How Many People Would We Need To Colonize Another Earth?

Various companies are working to settle on other planets. How long would it take and what issues would we face along the way?
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Read more:
– Space Future
– Space Exploration Books
– Spaceships & Rockets
– The Future of Mars Exploration
– The Future of Moon Exploration
– Asteroid Mining
Space Colonization, How Many People Would We Need To Colonize Another Earth