19 August 2008

Pop Quiz!

I heard someone's cellphone go off, so it's time for a pop quiz. Or if you prefer, think of it as a thought experiment. It's two questions. Answer me the best that you can, and explain your reasoning.

1) A tunnel is drilled straight through the Earth, straight from one side to the other and through the core. Let's suppose the tunnel is given strong enough walls that it doesn't collapse, and that it's well insulated so it isn't too boiling inside. A tourist sees this gigantic hole and decides "hey, there's no bottom to hit, so it's gotta be safe to jump into it," and follows word with deed. (a) Where does he end up? (b) If he could stop at the middle, what would be his weight there (as compared to his weight standing on the surface)?

2) Same tunnel through the Earth, this time you can walk along it with a barometer, reading air pressure throughout the tunnel. When you get to the center, will the air pressure be greater than that at the surface, the same, less than the surface, or entirely zero?

1 comment:

Datan0de said...

Taking a stab in the dark...

1a) After an interesting yo-yo effect, air friction and gravity would eventually cause you to settle in the middle.

1b) Being at the very center of the gravity well, with the mass of the Earth pulling at him roughly equally in all directions, his weight would be zero.

2) As one descends through a column of air the air pressure increases, so I would assume that at the core it would be higher than on the surface. Given that you'd have 2 columns of air pressing down on you it seems that it would be significantly higher.

I'd love to know if I'm right or not, and I'd especially like to know if there are flaws in my reasoning. Thanks!