Sun in a Bottle: The Strange History of Fusion and the Science of Wishful Thinking - Charles Seife (2008)

Chapter 1. THE SWORD OF MICHAEL

He took not away the pillar of the cloud by day, nor the pillar of fire by night, from before the people.

—EXODUS 13:22

The fires were still burning over Hiroshima, the charred and faceless victims were still slouching toward Asano Park, when President Harry S. Truman told the world about a new weapon. “The force from which the sun draws its power has been loosed against those who brought war to the Far East,” the announcement read. Mankind had unleashed unheard-of energy from deep within the atom and used it to destroy a city.

From the very beginning of the atomic age, Americans were enthralled and frightened by the prospect of this inconceivable power. By splitting uranium and plutonium atoms, scientists had made a weapon by using the very same principle that made the sun shine: E = mc 2.

The scientists who worked on the Manhattan Project, the super-secret program to build the first atom bomb, looked back on their achievement with a mix of awe and horror. To J. Robert Oppenheimer, the head of the Manhattan Project, the atom bomb represented a loss of innocence, a fall from grace that could mark the end of civilization. Others, however, such as the Manhattan Project physicist Edward Teller, saw that the atom bomb was just the beginning of a nuclear arms race. And just over the horizon, Teller realized, was a much greater weapon than even the atom bomb, one thousands of times more powerful.

This new weapon, the “Super,” would unleash a power not yet seen on Earth: fusion. Instead of breaking atoms apart to release energy (fission), the superbomb would stick them together ( fusion) and release even more. While this might seem to be a subtle difference, fusion, unlike fission, had the potential to produce weapons of truly unlimited power. A single Super would be able to wipe out even the largest city—a task far beyond even the bombs of Hiroshima and Nagasaki. A fusion bomb would be the ultimate weapon.

It would also split the scientific community in two and would drive humanity to the brink of ruin. The quest to unleash the power of the sun upon the Earth had an inauspicious start, to say the least.

The atom bombs that destroyed Hiroshima and Nagasaki were fission, not fusion, weapons. Fission and fusion are siblings. Both get their power from converting the mass at the heart of the atom into energy.

Scientists got their first taste of that power in 1898, when the husband-and-wife team of Pierre and Marie Curie discovered a substance with a curious property. Radium, as they called it, seemed to produce energy from nothing. This was, of course, impossible. The most rigid laws of physics, the laws of thermodynamics, seemed to forbid the spontaneous creation of energy. But the Curies were quite certain of what they were observing. A hunk of radium constantly produced heat like a little oven; every hour, a chunk of radium generated enough heat to melt its own weight in ice. It would do this, hour after hour, day after day, and year after year. No chemical reaction could possibly sustain itself for so long and generate so much energy. Whenever the Curies cooled a piece of radium, it would heat itself back up. Indeed, the radium would always be hotter than its surroundings, even though there were no external sources of heat. Marie Curie herself was baffled. She suspected that some sort of change was happening at the center of the radium atom, but she didn’t know what it could be—or how such a tiny chunk of matter could produce so much energy.

The answer would come a few years later when the young Albert Einstein formulated his theory of relativity. The theory revolutionized the way scientists perceive space, time, and motion. One of the equations that came out of the theory was E = mc2, the most famous scientific equation of all time. E = mc2 showed that matter, m, could be converted into energy, E. This was the secret to the seemingly endless fountain of energy coming from radium.

If you put a gram of radium in a sealed ampule, over many, many years the radium (a whitish metal) will gradually disappear. In fact, the atoms of radium spontaneously split apart and vanish from view. But they don’t disappear entirely. When an atom of radium breaks apart, it tends to split into two smaller pieces. The heavier of the two is a gas known as radon; the lighter is helium, and the Curies detected both helium and radon emanating from their radium sample.

Radium—a big heavy atom—breaks up into helium and radon, and when scientists looked carefully at the weights of those atoms, they realized the source of the heat. Some of the mass of the radium was missing. If you add up the mass of one atom of radon and one atom of helium, they make up 99.997 percent of the mass of the radium atom from which both sprang. The other 0.003 percent simply vanishes. When radium breaks apart, the parts are lighter than the original atom.

Here was the answer to the puzzle of excess energy. The whole atom weighed more than the sum of the parts. When the radium atom spontaneously broke apart, some of its mass changed into energy, just as Einstein’s equation allows. The m had become E. The missing mass was only a tiny fraction of what made up the atom, but even tiny chunks of mass are converted into enormous amounts of energy. It was energy on a scale much, much greater than humans had ever accessed before.

As World War II loomed, scientists began to realize that this energy could become a potent weapon. Less than a month before Germany invaded Poland in 1939, Einstein warned President Franklin Delano Roosevelt of the possibility of a bomb made from uranium, a metal that, like radium, releases energy when it breaks into pieces. Such a bomb would be extremely powerful—and there were ominous signs that the Nazis were already on their way to building one. For example, Germany had halted the uranium trade in occupied Czechoslovakia.

Uranium—in particular, one variety known as uranium-235—is an ideal material for a weapon. Its atoms are very sensitive; hit one with a subatomic particle and it fissions into fragments. Unlike decaying radium, which tends to cleave cleanly into two parts, a fissioning uranium atom shivers into a number of smaller chunks, including a handful of neutral particles known as neutrons. These neutrons then fly away from the shattered atom.

In a vacuum, the neutrons continue merrily on their way without bumping into anything else. However, a chunk of uranium is not a vacuum; it is a space crowded full of billions and billions of other uranium atoms. Once a single atom splits apart, within a tiny fraction of a second the resulting neutrons might slam into two or three other uranium atoms. These collisions cause those atoms to split, and in the process, each releases two or three more neutrons. All these neutrons slam into other atoms, splitting them, releasing even more neutrons. If the conditions are right—if enough uranium atoms are in a small enough space—then the process snowballs out of control in less than a blink of an eye. One atom fissions, and its neutrons cause two more to split. These cause four more to fission, causing eight to break apart, then sixteen, thirty-two, sixty-four, and so forth. After ten rounds, over two thousand atoms have split, releasing neutrons and energy. After twenty rounds, it’s more than two million atoms; after thirty rounds, two billion; after forty, more than a trillion. This is a chain reaction.

