National Geographic : 1939 Jul
NEWS OF THE UNIVERSE the position, spacing, intensity, and thick ness of these lines, an astronomer can tell you, in many cases, the distance of that star, its mass, or weight, its brightness, its temperature, size, speed of rotation, and atmospheric pressure. The giant mirrors of telescopes catch light that started toward Earth from the distant galaxies before the human race ex isted. These ancient light rays tell us that the farthest reaches of the Universe contain no materials different from those in our own bodies and our planet. Who, then, can say that man on his little Earth is insignificant? Seen from outside, the Earth would be a globe colored about the same blue as our sky, largely covered by clouds (Plate I). Outlines of some continents might be distinguishable at times, large patches of green would appear as spring came on, fading with autumn, and large white areas would surround the poles in winter. The Earth is built like a golf ball, with a core of nickel-iron, an outer layer of heavy rock, and a thin skin of lighter rock. Oceans cover three-fourths of its surface. HYPOTHETICAL BIRTH OF THE EARTH It is certain that the Earth, other planets, and the Sun are related, for all are made of the same materials. Probably big masses of gas somehow were ripped off the Sun and started circling around it. Gradually they cooled and formed into the planets, one of the smaller ones becoming the Earth. All this happened in the distant past, for we know that the Earth's crust has been solid for about two billion years. Perhaps the planets had two parents, the "mother" the Sun, and the "father" an other star, according to the theory of Drs. F. R. Moulton and T. C. Chamberlin. The "father" star, if such there was, circled in close to the Sun, and possibly there was even a sideswiping collision. In either case, while the two were close together great tides were raised on both by their mutual attraction. Vast masses of hot gas extended out into the space between them. The "father" star did not tarry, and, as he pulled away, his gravitational at traction detached much hot gaseous matter from the Sun. Some of it followed him off into space. The rest began revolving around the Sun. A few of the larger gaseous masses then perhaps became the planets, with smaller fragments evolving into the moons, comets, asteroids, and meteors we see today. Or the planets may have been slowly built up by the joining of smaller fragments. It may be, too, that the planets were born in a catastrophic breakup of the Sun, says Dr. Ross Gunn of the United States Naval Research Laboratory (Color Plate V). At some distant day when it was larger than now, the Sun may have gotten to spin ning too fast to hold together. Some stars today apparently are on the verge of such a breakup. First the spinning Sun developed huge bulges, according to this idea, making it lopsided. Then one of the bigger bulges broke clean away. At the same time, tides were raised on both the fragments, and masses of material were shot off from them. As the Sun broke in two, the terrific heat of its interior was suddenly released, as when steam bursts from a hot potato cut in half. Both halves of the sundered Sun thus had hot faces from which rushed forth the light and energy which until then had been pent up inside. As the recoil of ejected gases drives a rocket, the recoil of this outrushing energy drove apart the two halves of the Sun. The smaller one shot off into space to be come a separate star. The other remained as the Sun we know today. The smaller fragments of ejected material began revolv ing around it and became the planets. We know that stars sometimes do break up. Just recently a star known as Nova Pictoris split into three sections, and as tronomers have been watching them fly apart at the rate of a million miles per hour. If the Earth was created out of the Sun, by whatever means, we humans can truly say that we are the Sun's grandchildren, for we in turn are made of the Earth's mate rials. The atoms in a chorus girl's blond hair or in a beggar's ragged coat probably once danced in the flaming gases of our par ent star. THE MIRACLE OF LIFE APPEARS In the deepest oil well drill hole man has scratched less than three miles into the Earth's outer skin of rock, but with the aid of earthquakes he has explored to its very center. It's an ill temblor that shakes nobody good! The vibrations of earth quakes that pass through the Earth's center show by their behavior that the central core must be a mass of nickel and iron, 4,000 miles thick.