What happened to childhood imagination?

Conversation on the way to school.. as heard from the front seat...

Josh: I can't wait to get home and keep digging that hole... I bet we'll dig all the way to China

Ryan: No, that won't happen, cuz we'd have to go through the mantle, the earth's inner core, the outer core, and it's just too HOT!

Josh: oh, too bad.

Can you guess who's studying the parts of the earth at school??