God In The Equation Read online

  The paper describing this innovation was a masterpiece of concise writing: just one page in a 1948 issue of the journal Physical Review. It also was a showcase for Gamow's eager sense of humor. He was amused that Alpher's name sounded like alpha, the first letter of the Greek alphabet, while his own resembled gamma, the third. All he needed was a beta so that the byline would read a, 3, y—perfect for a paper about the beginning of the universe. He impetuously added Bethe's name to a paper that he had not written and credited the finished product to Alpher, Bethe, and Gamow. Gamow was so tickled by his little joke that he even attempted to persuade Robert Herman, a physicist at Johns Hopkins who had contributed to the nuclear-cooking concept, to sign onto the paper under the assumed name of Delter.

  While calculating the reactions in the ylem, Alpher and Herman recognized that the energy from that initial conflagration could not disappear. One of the most stringent principles of modern science is that energy cannot be created or destroyed. So the energy of the initial moment must still exist, though diluted tremendously by the subsequent expansion of the universe. Their 1948 calculations predicted that the fiery early life of the cosmos should leave a background ocean of radiation, a divine light that would keep the universe warmed to a temperature of five degrees centigrade above absolute zero, or -451 degrees Fahrenheit. Such radiation would mostly be in the form of short-wavelength radio waves, or microwaves. This prediction attracted little attention at the time but proved hugely important two decades later. One reason for the lack of interest was that the researchers did not explicitly state that the energy would be in the form of potentially observable microwaves. But the technology of the day probably could not have detected such a feeble signal anyway.

  The parallels between the alpha-beta-gamma theory and the story of Genesis provoked much comment from both the scientific and the religious sides of the fence. In fact, there is no indication that Gamow and Alpher were thinking about the Bible or that they had the slightest interest in using the new sci/religion to prop up the old Judeo-Christian one. Their ideas followed in the tradition of the primeval atom, which grew out of Lemaitre's desire to roll back the boundaries of science even if that meant constricting the Christian beliefs that meant so much to him. Gamow didn't even like hearing his model called the big bang. He felt that term emphasized the original instability over the nuclear reactions and subsequent evolution of the universe that formed the heart of his theory. To the general public, however, creation lay at the heart of this new cosmological model. In his dissertation defense, Alpher had remarked that the phase during which the elements formed took about five minutes. This comment was immediately satirized by Herblock, the Washington Post's influential editorial cartoonist, and picked up by a number of newspapers. “There were poignant responses from people who wanted to pray for my soul,” Alpher recalled. Gamow sent a copy of his paper to Einstein, who gave it a much warmer welcome. “The idea that the whole explosion process started with a neutron gas seems quite natural,” Einstein wrote in response. He approved of the way that Gamow had concocted a single, elegant mechanism to produce all of the different chemical elements and didn't seem too offended that Gamow's work implied a moment of origin for the universe.

  In his paper, Gamow did not specify why or how the initial expansion began, but off the record he certainly did think about the matter. His old mentor, Friedmann, had already pointed toward one possible explanation. An expanding universe need not expand forever. If the cumulative mass of the galaxies is great enough, the universe ultimately stops expanding and everything falls back together again. This was the oscillating or “phoenix” universe that Einstein briefly embraced in 1931. Gamow toyed with it again around 1950, giving it the whimsical name “the Big Squeeze.” Rather than the endless cycles of Hindu mythology, which Friedmann had envisioned, Gamow pictured one big pileup in which a thin, vast spread of matter and energy fell together, then rebounded to produce the modern universe. He didn't seem overly concerned with figuring out where that earlier universe had come from. Robert Dicke, a leading theorist at Princeton, also investigated oscillating solutions to Einstein's equations, as did some other mainstream thinkers well into the 1960s. They liked the big squeeze for the same reason it appealed to Friedmann: it allowed an expanding universe without demanding a beginning, and it echoed ancient mythologies describing endless cycles of cosmic history.

