Interplanetary colonization? Seneca advises against it

When I was a kid I was fascinated by astronomy, and particularly planetology, the study of the atmospheres, geologies, and — possibly — biologies of other planets in the solar system (extrasolar planets where yet to be discovered). And of course I was also attracted by science-based speculation about the possibility of colonizing, terraforming, even, places like Mars, or some of the moons of…