A chain reaction, if it gets big enough, can level a city. Every time a uranium nucleus splits, it releases energy. Like radium, a uranium atom loses mass when it splits. In a tiny instant, the mass is converted into energy, just as E = mc2 predicts. The more atoms that split in the chain reaction, the more energy is released. After forty rounds of splitting uranium atoms, the energy is roughly enough to light an incandescent lightbulb for about a second. After eighty rounds, a mere fraction of a second after the chain reaction begins, the result is more energetic than the explosion of ten thousand tons of TNT, roughly the size of the blast that eventually destroyed Hiroshima.

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FISSION CHAIN REACTION: When a neutron strikes a U-235 nucleus, the nucleus splits, releasing more neutrons, which strike more nuclei, and so on.

In 1939, though, the idea of fission—and a chain reaction that would release a tremendous amount of energy—was just a theory. Before World War II began, scientists were uncertain whether the theory was right—and if so, how to turn that theory into the hard reality of a useful weapon. It took two years of cogitation and experimentation for the consensus to build: it was possible to build a powerful bomb out of uranium-235 or plutonium-239 (an atom created in the lab by bombarding uranium with neutrons). Nuclear theory progressed quite rapidly; by 1942, the physicist Enrico Fermi was busy building the first nuclear reactor in a squash court1 at the University of Chicago. Fermi’s project was a major step toward releasing the power of the atom—and eventually bringing the wrath of the sun upon the Earth.

The core of a nuclear reactor is little more than a controlled chain reaction: a pile of fissioning material that is not quite at the stage of entering a runaway explosion. Scientists arrange the pile so that the number of neutrons produced by splitting atoms is almost precisely the right amount to keep the reaction going without getting faster and faster; each generation of fission has roughly the same number of atoms fissioning as the last. In physics terms, the pile is kept right near critical condition. Scientists can manipulate the rate of the reaction by inserting or removing materials that absorb, reflect, or slow neutrons. Pull out a rod of neutron-absorbing material and more neutrons are available to split atoms and release more neutrons: the pile goes critical. Drop the rod back in and more neutrons are absorbed than released: the reaction sputters to a halt.

At 3:36 PM on December 2, 1942, Fermi and his colleagues pulled a neutron-absorbing rod out of a pile of graphite and uranium oxide. The radiation counters chattered. Fermi had created the first self-sustained nuclear reaction. The pile had gone beyond critical; more neutrons were being produced by each generation of fission than the last. The reactor was producing more and more and more energy. About a half hour later, Fermi ordered the control rods back into the pile, and the reaction stopped. At its peak the reactor was producing about half a watt of power, almost enough to light a dim Christmas-tree lightbulb. Nevertheless, the possibilities were enormous: Fermi’s reactor showed that nuclear power could, in theory, light up a city. Or destroy it.

It was for the latter purpose that the Manhattan Project was born. At its head was a quirky and difficult scientist, J. Robert Oppenheimer, a man who would achieve fame through fission and be destroyed by fusion.

Oppenheimer was not an obvious choice to lead America’s race to build an atom bomb. He was a good physicist, but he was a theorist—and the Manhattan Project was, fundamentally, an engineering project. Oppenheimer was about as far from the stereotypical get-your-hands-dirty engineer as possible.

The aristocratic Oppenheimer grew up in a wealthy family, but what was particularly striking about him was his quick mind. He mastered more than half a dozen languages, including Sanskrit. He was an adept theoretician but struggled with the more practical side of science; he had difficulty even with basic tasks such as soldering copper wires. After graduating from Harvard, he went to Cambridge in England to work in the lab of the famous experimentalist J. J. Thomson. There, the already high-strung Oppenheimer became unglued.

Oppenheimer had a difficult time at Cambridge; in his mind, his experiments were failures, and he contemplated suicide. He also contemplated murder. In 1925, he suddenly tried to strangle a childhood friend, and his behavior got even more bizarre from there. On a vacation in Corsica with two friends, he abruptly announced, “I’ve done a terrible thing.” He said that he had poisoned an apple and put it on the desk of another brilliant physicist at Cambridge, Patrick Blackett. When everyone got back to the university, they found out that Blackett was unharmed, and Oppenheimer’s friends were left wondering whether the apple was real or just a figment of Oppenheimer’s feverish imagination.

The bizarre behavior became less acute once Oppenheimer relocated to the University of Göttingen in Germany. In the 1920s, Germany was the world leader in theoretical physics—home to Einstein, Max Planck, Werner Heisenberg, Max Born, and many of the other leading lights of the day—and Oppenheimer established himself as a brilliant young physicist. However, he was still depressive. He was also vain, arrogant, and occasionally nasty. He had a habit of making people feel small and insignificant; he detested his “beastliness” but was unable to control it. Nevertheless, soon after moving back to the United States to become a professor at the University of California at Berkeley, he acquired a circle of devotees thanks to his brilliance and wit.

Despite Oppenheimer’s prickliness, everyone—even the occasional general—was impressed with the young professor. “He’s a genius,” wrote General Leslie Groves, the military head of the Manhattan Project and the man who chose Oppenheimer to lead the scientific effort. “Why, Oppenheimer knows about everything. He can talk to you about anything you bring up. Well, not exactly. I guess there are a few things he doesn’t know about. He doesn’t know anything about sports.” This was by no means the most serious of his flaws, as far as the military was concerned.

Oppenheimer was a security risk—he was absolutely surrounded by Communists. His brother and sister-in-law were members of the Communist Party. His first fiancée, Jean Tatlock, had been a member, too. His wife Kitty’s first husband had been an official in the party and had been killed fighting on the leftist side during the Spanish Civil War. The army knew about all these connections, yet Groves insisted that Oppenheimer lead the most sensitive military project of World War II. In October 1942, Oppenheimer accepted his new post and began assembling the biggest scientific project in the history of mankind.

Laboratories devoted to the atom bomb effort sprang up around the country. Los Alamos, perched on a mesa in the New Mexico desert, was the intellectual heart of the Manhattan Project. Other facilities, such as one at Oak Ridge in Tennessee and another at Hanford in Washington, were crucial to figuring out the best way to separate bombworthy uranium-235 from the much more common uranium-238 and how to manufacture plutonium-239.2 However, the big minds roamed at Los Alamos: Oppenheimer, Hans Bethe, Richard Feynman, Stanislaw Ulam, John von Neumann, Enrico Fermi, and Edward Teller.

