Yes, we're really going to homeschool

A conversation in the car today between Dillon and Dave:

Dillon: "How big is the earth?"
Dave: "Really big."
Dillon: "But how big?"
Dave: "Well, about 25,000 miles around."
Dillon: "Are we in the earth?"
Dave: "We're on the surface of the earth."
Dillon: What's in the middle of the earth?"
Dave: "Oreo stuffing."