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.”