The achievements of Fred Hoyle, one of the twentieth century's great innovators in astronomy, were celebrated at a recent meeting. In many respects, it emerged, Hoyle's thinking was ahead of his time.
In 1952, Fred Hoyle delivered the first of the BBC's annual Reith Lectures under the title “Frontiers in Astronomy”. The five talks, delivered in consecutive weeks, electrified his audience and won Hoyle an instant reputation as a popularizer of science. Half a century later, and some eight months after his death last year at the age of 86, a symposium under the same titleFootnote 1 was convened to celebrate Hoyle's many achievements.
The meeting was held in Cambridge, UK, at the Institute of Astronomy, which Hoyle founded as the Institute of Theoretical Astronomy in 1966, and at St John's College, which elected him as a fellow while he was still a graduate student. The divided venue was a symbol of the spirit of the occasion: Cambridge's ambivalence towards Hoyle was matched only by Hoyle's ambivalence towards his old university. Another was that at the symposium even Hoyle's critics bit their tongues, acknowledging that he was “before his time”. And C. Wickramasinghe (Cardiff Univ.), best known as Hoyle's collaborator on some of his later and more controversial ideas, roundly declared that “It is a myth that everything he did in his early years was brilliant and that everything he did after a certain date was rubbish”. Nor was Wickramasinghe challenged on his dubious assertion that it is “now generally accepted” that the organic constituents of the first terrestrial living things were made in interstellar molecular clouds and were transported here by meteorites or comets.
The most telling account of Hoyle's precocity came from P. Solomon (State Univ. New York, Stony Brook), who had unearthed a paper published in 1943, in the Proceedings of the Cambridge Philosophical Society, when Hoyle was still a graduate student. The notion that molecular clouds cool by emitting radiation because of the rotational states of molecules was one of the ideas that first appeared there — and was then forgotten for almost 30 years. Solomon pointed out that, in the same paper, Hoyle used the idea to predict that the fragmentation of a cloud of gas (an early galaxy, say) into stellar nebulae would be constrained by the increasing opacity of collapsing regions, putting an upper limit on the mass of individual stars and restricting the numbers of Sun-like stars in galaxies (eventually pinned down in a paper dated 1949 to between 109 and 3 × 1011).
The symposium was opened by W. Sargent (Caltech), himself a distinguished observer and Hoyle's principal adjutant on the Northern Hemisphere Telescope Review Committee. This was the body, set up in the mid-1960s, that eventually established the pattern of observing time for British astronomers in the past quarter of a century. Like the master of ceremonies at an awards dinner (except that there was no food and drink at 10:00 in the morning), Sargent rattled through Hoyle's lifetime of accomplishments.
Among them is the recognition of accretion (onto red giants in the first instance) as a general process affecting the smallest objects in the Universe (such as planets) and the largest — galaxies, our own included. Sargent stressed the importance of Hoyle's 1953 prediction that there is a long-lived excited state of the 12C nucleus, the effect of which is to delay the conversion of 12C into 16O (by combination with 4He nuclei), thus providing enough carbon in the cosmic mix to support carbon-based life. The prediction was confirmed by measurements by W. H. Fowler at Caltech and is now widely cited as an illustration of the Anthropic Principle, the notion that the existence of living things implies that the Universe must have satisfied the pre-conditions for the existence of life as it is found, a biogenic supply of carbon included.
But, Sargent continued, Hoyle went on to explain the difference between supernovae of type I (with degenerate Fermi–Dirac cores) and type II (which implode), although in both cases Hoyle erred by underestimating the importance of neutrino emission in energy export.
Then there is the paper (known as B2FH), written with Geoffrey and Margaret Burbidge and W. H. Fowler on the synthesis in stars of the elements heavier than boron, which remains the universal framework for discussions of nucleosynthesis. Sargent went on to remind his audience that Hoyle had been the one to work out that stars 200 times as massive as the Sun could well have been formed in the early Universe and that he (with Wickramasinghe) first put the topic of interstellar dust on the astronomical agenda.
Sadly, of course, Hoyle was not present to receive the medal Sargent's talk seemed to presage. But others were. Margaret Burbidge (Univ. California, San Diego) gave a wistful account of how chance meetings at the Royal Astronomical Society in London, in Paris and at Cambridge grew into the collaboration that produced B2FH. And H. Bondi (Churchill College, Cambridge) spoke of the genesis of 'steady-state' theory, which, in contrast to the Big Bang, holds that expansion of the Universe can be accounted for by the continual creation of new matter. It was Bondi, along with Thomas Gold, who produced the first version of a steady-state cosmology; Hoyle joined them later and during the 1950s crossed swords publicly and acrimoniously with the late Martin Ryle. This great dispute, reflected Bondi, need not have happened if everybody had been more circumspect and respectful of the provisional nature of newly gathered data. “Perhaps we were too ambitious”, he acknowledged (in another context).
It fell to J. V. Narlikar (Inter-Univ. Centre for Astronomy and Astrophysics, Pune, India), another of Hoyle's former graduate students, to make the point that being ahead of your time is a dangerous business. The risk is that of being run over by the band-wagon that follows you.
* Frontiers in Astronomy, Institute of Astronomy/St John's College, Cambridge, UK, 16 April 2002.