by Adam Frank
BEGINNING THE BEGINNING: THE PRIMEVAL ATOM
The story of modern cosmology is often told as a straight line from Hubble’s expanding universe to the glorious confirmation of what in the 1960s would be called “hot” Big Bang theory. History, however, is far more complex and interesting. The Big Bang was proposed not once but three separate times over a span of thirty years. Until its final incarnation, it was resisted by a sizeable faction of physicists and astronomers with rival, alternative cosmologies gaining considerable attention and followers. But like any good story, the triumph of the Big Bang has its share of characters, obstacles and fortuitous accidents.
The Big Bang’s first incarnation originated with Lemaître, the same shy Catholic priest-scientist who provided a proper general relativistic account for Hubble’s expanding universe. Lemaître’s solution had come to be called the Eddington-Lemaître model because together the pair had successfully reintroduced it to the astrophysical community. But Eddington was a strong advocate for an eternally expanding universe and would brook no discussion of cosmic origins.13 “Philosophically, the notion of a beginning of the present order of Nature is repugnant to me”, Eddington said.14 Lemaître disagreed. Motivated by issues of science and not religion, he felt discussions of the universe at its earliest moments could be fruitful and productive, yielding real, measurable predictions.
In exploring the universe’s origins Lemaître took his cosmological cue from quantum physics. Knowing radioactivity to be fundamental to the process of splitting large nuclei into smaller ones, Lemaître imagined the same process might be writ large on the cosmos. Following his own expanding universe models backwards, Lemaître imagined an early stage of cosmic history in which all mass-energy was packed into a single primeval nucleus.
In Lemaître’s theory, first proposed in the mid-1930s, the history of the universe became a process of super-radioactivity. The primeval atom split and split again, with smaller and smaller “atoms” dividing out until, ultimately, all the particles present today were born. Once again the ancient questions of cosmology would return to be recast into a new era’s language. The most important aspect of Lemaître’s theory was its use of quantum physics’ infamous indeterminacy to avoid questions of what caused the universe (and time) to just begin. Lemaître was leaning hard on quantum physics to vault over a cosmological dilemma of origins known for centuries and often referred to as Kant’s First Antimony.15
Three hundred years before Lemaître, Immanuel Kant asked how the universe could be explained through a deterministic cause when it must embrace all causes. Since the universe encompasses all things and, therefore, all causes, what can exist outside to set it in motion? In essence the First Antimony states, “That which causes all effects cannot itself have a cause.” Quantum mechanics gave Lemaître a way around Kant’s dilemma. As if responding directly to Kant, Lemaître wrote,
Clearly the initial quantum could not conceal in itself the whole course of [cosmic] evolution; but according to the principle of indeterminacy, this is not necessary . . . the whole story of the world need not have been written down in the first quantum like a song on the disc of a phonograph. The whole matter of the world must have been present at the beginning, but the story it has to tell may be written step by step.16
Using the phonograph metaphor of his own culture’s material engagement, Lemaître saw that quantum mechanics allowed cosmic history to unfold in the moment, without a predetermined track set by Newtonian physics. In other words, the primeval atom by itself is enough. Uncertainty, built into the very foundations of quantum mechanics, let Lemaître off the hook in terms of specifying a cause for subsequent evolution. The primeval atom eventually would decay without a cause, leading to cosmic transformation and evolution, just as an atom of plutonium will eventually decay without a cause. Lemaître was able to use quantum mechanics’ inherent indeterminacy—its claim that randomness is intrinsic to nature—as a foundation to build a fully scientific narrative of cosmic evolution.
It is, however, important to see that this early version of the Big Bang is not a theory of creation ex nihilo. The primeval atom exists already, and no explanation is given for this brute fact. Lemaître’s theory of cosmic evolution begins after creation in the sense that the primeval atom already is. Like all versions of the Big Bang, including the modern one, Lemaître invented not a theory of creation but a theory of after creation.
