Hot on the heels of the Flat Earth theory comes the Hollow Earth belief, which is gaining followers.
They believe that rather than being magma filled, as it is, it has a huge empty space.
Believer Rodney Cluff has written of the theory in his book – Top Secret: Our Earth Is Hollow.
He jibed at believers of the Flat Earth theory, accusing them of being “so wrong”.
He said: “I don’t know how the Flat-Earthers can be so confused.”
Mr Cluff claims the shell of the Earth is only 800 miles thick, and that there is an interior sun at the centre of the planet.
He said a “superior” race of alien humans, who see themselves as the “guardians of the planet”, live at the centre of the Earth.
Mr Cluff said: “They regularly spy on us using spacecrafts and flying saucers.
“The majority of UFOs actually come from inside our planet.”
Most Hollow Earthers believe there are three entrances to the inner Earth: two near the poles and one in the Himalayas.
The theory has its origins in Ancient Greek, Buddhist and Christian beliefs.
And the theory gathered pace during the 1700s.
In the 18th century the astronomer Edmond Halley said unusual compass readings could be explained by the fact that the planet was a hollow shell.
North Pole explorer Olaf Jansen claimed he sailed through an entrance to the centre of the Earth in 1811.
He told author Willis George Emerson that they lived in a beautiful “city of Eden” for two years with a race of “super humans who were over 12ft tall.
As the theory has grown, so have the bizarre claims about who is hiding down there.
Other than aliens, there have been suggestions that Nazi survivors made it to the Antarctic, where they met with a hidden group of aliens, and worked together on UFO technology.
The Hollow Earth theory claims it was from there that they made it into the centre of the Earth.
Others have said Viking colonies from Greenland ended up down there.
Some Hollow Earthers believe a real-life ‘Garden of Eden’ exists at the planet’s core.
Last year conspiracy theorists said a photo of Earth proved NASA is hiding a huge hole leading directly to the centre of the planet.
There is also a separate theory that claims the Moon is hollow, and even a huge artificial alien space station.
There is, of course, no real evidence to support the existance of any base for aliens or Nazis at the centre of the Earth or the Antarctic.