Since, in the long run, every planetary society will be endangered by impacts from space, every surviving civilization is obliged to become spacefaring - not because of exploratory or romantic zeal, but for the most practical reason imaginable: staying alive.

A scientific colleague tells me about a recent trip to the New Guinea highlands where she visited a stone age culture hardly contacted by Western civilization.…

Imagine we could accelerate continuously at 1 g - what we're comfortable with on good old terra firma - to the midpoint of our voyage, and decelerate continuou…

Those who are skeptical about carbon dioxide greenhouse warming might profitably note the massive greenhouse effect on Venus. No one proposes that Venus's gree…

All civilizations become either spacefaring or extinct.

I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single p…

From now on it is only through a conscious choice and through a deliberate policy that humanity can survive.