"Yep. There's that expanse -- a big, wide universe full of all different things, and sometimes things in it come to Earth. But people like you and me that go up into space, we go into it. We get to see how big it all is. And how small we are, in the face of it all."

It made it a little harder to get a big head, to get all caught up in your own little world.

"On Earth, as scary as it gets, it's easy to feel like the good guys will win every time -- because we usually do. Up there, you can see how scary it really is. How easy it is for a whole world to die, or a whole species to get wiped out. Or more than one."

Wow, that sounded depressing, but that's not what he meant.

"So we care about worlds. And we care about people. And we have what we need to make sure that's what we always care about the most."