It sure looks like a lot of fun when we see videos of astronauts floating around in zero-gravity environments. But did you ever stop to think what prolonged weightlessness does to the human body? We’ll spare you the details, but suffice to say it isn’t pretty. And that means any crewed missions to the Moon, Mars, or anywhere else beyond the Earth’s gravitational field have an undeniable time limit on them. Until we solve the whole gravity problem, permanent off-world colonies are pretty much a non-starter. And, despite what a century of science fiction may have led you to believe,…

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