God In The Equation Read online

  A more serious cosmological heresy came from the pen of Edward A. Milne, a well-respected stellar astronomer at Oxford University who had previously had little interest in grandiose theories of the universe. His conversion began with, of all things, the letters page of The Times of London. In a series of exchanges published during May of 1932, the prominent British astronomer James Jeans spoke out staunchly in defense of Einstein's notion of curved space and insisted that it was the only way to make sense of Hubble's findings. Milne, a small, rigorous man who firmly believed that science should deal only with observable phenomena, worked himself to a slow boil while reading each round of the correspondence. He was appalled by all this abstract talk about the structure of space and dissatisfied with models that offered no explanation of why the universe is expanding rather than contracting, which should be just as mathematically plausible.

  One month after the epistolary brawl in The Times, Milne published what he considered a much simpler and more sensible explanation for the reddening of distant galaxies. He developed an alternative to general relativity, called “kinematic relativity,” which largely preserved classical, Newtonian conceptions of space. In essence, he treated the expansion of the universe the way a laboratory physicist would treat a ball of expanding gas. Milne considered a large group of galaxies scudding about at random. Over time, he pointed out, the fastest-moving ones would naturally migrate to the periphery of the group by virtue of their extreme velocities, while the slowest ones would remain toward the center. Such an arrangement, he noted, would create the illusion of an expanding universe from a vantage within the whole swarming mess. In this way, he could account for Hubble's observations with no curved space and no Lambda. Milne disapproved of applying relativity to the universe as a whole, which he saw as an unjustified extrapolation from known physical laws. “If the curvature of space cannot be determined, if it is essentially unobservable, then it should be rejected,” he wrote.

  The shock of Milne's comments reverberated through the 1930s. Unlike Zwicky, Milne was no fringe character; for several years his was one of the most widely discussed cosmologies in England, where many of the leading theorists then worked. Moreover, his cleverly constructed argument exposed philosophical issues that certain researchers might have preferred to remain hidden. In Milne's cosmology, galaxies could not be spread evenly through space, as Einstein and his followers had assumed; every observer would see redshifts, but kinematic relativity would not lead to a homogeneous universe. Hubble rejected this almost out of hand. It's not hard to see why: a lumpy universe would wreck his observing program. “The observable region is our sample of the universe. If the sample is fair, its observed characteristics will determine the physical nature of the universe as a whole,” he wrote.

  But if the cosmic regions accessible to Mount Wilson's one-hundred-inch telescope were not representative of the whole, then that extrapolation would be worthless. Hubble, who tried so hard to cast himself as the incorruptible reporter, could not bear to let go of his sweet faith that his scans of the heavens could reveal the master plan of the universe. Milne also got in a few digs by claiming that his picture of the universe adhered to Einstein's principles, sticking to observable phenomena and understanding them through reason and intuition. The implication was that Milne was not a heretic but in fact a more devout Einsteinian than Einstein.

