Astounding Science Fiction, British Edition — page 74: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

72 goes a whole series of transformations, giving seven different forms of ice, including one which under forty thousand atmospheres remains solid up to nearly 200° Centigrade. Each of these different forms is called a “phase,” a term applied in physical Chemistry to a homogeneous (uniform) sample of material in a nonhomo- geneous (nonuniform) system. A com- mon example is an ice cube in a glass of ice water. Here are represented the two phases of solid and liquid, and also the gaseous phase of the water vapor plus atmosphere. When solid substances are com- pressed, the atomic lattice of the crystal may become unstable and collapse to a denser configuration, but there is an ultimate limit on the amount of interatomic space that may be squeezed out in this manner. As an example, let us look at elemental cesium, the most compressible of metals. It exists under normal con- ditions in a body-centered cubic lattice, but becomes transformed by twenty- five thousand atmospheres into a phase made up of the more compact face- centered cubic lattice. At forty-five thousand atmospheres, a much more interesting change takes place; a sudden twenty-one per cent change in density tells us, unmistakably, that at this pressure something must have finally given way—and in this case it was the atoms themselves which have shrunk. This is not, of course, a nuclear effect, but some sort of collapse in the size or arrangement of the electronic orbits. This is a reversible change; that is, the metal pops back to its original volume when the pres- sure is released. On the other hand, yellow phosphorus undergoes an Ir- reversible lattice change at thirty-five thousand atmospheres to give the so- called “black phosphorus” which is quite inert chemically, looks like graphite, and is forty-eight per cent ASTOUNDING SCIENCE FICTION denser than the starting material. It is important to note that most of these phase changes at higher pres- sures, either reversible or irreversible, produce a material which is more metallic in nature—significantly denser and a better conductor of heat and electricity. The metallic modification of arsenic, for example, is 2.8 times as dense as the nonmetallic yellow form. Tellurium moves out of the class of semiconductors—such as germanium which is used in the transistor—into the class of true metallic conductors, its electrical conductance increasing six-hundred-fold by the time thirty thousand atmospheres is reached. The observed increase agrees well with the values calculated by means of quantum mechanics. The pressures thus far attained in the laboratory correspond to a pene- tration into the earth’s crust of only four hundred miles at the most, yet, as we have already seen, new forms of matter are produced which markedly differ in their properties from the same material under surface condi- tions.* We can guess, therefore, that perhaps similar things may be taking place in the earth’s interior. It is well known from data obtained from reflected earthquake waves that our earth is built up of a number of shells surrounding an inner core. The outer shell, on which we live, is a rocky one some six hundred miles thick. Beneath this is an intermediate layer which extends downward another eleven hundred miles, and in the center is the core with a diameter of some forty-six hundred miles. In passing, it * It is interesting to note that most of the matter of the universe exists under condi- tions that we cannot duplicate in any terres- trial laboratory; the matter making up planets and stars is largely at too high a pressure and or temperature, and the matter existing between the worlds is suspended in a vacuum far better than our best pump can attain. connicbooks.co nn