When Jules Verne published Journey to the Center of the Earth in 1864, multiple unsubstantiated hollow Earth theories were alive and well, speculating about what might exist deep beneath our feet.
That’s because, by many measures, we know less about Earth’s interior than we know about outer space. Still, we can confidently say it is dense and made up of multiple compact layers that humans have failed to reach, despite multiple attempts.
Various operations have set out to drill the deepest hole on Earth. Even after penetrating through many miles of our planet’s outer crust, none of them have reached the mantle or the other layers buried beneath it.
But they’ve dug up some valuable samples and findings.
