Brilliant Blunders: From Darwin to Einstein - Colossal Mistakes by Great Scientists That Changed Our Understanding of Life and the Universe

by Livio, Mario

  In October 1948, Hoyle, Bondi, and Gold attended a small meeting of the Royal Astronomical Society in Edinburgh. All three of them were invited to present their ideas about the steady state universe. Hoyle used the opportunity to advance for the first time a possible connection between an unchanging, self-sustaining cosmos and life:

  Modern astrophysics appears to be inexorably forcing us away from a universe of finite space and time, in which the future holds nothing but a general running down or heat death, towards a universe in which both space and time are infinite. The possibilities of physical evolution, and perhaps even of life, may well be without limit. These are the issues that stand to-day before the astronomer. Within a generation we hope that they can be settled with reasonable certainty.

  Paradoxically, even though later in life Hoyle criticized natural selection (claiming a role for panspermia, or life as a cosmic phenomenon), the origin of this line of thinking could be traced back to Darwin. Recall that Darwin was concerned about Kelvin’s estimate of the age of the Earth because he feared that with the restricted age there wasn’t sufficient time for evolution to operate. Hoyle here alludes to an advantage of the steady state theory: A universe that has always existed and will exist forever affords an infinite amount of time for life to emerge and to evolve. We shall return to this question later, when we’ll discuss the possible reasons for Hoyle’s stubborn clinging to the steady state idea.

  Following the presentations by Gold, Bondi, and Hoyle, the president of the Royal Astronomical Society, astronomer William Greaves, opened the subsequent discussion with a somewhat sarcastic remark: “Cosmology is one department of astronomy—sometimes I suspect its adherents of thinking it is the only part—but we all agree that it is a most important part.” As it so happened, one of the most distinguished physicists of the twentieth century, Max Born, was in attendance. When asked for his reaction to the steady state model, Born said:

  I am overawed by the whole character of the cosmologists! After the initial discoveries of atomic physics, physicists continue to find new particles at frequent intervals: so in cosmology we shall continue to discover new theories of world structure and evolution . . . I am filled with gratitude at hearing these papers, but I am skeptical.

  The first signs of trouble for the steady state model came not from optical telescopes but from radio astronomy. The universe is essentially transparent to radio waves, and, consequently, the antennae of radio telescopes could pick up signals even from distant (but “active” in the radio spectral range) galaxies that could barely be detected optically. In the 1950s, British and Australian scientists put to good use the expertise gained during World War II to develop a strong radio astronomy program. One of the pioneers in this endeavor was a physicist from the Cavendish Laboratory at Cambridge: Martin Ryle.

  Unlike Hoyle, Ryle came from a privileged background—his father was physician to King George VI—and he had received the best of what private education could offer. After some pioneering radio observations of the Sun in the late 1940s, Ryle and his group embarked on an ambitious program to detect radio sources beyond the solar system. Following some impressive improvements to the observational techniques that allowed them to discard background radiation from the Milky Way, Ryle and his colleagues discovered several dozen “radio stars” distributed more or less isotropically across the sky. Unfortunately, since most of the sources did not have visible counterparts, there was no way to determine their distances precisely. Ryle was of the opinion that these were peculiar stars within our own galaxy, and he was prepared to forcefully defend this view at a small gathering of radio astronomy enthusiasts.

  This so-called Massey Conference (named after atomic physicist Harrie Massey, who hosted it) took place at University College London in March 1951. Both Hoyle and Gold were present, and they did not hide their skepticism. At one point, Gold stood up and challenged Ryle’s conclusions. He contended that since the discrete radio sources were uniformly distributed in all directions, rather than being concentrated toward the plane of the Milky Way, they must be outside our own galaxy, at much larger distances. The only alternative, he argued, was that the sources were in fact so close that they were all contained within the relatively small thickness of the Galactic disk (distances shorter than one hundred light-years). Ryle’s hypothesis, that the sources were scattered all across the Milky Way, was untenable in Gold’s view. Hoyle fully supported Gold’s position, provoking a sarcastic comment from Ryle: “I think the theoreticians have misunderstood the experimental data.” Hoyle responded by pointing out that of the half a dozen sources or so that had actually been optically identified, five corresponded to external galaxies. Years later, he commented that Ryle used the word “theoreticians” in a way that implied some “inferior and detestable species.”

