In the past, on Earth, it has largely been to exploit foreign resources and to expand the domestic territory.

Antimatter is not a source of energy for us, it's a method of storing energy, compact but inefficient.

Above all, I would not expect a wise race, at great expense, to set loose an army of self-replicating robots.

Present annual world energy consumption is about equal to the annihilation energy of 4 tons of matter.

The factor most ignored in discussing interstellar flight is the kinetic energy that must be invested in the ship to make its tons of matter move at a substantial fraction of the speed of light.

In the past, on Earth, it has largely been to exploit foreign resources and to expand the domestic territory.

The sun and its retinue of planets drift as a group through the vast gulfs of space that separate the stars.