The nuts and bolts of after creation meant tracking general relativistic solutions for the universe as far back in time as the physics allowed. Using Einstein’s equations, physicists had learned to conceive of cosmic evolution in terms of what they called the universe’s radius. In general, the cosmic radius could be thought of as the distance between any two arbitrarily chosen points in the space-time fabric. If space expanded, then the radius of the universe increased and all points were carried away from one another. If space contracted, then the radius decreased and all points were carried towards one another. Lemaître knew that if he followed his cherished expanding universe solution backwards in time to its extreme, then at t = 0 the radius was zero. Thus, if the models were to be believed, at the beginning of time the universe had no volume at all. All its mass would be compressed into a single geometric point—an obvious absurdity. This singularity, as it was called, of infinite mass-energy density and zero size would haunt Big Bang cosmologies into our own era. For his part, Lemaître recoiled at the infinities of the singularity and denied it could have any physical meaning. He was sure that something, some other kind of physics, must come into play, allowing the universe to avoid the infinities of a singularity.
It is worth noting that Lemaître flirted with notions of a cyclic universe as one way of avoiding the singularity at the beginning of time. In 1922, Friedmann had been the first to find closed trajectories of cosmic expansion followed by contraction, and Lemaître was willing to consider these solutions as one turn in an ever-repeating cycle. He wrote that cyclic models possessed “an indisputable poetic charm and make one think of the phoenix of legend”.17 In the end, however, he abandoned the cyclic cosmos, believing it was ruled out by astronomical observations. This led to his primeval atom and a cosmology with the appearance of a beginning in the first atom’s primal decay.
The birth of the beginning did not go smoothly. Without firm supporting evidence, Lemaître’s primeval atom was simply too far on the hairy edge of conjecture for most scientists. John Plaskett, a Canadian physicist, called Lemaître’s theory “the wildest speculation of all . . . speculation run mad without a shred of evidence to support it”.18 Many cosmologists were wary of taking too seriously any mathematical models beginning with a singularity. The noted American cosmologist Richard Tolman warned of the “evils of autistic and wishfulfilling thinking” when it came to mathematics, reality and the origin of space-time.19 Others, including Eddington, continued their philosophical objections: “The beginning seems to present insuperable difficulties unless we agree to look on it as frankly supernatural”, quipped Eddington in a lecture.20 Lemaître did have an ally in Einstein, at least, who “was enthusiastic about the idea”.
The first attempt at Big Bang theory also faced a more serious difficulty in terms of astronomical data. Hubble’s simple, linear relation between galaxy recession velocity and distance (called Hubble’s law) could be used as a clock. By telling astronomers how rapidly the universe was expanding, Hubble’s law could be turned upside down to infer how long it had been since all the galaxies were piled on top of one another. In this way, Hubble’s law provided an “age of the universe” of about two billion years. While that may seem like an incomparably long time, it was, in fact, far too short. Astronomers had already found good reason to believe that the sun was ten billion years old. Geologists, working on their own, were ready to put the Earth at five billion years old.21 Thus, the notion that Hubble’s expanding universe implied a beginning ran straight into a paradox: the universe was younger than the objects in it. This discrepancy
became known as the “age problem” and neither Lemaître nor any of his supporters had a good answer for it. With no solution to the age problem in sight, opposition to Lemaître’s version of the Big Bang remained strong.22
By the beginning of the 1940s efforts to include quantum mechanics in accounts of cosmic origins all but stopped. As the battles of World War II swept across Europe and Asia most scientists were engaged in their own war-related work. Quantum mechanics would move from the realm of abstraction and experiment into the domain of material engagement as physicists worked round the clock to deploy the nucleus as a tool of war.
THE DOOMSDAY CLOCK: TURNING HOURS TO MINUTES IN NUCLEAR WAR
The clock face was a potent symbol. The hour hand was set at twelve. The minute hand was set a few minutes before the hour—midnight, the end of the world.
