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

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.

No one can deny the excitement of visiting another world.

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

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

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.