  But the cyclical universe never really caught on. Lemaitre rejected the idea of an endless succession of primeval atoms, which fit neither his science nor his philosophy. He believed he had found his own way out by appealing to the laws of quantum physics to obscure the manner in which the universe began. Eddington offered a withering philosophical critique of the cyclical models: “I would feel more content that the Universe should accomplish some great scheme of evolution and, having achieved whatever might be achieved, lapse back into chaotic changelessness, than that its purpose should be banalized by continual repetition.” He also disdained the fussy, microscopic nature of Gamow's analysis and preferred to pursue his idiosyncratic, big-picture view of the primeval atom. The theoretical problems were just as bad. Nobody could devise a plausible mechanism that would enable a collapsing universe to bounce and become a new expanding one. Careful calculations showed that radiation could not be destroyed at the end of a cycle, so each universe would be hotter and brighter than the one before; presumably this could not be an endless process after all. Although the oscillating universe never gained a serious scientific following, cosmologists have found ever more creative ways to have an expanding universe that does not require a magic moment when time began.

  Gamow's marriage of physics and cosmology established a new tradition of treating the universe as an enormous petri dish. With Alpher's and Herman's help, he assembled a set of equations describing nuclear reactions, plugged in assumptions about the temperature, density, and composition of the early universe, turned the crank, and compared the results to the actual universe. In essence, God's creation was being reduced to an engineering problem. This was also one of the first scientific applications of the newly developed electronic computer, adding to the impersonal connotations of the work. Einstein's original plan had grown much more elaborate. In addition to the equations describing the form of space, now there were equations to trace the history of matter. Yet with every push into the unknown came another mystery, another job for Lambda or one of the cosmologists' other hedges that reconcile beautiful theory with messy reality. In this case, one of the problems was very serious. The nuclear reactions in the ylem just plain didn't work as Gamow had hoped. They sputtered out too soon, so that the big bang produced only featherweight elements like helium and lithium. Gold, lead, and the other atomic bruisers had to come from somewhere else.

  The hard-charging British astrophysicist Fred Hoyle believed he had already deduced the location of that somewhere else. Hoyle was a determined individualist who proudly maintained his working-class Yorkshire accent during his tenure at Cambridge University. As a child he played with household chemicals, unleashing foul-smelling gases and fabricating batches of gunpowder; he never really outgrew this penchant for causing trouble. Although Hoyle started out working on quantum theory, in the late 1930s he switched directions and threw himself into astronomy, continuing his studies even while developing radar systems during World War II. From early on, Hoyle had no stomach for Gamow's big bang theory of cosmic origin, which he found philosophically objectionable. In fact, it was Hoyle who coined the name big bang, in the course of a series of radio lectures he performed for the BBC. Contrary to many reports, he claims the term was intended not as derisive, just colorful. Still, he had no doubt Gamow was barking up the wrong tree when it came to creating heavy elements. In the late 1930s, Bethe had already showed how nuclear fusion in stars might create elements as heavy as chemical middle-weights such as oxygen and nitrogen. It seemed that ordinary stars probably couldn't synthesize anything heavier. But what about extraordinary stars? Hoyle suspected
the source of the heavy elements was as plain as the specks of light on the old Mount Wilson photographic plates: supernova explosions, potent stellar detonations that can briefly shine as brilliant as an entire galaxy.

  The most common kind of supernova occurs when the interior of a massive star collapses, causing its internal temperatures and pressures to skyrocket. A wave of nuclear burning, just a fraction of an inch thick, tears through the star, consuming everything it encounters; all the fusion energy that is normally released gradually over a star's lifetime pours out in one burst. Physicists had not yet worked out these details in the 1940s, but Hoyle well understood the potential influence of supernovas on cosmic chemistry. The tremendous density of energy and matter at the center of a collapsing star creates the perfect place to synthesize heavy elements all the way to gold, uranium, and beyond. Supernovas have had a profound influence on the history of science. Bright stellar explosions in 1572 (studied by Tycho Brahe and known as Tycho's Supernova) and 1604 (similarly followed by Johannes Kepler and hence called Kepler's Supernova) proved to Renaissance sky gazers that the heavens are not fixed and unchanging. The Andromeda supernova of 1885 had confused the Great Debate by making it seem as if the spiral nebulae were much closer than their true distances. During the 1950s, supernovas showed Hoyle how to connect nuclear processes with the evolution of stars and the birth of the universe. And in the 1990s, studies of supernovas forced astronomers to revise their ideas of how the universe expands.

