What if one day we encounter aliens, and they are our descendants?

Societies living off-Earth sounds like a concept from science fiction. We spend our lives pinned to the planet. In half a century of human space flight, fewer than 600 people have traveled to low Earth orbit, and just 12 have stood on the surface of another world. The cost and difficulty of extracting humans from gravity's grip seem to have put dreams of space travel on ice.

Yet that is likely to change. Entrepreneurs like Elon Musk and Jeff Bezos are developing reusable rockets that can ferry people more easily into orbit. Richard Branson is hoping to show that there is a viable economic model for space travel based on recreation and tourism. Hotelier Robert Bigelow wants to make sure you have somewhere to stay for your dream vacation in 10 years. Meanwhile, governments are ramping up their efforts to get explorers to the Moon and Mars. NASA aims to put astronauts on Mars by 2035, and the Chinese intend to have an orbiting space station and a lunar colony around the same time.

These plans are being fueled by technological innovation. New materials will allow rockets to be lighter, stronger and cheaper to launch. Parts will be fabricated by 3D printers on the International Space Station. The Moon and Mars are remote and forbidding but it's fairly easy to turn their soil into construction material and mine it for water to drink and oxygen to breathe.

It may even be possible to build a space elevator on the Moon: a super-strong cable extending into the sky, suspended by its own weight and the Moon's spin, allowing materials to be ferried by elevators to zero gravity. A space elevator could spur new economic activity and further exploration of the solar system. Perhaps a brave crew will enter suspended animation and venture off in an interstellar ark to find a pristine habitable world.

Suppose this plays out in the next 50 years. We can imagine the first baby born off-Earth, a transition as profound as our leaving Africa 60,000 years ago. How will living off-Earth change us?

It may already have, with a little help from our 'friends.' ;-) To read more, click here.