The Hollow Earth hypothesis

Hypothesis

A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

 proposes that the planet Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 is either entirely hollow or otherwise contains a substantial interior space. The hypothesis has been shown to be wrong by observational evidence

Scientific evidence

Scientific evidence has no universally accepted definition but generally refers to evidence which serves to either support or counter a scientific theory or hypothesis. Such evidence is generally expected to be empirical and properly documented in accordance with scientific method such as is...

, as well as by the modern understanding of planet formation; the scientific community

Scientific community

The scientific community consists of the total body of scientists, its relationships and interactions. It is normally divided into "sub-communities" each working on a particular field within science. Objectivity is expected to be achieved by the scientific method...

 has dismissed the notion since at least the late 18th century.

The concept of a hollow Earth still recurs in folklore

Folklore

Folklore consists of legends, music, oral history, proverbs, jokes, popular beliefs, fairy tales and customs that are the traditions of a culture, subculture, or group. It is also the set of practices through which those expressive genres are shared. The study of folklore is sometimes called...

 and as the premise for subterranean fiction

Subterranean fiction

Subterranean fiction is a subgenre of adventure fiction which focuses on underground settings, sometimes at the center of the Earth or otherwise deep below the surface...

, a subgenre of adventure fiction.