Physics 101

The kids were in watching Gilligan's Island--the episode where they find clay tablets and Gilligan dreams about being a caveman--and caveman Skipper makes some remark about the earth being flat and people falling off the edge.
Cameron (knowing the earth is round) asked Cindy about what happens to people who live on the 'bottom' of the world, and why they don't fall off. She patiently explained that gravity makes a person feel like they are on top of the earth regardless of where they are, and that for all we kn ow we could really be upside down right now!
Cameron thought a second, and then said, 'We must be upside down when I get headaches!' (I.e., because the blood feels like it has rushed to his head.)
He's always thinking!

Which is sometimes not such a good thing......