  This was but one of the many major clashes between the steady state theorists and Ryle, and it left emotional scars on both Hoyle and Ryle. In this particular case, Gold and Hoyle prevailed.

  About a year after the Massey meeting, astronomer Walter Baade determined that the distance to a radio source in the constellation Cygnus was hundreds of millions of light-years, confirming Hoyle’s suspicion. Ironically, however, it was precisely the great distance of the radio sources that later became the cornerstone of Ryle’s argument in favor of an evolving universe and which led to the downfall of the steady state theory. (The steady state theory never created much resonance in the United States, but in 1952, following a lecture by the Astronomer Royal, Sir Harold Spencer Jones, it did manage to generate a few headlines. Two of these, one in the New York Times and the other in the Christian Science Monitor, are shown in figure 29.)

  Figure 29

  Ryle had to suffer one more temporary embarrassment in his campaign against steady state cosmology, even though that particular sequence of events started with what had appeared to be a victory. The big bang and steady state models made distinctly different predictions about the distant universe. When we observe galaxies that are billions of light-years away, we get a picture of those galaxies as they were billions of years ago. In a continuously evolving universe (the big bang model), this means that we observe that particular part of the universe when it was younger and therefore different. In the steady state model, on the other hand, the universe has always existed in the same state. Consequently, the remote parts of the universe are expected to have precisely the same appearance as the local cosmic environment. Ryle seized on the opportunity afforded by this testable prediction and started to collect a large sample of radio sources, and to count how many of them there were at different intensity intervals. Since he had no way of knowing the actual distances to most sources (they were beyond the detection range of optical telescopes), Ryle made the simplest assumption: namely, that the observed weaker radio sources were, on average, more distant than the sources of the strong signals. He found that there were dramatically more weak sources than strong ones. In other words, it seemed that the density of sources at distances of billions of light-years (and therefore representing the universe billions of years ago) was much higher than the current density nearby. This was clearly at odds with a model of a never-changing universe, but it could be made consistent with a cosmos evolving from a big bang, if one assumed (correctly, as we now recognize) that galaxies were more prone to emit intense radio signals in their youth than at present, in their older age.

  Ryle presented his results on May 6, 1955, when he was giving the prestigious Halley Lecture (named after the famous seventeenth-century astronomer Edmond Halley). Without ever mentioning Hoyle by name, referring only to “Bondi and others” as the originators of the steady state model, Ryle’s verdict was unambiguous: “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 continued his attack a week later, when at the May 13 meeting of the R
AS, he and his student John Shakeshaft were delighted to close by saying, “We must conclude that the remote regions of the Universe differ from those in our neighborhood, a result which is not compatible with steady-state cosmological theories, but which may well be accounted for in terms of evolutionary theories.”

  Confronted with this serious challenge, Gold and Bondi, who attended the RAS meeting, found themselves on the defensive. Gold decided to craftily remind the audience that Ryle had been wrong before. He pointed out that he was “glad to see that there is now agreement that many of these sources are likely to be extragalactic,” as he himself had suggested four years earlier, when “Mr. Ryle . . . considered that such a suggestion must be based on a misunderstanding of the evidence.” He then added that based on the information presented, it was “very rash to regard the great majority of weak sources as extremely distant.” He cautioned that if the sources were not all the same, but, rather, there was a wide range of intensities among the intrinsic radio signals, then Ryle’s counting of weak sources could represent a confusing mix of faraway sources with nearby ones. Bondi was also skeptical of the interpretation of Ryle’s results. In his view, the uncertainties that still existed in the counts did not allow for conclusive inferences. To drive home this point, he reminded his audience that earlier attempts aimed at determining the geometry of the universe based on galaxy counts resulted in totally disparate conclusions.