Teller, a Hungarian émigré and, arguably, a better theoretician than Oppenheimer, was brought to the University of Chicago in mid-1942 by the Manhattan Project just as it was getting under way. When Teller arrived, nobody assigned him a task, so he set to work trying to design the ultimate weapon, more powerful even than the one the project’s scientists were trying to build. He envisioned a superbomb that used fusion instead of fission. If it worked, it would dwarf an atom bomb just as surely as an atom bomb would dwarf conventional explosives. Teller became obsessed with wielding the power of the sun. It was an obsession that molded him into one of the darkest and most twisted figures of American science. “He’s a danger to all that’s important,” said his fellow physicist Hans Bethe. “I really do feel it would have been a better world without Teller.”

Teller was born in Budapest, the child of a successful lawyer. In 1919, when he was eleven years old, the Communist Béla Kun swept to power and declared Hungary a Soviet state. “The communists overturned every aspect of society and the economy,” Teller later wrote. “My father could no longer practice law.” Two soldiers moved into the Tellers’ home, and young Edward came to know hunger. “There was no food (or any other kind of goods) for sale in the stores now owned by the communists. . . . As I recall, cabbage was often all we could find. I still dislike cabbage.”

After rampant inflation, a coup attempt, a purge, and a military defeat, Kun’s regime ended before the year was out. But the whole experience left Teller with an almost monomaniacal hatred of Communism. In large part, his actions over the next few decades—his attempt to build an arsenal of unlimited power—would be driven by that hatred.3

Thus Teller’s vision of a superweapon was possible because there is more than one way to extract energy from the atom. Fission is the easy way. Just get enough fissile material (such as uranium-235 or plutonium- 239) in a small enough space and a chain reaction will start on its own. Heavy atoms will split into fragments, converting mass into energy and creating an enormous explosion. The main problem is getting that fissile material. Neither uranium-235 nor plutonium-239 was easy to obtain, especially with the state of knowledge in 1942 and 1943.

Fusion is another way to convert mass into energy; it’s the opposite of fission. In fission, heavy atoms split and the sum of the parts is lighter than the original atoms. In fusion, light atoms stick together, and the whole resulting atom is lighter than the sum of the parts that made it. The missing matter—the stuff that disappears when the light atoms combine—becomes energy.

Fusion is several times more powerful than fission; more of the mass of each reacting atom is converted into energy. Better yet, it is much easier to find the fuel for fusion—light atoms like hydrogen—than it is to find the uranium or plutonium fuel for fission. The oceans are filled with hydrogen’s heavier sibling, deuterium, a great fuel for fusion reactions. It’s not terribly difficult to extract a practically unlimited amount of the stuff.

Of course, there is a downside. The fusion reaction is extremely difficult to start, and even harder to keep going long enough to produce large quantities of energy. Atoms tend to repel each other, so it is very hard to get them close enough so that they stick together. You need an enormous amount of energy to slam two atoms together forcefully enough to overcome that repulsion and get them to fuse.

For a fission reaction, you just need to get a lump of uranium big enough. For fusion, you need to manipulate your fuel in some tricky ways. First, you’ve got to compress the fuel into a tiny parcel. This keeps the atoms in close proximity to one another (so they have a chance of colliding). That, in itself, is not so hard; the trick is to keep the atoms very hot as well. Only at tens or hundreds of millions of degrees are the atoms moving fast enough to have a chance of fusing when they do collide. When you heat something, it expands—the atoms try to escape in all directions. Thus, it is very hard to keep a very hot thing compressed very tightly. So, the basic problem in fusion is that it is very difficult to heat something to the right temperature and, simultaneously, keep the atoms close enough together. Without both things working concurrently, a fusion reaction won’t get going.

Making matters worse, if you are lucky enough to start a fusion reaction, your own success works against you. When the fusing atoms release energy, they pour heat into their surroundings. This makes the neighboring atoms hotter. The hotter the atoms get, the more the fuel expands and the harder the atoms try to escape. The packet of fuel attempts to blow itself apart. Unless the conditions are just right, a fusion reaction will snuff itself out before it produces any appreciable energy.

Nevertheless, if scientists could get a fusion reaction going even for a few fractions of a second, its power would be virtually limitless. It could be much, much more deadly than a mere fission bomb.

This is the idea that obsessed Teller soon after he arrived in Chicago. Unlike most of his colleagues, he was not terribly interested in working on the fission bomb. In his mind, the theoretical problems had already been solved, so he spent his energy trying to come up with even better weapons: fusion bombs. Within a month of his arrival, Teller had not only concluded that it was possible to create a fusion bomb that would dwarf anything the Manhattan Project would be able to offer, but had also convinced himself that he knew precisely how to build one. It would be years before he figured out how wrong he was.

In 1942, though, Teller, full of enthusiasm, brought the idea to the attention of his colleagues. They quickly dubbed the new weapon the Super. By August, he and his fellow physicists were giving astounding estimates of the destructive power of a Super-like fusion weapon. A report at the time estimated that one would blow up with the energy of one hundred megatons of TNT, about seven thousand times bigger than the eventual size of the Hiroshima bomb. Teller, a tremendous optimist,4 was convinced that fusion was easy.

Once you have an atom bomb, he argued, you can dump the enormous power of an exploding atomic weapon into a tank of deuterium—heavy hydrogen. The hydrogen, heated to millions of degrees, would begin to fuse and generate energy in a thermonuclear reaction. This was essentially the idea behind Teller’s Super: it was, more or less, an atom bomb at one end of a vessel full of heavy hydrogen. The exploding bomb would trigger a wave of fusion in the vessel. If it worked, Teller argued, this Super had unlimited capacity for destruction.5

To Teller, the easy part was building a weapon of tremendous power. The hard part was building a weapon that would not be so destructive that it would kill everybody on Earth. In Teller’s fertile imagination, an atom bomb that ignited a tank of hydrogen might ignite the air itself. (The nitrogen that makes up 80 percent of the atmosphere is a light atom, and just like hydrogen it will fuse if the conditions are right.) Teller’s initial calculations showed that an atomic explosion might induce nitrogen atoms in the air to fuse with each other. The runaway explosion would quickly destroy the world in a gigantic nuclear furnace—even the weak Manhattan Project bomb might mean the end of life on Earth. When Hans Bethe double-checked Teller’s assumptions, though, he found reason to relax. “I very soon found some unjustified assumptions in Teller’s calculation that made such a result extremely unlikely, to say the least.” If a fusion reaction got going, there was too much energy lost through radiation to get the atmosphere hot enough to cause a chain reaction of fusing nitrogen.6 The world was safe. Fusion was much more difficult than Teller initially imagined.

