Nebular Hypothesis
in astronomy, a hypothesis first suggested by Sir William Herschel, though the germs of it may be found in Kant's "General Natural History and Theory of the Heavens," printed in 1755. It was de. veloped by La Place, with whose name it came to be associated. The hypothesis assumes that originally all suns were in a nebulous or ultra-gaseous state. The nebulous matter from which they were originally formed was at first scattered pretty uniformly through all space, but ultimately began to gravitate toward certain centers. Further contraction producing increased velocity, ring after ring would be cast off, till the central body or sun generated a whole system of planets revolving around it. They, in turn, might in the same way produce satellites.
La Place believed that the sun thus produced our earth and the other attendant planets. On this hypothesis the rings of Saturn were produced by Saturn himself, and have remained in the annular form instead of condensing into nearly spherical satellites. Many people supposed that the resolution of various nebulæ into stars (see NEBULA) was necessarily fatal to the nebular hypothesis, but the discovery that some are not only irresolva- NECHES ble, but can be actually proved by spectrum a analysis to consist of glowing gas, has re-established it on a firmer basis than ever, though the original the ory may need revision in points of detail.