  Five years later, Herbert Dingle, a grand eminence in British astronomy, attacked Milne in an essay entitled “Modern Aristotelianism.” Dingle accused Milne of behaving like Aristotle reincarnate, plucking ideas directly from his mind rather than arriving at them inductively from observable truths. The charge, though not unfounded, could have been leveled quite plausibly against every theoretical cosmologist then, and against a fair number of them today as well. During the 1940s, Milne revealed more and more of a neo-Christian religious agenda behind his work. In his view, the only universe that reflects the glory of God is one that begins from a point and expands outward to infinite dimension over infinite time. “In creating an infinite universe, we can say that God has provided himself with the means of exhibiting and practicing his own omnipotence,” Milne explained. This belief in the infinite cosmic life span echoed Einstein's initial conception of the universe, not to mention Aristotle's, which placed Milne's cosmology distinctly behind the times. It didn't have any clear grounding in traditional Christian doctrine, but neither did it contribute to the unified picture of the universe growing out of general relativity. Kinematic relativity was a curiosity but, for a few years, at least, a high-profile possibility that scientists had to investigate. In principle, it should have been possible to distinguish the Milne and Zwicky cosmologies from the orthodox expanding universes promoted by Einstein and his followers. Until the verdict was in, Hubble tried to stay above the fray, continuing to describe the redshifts as “apparent velocities” of galaxies. Seeking guidance from the brain trust at Caltech, Hubble arranged biweekly meetings at his home, where the observers and theorists would sip whiskey, nibble at Grace Hubble's sandwiches, and jot down their latest ideas on a borrowed blackboard. Most fruitfully, Hubble teamed with his friend Richard Tolman, a Caltech physicist well versed in matters of relativity, to find ways to use the images and spectra from Mount Wilson's one-hundred-inch brute to distinguish among the competing cosmologies. His data were not nearly detailed enough to settle the matter, however. If anything, they fit better with Zwicky and Milne than with Lemaitre and Einstein, but mostly they proved nothing. Mapping the large-scale distribution of galaxies and pattern of redshifts required even greater light-gathering power. World War II delayed the inauguration of the two-hundred-inch Hale telescope on Mount Palomar until 1948. For the next decade and a half, therefore, Hubble and the other observers had no significant new findings to contribute. Yet on the theoretical side, cosmology progressed at an extraordinary clip during that time, continuing to grow in explanatory power by drawing authority from other corners of science.

  The key change was that scientists started thinking much more realistically about the past state of the universe. If galaxies really are moving away from one another—as nearly everyone but Zwicky accepted—then the conditions of the universe must have changed greatly over time. Maybe the powerful telescope atop Mount Wilson could not see those early conditions directly, but there might be ways to search for relics from past eras. Just as archaeologists reconstruct the history of long-lost civilizations from bone fragments and shards of pottery, cosmologists could retrace the history of the universe from elements or radiation created under physical conditions that no longer exist. A few decades earlier, such investigations would have seemed absurd. Everyone still believed, like Aristotle and Newton, that the universe was eternal and unchanging. Individual stars, even galaxies, might evolve and change, but the physical state of the universe was a constant.

  Alexander Friedmann took the first step toward tracking the construction of the cosmos back to an initial point, but it was Lemaitre who really showed the way into the promised land. His primeval atom hypothesis, introduced in 1931, brushed aside ancient scientific and religious taboos. For the first time, a scientist dared to speculate in a specific, physical way about the origin of the universe. He took into consideration the way that radiation would exert a dominant outward pressure when the universe was very small and even tried to imagine how the rules of quantum physics would play out in such a situation. Equally noteworthy, Lemaitre thought seriously about aftereffects of the eruption of the primeval atom that might still be noticeable today: “This highly unstable atom would divide in smaller and smaller atoms by a kind of super-radioactive process. Some remnant of the process might, according to Sir James Jeans's idea, foster the heat of stars until our low atomic number atoms allowed life to be possible.” Since scientists at the time did not understand the exact nuclear reactions that powered stars, this was not an implausible idea. Lemaitre also mused that some fragments from the primordial cosmic fireworks might still survive. He thought thes
e might explain the existence of cosmic rays, energetic subatomic particles that shower down onto the Earth from space.

  Lemaitre was no nuclear physicist, so his entire picture of the primeval atom was highly impressionistic. At any rate, scientists had only a vague conception of the workings of the atomic nucleus. The discovery of the neutron, crucial for the development of nuclear theory, occurred in 1932, a year after Lemaitre proposed the primeval atom. In general, his ideas received a warmer reception in the popular press than in the scientific literature. Eddington still resisted the idea of “a single winding up at some remote epoch.” Hubble considered Lemaitre's model “dubious” because it seemed to lead to a universe much smaller and denser than indicated by the photos from Mount Wilson. The search continued for a model that satisfied both the stars and the psyche. Nevertheless, Lemaitre's fireworks cosmology got scientists thinking about how to investigate the conditions in the very early universe and connect them to today's observed reality.