Fusion was so hard, in fact, that the Super, at least as originally designed by Teller, wouldn’t work at all. According to the physicist Robert Serber, “Edward first thought it was a cinch. Bethe, playing his usual role, knocked it to pieces.” Hans Bethe showed that the fireball in Teller’s Super device would cool very rapidly. Here, too, the energy of a budding fusion reaction would quickly drain away through radiation; the fusion would snuff itself out before it really got going. It wasn’t an insurmountable obstacle, but it was enough of a problem for the Manhattan Project physicists to put Teller’s idea on the back burner. In 1943, a review committee decided that all the lines of research for the project—and for its theoretical physics division, which had relocated to Los Alamos—were worthwhile except for one: fusion. Instead of trying to build superweapons, the committee argued, the lab must concentrate its efforts on building atomic weapons to end the war.

Teller was disappointed that his pet project was stalled. Bruising his ego further, Oppenheimer appointed Bethe to be the head of the theoretical physics division. Teller thought the appointment would be his—and he apparently took both slights personally.

This was the turning point in Teller’s career. It was at this moment that Teller, the brilliant physicist, started becoming defined by his character flaws: his egocentrism, his nearly manic optimism, and his paranoia. All these traits would play a role in the coming tragedy, but it was the paranoia that led Teller to blame a single individual for all the insults he received at the hands of the Manhattan Project. He was refused his rightful position as head of theory at Los Alamos, and the Super was mothballed all because of one man: J. Robert Oppenheimer.

Oppenheimer and Teller would soon become bitter enemies. The two were very different. Oppenheimer, gaunt and aristocratic, was quite unlike the limping, bushy-browed Teller.7 The most striking difference was their politics. Oppenheimer, a leftist who flirted with Communism, was bound to clash eventually with Teller, the rabid anti-Communist.

However, in July 1945 the Teller-Oppenheimer feud was yet to ignite. It was a triumphant time for both physicists. The Los Alamos scientists had nearly overcome all the technical problems that faced them; they had manufactured and machined enough plutonium to build a “gadget” named Jumbo and had built an intricate cage of explosives that would force all the metal to assemble into a critical mass and explode. The scientists began to wager about how big the first atomic explosion—Trinity—would be. Oppenheimer bet that it would be the equivalent of a mere three hundred tons of TNT. Teller, ever the optimist, guessed that it would be forty thousand tons. It was raining in the predawn hours the day of the test, yet Teller was sharing his bottle of sunscreen with his colleagues.

When the New Mexico desert suddenly erupted with a light brighter than the noonday sun, the Manhattan Project scientists were relieved and jubilant. When a similar flash erupted over Hiroshima, the feelings were much more somber. When the war ended with Japan’s unconditional surrender, Oppenheimer, like many of his scientific colleagues, lost his taste for weapons work.

By mid-September, half the staff at Los Alamos was already gone. Oppenheimer stepped down a month later—and he was warning about the dangers of adding atomic weapons to the world’s arsenal. “The time will come when mankind will curse the names of Los Alamos and Hiroshima,” he prophesied while accepting a military award in November. Bethe’s departure left Los Alamos without a head of theory, the very post that Teller coveted, and Teller was offered the job. But Teller would only accept if the lab would devote its resources to developing better bombs—most likely a fusion weapon. Alas, the lab was to turn its attention to production rather than to designing fusion weapons. “There was no backing for the thermonuclear work. No one was interested in developing a thermonuclear bomb,” huffed Teller. “No one cared.”

Los Alamos was dissolving around him, and few Manhattan Project scientists seemed interested in developing the fusion bomb. Teller decided to pack his bags and move back to the University of Chicago. His relationship with Los Alamos wasn’t over, however. He would consult for the laboratory during the postwar years, and he would soon return to the New Mexico complex.

Teller’s dream of unlimited power was just a little premature. In just a few years, the United States would embark on a crash effort to develop fusion weapons.

The decision to build fusion weapons came from paranoia and fear. Even though the Americans had a monopoly on nuclear bombs, there was the nagging worry that the Soviets would soon build their own atomic weapons. Once that happened, Teller reasoned, they would certainly invade—unless America had an even bigger weapon in its arsenal: the Super. “Edward offered to bet me that unless we went ahead with his Super,” wrote a colleague, “he, Teller, would be a Russian prisoner of war in the United States within five years!”

Just after the war ended, Teller tried to get the Super program started again. At a conference in April 1946, Teller and two dozen key scientists met to discuss whether a superbomb was feasible, and if so, what its future should be. There is some debate as to what the conference participants actually concluded, but the report was sanguine: “It is likely that a super-bomb can be constructed and will work,” it said, adding that if doubts about the design proved to be true, “simple modifications of the design will render the model feasible.” The report reflected Teller’s unflagging optimism. (After all, he wrote the thing.) He was promising that fusion was within reach.

In truth, though, the road to the superbomb would be harder than Teller imagined. Not only was his design flawed, but he also had to overcome political opposition. Oppenheimer and his cronies were trying to get the United States to give up its monopoly on atom bombs—by giving nuclear secrets to the Communists. To Teller, it was madness; it was almost treasonous.

In March 1946, the month before Teller’s Super conference, Oppenheimer and a government committee made the radical suggestion that “inherently dangerous” activities such as mining uranium should be put under international control and that all nations, including the Soviet Union, should have access to nuclear knowledge. As idealistic as this scheme might seem, at least in retrospect, it became official U.S. policy within a few months. The United States’ representative to the UN Atomic Energy Commission, Bernard Baruch, presented such a plan to the United Nations. It was “a choice between the quick and the dead,” he told the world. “We must elect world peace or world destruction.” Not all nations agreed with that simplistic dichotomy. The Soviet Union opposed the proposal, and by the end of 1946 the plan was dead. It soon became clear why.

On September 3, 1949, a modified B-29 bomber flying off the coast of the Kamchatka Peninsula picked up alarming traces of radiation. It was the first sign of a radioactive cloud that soon drifted across the Pacific, the United States, and Canada before crossing the Atlantic and circling the world. Physicists around the United States scrambled to figure out the source of the radiation. It did not take long. The radioactive cloud had elements that showed that it was the result of nuclear fissions. It was fairly clear: the Russians had their own atom bomb. America’s nuclear monopoly had ended much more quickly than anyone expected. On August 29, 1949, in the middle of the Kazakh steppe, a nuclear cloud had mushroomed to life. The Soviets called it “First Lightning”; the stunned Americans nicknamed the first Russian atom bomb test “Joe-1.”

