I am terrified of Geoffrey Burbidge. I admit it. He makes me quake in my boots. The larger by a considerable margin of the famous husband-and-wife team that has earned the moniker “B-squared”, Geoff is certainly a different kettle of fish. Margaret, on one hand, is a motherly figure, treating visitors to their lovely San Diego home to tea and crumpets in the glorious English tradition. Dealing with her husband is quite another matter. Geoffrey does not suffer fools gladly, and it would seem to me that by his definition, all the world’s a fool. And that includes me, of course.
Over the years, I have enjoyed a cordial relationship with the Burbidges, and hasten to assure you that Geoff has never been unkind to me. We are, after all, on the same side (I think, I hope!). It’s just that he’s direct. Very direct. Dr Burbidge’s brand of civility is unadorned by frills or meaningless platitudes. If you’re a spade, he will certainly not call you a shovel. My point is this: Whether or not Geoffrey Burbidge’s social skills make you feel all warm and cuddly, you will ignore him at your peril. He is arguably the most accomplished theoretical astrophysicist alive today, and although I disagree with him on the fundamental issues of universal expansion and what energises the Sun, I use every opportunity that comes my way to learn from him. He is without doubt one of the giants of the modern era.
So it was that a significant paper by Geoff Burbidge came my way towards the end of last year. I had been corresponding with him about my presentation to the ASSA symposium, and he referred me to it. It’s called B2FH, the CMB, and Cosmology (arXiv:astro-ph/0806.1065). I’d like to share some of it with you today.
Let me first explain what B2FH means. It refers to a paper published in 1957 that would become a standard reference in cosmology and related fields. The decade of the 1950s was an era when there was still open debate about aspects of Big bang Theory. Just as well for the burgeoning Standard Model, because its architect, George Gamow, had given up trying to explain the origin of the elements. He simply could not get the theory to work, despite the plethora of adjustable parameters at his disposal. But help was at hand, ironically in the form of his arch-adversary, Sir Fred Hoyle. It was the scheme devised for a Steady State Universe model, first by Hoyle, and later perfected together with some of his close colleagues, that helped plug a few serious leaks in the good ship Big Bang. Gamow’s team adopted the nucleosynthesis model from Steady State, and the rest is history. The fact that it still doesn’t work—by a country mile!—in standard cosmology bothers very few people in the game, it seems.
The paper that defines stellar nucleosynthesis to this day, and came to represent an entire field of science, was published in 1957. It was called Synthesis of the Elements in Stars and the authors were Margaret Burbidge, Geoffrey Burbidge, Willie Fowler, and Fred Hoyle—hence, B2FH. Although the first draft was compiled by the Burbidges, and was based upon the groundbreaking earlier published work of Hoyle, it was Fowler who was singled out from this team to receive the 1983 Nobel Prize in Physics, in recognition of his contribution to the paper. We can only speculate why three authors overtly critical of Big Bang Theory were overlooked in favour of the one who kept his criticism private.
In 2007, a conference entitled “Nuclear Astrophysics 1957 – 2007” was held in Pasadena to mark the 50th anniversary of B2FH, and Geoff was invited to contribute. That’s where B2FH, the CMB, and Cosmology came in. Here follow some selected quotes:
In the late 1940’s Gamow and other leading physicists tried to build the elements in an early big bang phase. Of course they all failed. But Gamow et al were fascinated by the idea of a beginning involving a hot fireball and predicted that it would continue to expand in a black body form. They believed in it. Thus the idea that the lightest isotopes were made in a big bang was accepted, and today is one of the pillars of the standard cosmology. What is not pointed out is that there is no basic theory behind it.
I gave a talk about this in Cambridge in the winter of 1953-54, and afterwards. Willy Fowler, who was a Fulbright professor there, came up to me and told me how interested he was although at that time he only worked on light elements! Thus I started to work in this field while I was also trying to understand radio sources, and also contend with Martin Ryle, (who could be very nice, but also extremely difficult). Willy Fowler re-introduced us to Fred Hoyle whom we had originally met in Paris in 1950. Willy of course knew Fred from his earlier visits to Caltech. We soon developed a pattern: Tea in the Cavendish, followed eventually by all of us often going over to Willy’s rented house where I first found out about martinis. Frequently, we went to dinner together. In the midst of all of this quite a lot of work got started. This led me to realize that stellar nucleosynthesis as pioneered by Fred had completely vanquished the earlier ideas of Gamow, Alpher, and Herman, except for the x-process.
Who would publish it and where? I tried Chandra who was editor of The Astrophysical Journal at the time. He answered and asked questions like how much of it was original, and how much a review? He dithered though it was at least 95% original. Willy was impatient. He called up his friend, Ed Condon, who was editor of Reviews of Modern Physics, who simply accepted it and published it in the late summer of 1957. (If it were fifty years later, it would have been in the hands of referees for months, if not years! As you know I believe that the refereeing system is completely broken).
It is often claimed, that the abundances calculated originally by Gamow and his collaborators, and later by many others agree so well with the observed abundances, that this is proof that the big bang occurred. But this is simply not correct. The statement that the big bang theory explains the observed microwave background and also explains the light element abundances is to distort the meaning of words. Explanations in science are normally to be considered like theorems in mathematics, to flow deductively from axioms and not to be restatements of axioms themselves. Thus the radiation-dominated early universe is an axiom of big bang cosmology, and the supposed explanation of the CMB, and the light element abundances, is a restatement of that axiom.
The largest amount of energy released in nuclear reactions in stars comes through the burning of hydrogen into helium. Thus it is natural to suppose that, since the steadiest and most visible energy sources in the universe appears to be stars, that they are ultimately the source of the largest of the diffuse energy fields. In 1926 Eddington made an estimate of the energy density of starlight and found (it) corresponded to a temperature of about 3ºK. The first measurement of the CMB was made in 1941 by McKellar. He showed that the rotational levels indicated that the temperature must lie in the range 1.8ºK < T < 3.4ºK. This fundamental result predates the Penzias and Wilson by 24 years. It is natural to suppose that the energy carried by the CMB is most likely to have been generated by hydrogen burning in stars, since this is the most effective process of conversion of mass to energy involving a set of nuclear reactions.
To reiterate, the baryon density and temperature relation has to be fixed suitably in order to explain the light element abundances. Thus it must be remembered that the whole argument is based on the idea that helium was made by such a fireball, and much as most people want to believe it there is no independent evidence that this ever did take place. Most of the helium was made in a big bang, and the parameters required are those chosen in the conventional model. This is the most popular view but in its present form it requires that we choose an initial photon/baryon ratio, invoke a ‘magical’ inflation era, and assume the presence of a large amount of dark nonbaryonic matter, and dark energy (creation energy). These are four assumptions for which we have no basic theory, nor direct observational evidence. Just authoritarian belief.
Thus (Gamow) and his colleagues chose parameters for an early universe that would solve the problem. Since there is no theory from which the initial condition can be predicted they had to choose an initial ratio of baryons to photons.
B2FH and Cameron in 1957 were able to explain how all of the isotopes in the periodic table with the exception of (four) could have been synthesized in stars. In the cyclic (quasi-steady state) cosmological model, the long time scale means that the other light isotopes, and particularly the high abundance of helium, could have been synthesized as a result of creation in the centres of active galaxies. Thus Oppenheimer’s cynical view of the steady state cosmology can be stood on its head. From our standpoint, the observational data, and in particular the energy which must been released in the burning of hydrogen to produce helium, suggests that it has given rise to the observed microwave background. This release has taken place over a long period, too long for a big bang universe. Thus the observational data favour a cyclic universe model.