  Tolman and his friend Howard Robertson, another Caltech theorist, brought greater mathematical rigor to Lemaitre's speculations. During the early 1930s, they explored the thermodynamics of the cosmos, analyzing how the background temperature of the universe would have changed over time. Today it is extremely cold in space. In the distant reaches between the stars, temperatures hover just three degrees centigrade above absolute zero. (Absolute zero is the coldest possible temperature, the point at which essentially all molecular motion ceases.) Tolman and Robertson constructed a mathematical model of the universe, filled it with radiation, and watched what happened when they ran the clock backward. If you compress a mass of air—by pumping a bicycle tire, for instance—it grows hot. In these theoretical simulations, the expanding universe behaved much the same way. The cosmic temperature increased in inverse proportion to the average distance between galaxies, the researchers found. When the universe was tiny, a tremendous amount of radiation was crammed into a small space and the universe must have been a hellish place.

  Tolman and Robertson considered their work an interesting game, but not necessarily indicative of the real universe. As Tolman wrote in 1934, “We must be specially careful to keep our judgments uninfected by the demands of theology and unswerved by human hopes and fears. The discovery of models, which start expansion from a singular state of zero volume, must not be confused with a proof that the actual universe was created at a finite time in the past.” But his warning was instantly self-destructing, like one of those narrated cassette tapes from an old Mission: Impossible episode. By pursuing this line of inquiry, Tolman had already displayed a profound hope that mathematical extrapolations from laboratory physics could reveal how the entire universe had evolved. He was grasping for the one dimension that Einstein had sidestepped in his 1917 cosmology, the dimension of time. Still, Tolman wasn't yet prepared to take the plunge and seriously consider what the universe might have been at that “singular state” far in the past. Lemaitre, on the other hand, had no trouble speaking eloquently about his ancient primeval atom but lacked the detailed physics knowledge to give more than a hand-waving account of how that atom might have led to the modern universe.

  All the elements were out there for sci/religion to take a leap back to the earliest moments of the universe. George Gamow—an energetic and sportive physicist who had a deep grounding in the nascent science of the atomic nucleus—was the first to step forward and seize the opportunity. Many others quickly followed. Born in Odessa in 1904, Gamow decided early in life that traditional religion could not be trusted. After watching Communion in the Russian Orthodox Church, he decided to see for himself whether red wine and bread could transform into the blood and flesh of Jesus. He held a bit of the blessed bread and wine in his mouth, ran home from church, and placed the specimen under the lens of his new toy microscope. It looked identical to an ordinary bread crumb that he had prepared at home earlier for comparison. “I think this was the experiment which made me a scientist,” he recalled.

  While a student at Petrograd University, located in what is now St. Petersburg, Gamow studied under Alexander Friedmann. The young Gamow fell in love with general relativity and with his professor's visionary notions about cosmology. Other, less pleasant experiences hardened Gamow's distaste for dogma. Russia's new rulers required that university education include training in the Marxist-Leninist philosophy known as dialectical materialism, a confusing hash of ideas based around the notion that progress occurs through the interaction of opposites. Gamow, a natural prankster, didn't take well to being tested on this nonsense and nearly flunked his exam. The Soviet philosophy, he wrote, “played very much the same role as that of Church dogma in the Middle Ages, sometimes assuming grotesque forms.” Dialectical materialism was used to justify all manner of arcane beliefs, including, for a time, an official state position disputing the theory of relativity and affirming the existence of the ether. His reaction against the perceived absurdities of Leninist thinking and church doctrine only encouraged Gamow in his playful approach to science.

