Brilliant Blunders: From Darwin to Einstein - Colossal Mistakes by Great Scientists That Changed Our Understanding of Life and the Universe (30 page)

The idea of matter being continuously created out of nothing may appear crazy at first. However, as Hoyle was quick to point out, no one knew where matter had appeared from in the
big bang cosmology, either. The only difference, he explained, was that in the big bang scenario all the matter was created in one explosive beginning, while in the steady state model matter has been created at a constant rate throughout an infinite time and is still being created at the same rate today. Hoyle contended that the concept of continuous creation of matter (when put in the context of a specific theory) was much more attractive than creation of the universe in the remote past, since the latter implied that observable effects had arisen from “
causes unknown to science.” To achieve a steady state, Hoyle added to Einstein’s general relativity equations a “creation field” term, the effect of which was to create matter spontaneously. What sort of matter? Hoyle did not know for sure, but he conjectured,
“Neutron creation appears to be the most likely possibility. Subsequent disintegrations might be expected to supply the hydrogen required by astrophysics. Moreover, the electrical neutrality of the universe would then be guaranteed.” The rate at which new atoms were supposed to materialize out of empty space was too small to be directly observable. Hoyle described it once as “about one atom every century in a volume equal to the Empire State Building.”

Figure 28

The key virtue of the steady state scenario was that, as expected
from all good scientific theories, it was falsifiable. Here is how philosopher of science Karl Popper expressed his views on what constitutes a theoretical system of natural science:

I shall not require of a scientific system that it shall be capable of being singled out, once and for all, in a positive sense; but I shall require that its logical form shall be such that it can be singled out, by means of empirical tests, in a negative sense:
it must be possible for an empirical scientific system to be refuted by experience.

The steady state model predicted that galaxies that are billions of light-years away should look, statistically speaking, just like nearby galaxies, even though we see the former as they were billions of years ago because of the time it takes their light to reach us. Bondi used to challenge the supporters of the evolving universe (big bang) model by saying, “If the universe has ever been in a very different state from what it is now, show me some fossil remains of what it was like a long time ago.” In other words, if, for instance, extremely remote galaxies were found to look (on the average) very different from galaxies in the neighborhood of the Milky Way, our universe could not be in a steady state.

When Hoyle, and, separately, Bondi and Gold, published their steady state papers, they presented the astrophysics community with a choice between two very different world views. On one hand, there was the big bang model, in which the universe was assumed to have had a beginning in the form of a dense and hot state (which Lemaître called the “primeval atom”). In addition to Lemaître, George Gamow was perhaps the strongest advocate for this scenario. As we saw in the last chapter, Gamow even (mistakenly) thought that all the chemical elements had been forged in this cosmic initial explosion.

In contrast to the big bang stood the steady state model, with
its infinite past and unchanging cosmic scenery, despite the overall expansion. However, the telescopes of the late 1940s were not powerful enough to detect whether an evolutionary trend of the type implied by the big bang model existed or not. When Hoyle met Edwin Hubble for the first time, in August of 1948, he was delighted to hear from the latter that what was supposed to become the world’s largest telescope—the two-hundred-inch telescope on Mount Palomar in California—was undergoing its final testing. Hubble hoped to start observing remote galaxies soon thereafter. Disappointingly, however, even the large mirror of the Mount Palomar telescope could not collect enough light from very distant, ordinary galaxies to distinguish unambiguously between the two rival theories.

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.