The Hollow Earth hypothesis says that the planet Earth is either wholly hollow or otherwise contains a substantial interior space. The hypothesis has long been contradicted by overwhelming observational evidence, as well as by the modern understanding of planet formation. The scientific community has dismissed the notion since at least the late 18th century.
The concept of a hollow Earth still recurs in folklore and as the premise for subterranean fiction, a subgenre of adventure fiction. It is also featured in some present-day pseudoscientific and conspiracy theories.
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