The timing could hardly have been worse. On September 21, Mao Tse-tung announced the formation of the People’s Republic of China. A quarter of the world’s population suddenly had a red flag flying above their heads. Two days later, President Truman had to announce the news of Joe-1. “We have evidence that within recent weeks an atomic explosion occurred in the U.S.S.R.,” he said, and attempted to reassure a frightened nation. “Ever since atomic energy was first released by man, the eventual development of this new force by other nations was to be expected.” Even so, the Russians had caught up with the Americans much more quickly than anticipated.8 The hope of unilateral disarmament was gone forever. When Teller heard the news, he called Oppenheimer on the telephone, perhaps hoping to spur him to pursue fusion weapons. “Keep your shirt on!” was Oppenheimer’s curt rejoinder.

It wasn’t the response that Teller hoped for. He thought his Super provided an easy answer to the crisis. By developing a superbomb more powerful than even atomic weapons, the United States could keep its lead over the Soviet Union. But some scientists viewed pursuing fusion weapons as an inherently immoral act, one that might lead to the destruction of humanity. Physicists began to divide into two groups: pro- and anti-fusion.

Oppenheimer was in the latter camp. A month after Truman’s announcement, Oppenheimer convened a meeting of a handful of scientists, politicians, and engineers—the General Advisory Committee (GAC)—who advised the new Atomic Energy Commission (AEC). The AEC had been formed in 1945 to oversee nuclear research, so the GAC, chaired by Oppenheimer, was extremely influential in setting the direction of America’s nuclear weapons program. Oppenheimer’s GAC was firmly anti-fusion. While the committee stated that it would be wise to increase the United States’ capacity to build and research nuclear weapons, the GAC raised technical questions about the feasibility of the Super—and also made a firm statement about the morality of pursuing Teller’s dream of weapons of unlimited power. “We are all agreed that it would be wrong at the present moment to commit ourselves to an all-out effort toward its development.” Some scientists on the committee went further. Oppenheimer and five others railed against the morality of a fusion weapons program. “A super bomb might become a weapon of genocide,” they wrote. “We believe a super bomb should never be produced.” To Enrico Fermi and fellow physicist Isidor Rabi, also on the committee, Oppenheimer’s statement didn’t go far enough. “The fact that no limits exist to the destructiveness of this weapon makes its very existence and the knowledge of its construction a danger to humanity as a whole,” they argued. “It is necessarily an evil thing considered in any light.” The GAC recommended shelving the Super project.

To Teller, who had returned to Los Alamos full-time, Joe-1 was the realization of his worst fears. A militant Communist state had just destroyed his home country; in August, Hungary officially declared itself Communist and became a satellite of the Soviet Union. And now the belligerent USSR was menacing his adopted home, the United States. Oppenheimer, with his Communist sympathies, was setting the United States on a course of self-destruction. Teller was certain that forsaking the Super, as Oppenheimer wanted, would ensure Soviet world domination within a few years. He had to thwart Oppenheimer’s destructive influence. Teller started to make his case directly to Congress, and the Oppenheimer-Teller war began in earnest.

Teller had many allies also lobbying for the Super. A number of scientists and politicians agreed that an arms race with the Soviet Union was inevitable and thought that the Super was crucial to keeping the Soviets at bay. Lewis Strauss, a commissioner of the AEC, urged President Truman to launch a crash project to build a fusion weapon—even raising the specter that the Russians had taken the lead. The influential Berkeley physicists Luis Alvarez and Ernest Lawrence, too, stumped for a fusion bomb program. Congress was receptive to the fusion hawks’ arguments. When Teller traveled to Washington, he quickly found an ally in Brien McMahon, the chairman of the Senate’s Special Committee on Atomic Energy.

Even before the nuclear ash from the Joe-1 test had dispersed, the battles were under way. Hans Bethe, after being approached by Teller, initially agreed to work on the fusion bomb. Shortly after talking to Oppenheimer, however, Bethe backed out. Teller blamed Oppenheimer for the reversal. And those on either side of the divide—the pro-fusion and anti-fusion camps—began to distrust and dislike each other.

Teller and his allies looked upon Oppenheimer as an obstructionist and began to conclude that his actions damaged the military capability of the United States. Teller would later testify that Oppenheimer and his allies set back the fusion bomb effort by five years. The anti-fusion weapons side looked on with disgust as the hawks lobbied for the superweapon. For example, David Lilienthal, the first chairman of the AEC, was shaken by the “bloodthirsty” push for a fusion bomb. “The day has been filled, too, with talk about supers, single weapons capable of desolating a vast area,” Lilienthal wrote in his journal in October 1949. “Ernest Lawrence and Luis Alvarez in here drooling over the same. Is this all we have to offer?” Teller’s image, too, suffered, as he pressed harder and harder for the Super. “Now I began to see a distorted human being, petty, perhaps nearly paranoid in his hatred of the Russians, and jealous in personal relationships,” wrote the Los Alamos physicist John Manley.

The scientists battled about whether or not to pursue fusion weapons, and the fight worked its way up to the president. Truman deliberated. Would he back the Super project or not? The pressures were building. Anti-Communist hysteria was sweeping the country, and the populace would clamor for a fusion bomb if they knew it existed.

They soon knew. On November 18, 1949, the Washington Post carried an alarming story on page 1. “[Scientists] are working and ‘have made considerable progress’ on ‘what is known as a super-bomb’ with ‘1000 times’ the effect of the Nagasaki weapon,” the article read. Soon, Truman was fielding questions at press conferences about the hydrogen bomb. The public clearly wanted a superweapon to counter the Soviet threat. The easy solution to the Russian problem—the Super—was becoming hard to resist. And then came the final blow.

On January 27, 1950, British police arrested Los Alamos physicist Klaus Fuchs, who confessed to being a spy. All of a sudden it became clear why the Russians were able to build an atom bomb so quickly. Worse yet, Fuchs had been involved in discussions about the fusion bomb; in fact, he was coholder of a key secret patent having to do with the method used to ignite the first working hydrogen bombs. The Russians knew all about the fusion bomb—and they had likely already begun research. Truman felt he had little choice.

