Who are hollow Earthers? These conspiracy theorists think aliens and Nazis live inside Earth's core

Is the Earth flat, spherical or hollow? There are varying theories on the plant's shape and size presented by different scientists over the years, who have even backed up their opinions with logical and scientific evidence, but the debate continues.

According to a small group of theorists termed as hollow Earthers, our planet is hollow — somewhat like a donut, with the core inhabited by aliens, Nazis and Vikings. Rodney Cluff, a self-proclaimed "scientist" and a hollow-Earth theorist himself, has recently penned a book detailing the doughnut-shaped "hollow Earth" and its hidden residents.

Hollow Earthers also believe that other celestial bodies such as the Moon, Sun, stars, others planets are all hollow bodies.

Hollow Earthers like Cluff reportedly believe that our planet has secret routes from the poles and Himalayas that lead straight to the inner world, which resembles the "Garden of Eden" and has its own sun.

"Suspended in the centre of that hollow is an interior sun that is divided by day and night sides," Cluff told The Sun. His theory even suggests that the inner central core of the so-called "hollow Earth" is inhabited by a "superior" human race, a population that considers itself "guardian of the planet" and flies out occasionally on UFOs to spy on us and keep us from starting a nuclear war. "The majority of UFOs actually come from inside our planet," he pointed out.

Cluff, with complete faith on his theory, had even launched a £15,000 ($20,000) expedition to the North pole to look for the massive hole that would lead him to the Earth's core. However, the trip never happened.

Some of the believers who claimed to have visited the world within the Earth said that people living there never fall sick and are 12ft tall. Others think that the inner place is a secret haven to aliens, Vikings, and Nazis from World War II.

"The city of 'Eden' is located in what seems to be a beautiful valley, yet, in fact, it is on the loftiest mountain plateau of the Inner Continent," a Norwegian sailor, Olaf Jansen, had reportedly said decades ago, claiming that he sailed with his father to the core through an entrance at the North Pole in 1811.

Dianne Robbins, another hollow Earth theorist, believes that the creatures living at the centre are immortal. "They are physical humans like we are, but they live in peace, isolation and seclusion, and through this they have gained their immortality."

Cluff claimed that the pseudoscientific theory has already gained popularity and the number of hollow Earthers has been increasing progressively. "More and more people are coming to terms with the fact that the Earth is hollow. I get emails from people learning about it every day," Cluff told the paper. "It's definitely growing in popularity - certainly not in the millions but maybe in the thousands."

Scientists, on the other hand, have rubbished this theory with substantial evidence that proves Earth is not only round but also has four layers — hot inner core, outer core, mantle and finally the crust on the outside.