I know only two of them but in my research thier descover
The earth hallow 800miles from main earth shell and the main sun inside of earth hallow is our inner core and the only way to get in is south and northpoll
Edmond Halley in 1692 conjectured that the Earth might consist of a hollow shell about 800 km (500 mi) thick, two inner concentric shells and an innermost core
