Page:The Solar System - Six Lectures - Lowell.djvu/43



ever, from many of its neighbours in being a single-sun system. This is a very important and fundamental distinction. To begin with, it makes cosmic principles much easier to understand. We think celestial mechanics abstruse enough as they are, but ours are child's play to the complications which two suns, to say naught of three or four, would introduce into any system over which they jointly held sway. It is problems of this nature which Professor Darwin and other modern analysts are trying to unravel. Difficult as the conceptions are, it is a question whether life itself would not be quite as difficult, under such conditions. Take our nearest stellar neighbour, Centauri, for instance, and consider what a planet circling round either or both of its suns would be called upon to undergo. Certainly our orderly succession of phenomena would be seriously disturbed to the consequent inconsequency of development upon its surface. Day and night would become meaningless terms, and organisms would have to put up with variations which make imagination stare.

For fashioning worlds like the terrestrial, a single-star system is, in general, a prerequisite.

This oneness is due to the system's original small moment of momentum. A minimum moment of momentum is caused by the centralization