Why I thus compute 1,000 millions of years of light’s radius is because it is possible with powerful telescopes to detect light coming that distance; and when we contemplate that our nearest star, Alpha Centauri, is twenty trillions of miles distant, and 61 Cygni more than twice as far,—or _seven_ year’s flight of light,—and that the Polar star is some fifty years of light’s flight removed from us; then, if all suns are no nearer to each other than these are to our sun, we are led to believe we may see light with our unaided vision that has been on its journey for a million years. Some detect with the naked eye the light that comes from the nebula in the Sword’s-Handle of Orion, which is thought to contain two trillions, two hundred billions of stars; and if all these stars are no nearer to each other than Alpha Centauri is to our sun, it cannot be otherwise than that some of them are so distant their light may have been travelling for a million years before it comes to our sight. If this be true, with telescopes that penetrate a thousand times farther into the heavens, we may possibly see light that has been on its voyage to earth one thousand millions of years. But the number of earths a sphere of 1,000 millions of years of light’s flight would contain makes the number of drops of water in sixty millions of millions of cubic miles (equalling but the earths in a sphere of _ten_ years radius) sink into utter insignificance. And yet a sphere of this dimension, even, may be small beside the whole universe of ether whose every atom in all the millions of years past, as far as known, has not in the least diminished its wonderful energy; and, with lightning-like transmission, still brings to our sight light from distant stars, all of which are so distant that they do not materially increase the present flow of light. For if but a single one were to come between us and the sun the increase of that light and heat would be unendurable.