Through all the ages, man has fought against two great enemies — time and space. Time he may never wholly conquer, and the sheer immensity of space may also defeat him when he has ventured more than a few light-years from the Sun. Yet on this little Earth, at least, he may one day claim a final victory.

Profiles of the Future: An Inquiry into the Limits of the Possible, Chapter 8 (p. 81)