the Sun). The supernova explosion creates elements heavier than iron, which are then hurtled into space by the explosion's force. It was from stellar debris such as this, Hoyle hypothesized, that the second generation stars with the heavier elements were formed.

Hoyle further proposed that the Sun was once part of a binary (double) star system whose companion became a supernova eons ago. The resulting heavy elements it ejected into space became the material from which the planets were formed. Hoyle's remarkable theory of stellar evolution appeared to be correct; it agreed with scientists' observations and accounts for the heavy elements in the solar system. However, whether the Sun had a companion star or not is still disputed; some believe a passing star was the culprit.

Following the war, Hoyle returned to Cambridge and became a professor of astronomy and mathematics. The pivotal point in his career came in 1948 when nuclear physicist George Gamow, building upon a theory first suggested by Georges Lemaître, a Jesuit priest and astonomer, and supported by the telescopic observations of the astronomer Edwin Powell Hubble, published what became known as the big bang theory of the creation of the universe. The big bang theory states that billions of years ago there was an enormous explosion in which all the matter of the universe was created. Galaxies formed and evolved from this matter and are still moving away from each other at tremendous velocities as a result of the explosion.

The concept that the universe had a specific beginning—and the implication that it will have an end—was abhorred by many scientists and laymen. Consequently, Thomas Gold and Hermann Bondi, an astronomer and mathematician respectively, proposed the steady state theory that theorized that the universe was perpetual, an idea that appeared to agree with scientific observation. Through the steady state theory, Gold and Bondi conceived of a universe in which matter was created continuously. As galaxies drift apart, new matter appears in the void and evolves into new galaxies. Since the universe seemed homogeneous (the same) regardless from which direction it was observed, or how far away (i.e. how far back in time) it was observed, Gold and Bondi suggested the cosmos was the same every "where" and every "when." That is, the physical state of the universe remains the same in the past, the present, and the future. The steady state concept had several virtues, not the least of which was avoiding the troublesome issue of the beginning and end of creation. It was simple, symmetrical, and attracted as many adherents as did Gamow's big bang theory. Hoyle became one of steady state's most influential and talented supporters.

Gold and Bondi had not based their concept on general field theory, but instead on an intuitive physical principle. To rectify this, Hoyle delved into the complex equations of Albert Einstein, modified them, and produced a mathematical model that supported the steady state theory, thereby giving it both respectability and plausibility. He became the official spokesperson for the theory and produced many books, some extremely technical, others geared for popular consumption, that publicized steady state cosmology.

The greatest objection to the steady state theory concerned the issue of the continual creation of new matter forming from nothing—an idea that seemed to violate the laws of nature. Hoyle claimed it was easier to accept the idea of matter being created slowly and continuously over the eons than believing that all matter in the universe was created in a single instant from a single blast. For the next fifteen years, proponents of each side interpreted new astronomical discoveries in ways that supported the theory to which each adhered.

In 1952, however, astronomer Walter Baade demonstrated that the accepted cosmological "yardstick" of measurement was seriously flawed. This "yardstick" was derived from the relationship between the brightness and the rate of pulsation of certain stars called Cepheid variable stars. According to Baade's findings, such stars were much farther away than had been previously calculated. This meant that the universe was much older, had been evolving longer, and was more than two times larger than had been believed. If the steady state theory were to hold up, astronomers surveying space would expect to see "old" galaxies created billions of years ago and containing aging stars, as well as "new," recently-created galaxies containing lighter elements and new stars. Yet observed galaxies appeared to be similar in age, supporting the big bang theory. Proving that matter is continuously created was more complicated than it seemed for the steady state theorists. Since space is so vast and the amount of matter that needs to be created at a given moment for the theory to be proven was so small, scientists were not able to detect the instantaneous creation of matter.

The debate between the factions continued. Hoyle acknowledged in his 1962 book Astronomy that there are "cosmological theories in which the universe had a finite and 'explosive' origin," but he manages to discuss them without once using the contentious phrase "big bang"; an ironic point since the term "big bang" is attributed to Hoyle. A decade earlier, Gamow's book The Creation of the Universe remarked that "Astronomical observations" concerning the brightness of the Milky Way stars in relation to the brightness of neighboring stars suggest "that the theory of [Bondi, Gold, and Hoyle] may not correspond to reality." In order to maintain the relevance of his work, Hoyle made several modifications to the steady state theory throughout the 1950s and 1960s.

The 1963 discovery of quasars by Maartin Schmidt created an awkward complication for the steady state theory. Quasars, distant objects brighter than and emitting more energy than stars, did not fit into the steady state explanation of the universe. This tipped the balance toward the big bang theory, which had no trouble embracing these "quasi-stellar" objects. In the following year, Arno Penzias and Robert W. Wilson discovered background microwave radiation in outer space by using radio telescopes. Claiming they had discovered the "remnants" of the big bang explosion with their telescopes, which had evolved from Hoyle's work on radar during World War II, Penzias and Wilson sealed the fate of the steady state theory, which was now abandoned in favor of the big bang theory. Subsequently, Hoyle found working with radio astronomers at Cambridge University increasingly difficult. When his proposed grant for a computer was rejected by the Science Research Council in 1972, Hoyle left the university in favor of working elsewhere.

Hoyle stirred up controversy again in 1981, when he proposed that one-celled life could be found in interstellar dust or comets and life on Earth may have originated from a close encounter with a comet. He also suggested that the abrupt appearance of global epidemics could be caused by space-borne contaminants, a suggestion not taken seriously by most scientists. In 1985, Hoyle ignited yet another controversy when he claimed that the British Museum's fossil of Archaeopteryx was a fake, but he had not been alone in that contention.

A prodigious amount of information has flowed from Hoyle's pen during his career. With his talent for simplifying complex theories for general audiences, he has produced technical treatises, textbooks, popular science fiction stories, an opera libretto, even a radio and a television play. The radio play, Rockets in Ursa Major, and the television play, A for Andromeda, were both written in collaboration with his son, Geoffrey, in 1962. His research on the development of stars and their age, including giants and white dwarfs, helped establish some of cosmology's major theories.

During his career, Hoyle was widely recognized for his achievements with many honors. In 1956, he became a member of the staff at Mount Wilson and Palomar observatories. In 1957, he was elected to the Royal Society of London; the following year he became Plumian Professor of Astronomy and Experimental Philosophy at Cambridge, and in 1962, he became the director of the Institute of Theoretical Astronomy. Following his departure from Cambridge in 1972, he became professor-at-large at Cornell University. Hoyle died at the age of 86.

See also Stellar life cycle