The Doomsday Clock was the 1947 brainchild of the editors of the Bulletin of the Atomic Scientists.23 Many of them had helped develop the first atomic bomb, and now they hoped to alert the public to the dangers of atomic weapons. The clock was a graphic representation of their best estimate of nuclear war’s proximity. Originally set at seven minutes to midnight, the clock would be reset nineteen times up to the present day. The invention of the intercontinental ballistic missile in the 1950s would be one critical pressure point pushing the hands of the clock closer to midnight.
The weapon dropped over Hiroshima, Japan, on August 6, 1945, was an atomic bomb, meaning it relied on nuclear fission: the splitting of a large atomic nucleus into smaller daughter nuclei with an ensuing release of energy. “Little Boy” incinerated Hiroshima in seconds, killing more than a hundred thousand people. It had an explosive yield of twelve thousand tonnes of TNT.24 In the aftermath of the war and the instant rivalry with the Soviet Union, the United States began planning for the possibility of atomic war with its former ally. When the Soviets exploded their own device in August 1949 (using plans stolen from the United States by scientist-spy Klaus Fuchs) the atomic arms race was on.25
During the Manhattan Project scientists had discussed the possibility of a “superbomb” using nuclear fusion rather than fission. By fusing light elements together, Edward Teller, the project’s chief advocate, calculated possible explosive yields that were a hundred times higher than those of atomic weapons. After extensive debate, including condemnation of the project as immoral, the United States began work on the superbomb. In 1952 the first U.S. fusion device, code-named “Mike”, was exploded in the Pacific.26
The destructive power of the new weapon was staggering. One physicist involved with tests remembers watching his first fusion explosion: “Now, on kiloton shots it’s a flash and it’s over, but on those big shots it’s really terrifying. . . . I never will forget that experience of the thermal effects from the very high yield shots.”27
One year later the Soviet Union detonated its own thermonuclear weapon. Watching newsreels of the hydrogen bomb tests, it was easy to feel the old myth of Armageddon—the end of time—had become real and manifest in this device.
With nuclear weapons in hand, both the United States and the Soviet Union soon turned their attention to the mechanics of weapon delivery. In the United States, the Strategic Air Command (SAC) was given the task of waging nuclear war. With the cigar-chomping General Curtis LeMay leading the way, SAC built a strategy relying on long-range atomic bombers. For General LeMay the totality of a nuclear weapon’s violence led to strategy focused on lethal “country-killing” blows early in a conflict. Beginning in the late 1940s and into the 1950s LeMay and SAC developed the technological capacity to keep bombers “orbiting” on the edges of Soviet airspace, always ready to deliver their small Armageddons.28
FIGURE 7.2. XB-47 Bomber prototype, circa 1957. Long-range bombers and in-flight refueling kept nuclear armed planes “orbiting” close to their targets, reducing the time to attack down to hours. The development of intercontinental missiles would reduce that time even further to tens of minutes.
The introduction in 1954 of the KC-135 Stratotanker meant that American nuclear bombers could refuel in the air, essentially giving them unlimited range. This was part of LeMay’s strategy of counter-force. If war came, SAC would destroy, or “counter”, Soviet nuclear forces on the ground (as opposed to targeting Soviet industrial capacity). The Soviets, for their part, adopted a first-strike strategy, stressing “the importance of landing the first, preemptive nuclear blow”. The Soviet emphasis on surprise and the continual presence of U.S. bombers near the Soviet landmass gave rise to a sense that both nations were on a nuclear hair trigger. The “time to target” in the early 1950s, for both U.S. and Soviet bombers, was only a few hours.29
The public became increasingly aware of this nuclear hair trigger as the 1950s progressed. The development of civil defence programmes in these years was meant simultaneously to prepare the population for a nuclear war and convince them they might survive. Massive, multicity nuclear preparedness drills—Operation Alert—were run once a year. The lengths to which the drills were made realistic were as impressive as their expected results were dubious. Newspapers ran fake stories the day after each Operation Alert recounting the numbers of civilians killed and wounded. On July 20, 1956, the Buffalo Evening News published a special “emergency” edition as part of that year’s operation. The headline screamed, “125,000 Known Dead, Downtown in Ruins”.
