We stand now at the turning point between two eras. Behind us is a past to which we can never return... The coming of the rocket brought to an end a million years of isolation... the childhood of our race was over and history as we know it began.
Arthur C. ClarkeThe choice, as Wells once said, is the Universe-or nothing. . . . The challenge of the great spaces between the worlds is a stupendous one; but if we fail to meet it, the story of our race will be drawing to its close. Humanity will have turned its back upon the still untrodden heights and will be descending again the long slope that stretches, across a thousand million years of time, down to the shores of the primeval sea.
Arthur C. Clarke