Page:The evolution of worlds - Lowell.djvu/276

234 flooding with radiance our winter nights, the lifeless statue of its former self.

The same inevitable end, in default of others, is now overtaking the planetary group. Its approach is stamped on the face of Mars. There we see a world dying of exhaustion. The signs of it are legible in the markings we descry. How long before its work is done, we ignore. But that it is a matter of time only, our study of the laws of the inexorable lead us to conclude. Mars has been spared the fate of Mercury and Venus to perish by this other form of planetary death.

Last in our enumeration of the causes by which the end of a world may be brought about, because the last to occur in order of time, is the extinction of the Sun itself. Certain to come and conclude the solar system's history as the abode of life, if all the others should by any chance fail to precede it, it fittingly forms the climax, grand in its very quietude, of all that went before.

By the same physical laws that caused our Earth once to be hot, the Sun shines to-day. Only its greater size has given it a life and a brilliancy denied to smaller orbs. The falling together of the scattered particles of which it is composed, caused, and still is causing, the dazzling splendor it emits. And so long as it remains gaseous, its temperature must increase, in spite of its lavish expenditure of heat, as Homer Lane discovered forty years ago.