  It goes without saying that Hoyle himself did not agree with Ryle’s interpretation. Rather than engaging in long arguments, however, he decided to wait for superior observational data to surface and refute Ryle’s finding. To the surprise of many astronomers, such contradictory results have indeed emerged. Australian radio astronomers showed in 1957 that Ryle’s earlier survey was seriously flawed: The map of radio sources that Ryle had produced was so blurred that blends of two or more radio sources were often counted as one. The consequences were clear to the Australian astronomers: “Deductions of cosmological interest derived from the analysis are without foundation.”

  Hoyle did not bother to rejoice. The year 1957 witnessed the publication of the celebrated B2FH, and he was deeply engrossed in the synthesis of the elements rather than in steady state cosmology. It had not escaped him, though, that forging most of the nuclei in stellar cores (instead of in a big bang) could also be seen as supporting (at least partially) a steady state perspective. In the same year, Hoyle was also elected as Fellow of the Royal Society, an honor that put him on par with Ryle in terms of his academic status. But Ryle did not give up. He and his team continued to introduce significant upgrades both to their instrumentation and to the data reduction and analysis. Their efforts resulted in the production of the third generation of the Cambridge catalogue of radio sources (known as the 3C Catalogue).

  By the early 1960s, Ryle’s group had at its disposal even an entirely new radio observatory, funded by the Mullard electronics company. The intellectual skirmishes between Ryle and Hoyle continued, culminating in one particularly unpleasant incident. Hoyle later described this traumatic experience in his autobiographical book Home Is Where the Wind Blows. It all started with what appeared to be an innocent phone call from the Mullard company in early 1961. The person at the other end of the line invited Hoyle and his wife to attend a press conference at which Ryle was expected to present new results that were supposed to be of great interest to Hoyle. When they arrived at the Mullard headquarters in London, Hoyle’s wife, Barbara, was escorted to a seat in the front now, while Hoyle was led to a chair on stage, facing the media. He had no doubt that the announcement would be related to the counting of radio sources according to their intensity, but he couldn’t believe that he would have been invited if the results were to contradict the steady state theory. In his words:

  Was I being uncharitable in thinking that the new results Ryle would shortly be announcing were adverse to my position? Surely, if they were adverse, I would hardly have been set up so blatantly. Surely, it must mean that Ryle was about to announce results in consonance with the steady-state theory, ending with a handsome apology for his previously misleading reports. So, I set about composing an equally handsome reply in my mind.

  Unfortunately, what Hoyle found utterly unthinkable did happen. When Ryle appeared, rather than making a brief announcement, as advertised, he launched into a technical, jargon-filled lecture on the results of his larger, fourth survey. He finished by claiming confidently that the results now showed unambiguously a higher density of radio sources in the past, therefore proving the steady state theory wrong. The shocked Hoyle was merely asked to comment on the results. Incredulous and humiliated, he barely mumbled a few sentences and rushed away from the event. The media frenzy that followed in the subsequent days disgusted Hoyle to the point that he avoided phone calls for a week and was absent even from the following RAS meeting on February 10. Even Ryle realized that the press conference had crossed the border of common decency. He called Hoyle to apologize, adding that when he agreed to the Mullard event, he “had no idea how bad it would be.”

