Terraforming is the process of making non-Earth-like worlds, well, Earth-like. Habitable to human and other terrestrial life in the same way that Earth is. To be honest, I don’t really see the need for terraformation. If we upload ourselves, or even just move our brains over to robotic bodies, we become able to survive in a much wider range of environments than the 1 bar, Nitrogen-Oxygen, 0-100 degree Fahrenheit one we currently live in. Granted there is some leeway there (a human can survive in 0.2 bar of pure oxygen, for example) but the hard vaccuum of space? Nope. The crushing 90 bar CO2 atmosphere of Venus? Nope. Of course, these present challenges of their own for uploaded people in robotic bodies (especially Venus), but it is much more conceivable that we might one day be able to.
Of course, I think the human race might end up terraforming other planets anyway, for asthetic reasons. We like life. We are life, and we feel a special kinship with other forms of life and are more attracted to it than rock and ice. If people are going to start living on other worlds for their entire lives, they’ll probably want a place much more Earth-like than anything.
As an example, I’ve stitched together several speculative images made by others of Mars, Venus, the Moon, and Mercury, all terraformed and adjusted to relative scale. Tell me it just isn’t beautiful:
(Note: click for a larger image. Warning: 1.4 MB)
Interesting story while making this. I found all the images of the terraformed worlds on Wikipedia (Mercury is actually an alternate image of the Moon, just flipped vertically). I wanted to use an actual picture for Earth, but I noticed something strange. All the terraformed worlds were lit from the right, while all the images of Earth I could find were lit from the left. Why this might be I have no idea. Anyway, I didn’t just want to stick in a wrongly lit Earth because it would just look wrong, and, to me, having a world lit from the right just looks better than one lit from the left. And, obviously, I couldn’t just flip the Earth because that would be blatantly noticeable. (If any of these links don’t work right, just right-click and say “Save Target As…”, though maybe it’s just my computer being being a @#$&ing %^&$. )
So what’s a phenomenally intelligent human of the year 2009 to do? Why, go into orbit and take the photograph myself, of course! Well, no… I used the space software Celestia.
Anyway, my original point was that, though we might not need to terraform worlds, we might want to anyway. And, as you know, if we as a species want to do something, and there’s nothing preventing us from doing it, it’s going to happen. Period.