The Perfect Theory

by Pedro G. Ferreira

  A billion years might seem like quite a long time, but in fact it was simply not long enough. In the 1920s, radioactive dating had determined that the Earth was over 2 billion years old. And work by the astronomer James Jeans seemed to pin the age of clusters of stars at hundreds to thousands of billions of years. The ages of star clusters were later revised down, but there was no doubt about it: it seemed as if the universe was younger than the stuff it contained. That simply couldn’t be true, but there seemed to be no way around the paradox. Willem de Sitter summed up the situation in 1932 by saying, “I am afraid all we can do is to accept the paradox and try to accommodate ourselves to it.” The situation hadn’t improved by the time Hoyle, Bondi, and Gold became interested in the expanding universe.

  When the Cambridge trio started thinking about cosmology, the age paradox seemed like a glaring failure of Friedmann’s and Lemaître’s models. But what really troubled Hoyle, Bondi, and Gold was something much deeper and much more conceptual. In winding back the clock of Friedmann’s or Lemaître’s model the beginning of the universe corresponds to a moment when the whole of space is infinitely concentrated at a single point. In other words, space, time, and matter came into being at that one, initial instant. To Hoyle and his friends this was anathema. As Hoyle would put it, “It was an irrational process that cannot be described in scientific terms.” What laws of physics could be used to describe the creation of something out of nothing? It was inconceivable, and for Hoyle it was “a distinctly unsatisfactory notion, since it puts the basic assumption out of sight where it can never be challenged by a direct appeal to observation.” Their dismissiveness echoed Eddington’s appalled assessment of Lemaître’s primordial egg.

  It was a movie, Dead of Night, that led Hoyle and his colleagues to take a fresh look at the universe. Made in 1945, Dead of Night is a horror movie with a circular structure, the ending neatly matching the beginning. With no real beginning and end it is a claustrophobic vision of an endless universe. And it intrigued Hoyle, Bondi, and Gold. What if the universe was in fact like that? There would be no initial time, no primordial egg.

  Bondi and Gold viewed the problem of the initial time—or as Hoyle would later call it, the “Big Bang”—from an almost abstract, aesthetic point of view. Over the centuries, descriptions of the universe had moved away from having special, preferred positions in space. Friedmann and Lemaître, like Einstein before them, postulated that the universe was completely featureless, with no center or preferred place from which things evolved or were observed. There was true democracy among all points in space. So why not promote this principle, the cosmological principle, to something far more complete and all-encompassing? Why not assume that all points in space and moments in time were the same? There would be no beginning, just an eternal universe that would remain in a steady state for all time.

  Hoyle set about figuring out the details of such a proposal. In Friedmann and Lemaître’s universe, energy would be diluted with the expansion and slowly decrease with time. If the universe was to be truly in a steady state, the energy would have to be replenished somehow to keep the universe chugging along. And so Hoyle decided to fix Einstein’s field equations, much as Einstein had tried to do when he was constructing his now-defunct static universe. Hoyle postulated the existence of what he called the creation field, or C-field as it became known, that would create energy over time. Hoyle’s steady-state universe would be sustained by this mysterious source of energy, which had never before been seen. In Hoyle’s universe one of the sacrosanct laws of physics—conservation of energy—went down the drain. Hoyle argued it wasn’t that big a deal, for all that was needed was “about one atom every century in a volume equal to the Empire State Building.” Almost nothing.