Four days later, the president of the United States issued a public statement to his citizens. “It is part of my responsibility as Commander in Chief of the Armed Forces to see to it that our country is able to defend itself against any possible aggressor,” it read. “Accordingly, I have directed the Atomic Energy Commission to continue its work on all forms of atomic weapons, including the so-called hydrogen or superbomb.”

Truman’s hand had been forced, but he had just made a dangerous decision. He had committed the United States to an arms race with the Soviet Union that would make both countries insecure and lead the world to the brink of destruction, all for the sake of a fusion weapon that, at the time, was merely a figment of Teller’s fertile imagination.

Truman almost certainly didn’t know this, but when he made his announcement, the fusion project at Los Alamos was entering its darkest time. Just weeks before, calculations from Los Alamos were starting to prove that Teller’s fusion bomb was a flop.

It was hard—damnably hard—to get enough light atoms hot enough and dense enough to create a hydrogen bomb. Teller, as a theorist, made his best guesses as to how to engineer such a device and estimate what was needed to get it to explode. However, theorists sometimes overlook little niggling practicalities that make the job harder than they originally imagine. Teller’s initial plans for the Super were little more than an atom bomb at one end of a tank of deuterium. The energy from the atom bomb would make the deuterium so hot that the atoms would slam together and stick, fusing and releasing energy. But Teller’s deuterium bomb ran into problems from the start. Even deuterium, which is much easier to fuse than ordinary hydrogen, would be hard to ignite. In 1942, mere months after Teller’s initial visions of the Super, scientists realized that a “hydrogen bomb” should have tritium, a still heavier version of hydrogen, mixed in with the deuterium if it was to have any chance of exploding. The problem is that tritium doesn’t occur much in nature; it has to be manufactured if you want a large quantity of it. And this process required the same resources—and was about as expensive—as manufacturing plutonium.

Even though tritium was scarce, the unlimited power promised by the Super made it worth producing. According to Teller’s estimates, it would require a few hundred grams of tritium—a significant, but manageable, amount of the rare substance—to get the Super working. Those estimates were wildly optimistic.

In December 1949, the month before Truman’s fateful announcement, the Polish mathematician Stanislaw Ulam, along with his colleague, Cornelius Everett, began extremely tedious calculations to figure out whether, in fact, Teller’s Super would work. They worked with pencil and paper, slide rules, and a set of dice.9 With each roll of the dice, it became more and more evident that Teller’s Super would fail to ignite the tank of deuterium and tritium. Françoise Ulam, Stanislaw’s wife, noted how Teller reacted to the ever-worsening news. “Every day Stan would come into the office, look at our computations, and come back with new ‘guestimates,’ while Teller objected loudly and cajoled every one around into disbelieving the results,” she wrote. “What should have been the common examination of difficult problems became an unpleasant confrontation.” Ulam wrote that the calculations made Teller “pale with anger.” Ulam and Teller already disliked each other, and it was reported that Ulam “took real pleasure” in knocking down Teller’s pet project.

By February, it was absolutely clear that the Super wouldn’t work. Instead of requiring a few hundred grams of tritium, the Ulam-Everett calculations implied that a Super would need ten times that—a few kilograms. There was no way the United States could manufacture that amount of tritium in a reasonable period of time. Teller’s device was impractical.

“Teller was not easily reconciled to our results,” wrote Stanislaw Ulam years later. “I learned that the bad news drove him to tears of frustration.” Nevertheless, the calculations were solid. It was less than a month after Truman announced the superbomb project—and a month before Truman signed an executive order that officially jump-started the crash program. The Super design was crumbling in front of Teller’s eyes.

Ulam and Fermi then put another nail in the coffin. Even with an enormous amount of tritium, they found, a pipe full of the stuff simply wouldn’t fuse. If you managed to ignite one end, the reaction would not travel down the pipe. “You can’t get cylindrical containers of deuterium to burn because the energy escapes faster than it reproduces itself,” explained the Los Alamos physicist Richard Garwin a number of years later. He added that “The classical Super could not work. . . . All the time [on the classical Super] was wasted. There had been miscalculation because Teller was optimistic.” After all the commotion and heartache, after the scientific community chose sides in a growing schism, the Super was a fizzle.

The calculations suggested that the enemies of fusion were right all along. “[Teller] was blamed at Los Alamos for leading the Laboratory, and indeed the whole country, into an adventurous program on the basis of calculations which he himself must have known to be very incomplete,” wrote Hans Bethe years afterward.

Teller persisted. He had already dreamed up alternate designs for a fusion bomb. One was made out of alternating layers of fissionable heavy atoms and fusionable light atoms. Dubbed the “Alarm Clock” design (because it would wake the world to the prospect of fusion weapons), it had a serious drawback. To make it more and more powerful, designers had to add layer after layer to the bomb. By the time it reached the megaton range, it was too big to deliver. It was not a practical superweapon. It did not promise the unlimited power that Teller was seeking. Neither did his other suggestion. Teller realized that by adding a tiny bit of tritium to the center of an exploding fission warhead, the tritium would fuse and “boost” the yield of the atom bomb. This was a practical idea—and it ultimately did work—but it was just a way of making a slightly better fission weapon. It was far from the thermonuclear fusion superbomb that Teller had promised.

Teller kept up a brave face in public. He tried to recruit scientists to come to Los Alamos to work on fusion weapons. “The holiday is over,” he wrote in the Bulletin of the Atomic Scientists. “Hydrogen bombs will not produce themselves.” However, Teller was fresh out of ideas. Neither the Alarm Clock nor boosted bombs provided the unlimited-power weapons Teller—or Truman—wanted. The crash program was stalling even before it started.

World politics made the situation dire. On June 25, North Korean soldiers marched across the thirty-eighth parallel into South Korea. Seoul fell within days. And within two weeks, General Douglas MacArthur was figuring out how best to use nuclear bombs in the conflict. The battle went back and forth. Then, in November, soon after China entered the war, Truman threatened the use of atomic weapons. MacArthur asked for the discretion to use them on the battlefield. The world seemed on the brink of nuclear war.10 The fusion bomb, the weapon that was supposed to restore America’s military advantage, was nowhere to be found.