  On the purely scientific front, however, despite these disturbing failures in etiquette, Ryle’s arguments grew increasingly compelling, and by the mid-1960s, the vast majority of the astronomical community agreed that the proponents of the steady state theory had lost the battle. (Figure 30 shows, from left to right, Gold, Bondi, and Hoyle, attending a conference in the 1960s.) The discovery of extremely active galaxies, in which the accretion of mass onto central, supermassive black holes releases sufficient radiation to outshine the entire galaxy, cemented the evidence against a steady state universe. These objects, known as quasars, were luminous enough to be observed by optical telescopes. The observations allowed astronomers to use Hubble’s law to determine the distance to these sources, and to show convincingly that quasars were indeed more common in the past than at present. There was no escape from the conclusion that the universe was evolving and that it had been denser in the past. At that point, the floodgates opened, and the challenges to the steady state model kept pouring in. In particular, in 1964 scientists Arno Penzias and Robert Wilson made a discovery that to all but its diehard supporters represented the last nail in the coffin of the steady state theory.

  Figure 30

  Penzias and Wilson were working at the Bell Telephone Laboratories in New Jersey with an antenna built for communication satellites. To their annoyance, they were picking up some sort of pervasive background radio noise: microwave radiation that appeared to be the same from all directions. After failing to explain away this disturbing “hiss” as an instrumental artifact, Penzias and Wilson finally announced the detection of an intergalactic temperature excess of about 3 Kelvin (3 degrees above absolute zero). Lacking the necessary background, Penzias and Wilson did not realize initially what they had found. Robert Dicke of Princeton University, however, recognized the signal immediately. Dicke was in the process of building a radiometer to search for the relic radiation from the big bang, previously predicted by Alpher, Hermann, and Gamow. Consequently, his correct interpretation of the results of Penzias and Wilson literally transformed the big bang theory from hypothesis into experimentally tested physics. As the universe expanded, the incredibly hot, dense, and opaque fireball cooled down continuously, eventually reaching its present temperature of about 2.7 Kelvin.

  Since then, observations of the cosmic microwave background have produced some of the most precise measurements in cosmology. The temperature of this radiation is now known to four significant figures to be 2.725 K, and its intensity changes with wavelength precisely as expected from a thermal source—confirming the predictions of the big bang. Even in the face of this overwhelming, contradictory evidence to the steady state theory, Hoyle was never convinced. He proposed that instead of representing a relic of the big bang, the cosmic microwave background is produced by some extragalactic iron “whiskers,” which absorb and scatter the infrared light of galaxies at microwave wavelengths. These iron whiskers were supposed
to have condensed from metallic vapors—for instance, in the material ejected by supernova explosions.

  In spite of Hoyle’s valiant efforts, beginning in the mid-1960s most scientists stopped paying attention to the steady state theory. Hoyle’s continuing attempts to demonstrate that all the confrontations between the theory and emerging observations could be explained away looked increasingly contrived and implausible. Worse yet, he seemed to have lost that “fine judgment” that he had once advocated, which was supposed to distinguish him from “merely becoming a crackpot.” At an international symposium on the topic “Modern Cosmology in Retrospect,” which took place in Bologna, Italy, in 1988, he gave a talk entitled “An Assessment of the Evidence Against the Steady-State Theory.” In that downright anachronistic talk, Hoyle tried (unsuccessfully, I should add) to convince his audience that all the compelling pieces of evidence for the big bang—the existence of the cosmic microwave background; the implied need for a primordial synthesis of the light elements deuterium, helium, and lithium; and the counts of the radio sources—could all still be explained by the steady state theory. Hoyle’s obstinate resistance to changing his views stood in stark contrast to the attitude adopted, for instance, by co-originator of the steady state theory Hermann Bondi. Recall that Bondi had insisted on being shown some fossil remains of what the universe was like in the past, if the universe was indeed evolving. In his own talk at the same conference in Bologna, Bondi admitted that such fossil evidence had indeed emerged, both in the form of the cosmic helium abundance, which had been shown to have most likely formed in the big bang, and in the cosmic microwave background, which beautifully matched the big bang predictions. Bondi therefore concluded graciously, “So my challenge of whether fossils could be found has had an answer long after I posed it.”