  Two papers, one by Hoyle and another by Bondi and Gold, came out in 1948 in the Monthly Notices of the RAS. The reception was mixed. One of the fathers of quantum physics, Werner Heisenberg, who had stopped by in Cambridge when Hoyle presented his C-field paper, thought it was the most interesting idea to come out of his visit. E. A. Milne, an Oxford professor of mathematics, rejected it outright, stating, “I do not believe the hypothesis of the continual creation of matter is necessary, nor do I consider that it is on the same footing as the assumption that the universe as a whole was created at a particular epoch.” Max Born, who had supervised Robert Oppenheimer in Göttingen, simply couldn’t stomach the changes Hoyle was proposing, “for if there is any law which has withstood all changes and revolutions in physics, it is the law of conservation of energy.” And the great man himself, Albert Einstein, paid little attention to Hoyle’s model, claiming it was simply a piece of “romantic speculation.” What seemed to the trio of astronomers like a simple, obvious solution to such a fundamental problem in cosmology was being dismissed as outlandish and unnecessary. Hoyle was frustrated by what he perceived as the unreasonableness of his colleagues. As he put it, he was quite “worn out with explaining points of physics, mathematics, fact and logic to obtuse minds.”

  And then, an opportunity to promote his model that would far surpass the impact of any paper or seminar series landed in Hoyle’s lap. The BBC was planning a series of radio lectures by the Cambridge historian Herbert Butterfield. Butterfield pulled out at the last minute and the young Fred Hoyle, who had some experience of broadcasting, was invited to take Butterfield’s place and record a series of programs on the universe and cosmology, five in total. In them Hoyle could expound on the problems of cosmology, the young universe with old galaxies, and how Friedmann and Lemaître’s universe created more problems than it solved. And he could describe the virtues of his steady-state universe. Hoyle could bypass all the conventional methods and present his ideas to the whole country as a fait accompli. Everyone would know about his theory.

  Hoyle’s BBC lectures were incredibly successful and Hoyle became a well-known figure, one of the first media dons. The public warmed to his description of the universe, and it took hold in the popular imagination. But by taking such a public stage to promote his own model above the much more well-established and accepted expanding universe discovered by Friedmann and Lemaître, Hoyle rankled his colleagues, and the concept of a steady-state universe suffered a backlash as a result. While Hoyle had succeeded in placing the steady-state universe on a public stage, resistance among his colleagues became more firmly entrenched. As Hoyle later recalled, “I found it difficult to get my papers published during the first two or three years of the 1950s.”

  Nevertheless, the steady-state universe took hold as a viable alternative to the expanding universe of Friedmann and Lemaître that had won over Einstein. The great discoveries of the 1920s in cosmology and general relativity were under assault. But in the next few years, a completely new window on the universe would open up and cast all these models in a different light.

  “I do not think it unreasonable to say that [Martin] Ryle’s motivation in developing a program for counting radio sources . . . was to exact revenge,” recalled Hoyle of his former colleague. It was an uncharitable thing to say, but there was definitely an element of truth in it. For Martin Ryle was a volatile, irascible character, competitive and suspicious. Even within Cambridge, Ryle would isolate himself from the rest of the faculty, going to work near the radio telescopes based at what used to be the Lord’s Bridge railway station, “in a shed in the fields,” as one of his colleagues recalls. He would have a distinguished career—he would become the Astronomer Royal in 1972 and win the Nobel Prize in 1974—yet throughout, Ryle behaved as if he were constantly under threat, enforcing a bunker mentality in his group.

  Martin Ryle had also come out of the radar generation. The son of a Cambridge professor, Ryle graduated from Oxford in 1939 with a first-class degree. Like Bondi, Gold, and Hoyle, Martin Ryle worked on radar during the war, coming up with tricks for jamming the German radar systems and subverting German rocket guidance systems. After the war Ryle went to Cambridge, where he set about applying his skills to developing, and at some
point dominating, the new field of radio astronomy. He was not alone, for when Bernard Lovell, who had also spent the war enmeshed in the development of radar, moved to Manchester, he set about building one of the largest steerable radio telescopes in the world at the Jodrell Bank Observatory. In Australia, Joseph Pawsey spent his war years developing radar for the Royal Australian Navy before setting up his own radio astronomy group in Sydney.

  The first steps in radio astronomy had been taken a few years before, when Karl Jansky, an engineer working for Bell Telephone Laboratories in New Jersey in the early 1930s, realized that the universe was hissing at him. Jansky had been asked to find the source of the annoying static that was making conversations over the radio and even broadcast radio programs sometimes impossible to hear. Jansky just wanted to fix the radios—he had little interest in the mysteries of outer space.

