It may be that the old astrologers had the truth exactly reversed, when they believed that the stars controlled the destinies of men. The time may come when men control the destinies of stars.

The difference between machines and human beings is that human beings can be reproduced by unskilled labour.

Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering.

The numbers of distinct human societies or nations, when our race is twice its present age, may be far greater than the total number of all the men who have ever lived up to the present time.

One can imagine a time when men who still inhabit organic bodies are regarded with pity by those who have passed on to an infinitely richer mode of existence, capable of throwing their consciousness or sphere of attention instantaneously to any point on land, sea, or sky where there is a suitable sensing organ. In adolescence we leave childhood behind; one day there may be a second and more portentous adolescence, when we bid farewell to the flesh.

The exploration of the planets is now closer to us in time than the exploration of Africa by Stanley and Livingstone.

Every age has its dreams, its symbols of romance. Past generations were moved by the graceful power of the great windjammers, by the distant whistle of locomotives pounding through the night, by the caravans leaving on the Golden Road to Samarkand, by quinqueremes of Nineveh from distant Ophir . . . Our grandchildren will likewise have their inspiration-among the equatorial stars. They will be able to look up at the night sky and watch the stately procession of the Ports of Earth-the strange new harbors where the ships of space make their planetfalls and their departures.