The Associated Press put together several quotes from astronauts who have travelled into space to orbit our planet about what our fragile, blue orb means to them.
"It's hard to appreciate the Earth when you're down right upon it because it's so huge.
"It gives you in an instant, just at a position 240,000 miles away from it, (an idea of) how insignificant we are, how fragile we are, and how fortunate we are to have a body that will allow us to enjoy the sky and the trees and the water � It's something that many people take for granted when they're born and they grow up within the environment. But they don't realize what they have. And I didn't till I left it."
-Jim Lovell, Apollo 8 and 13.http://www.ibtimes.com/articles/20070421/earth-day-view.htm