Science: In the Beginning

Among modern astronomers, an old theory of the origin of the solar system was back in fashion. German Philosopher Immanuel Kant had speculated in 1755 that the sun and its planets were formed by condensation out of a gaseous cloud. For a while astronomers supported Kant, but later his “nebula hypothesis” lost scientific favor. More modern astronomers, notably Sir James Jeans, have conceded that the sun may have been formed that way, but not the planets. To explain the planets, Jeans suggested that another star must have grazed the sun, pulling out a thread of sun-matter that gathered into beadlike planets.

Such “catastrophic” explanations of the solar system made fair sense scientifically, and got grateful support from nonscientific people who preferred to believe that man and his earthly home are unique n the universe. Collisions or near-collisions between stars must be excessively rare. If it takes such a cosmic catastrophe ;o produce a planetary system, there is a good chance that man’s earth may be the only chunk of matter with proper conditions for life to develop.

Whirling Discs. But Kant’s hypothesis was not entirely discarded by astronomers. Recently, armed with a vast amount of detailed knowledge that Kant did not possess, modern astronomers have busied themselves reconsidering his theory and plugging holes in it. Last week, in a Chicago lecture, Astronomer Gerard P. Kuiper of the University of Chicago presented bis own neo-Kantian hypothesis. Basing his reasoning on hydrodynamic data, Kuiper concluded that the cloud around the nascent sun passed through a stage with about one-third of the system’s matter forming a thin, pancake-shaped disc like the rings of Saturn. The disc, said Kuiper, grew denser and denser until it became unstable and broke into whirling eddies.

The “proto-planets” (as Kuiper calls the eddies) condensed into planets, each with a disc of loose material around it. Then the planets’ discs turned into satellites. One planet, Saturn, retains part of its disc as the famous rings.

Cousins in Space? Kuiper does not think that the earth’s satellite, the moon, was formed in this way. The earth-moon pair, he thinks, is a double planet, formed when the planets were formed. The pockmarks on the moon’s face were made by material raining down from the double planet’s common disc. The earth must have had similar marks, originally, he thinks, but since it was big enough to hold an atmosphere, the marks were erased long ago by wind-and-water erosion.

All this happened, Kuiper believes, about three billion years ago. It was over in a few thousand years—a mere jiffy on the astronomical timescale.

Kuiper is a serious astronomer who holds himself loftily above the little vanities of man. But his theory, which requires no rare catastrophe for the formation of planets, makes it much less likely that man is alone in the universe. The sun is an ordinary star, of very common size, temperature and chemical composition. If it has acquired planets in the normal course of its development, many millions of similar stars may have planets too. If so, there is a chance that high forms of life, perhaps higher than man, have developed on some of them.