  Radio waves behave just like light waves, but their wavelengths are a billion times longer than those of visible light. The light we can actually see, which makes up the bulk of the sun’s rays, has a wavelength that is less than a millionth of a meter. Radio waves have gigantic wavelengths, ranging from a millimeter all the way up to hundreds of meters. Jansky had found that the Milky Way was emitting an extraordinary amount of radio waves, day in and day out. Even though the sun was much brighter in the sky than the whole Milky Way put together, it didn’t emit as many radio waves. In an article “Electrical Disturbances Apparently of Extraterrestrial Origin,” published in 1933, Jansky systematically took apart all possible sources of static and showed a map of where the radio waves were coming from. His methods revealed a different way of looking at the cosmos. Instead of using giant telescopes with lenses on mountaintops, this kind of observation could be done with chicken wire, steel, and dishes out in the open plains. Rather than looking at the faint light of distant objects, astronomers could pick up the radio waves coming from outer space.

  Jansky’s discovery was mostly ignored. When he proposed that Bell Labs build a new, improved antenna, he was refused. They weren’t in the business of astronomy. And so Jansky moved on to other things. But his work wasn’t completely forgotten. An idiosyncratic radio engineer and amateur astronomer from Wheaton, Illinois, by the name of Grote Reber read about Jansky’s discovery in Popular Astronomy and set about building a bigger and better antenna in his backyard in Wheaton. Reber’s antenna had a 9-meter dish, with metal scaffolding that extended out in front to capture the reflected waves. It was the first proper radio telescope, much like the ones we see today. With it, Reber set out to make a finer map of the radio emissions of the Milky Way and build a detailed map of the radio sky. He submitted his work to the Astrophysical Journal where Chandra, who was the editor at the time, was intrigued by Reber’s results and bemused by his persistence—he accepted the paper for publication. And so in 1940, Reber’s “Cosmic Static” was published with his very own maps.

  Reber’s new radio maps of the Milky Way were interesting, helping to map out in detail where all the mysterious waves were actually emanating from. But Reber’s measurements also revealed something else: a few isolated points on the maps were beaming copious amounts of radio waves. While Reber was able to place each of the points near a constellation—Cygnus, Cassiopeia, and Taurus—they did not correspond to objects emanating visible light. Reber had discovered a new type of astronomical object that became known as a radio source or radio star.

  “Cosmic Static” opened up a new window on the universe. Unfolding before a new generation was perfectly uncharted territory, and Martin Ryle was ready to explore. Along with Lovell’s and Pawsey’s groups, from the late 1940s onward, Ryle and his group at Cambridge began mapping the cosmos. Deploying the techniques that he had learned while working on radar, Ryle designed a new generation of radio telescopes that would transform Cambridge into one of the premier centers for radio astronomy. But it also would bring him up against Hoyle and his collaborators.

  Martin Ryle was more of a radio-ham amateur and an electrical engineer than a cosmologist, so it was surprising that he would get caught up in a fight with “theoreticians,” as he would disparagingly call Hoyle and his colleagues. But he had walked right into it. He had first tried to find more bright radio sources, like those Reber had observed, and pinpoint their locations, but unfortunately he made the wrong call. It seemed clear to him that all these objects were firmly embedded in the Milky Way. In a clearly argued paper in 1950 he made the case that the majority of radio sources should lie within our galaxy. There could be a few odd outliers, but on the whole they must be close by. What he said made sense and was entirely reasonable.

  Ryle presented his results at a meeting of the Royal Astronomical Society in 1951. In the audience were his Cambridge colleagues Gold and Hoyle, who stood up and casually conjectured that the radio sources might actually be extragalactic. Ryle, who had carefully thought through his arguments, was annoyed and dismissed Gold and Hoyle, saying, “I think the theoreticians have misunderstood the experimental data.”

