Then, in January 1939, came the world-shaking discovery of the phenomenon known as uranium fission. In simple language, we had found a proper “match” for lighting a fire with a twin of uranium, the ninety-second, and last, natural element. This twin is a rare form of uranium known as uranium 235—the figure signifying that it is 235 times heavier than common hydrogen. Doubly phenomenal, the discovery of uranium fission meant that to light the atomic fire, with the release of stored-up energy three million times greater than that of coal and twenty million times that of TNT (on an equal-weight basis) would require no match at all. When proper conditions are met, the atomic fire would be lighted automatically by spontaneous combustion. What are these proper conditions? In the presence of certain chemical agencies, spontaneous combustion will take place when an easily burning substance, such as sawdust, for example, accumulates heat until it reaches the kindling temperature at which it ignites. The chemical agencies here are the equivalent of a match. The requirement to start the spontaneous combustion of uranium 235, and also of two man-made elements named plutonium and uranium 233 (all three known as fissionable materials or nuclear fuels), is just as simple. In this operation you do not need a critical temperature, but what is known as a critical mass. This simply means that spontaneous combustion of any one of the three atomic fuels takes place as soon as you assemble a lump of a certain weight. The actual critical mass is a top secret. But the noted British physicist, Dr. M. L. E. Oliphant, of radar fame, published in 1946 his own estimate, which places its weight between ten and thirty kilograms. If so, this would mean that a lump of uranium 235 (U-235), plutonium, or U-233, weighing ten or thirty kilograms, as the case may be, would explode automatically by spontaneous combustion and release an explosive force of 20,000 tons of TNT for each kilogram undergoing complete combustion. In the conventional A-bomb a critical mass is assembled in the last split second by a timing mechanism that brings together, let us say, one tenth and nine tenths of a critical mass. The spontaneous combustion that followed such a consummation on August 6 and 9, 1945 destroyed Hiroshima and Nagasaki. Thus, if we substitute the familiar phrase “spontaneous combustion” for the less familiar word “fission,” we get a clear understanding of what is known in scientific jargon as the “fission process,” a “self-multiplying chain reaction with neutrons,” and similar technical mumbo-jumbo. These terms simply mean the lighting of an atomic fire and the release of great amounts of the energy stored in the nuclei of U-235 since the beginning of the universe. The two so-called man-made elements are not really created. They are merely transformed out of two natural heavy elements in such a way that their stored energy is liberated by the process of spontaneous combustion.