FIGURE 7.3. Operation Alert wipes out Buffalo, New York. “Fake” front page prepared by the Buffalo Evening News as part of national civil defence’s Operation Alert.
The culture of atomic age nuclear preparedness—from a civil defence film called Duck and Cover, featuring an animated character called Bert the Turtle, to backyard bomb shelters—seems both contrived and bizarre. For those who lived through the era, however, the sense of angst was both real and pervasive. A nuclear sword hung over everyone’s head, swaying like a pendulum ticking off final moments.
By the end of the 1950s, the introduction of a radical new technology would heighten tensions. Both the United States and the Soviet Union had taken notice of Germany’s V-2 rocket bombs in the closing days of World War II. The fourteen-metre-tall liquid-fuelled rockets were the world’s first long-range ballistic missiles.30 While the V-2s did little to affect the outcome of the war, their range and accuracy were astonishing. When the war ended, both U.S. and Soviet forces did their best to accumulate as many of the unused German rockets as possible, along with German rocket scientists. With Wernher von Braun leading the Americans and the legendary Sergey Korolyov driving the Soviets, the race was on for continent-bridging nuclear-tipped missiles.
The Soviets won the race. In August 1957, under Korolyov’s direction, the Russians tested their R7 rocket. It was truly an intercontinental ballistic missile (ICBM), soaring across 3,700 miles in its first successful flight. Two months later another R7 hurled a sixty-centimetre silver ball packed with electronics into orbit. The payload was called Sputnik, and its incessant chirps from more than two hundred miles overhead let the world know that even the stars were now a frontier in the Cold War. Two years later the United States joined the ICBM club when its Atlas D missile was successfully tested. The era of the nuclear bomber’s superiority was ending; the future belonged to the missile.31
The ICBM changed both nuclear war strategies and the public perception of its fate. After launch a typical ICBM will spend just three to five minutes in its boost phase, rising into space. The midcourse phase, when the missile reaches heights of 625 miles or more, lasts only twenty-five minutes.32 The re-entry phase, during which the missile dives back through the Earth’s atmospheric blanket, lasts a little more than two minutes. All told, from launch to delivery, a population targeted by an ICBM would have less than thirty minutes’ warning before their annihilation.33
In 1986, the United States, the United Kingdom and the Soviet Union had more than seventy thousand nuclear weapons targeted at one another.34 The addition of multiple independent re-entry vehicles (MIRVs) in this final pha
se of the arms race meant that a single missile could vaporize up to ten separate targets. Had these full arsenals ever been unleashed, the apocalyptic conclusion of human civilization would have been fast and horrifically efficient, with the last missiles simply “bouncing the rubble around”. Just as the Bendix had done for wash day, the ICBM compressed the apocalypse into just under an hour.35
A NUCLEAR UNIVERSE: THE BIG BANG, TAKE TWO
The nuclear revolution transformed cosmology just as surely as it changed world politics. However, it would take just a little more time for the shift to be recognized in cosmology. The Big Bang—that is, a universe evolving from a primal state—would be re-invented theoretically once more after World War II. Unlike Lemaître’s first primeval atom incarnation, the Big Bang’s second “discovery” would take the form of a full-blown nuclear cosmology.
A few years before the start of World War II, the geochemist Victor Goldschmidt completed the first full census of elements.36 Goldschmidt’s work showed that hydrogen and helium, the lightest elements with the simplest nuclei, made up the bulk of matter. The profusion of heavier elements generally dropped with weight and nuclear complexity. Thus iron, with 26 protons and 30 neutrons, was less abundant than oxygen, with 8 protons and 8 neutrons, but more bountiful than uranium, with 92 protons and 143 neutrons.37
