I first heard about the hydrogen bomb in the spring of 1945 in Los Alamos, New Mexico, where our scientists were putting the finishing touches on the model-T uranium, or plutonium, fission bomb. I learned to my astonishment that, in addition to this work, they were already considering preliminary designs for a hydrogen-fusion bomb, which in their lighter moments they called the “Superduper” or just the “Super.”
I can still remember my shock and incredulity when I first heard about it from one of the scientists assigned to me by Dr. J. Robert Oppenheimer as guides in the Dantesque world that was Los Alamos, where the very atmosphere gave one the sense of being in the presence of the supernatural. It seemed so fantastic to talk of a superatomic bomb even before the uranium, or the plutonium, bomb had been completed and tested—in fact, even before anybody knew that it would work at all—that I was inclined at first to disbelieve it. Could anything be more powerful, I found myself thinking, than a weapon that, on paper at least, promised to release an explosive force of 20,000 tons of TNT? It was a screwball world, this world of Los Alamos, I kept saying to myself, and this was just a screwball notion of my younger scientific mentors.
So at the first opportunity I put the question to Professor Hans A. Bethe, of Cornell University, one of the world’s top atomic scientists, who headed the elite circle of theoretical physicists at Los Alamos. Dr. Bethe, I knew, was the outstanding authority in the world qualified to talk about the subject, since he was the very man who first succeeded in explaining how the fusion of hydrogen in the sun is the source of energy that will make it possible for life to continue on earth for billions of years.
“Is it true about the superbomb?” I asked him. “Will it really be as much as fifty times as powerful as the uranium or plutonium bomb?”
I shall never forget the impact on me of his quiet answer as he looked away toward the Sangre de Cristo (Blood of Christ) mountain range, their peaks turning blood-red in the New Mexico twilight. “Yes,” he said, “it could be made to equal a million tons of TNT.” Then, after a pause: “Even more than a million.”
The tops of the mountains seemed to catch fire as he spoke.
Long before it was discovered that vast amounts of energy could be liberated by the fission (splitting) of the nuclei of a twin of the heaviest element in nature—namely, uranium of atomic mass 235 (235 times the mass of the hydrogen atom, lightest of all the elements)—scientists had known that truly staggering amounts of energy would be released if one could fuse together four atoms of hydrogen, the first element on the atomic table, into one atom of helium, element number two on that table, which weighs about four times as much as hydrogen. In December 1938—three weeks before the discovery of uranium fission was announced in Germany—Dr. Bethe had published his famous hypothesis about the fusion of four hydrogen atoms in the sun to form helium. This provided the first satisfactory explanation of the mechanism that enables the sun to radiate away in space every second a quantity of light and heat equivalent to the energy content of nearly fifteen quadrillion tons of coal. And while Dr. Bethe was the first to work out the fine details of the process, scientists had been speculating for more than twenty years on the likelihood of hydrogen fusion in the sun as source of the sun’s eternal radiance.
American audiences first heard about hydrogen as the solar fuel in a lecture, on March 10, 1922, at the Franklin Institute, Philadelphia, by Professor Francis William Aston, famous British Nobel-Prize-winning chemist, who even at that early date warned mankind against what he called “tinkering with the angry atoms.” His words on that occasion have a strange prophetic ring, though most of what he said is now known to be wrong. “Should the research worker of the future discover some means of releasing this energy [from hydrogen] in a form which could be employed,” he predicted, “the human race will have at its command powers beyond the dreams of scientific fiction, but the remote possibility must always be considered that the energy, once liberated, will be completely uncontrollable and by its violence detonate a neighboring substance. If this happens, all of the hydrogen on earth might be transformed [into helium] at once, and this most successful experiment might be published to the rest of the universe in the form of a new star of extraordinary brilliance, as the earth blew up in one vast explosion.”
By 1945 we had learned that many things were wrong in Professor Aston’s prophecy. It had been definitely established, for example, that it would be impossible to “transform all the hydrogen on earth at once,” no matter how many superduper hydrogen bombs were to be exploded. In fact, we had learned that, under conditions as they exist on earth, we could never use common hydrogen, the element that makes up one ninth by weight of all water, either in a superduper bomb or as an atomic fuel for power. On the other hand, ten years after Dr. Aston’s lecture a new type of hydrogen was discovered to exist in nature. It was found to constitute one five-thousandth part of the earth’s waters, including the water in the tissues of plants and animals. It was shown to have an atomic weight of two—double the weight of common hydrogen—and was named deuterium. The nucleus, or center, of the deuterium atom was named the deuteron, to distinguish it from the nucleus of common hydrogen, known as the proton. Deuterium also became popularly known as “heavy hydrogen.” Water containing two deuterium atoms in place of the two atoms of light hydrogen became known as “heavy water.”
The most startling fact learned about deuterium soon after its discovery in 1932 was that it offered potentialities as an atomic fuel, or an explosive, of tremendous energy, provided one condition could be met. This condition was a “match” to light it with. And here was the catch. The flame of this match, it was found, would have to have a temperature of the order of 50,000,000 degrees centigrade, two and a half times the temperature in the interior of the sun.