By the autumn of 1950, Teller was desperate. “He proposed a number of complicated schemes to save [the Super], none of which seemed to show much promise,” wrote Bethe. “It was evident that he did not know of any solution.” The head of Los Alamos, Norris Bradbury, a man whom Teller viewed as an ally of Oppenheimer’s, halted design work on the Super until some important tests, scheduled for early 1951, could be run. Teller was furious at the delay. He was at the brink of despair when Bradbury wrote a report summarizing the project for the GAC, Oppenheimer’s advisory committee. In Teller’s eyes “his report was focused on the Super and was so negative that it seemed an outright attempt to squash the project.” Teller and John Archibald Wheeler, a theoretical physicist and fusion hawk, wrote a second report “in a very different tone” to counteract Bradbury’s negativity. But there was little way to put a positive spin on the status of the Super. The project was dead in the water. The deuterium wouldn’t ignite. Teller was devastated. The unlimited power of fusion was slipping away.

Ironically, it was Ulam, the man who brought Teller to tears, who would lift him out of his despair. Ulam saw a way to build a working fusion weapon. In January 1951, he realized that he could use the stream of particles coming off an atom bomb to compress the hydrogen fuel, making it hot and dense enough to ignite in a fusion reaction.11 Instead of a simple bomb with a tank of deuterium, the new hydrogen bomb would have an atom bomb primary separated from a deuterium-tritium secondary. Particles from the atom bomb—radiation that would ordinarily stream away from the explosion—could be focused onto the secondary to compress, heat, and ignite it. It would be tricky to engineer such a device, but it seemed to overcome the problems that dogged the classical Super. “Edward is full of enthusiasm about these possibilities,” Ulam reported to von Neumann. “This is perhaps an indication they will not work.” Nevertheless, the enthusiasm was justified. It would mark the end of the dark times for the fusion hawks, and for Teller. By May, Los Alamos would have experimental data to back up the theoretical calculations.

In the Marshall Islands, isolated in deep Pacific waters, a nearly circular atoll of a few dozen islands had been drafted into the Cold War effort. Since 1948, the United States had used the Eniwetok atoll—some of whose islands were inhabited—for testing nuclear weapons. In April 1951, a new series of tests began. They were code-named Greenhouse.

Greenhouse consisted of four explosions. The first two, Dog and Easy, tested two of the compact fission weapon designs that Los Alamos was furiously generating to keep the United States one step ahead of the Russians. The third and fourth, George and Item, were entirely different. They were the world’s first fusion devices.

Greenhouse George was a curious gadget. It wasn’t a design that could ever be dropped on an enemy. It was an enormous cylindrical device with a hole in the center. As the device imploded, radiation would stream out of the hole and strike a small target filled with a few grams of deuterium and tritium. It was a science experiment, not a practical weapon, something with which to study the process of fusion rather than to drop on a city. After all, scientists had never achieved fusion before; Greenhouse George, if it worked, would allow them to see it up close for the first time.

It worked. On May 9, Teller, slathered in suntan lotion, watched as a mushroom cloud boiled obscenely into the sky. It was a doozy of an explosion: at 225 kilotons it was a record breaker, an order of magnitude bigger than the bombs that leveled Hiroshima and Nagasaki. George’s fission bomb probably generated about 200 kilotons’ worth of energy. The remaining 25 kilotons came from the tiny capsule of deuterium and tritium. Scientists had finally unleashed the energy of the sun. Fusing a few grams of hydrogen released the same amount of energy as the fission of many kilograms of plutonium or uranium. And Greenhouse Item, the first test of a fission weapon “boosted” by a little dollop of deuterium and tritium at its center, was also a success. Teller’s dream of a weapon of unlimited power was back on track. “Eniwetok would not be large enough for the next one,” he gloated.

The next month, Teller and some colleagues met in Princeton to report on their success to Oppenheimer’s GAC. The resistance to the fusion bomb—moral and political—crumbled under the evidence provided by the Greenhouse tests. Even Teller admitted that Oppenheimer was enthusiastic about proceeding. “I expected that the General Advisory Committee, and particularly Dr. Oppenheimer, would further oppose the development [of the hydrogen bomb],” Teller would later testify. But after hearing about the Teller-Ulam design and the results of the Greenhouse tests, “Dr. Oppenheimer warmly supported this new approach.” The GAC endorsed a full-scale test of a superbomb.12 Nevertheless, Teller saw opposition to the hydrogen bomb everywhere, and Oppenheimer—Teller’s Moriarty—was almost certainly behind it all.

Teller’s return to Los Alamos should have been triumphant after the success of the Greenhouse tests. Norris Bradbury took the fusion project off its hold and formally started a thermonuclear weapons research program at Los Alamos. The project for the Super was officially back on track. But even this victory contained a defeat. Once again, Teller was passed over—he wasn’t appointed the head of the new program. Instead, Bradbury appointed Marshall Holloway, a theoretician. Teller considered Holloway a member of Oppenheimer’s clique who “had created difficulties in connection with the hydrogen bomb at every turn.” It was a slap in the face, and Teller was horrified to see Holloway and Bradbury dragging their feet on the date of the full-scale test. Teller wanted to see it happen in July 1952; Bradbury and Holloway thought a summer date was too optimistic and scheduled it for later in the year. A week after Holloway’s accession, Teller quit. On November 1, 1951, he stormed out of Los Alamos. He hoped to take his fusion program with him.

For more than a year, Teller, along with some of his hawkish allies, had been lobbying to create a second laboratory—one dedicated to thermonuclear fusion. Oppenheimer’s GAC consistently opposed the proposal, fearing that it would split the pool of talented physicists rather than keep them concentrated in one place. However, Teller’s behind-the-scenes lobbying had yielded some powerful allies, including high air force brass such as James Doolittle, who led the heroic first air raid on Tokyo in 1942. Rather than lose control of hydrogen bomb research to the military, the Atomic Energy Commission began to capitulate. Oppenheimer and the GAC still opposed the new laboratory, but Oppenheimer’s influence was waning. New members of the GAC were more hawkish than the ones they had replaced. Worse yet, Oppenheimer’s political enemies—Teller, Luis Alvarez, air force scientist David Griggs, AEC director of research Kenneth Pitzer, and GAC member Willard Libby—had been chatting with the FBI about Oppenheimer. Pitzer went so far as to publicly question Oppenheimer’s loyalty.

Oppenheimer’s critics had taken their toll. In June 1952, he stepped down from the GAC. The following month the AEC green-lighted the second laboratory, to be based at Livermore in California (and is today the Lawrence Livermore National Laboratory). Ironically, Teller was slighted yet again; he was surprised to hear that he wasn’t the director. After some arguing he signed up. “I am leaving the appeasers to join the fascists,” Teller reportedly joked.

