Why is it that when someone tells you that there's billions of stars in the universe, you believe them. But if they tell you there's wet paint somewhere you have to touch it?
It's really funny that you asked me that, because I was just thinking about that earlier today.
I think it's because the paint is right there so you can touch it, and the paint can also dry. The stars, on the other hand, are millions of kilometers away, so you can't really go out and count them, and they aren't falling out of the sky at the rate of millions per day, so there's no need to verify that they're still there.
And then there's the simple fact that you don't permanently leave a mark on the stars by trying to count them. :P
