The boys and I were driving home from school talking about lava.
This is not as strange as it seems. According to a recent AskMe thread over at Metafilter, one of my very favorite sites, almost every child has a version of the Lava Game. You know that game, right? Sure you do.
In the Lava Game, you're stuck on a chair, or a bed, and the FLOOR IS MADE OF LAVA, OH NOES!!
And the Owl, whose mind travels along circuitous paths it is best not to attempt to follow, pipes up with, "You know, you really SHOULD be able to dig a hole to China. Wouldn't that be cool?"
So, naturally, the Rhino wants to know why you couldn't. "I get that it would take a long time," he conceded, "but if you had a lot of shovels and friends to help you..couldn't you just dig around the middle?"
So I explained that, in addition to being incredibly hard, and the overwhelming pressure there, the earth's core is surrounded by layers of molten lava (Aha! So that's where the Owl was coming from!).
Which led to us deciding that, in the end? The world is like a tootsie-roll pop, only inside out.
It's soft on the outside, very hard in the middle, and no one knows how long it takes to get to the center!