Teller had won. Los Alamos now had a rival, and Teller had a facility that was free from the influence of Oppenheimer’s cronies, the Soviet appeasers, the Communist sympathizers. However, it was Los Alamos that would initiate the age of fusion.

At 7:14:59 AM on November 1, 1952, roughly a half second ahead of schedule, the island of Elugelab suddenly disappeared. A compact eighty-ton device, nicknamed “the sausage,” unleashed the power of the sun upon the Earth for a few moments. The fusion reaction from this device—the first hydrogen bomb—vaporized Elugelab. All that remained was a cloud of dust and fire that stretched twenty miles into the stratosphere.

The nuclear test, known as Ivy Mike, was the first test of a thermonuclear weapon. The Ulam-Teller design had paid off. The energy it produced was an astonishing ten megatons, fifty times bigger than the Greenhouse George shot and about the size of seven hundred Hiroshima bombs. Eniwetok atoll was now missing an island; Elugelab had evaporated under the cloud of fusing hydrogen, leaving behind a crater that could swallow fourteen buildings the size of the Pentagon.

Teller, the prime architect of the cataclysm, was half a world away. Having left Los Alamos, he was in a darkened room at Berkeley where a seismograph recorded the trembling of the Earth with a tiny beam of light. When that dot of light danced wildly, Teller knew he had succeeded. Ivy Mike had worked. Teller had created a weapon of virtually unlimited power. It was as if the United States had been handed the sword of Michael, the ultimate weapon.

It had taken too long. The Russians were already hot on the fusion trail. Shortly after World War II, all across the Soviet Union, mysterious secret cities began sprouting up. Among them: Arzamas-16, near Novgorod; Semipalatinsk-21 in Kazakhstan; Chelyabinsk-70 in the Ural Mountains. After decades of speculation and spying, we now know that these were the cities devoted to designing, testing, and building nuclear weapons. And in the early 1950s, the Soviets were progressing rapidly. Just weeks before Teller left Los Alamos, the third Russian test, Joe-3, yielded forty-two kilotons. Two years later, in August 1953, Joe-4 yielded more than four hundred kilotons. Again, American scientists were shocked. This bomb was more powerful than standard fission weapons—it was clearly a fusion device.

Russian scientists had come up with a design similar to the Alarm Clock idea, the very one that Teller had rejected as a dead end. It was still a dead end; there was no way the Russians could use the design to create a practical weapon in the megaton range. And the fact that they relied on this design shows they hadn’t yet made the Ulam-Teller breakthrough. Nevertheless, the Russian alarm clock was waking up the American public to the likelihood that the Soviet Union would have a full-fledged hydrogen bomb in a few years. The American advantage, once again, was dissolving faster than expected.

Teller knew just whom to blame. So did Senator Joseph McCarthy. In April 1954, the senator accused Oppenheimer of deliberately delaying the H-bomb by eighteen months. After years of maneuvering—and after Lewis Strauss, a Teller ally, became the head of the Atomic Energy Commission—Oppenheimer’s enemies finally had enough power to break him. The AEC began formal hearings to strip Oppenheimer of his security clearance. The charges against him: various associations with Communists, lying to the FBI about Communist meetings, and strong opposition to the development of the hydrogen bomb in 1949. Oppenheimer was being punished, in part, for not jumping on the fusion bandwagon.

The Communist associations would probably have been enough to sink Oppenheimer.13 Nonetheless, Teller and his allies hammered the hapless physicist for dragging his feet about the Super project. Mercilessly. Ernest Lawrence, Luis Alvarez, and Kenneth Pitzer expressed their doubts, in testimony or in affidavits, about Oppenheimer’s resistance to building a fusion superbomb. Teller testified, too, and he seemed to relish twisting the knife. “It is my belief that if at the end of the war some people like Dr. Oppenheimer would have lent moral support, not even their own work—just moral support—to work on the thermonuclear gadget . . . I think we would have had the bomb in 1947.” When asked what it would mean to atomic science if Oppenheimer was to “go fishing for the rest of his life,” Teller said that Oppenheimer’s post-Los Alamos work was simply not helpful to the United States. Scientists sympathetic to Oppenheimer would never forgive Teller for his testimony. Teller likened the reception he got from his fellow physicists to his exile from Europe. He wrote: “In my new land, everything had been unfamiliar except for the community of theoretical physicists. . . . Now, at forty-seven, I was again forced into exile.”

The outcome of the Oppenheimer hearing was almost preordained. The panel stopped short of branding Oppenheimer disloyal, but it revoked his security clearance, stating, among other things, “We believe that, had Dr. Oppenheimer given his enthusiastic support to the [Super] program, a concerted effort would have been initiated at an earlier date.” Furthermore, the panel found his opposition to the hydrogen bomb “disturbing.” Oppenheimer was to blame for the slow progress in building the hydrogen bomb.

The scapegoat had been cast out. Oppenheimer’s nuclear career was over.

The bitterness on both sides of the debate would last for decades, but the hawks had won. The weapons project at Los Alamos (and at Livermore) steamed ahead, buoyed by the urgency of keeping out in front of the Soviets. Los Alamos would quickly turn Ivy Mike into a deployable bomb. By 1954, the Castle Romeo test detonated a practical weapon (eleven megatons strong) designed to provide “emergency capability” to U.S. nuclear forces. And there was, in fact, an emergency brewing.

Dwight D. Eisenhower became president in 1953, and like Truman, he threatened to use nuclear weapons against China. In May 1953, American diplomats made veiled but clear nuclear threats that seem to have helped end the Korean War. Even after that conflict was essentially settled, the nuclear saber rattling against China continued. As the United States was drawn into the China-Taiwan standoff, Eisenhower contemplated the use of nuclear weapons. He considered them similar to any other munition, and in March 1955, at the direction of the president, Secretary of State John Foster Dulles announced that nuclear bombs were “interchangeable with the conventional weapons” used by U.S. forces. Dulles also lamented, in a meeting two days later, that a lot of public relations still had to be done with the American people if the nation was to use nuclear bombs within the “next month or two.” Luckily, the crisis ended without a nuclear exchange.

Even as the United States used its fusion weapons to try to black-a mail China and assert its nuclear primacy, its advantage was slipping away once again. On November 22, 1955, the Soviet Union tested their own Mike: a 1.6-megaton hydrogen bomb. It, too, was a two-stage device. The Soviets had also unshackled the fury of the sun upon the inhabitants of the Earth.