  Not surprisingly, Gamow left Russia as soon as he had the chance, in 1928. He took a fellowship at Cambridge University, where he learned the latest thinking about the atomic nucleus from Ernest Rutherford, a pioneer in the study of radioactivity. In 1934 Gamow settled at George Washington University. During these years, he helped make the first connection between astronomy and nuclear physics by investigating one of astronomy's most visible unsolved questions: How do the stars shine? By this time, most scientists felt the origin of star power must lie at the center of the atom; no other known source of energy could keep a sun shining for billions of years. Another clue came from recent studies of the composition of the stars. Astronomers had long assumed that the stars contained the same mix of elements as the Earth. Around 1925, Cecilia Payne-Gaposchkin, once again hovering at the edges of great discoveries, carefully studied the atmospheres of stars and found them full of hydrogen and helium, the two lightest elements. On the Earth, hydrogen is a secondary constituent mostly locked away in water (the H in H2O), and helium is virtually nonexistent. The discovery was so shocking that her colleagues refused to believe it until it was repeatedly verified over the next few years. The abundance of hydrogen turned out to be the crucial clue not only for finding the energy source of stars, but also for decoding the first moments of cosmic history.

  If stars are full of light elements, Gamow reasoned, then perhaps the heavier elements arose as a result of nuclear reactions in the stellar interiors. Under everyday conditions, such reactions never happen. Positively charged hydrogen nuclei stay away from other hydrogen nuclei, because like charges repel one another. But Gamow recognized that in accordance with quantum physics, particles can briefly bend the rules and overcome that repulsion. If the particles are moving quickly enough—that is, if they are tremendously hot—they can get close enough to fuse together into helium nuclei and release a great deal of energy in the process. Hans Bethe, a German theoretical physicist with similar obsessions, figured out the details of how such nuclear reactions power a star. Gamow was more interested in how the reactions could keep going and synthesize everything in the universe out of two simple particles, the proton (which is the same as a hydrogen nucleus) and its uncharged twin, the neutron. Physicists soon discovered that the reactions in stars could not produce the heaviest elements, but now a fresh idea took root in Gamow's fertile brain. If Tolman and Robertson were correct, the whole universe started out like the center of the sun, only far larger, hotter, and denser. The stars, Gamow suspected, were the bit players. All of the heavier elements—the carbon in our bodies, the iron in our cars, the silicon in the mountains, everything—might have formed in rapid succession in a primordial cosmic fireball.

  Gamow had plenty of time to develop these ideas. While many of his colleagues worked on the Manhattan Project, he did not receive clearance and so continued his research. Initially he had pictured a top-down scenario, in which Lemattre's radioactive superatom decayed explosivel
y into lighter elements. But his ideas began to change after the end of World War II, aided by the rapid advances in nuclear physics in the United States. In 1946 he reversed course and imagined a world starting with a thick soup of neutrons—which spontaneously decay into protons and electrons, providing all the necessary ingredients for atoms—merging into heavier elements, bottom-up. Ralph Alpher, then a graduate student at George Washington University and Johns Hopkins, performed the difficult calculations needed to transform the concept into a detailed physical model. This new theory of the early universe mirrored Hubble's discoveries at Mount Wilson. Hubble stretched the reach of science through space; Gamow extended it through time. Both discoveries showcased the growing technological power of the United States, and with it the implied mastery over physics at the largest and smallest dimensions. When he witnessed the first nuclear test, J. Robert Oppenheimer unforgettably quoted from the sacred Hindu text Bhagavad Gita: “I am become death, the destroyer of worlds.” Gamow offered an inverse kind of hubris. He promised that the same nuclear theory that obliterated Hiroshima and Nagasaki could read the story of creation back to its very first page. Now Adam could understand how God built the Garden of Eden.

  In the beginning, there was light. More specifically, there was a blazingly hot mixture of neutrons and energy, seething and interacting with one another. Gamow called the initial particle soup ylem, taken from the Greek word for the unformed state of existence that preceded the creation of the world. In a period of just forty-five minutes, a wave of nuclear cooking swept through the ylem and created heavier atomic nuclei. Alpher had calculated the recipe by which an element captures a neutron and moves up one rung in the periodic table, using newly declassified data from the Manhattan Project. The theory worked well, up to a point. It correctly indicated that one-quarter of the mass of the universe should be helium, but it could not account at all for the heavier elements. Nevertheless, this was the first time anyone had dared use modern physics to try to understand a phenomenon that occurred billions of years ago.