Bill Watterson

- Hey dad, what are clouds made of?
- Hmm... I used to know that. I think they're mostly water.
- So how come they float?
- Well, it's sort of evaporated water. Maybe there are some other gases, too. I'm not sure.
- So why are they white when the rest of the sky is blue?
- Heck, beats me. I guess we ought to look this stuff up.
- I take it there's no qualifying exam to be a dad.