Living in space should be an amazing challenge, but however practical and (relatively) easy to create will be spaceships and habitats, there is nothing above a genuine planet to live on. Besides, it's much safer during those galactic wars than fragile space bases, where a single hit can leave you grasping for air... or maybe not, considering planets cannot escape. But I digress.
If we ever rise into space, and find planets close enough to ours, then, no doubt, our kind will seek to change them to our own image, and make them habitable.
This is a collection of ideas around the concept of terraforming. Which of them are likely to be used will depend on the level of technology, and too many other factors.
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Considered aspects:
Other topics:
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Additional thoughts are welcome. Please try to keep the format (major themes as scroll comments, lesser topics as replies).
And sorry for the broken outside links. :|