I’ve read most responses to this, here’s my take: 1) The overall concept would be a lot clearer if it were called Earth2 instead of “Planet B”. I agree it’s un

I’ve read most responses to this, here’s my take: 1) The overall concept would be a lot clearer if it were called Earth2 instead of “Planet B”. I agree it’s unlikely we’ll find something suitable “nearby” without terraforming. 2) We know there’s no Earth2 in our solar system. 3) There is no foreseeable path to interstellar travel other than generation ships, presumably after advance scouting. This is not worth considering with present technology. Time horizon for suitable technology is unknown. 4) Saving Earth and colonizing space are NOT mutually exclusive. 5) Abundant, clean energy resources are the only sane path to preserving Earth in more or less its present state. A rising standard of living is associated with lower (or no) population growth, and a cleaner environment. 6) Given sufficient energy, and expertise in interplanetary travel, the Moon and Mars can both become very nice habitats for humans. Almost all day-to-day existence will take place underground. Centrifuges may be needed for physiological reasons (shame on NASA for not studying this sufficiently). 7) Strictly space-based habitats may be better (one G centrifugal force is easy), the downside being that all materials must be transported from elsewhere unless asteroids are converted to habitats. Space habitats will require radiation shielding equivalent to a few feet of concrete. 8) The key thing for all of this, and also for improving standards of living for Earth-dwellers, is abundant energy. The only way to clean up our act on Earth is with massive energy abundance. 9) Solar can help everywhere, and wind can be part of Earth-based solutions, but advanced energy sources like fission and fusion MUST be used as part of the solution. 10) Nuclear powered space travel should be (and is in fact becoming) a priority. An intense focus on advanced space travel may eventually make interstellar travel possible. 11) It’s likely possible that given robust interplanetary travel, the Solar System alone could support a sustainable human population in the tens to hundreds of billions, as well as Earth being a near-pristine “life preserve” with a population of just a few billion. 12) More people should be getting STEM educations. ;-)