The supply of matter in the universe was never more tightly packed than it is now, or more widely spread out. For nothing is ever added to it or subtracted from it. It follows that the movement of atoms today is no different from what it was in bygone ages and always will be. So the things that have regularly come into being will continue to come into being in the same manner; they will be and grow and flourish so far as each is allowed by the laws of nature.