  The success of Hoyle's supernova analysis cemented his innate skepticism about the big bang. Knowing that some heavy elements could form in exploding stars, he wondered whether all heavy elements might have originated there. This simplifying assumption would eliminate the need for Gamow's hypothetical cosmic egg. And at the time, there were a several good reasons to look for an alternative cosmological model. The most concrete of these was the nagging age paradox. Hubble thought he had obtained a reasonably accurate measure of the rate at which the universe is expanding, and his authority was such that nobody questioned his results for years. If one extrapolates backward from Rubble's reported galactic motions, the cosmos should have been compressed into a white-hot dot less than two billion years ago. But geologists knew the Earth was older than that, and astronomers had strong evidence that stars and galaxies were billions of years older still. The big bang might be a nice creation story, but it didn't seem to leave enough time for the creation part.

  Beginning in the 1940s, however, the German-born astronomer Walter Baade gathered startling new evidence that would ease the age problem considerably. Baade, another member of the Mount Wilson brigade, was a skilled and cautious observer. He was considered an enemy alien during World War II, so he was not allowed to participate in military science projects or even to leave the county of Los Angeles. The upside was that he suddenly found it much easier to schedule time on the Hooker telescope. Taking advantage of sensitive new photographic films and exceptionally dark skies—the city lights were extinguished for wartime security—Baade systematically studied the Cepheid variable stars that Hubble and others relied on for determining the scale of the universe. After the war Baade continued this work on the most powerful instrument in the world, the enormous new two-hundred-inch reflector on California's Mount Palomar. Finally, in 1952, he dropped his bombshell. Contrary to what every astronomer believed, there are two kinds of Cepheid variable stars, one much brighter than the other. The ones that Hubble had studied were the brighter variant. Thinking that he was looking at a much fainter population of stars, Hubble had systematically erred and seriously underestimated the distances to his galaxies. Using the recalibrated data, Baade found that all the galaxies were twice as far away, and the universe twice as old, as Hubble originally estimated. Allan Sandage, Hubble's protege at Mount Wilson, continued this effort and made additional corrections that kept nudging the cosmic age further upward. By the end of the decade, he estimated the universe could be as much as thirteen billion years old. At the same time, astronomers realized that star clusters need not be nearly as old as they had believed. The age problem was a problem no more.

  But Hoyle also objected to the big bang on philosophical grounds, and these points of contention never went away. Einstein's original static cosmology had at least offered a single, eternal description of the universe. The expanding universe, on the other hand, had spawned an entire family of interpretations, including de Sitter's, Friedmann's, Lemaitre's, Eddington's, and Einstein's own 1932 revision. It was no longer a single doctrine that offered a single picture of the universe. Hoyle found the absence of a unique solution unsatisfying. Models that incorporated some arbitrary amount of Lambda in order to get around the age paradox only made them uglier to his eyes. The big bang implied that the universe evolves over time, which implied that natural laws might also evolve over time. Such evolution would undermine the repeatability of experiments and so undermine the cornerstone of scientific method.

  Moreover, the big bang does not specify the initial conditions that gave rise to the universe. Matter and the laws that govern it just came into being. Einstein's cosmological principle required that the universe be homogeneous and uniform in all directions. By every measure, he appeared to be correct. But again the big bang didn't explain why the universe is built that way; it just assumed it happened. To Hoyle, the big bang suggested a horrible limit to human inquiry. It ruled out any exploration of the physical laws and conditions that preceded the initial neutron fireball, leaving science emasculated. “We are forbidden to calculate what happened before a certain moment in time,” Hoyle complained. While reading Howard Robertson's massive summary of cosmological thinking, originally published in 1933 but still very relevant, Hoyle found himself deeply dissatisfied. “Has he thrown his net wide enough? Are there any other possibilities?” he wondered. Like Milne before him, Hoyle decided to challenge the new orthodoxy.

