The hell bomb

by William L. Laurence

While we do not know how and when matter and energy came into being, or whether they ever had a beginning in time as we perceive it, we do know that while the relative amounts of matter and energy are constantly changing, the total amount of both, in one form or the other, always remains the same. When a plant grows, energy from the sun, in the form of heat and light, is converted into matter, so that the total weight of the plant is greater than that of the elementary material constituents, water and carbon-dioxide gas, out of which its substance is built up. When the substance of the plant is again broken up into its original constituents by burning, the residual ashes and gases weigh less than the total weight of the intact plant, the difference corresponding to the amount of matter that had been converted into energy, liberated once again in the form of heat and light.

All energy as we know it manifests itself through motion or change in the physical or chemical state of matter, or both, though these changes and motions may be so slow as to be imperceptible. As the ancient Greek philosopher Heraclitus perceived more than two thousand years ago, all things are in a constant state of flux, this flux being due to an everlasting conversion of matter into energy and energy into matter, everywhere over the vast stretches of the material universe, to its outermost and innermost limits, if any limits there be.

Each manifestation of energy involves either matter in motion or a change in its physical state, which we designate as physical energy; a change in the chemical constitution of matter, which we know as chemical energy; or a combination of the two. Physical energy can be converted into chemical energy and vice versa. For example, heat and light are forms of physical energy, each consisting of a definite band of waves of definite wave lengths in violent, regular, rhythmic oscillations. A mysterious mechanism in the plant, known as photosynthesis, uses the heat and light energy from the sun to create complex substances, such as sugars, starches, and cellulose, out of simpler substances, such as carbon dioxide and water, converting physical energy, heat, and light into the chemical energy required to hold together the complex substances the plant produces. When we burn the cellulose in the form of wood or coal (coal is petrified wood), the chemical energy is once again converted into physical energy in the form of the original heat and light. As we have seen, the chemical energy stored in the plant manifested itself by an increase in the plant’s weight as compared with that of its original constituents. Similarly, the release of the energy manifests itself through a loss in the total weight of the plant’s substance.

It can thus be seen that neither matter nor energy can be created. All we can do is to manipulate certain types of matter in a way that liberates whatever energy had been in existence, in one form or another, since the beginning of time. All the energy that we had been using on earth until the advent of the atomic age had originally come from the sun. Coal, as already said, is a petrified plant that had stored up the energy of the sun in the form of chemical energy millions of years ago, before man made his appearance on the earth. Oil comes from organic matter that also had stored up light and heat from the sun in the form of chemical energy. Water power and wind power are also made possible by the sun’s heat, since all water would freeze and no winds would blow were it not for the sun’s heat energy keeping the waters flowing and the air moving, the latter by creating differences in the temperature of air masses.

There are two forms of energy that we take advantage of which are not due directly to the sun’s radiations—gravitation and magnetism—but the only way we can utilize these is by employing energy derived from the sun’s heat. In harnessing Niagara, or in the building of great dams, we utilize the fall of the water because of gravitation. But as I have already pointed out, without the sun’s heat water could not flow. To produce electricity we begin with the chemical energy in coal or oil, which is first converted into heat energy, then to mechanical energy, and finally, through the agency of magnetism, into electrical energy.

The radiations of the sun, of the giant stars millions of times larger than the sun, come from an entirely different source, the greatest source of energy in the universe, known as atomic or, more correctly, nuclear energy. But even here the energy comes as the result of the transformation of matter. The difference between nuclear energy and chemical energy is twofold. In chemical energy, such as the burning of coal, the matter lost in the process comes from the outer shell of the atoms, and the amount of matter lost is so small that it cannot be weighed directly by any human scale or other device. In nuclear energy, on the other hand, the matter lost by being transformed into energy comes from the nucleus, the heavy inner core, of the atom, and the amount of matter lost is millions of times greater than in coal, great enough to be weighed.

An atom is the smallest unit of any of the elements of which the physical universe is constituted. Atoms are so small that if a drop of water were magnified to the size of the earth the atoms in the drop would be smaller than oranges.

The structure of atoms is like that of a minuscule solar system, with a heavy nucleus in the center as the sun, and much smaller bodies revolving around it as the planets. The nucleus is made up of two types of particles: protons, carrying a positive charge of electricity, and neutrons, electrically neutral. The planets revolving about the nucleus are electrons, units of negative electricity, which have a mass about one two-thousandth the mass of the proton or the neutron. The number of protons in the nucleus determines the chemical nature of the element, and also the number of planetary electrons, each proton being electrically balanced by an electron in the atom’s outer shells. The total number of protons and neutrons in the nucleus is known as the mass number, which is very close to the atomic weight of the element but not quite equal. Protons and neutrons are known under the common name “nucleons.”

There are two important facts to keep constantly in mind about protons and neutrons. The first is that the two are interchangeable. A proton, under certain conditions, loses its positive charge by emitting a positive electron (positron) and thus becomes a neutron. Similarly, a neutron, when agitated, emits a negative electron and becomes a proton. As we shall see, the latter process is taken advantage of in the transmutation of nonfissionable uranium into plutonium, and of thorium into fissionable uranium 233. The transmutation of all other elements, age-old dream of the alchemists, is made possible by the interchangeability of protons into neutrons, and vice versa.

The second all-important fact about protons and neutrons, basic to the understanding of atomic energy, is that each proton and neutron in the nuclei of the elements weighs less than it does in the free state, the loss of weight being equal to the energy binding the nucleons. This loss becomes progressively greater for the elements in the first half of the periodic table, reaching its maximum in the nucleus of silver, element 47. After that the loss gets progressively smaller. Hence, if we were to combine (fuse) two elements in the first half of the periodic table, the protons and the neutrons would lose weight if the newly formed nucleus is not heavier than that of silver, but would gain weight if the new nucleus thus formed is heavier than silver. The opposite is true with the elements in the second half of the periodic table, the protons and neutrons losing weight when a heavy element is split into two lighter ones, and gaining weight if two elements are fused into one.