Space is about 100 kilometers away. That’s far away—I wouldn’t want to climb a ladder to get there—but it isn’t that far away. If you’re in Sacramento, Seattle, Canberra, Kolkata, Hyderabad, Phnom Penh, Cairo, Beijing, central Japan, central Sri Lanka, or Portland, space is closer than the sea.

The scholarly authorities on freezing to death seem to be, unsurprisingly, Canadians.

What people don't appreciate, when they picture Terminator-style automatons striding triumphantly across a mountain of human skulls, is how hard it is to keep your footing on something as unstable as a mountain of human skulls. Most humans probably couldn't manage it, and they've had a lifetime of practice at walking without falling over.

You don't become great by trying to be great. You become great by wanting to do something, and then doing it so hard that you become great in the process.

One of the things I've learned with doing 'xkcd' is that you sort of give people, 'Here's the thing, and here's the button you can press to get another thing.' Sometimes that can be more easy to digest than, 'Here's a long page of things.

The universe is probably littered with the one-planet graves of cultures which made the sensible economic decision that there's no good reason to go into space-each discovered, studied, and remembered by the ones who made the irrational decision.

I've always thought that one of the the great thing about physics is that you can add more digits to any number and see what happens and nobody can stop you.