Nice description of science (physics in particular) from the JREF forums.

As it turns out, we know enough to make really incredibly detailed descriptions. So detailed, we can describe things that we can’t actually sense directly with our own senses. We can measure those things, and we can describe them, but we can’t see them. So how do we know they’re right?

The answer is, reality appears to be consistent. In other words, our universe appears to be a place where, although random things can happen, not just anything can happen. Only certain sorts of random things can. For example, if you get out of bed and walk to the store and buy some brewskis and come home and sit on the couch and drink one, you’re still you. You don’t turn into a penguin when you walk around the corner, and you don’t cease to exist when you sit down on the couch. And this implies some things about the nature of our universe- and those things add up to consistency. Rocks don’t just disappear, or appear out of nowhere. The planet beneath our feet is there all the time, and holds us to itself.