  It was a clash of cultures pitting the highbrow theoretical astronomers, versed in mathematics and physics with elegant yet odd theories that explained the whole universe, against the tinkerers, the radio operators who built kits and played with electronics. Ryle couldn’t stand the perceived condescension of his colleagues. He felt he understood the data in a way that these people who worked solely with pencil and paper couldn’t. Unfortunately for Ryle, Gold and Hoyle were eventually proved right as more and more radio sources came to be associated with objects outside the Milky Way. They were indeed extragalactic, and Ryle had to accept that the theorists did in fact understand the data.

  But Ryle didn’t accept defeat quietly. Given that these radio sources lay outside the galaxy, they could be used to say something about the universe. So Ryle turned to amassing more observations and using his data to go after Hoyle and Gold’s baby, the steady-state theory. He did so by counting the number of radio sources as a function of their brightness and trying to relate this number to the underlying properties of the universe. The farther away a radio source is, the dimmer it will be, so the dimness of a source can be seen as an indicator of its distance. The universe is a big place and there is a lot of space out there, so one would expect to see more dim, distant sources than bright, close ones. It turns out that the ratio of the number of dim sources to bright ones is a good way of figuring out what type of universe we might live in. When we look at distant sources, their light has taken time to reach us, so we are looking at the universe when it was younger. If we live in Hoyle, Gold, and Bondi’s steady-state universe, the density of sources remains constant over time, so the total number of sources within a certain volume should be directly proportional to that volume. In an evolving universe like the one Friedmann and Lemaître proposed, the universe was denser in the past than it is now, so there should more distant, dimmer sources than close, bright ones. By counting the number of dim sources relative to the bright sources, it should be possible to determine whether our universe adheres to the Big Bang or the steady-state model.

  Ryle compiled a list of almost two thousand sources in what was called the 2C Catalogue (C stands for Cambridge). It built on a much smaller list of fifty sources (known as the 1C Catalogue) and seemed, to Ryle’s satisfaction, to have far too many dim sources compared with bright sources for it to be consistent with the steady-state theory. Ryle saw this as the killer blow for Hoyle’s theory and immediately set about advertising his results. In a prestigious lecture he was invited to give at Oxford in May 1955, he came out with a bold indictment of his rivals: “If we accept the conclusion that most of the radio stars are external to the galaxy, and this conclusion seems hard to avoid, then there seems to be no way in which the observations can be explained in terms of a steady state theory.” Ryle had seemingly demolished Hoyle and Gold’s model.

  After Ryle’s lecture at Oxford, Hoyle and his collaborators were on the defensive. Hoyle took the data seriously, but Gold was suspicious of
the results, advising Hoyle, “Don’t trust them, there might be lots of errors in this and it can’t be taken seriously.” Gold was right. This time Ryle was thwarted by his own cohort, the same tinkerers who were building radio astronomy into a bona fide science. Two young Australian radio astronomers, Bernard Mills and Bruce Slee from Sydney, reanalyzed the 2C data and found a completely different result from Ryle’s. Instead of trying to come up with a catalogue of thousands of sources to rival Ryle’s, they opted to focus on a small subset of the whole survey, about three hundred sources, and measured them in exquisite detail. This small catalogue was picked so it overlapped with Ryle’s catalogue and could be used to actually check Ryle’s measurements.

  Mills and Slee’s published results completely destroyed the credibility of Ryle’s survey. In their paper, they said that their “catalogue is compared in detail with a recent Cambridge catalogue . . . it is found that they are almost completely discordant.” Mills and Slee went on to suggest that “the Cambridge catalogue is affected by the low resolution of their radio interferometer.” Ryle’s results were simply not good enough—Mills and Slee were working with a better telescope that was more precise, and their results could not exclude the steady-state model as a possible model of the universe. A radio astronomer from the rival group in the UK named Jodrell Bank chimed in, saying, “Radio astronomers must make considerable progress before they can offer the cosmologists anything of value.” It seemed that the radio astronomers couldn’t agree on their data, let alone use it to test cosmological models, so it was deemed best to ignore that data for now. Hoyle and his collaborators had a field day.