How We Know What’s Deep Inside the Earth, Despite Never Traveling There.
I have read Tanar of Pellucidar and Journey to the Center of the Earth, so I know what’s there.
Dinosaurs. And primitive men. Maybe some lizard men and/or ape men.
These books are at the very least as reliable as what you read on the Internet about anything in 2020.
(Link via Neatorama.)