Q. Is the Earth hollow?
A. According to science, no. According to pseudo-science, maybe. According to religion, you bet.
Q. What does science say?
A. The Earth is a spheroid of molten lava. The oceans and the continents float on top like Magic Shell.
Q. What is Magic Shell?
A. A kind of chocolate that is designed to automatically freeze when it hits ice cream.
Q. So the Earth is made of ice cream?
A. No. That was a simile.
Q. What's a simile?
A. Like a metaphor, only with the word "like" in there.
Q. Was that a simile?
Q. What does pseudo-science say about the Hollow Earth?
A. Depends on the flavor of pseudo-science. Blavatsky-style spiritism held that the center of the Earth was a series of tunnels and tubes, connecting the Secret Ascended Masters to the world above. According to Victorian era lunatic scientists, the poles are hollow and it is possible to sail to the inside of the Earth, where a teeny weeny little sun warms the eerie beings who live there.
Q. What about the Nazis? I'm sure they had a theory.
A. We are not allowed to discuss the Antarctic Inner-Earth Nazis, lest the Moon Nazis find out about it and kidnap us to their concentration camp in the Sea of Tranquility.
Q. What does religion say about the Hollow Earth?
A. Underneath our tender, flaky crust, Hell exists, as well as Purgatory (if you're Catholic) and a now empty Abram's Bosom (if you're not). Catholic Limbo is also there, but Catholic Limbo is also synonymous with Abram's Bosom under very specific circumstances, too complicated and ridiculous to cover here.
Q. What is Abram's Bosom?
A. Abram's Bosom is a temporary holding space for the pre-Christian virtuous. Jesus went and cleared it out in the three days he was dead. It now lies completely empty, but within sight of people in Hell, just to really rub it in.
Q. That's killer but also very silly. Who was there?
A. All the awesome dudes. Abraham, David, Solomon, Aristotle, Buddha and anybody that could open the Ark of the Covenant without the Wrath of God hitting them. This is very ironic because neither Buddha and Aristotle believed in literal afterlives. To be fair, this list is far from complete and was compiled in the Middle Ages by apologists, so take it, as well as everything else involved in this subject, as bullshit.
Q. What is Limbo?
A. Limbo is a place for virtuous pre-Christians, unbaptized infants and dudes who have cleared out their time in Purgatory but still aren't allowed into Heaven due to some minor quibbling point of dogma, like the Antipopes or people who died having met Christ before Christ was crucified. It is also where ghosts come from, apparently.
Q. What is The Limbo?
A. An engaging Latin dance phenomenon.