  To build a better creation mythology, Hoyle teamed up with two newcomers to cosmology. Thomas Gold was a brash young engineer whose only published work was on the physiology of the inner ear. Hermann Bondi was a highly adept mathematician with little grounding in astronomy. Both men were technically enemy aliens—they were Austrian citizens living in England—who became fast friends during their months in an internment camp in Quebec. After their release from internment, they worked on wartime radar research with Hoyle. When World War II ended, Hoyle guided the group toward problems in astronomy, particularly the matter of the expanding universe. Hoyle would ride his bicycle to a house that Bondi and Gold rented, some fifty miles from Cambridge. Then the three men would spend evenings together pondering the workings of the universe, while Hoyle would pace about and ask, “What could the Hubble observation mean? Find out what it could mean!”

  After many days like this, Gold hit on the idea of a universe that keeps growing but never changes. Hoyle later claimed, perhaps a bit too colorfully, that the idea was inspired by the 1945 British film Dead of Night, a ghost story whose hallucinatory plot ends up exactly where it began. According to Hoyle's reminiscences, “Tommy Gold was much taken with it and later that evening he remarked, 'How if the universe is constructed like that?' One tends to think of unchanging situations as being necessarily static. What the ghost-story film did sharply for all three of us was to remove this wrong notion.” The three researchers proposed a radical alternative to the big bang. In their cosmological model space still expands, ferrying galaxies apart from one another, but new matter spontaneously appears in the gulfs that arise. Over time, that matter would coagulate into baby galaxies that fill the voids. “So we have a situation in which the loss of galaxies, through the expansion of the universe, is compensated by the condensation of new galaxies, and this can continue indefinitely,” Hoyle said. Plus fa change, plus c'est la meme chose—the more things change, the more they stay the same. Such a universe would conform to what Gold called the “perfect cosmological principle.” Not only does it look the same in all places, it looks the same at all tim
es.

  This “steady state” rival to the big bang arrived in two papers, one by Hoyle, the other by Gold and Bondi, published in the summer of 1948 in Monthly Notices of the Royal Astronomical Society. The two camps differed in their approaches: Hoyle's was more mathematical, Gold and Bondi's more conceptual. The latter paper emphasized the key importance of the perfect cosmological principle, which Gold and Bondi saw as an essential reform for the Temple of Einstein. “If it does not hold, one's choice of the variability of the physical laws becomes so wide that cosmology is no longer a science,” they wrote. Hoyle was less interested in this argument than in the practicalities of grafting a steady, unchanging interpretation onto the existing mathematical descriptions of the expanding universe. But overall, the papers struck very similar themes. The steady state universe required the continuous creation of matter from nothing. In the wide-open and constantly expanding stretches of intergalactic space, new particles would simply pop into existence. The universe is so huge that the creation events need not happen very often. In Hoyle's words, it would require only “one atom every century in a volume equal to the Empire State Building.”

  Hoyle recognized that many of his colleagues would object that the spontaneous creation violated well-known conservation laws, which state that matter and energy cannot be created or destroyed. “This may seem a strange idea and I agree that it is, but in science it does not matter how strange an idea may seem so long as it works—that is to say, so long as an idea can be expressed in a precise form and so long as its consequences are found to be in agreement with observation. In any case, the whole idea of creation is queer. In the older theories all of the material in the universe is supposed to have appeared at one instant of time, the whole creation process taking the form of one big bang. For myself, I think this idea very much queerer than continuous creation,” he explained in one of his BBC presentations. Thus Hoyle cast himself as a purist whose cosmological model flouted conservation laws but strictly followed the most hallowed scientific doctrine, the falsification of theory through observation. The steady state model made testable predictions about how new matter appears. The big bang placed the creation process at some unknowable first moment and so was inherently less scientific in Hoyle's estimation. The steady state also provided a ready explanation for the overall smoothness of the universe: the incessant expansion and regeneration would eventually erase any irregularities, no matter how large. The big bang had to assume smoothness as an inherent condition of the universe. In the 1980s, supporters of the big bang developed a substantially revised version of the theory to address these serious criticisms.