Earth contains a vast habitable hollow interior

Topic summary

Hollow Earth claims argue that Earth is empty inside or contains a vast inner world. The idea is historically interesting and common in adventure fiction, but modern seismology and geophysics support a layered internal structure.

Core counterpoints

• USGS describes Earth as having four major layers: crust, mantle, outer core, and inner core.
• P-wave and S-wave paths, especially S-waves failing to pass through the liquid outer core, strongly constrain Earth's interior.
• Mean density and gravity measurements favor internal mass distribution rather than a thin inhabited shell.

References

• Library of Congress, "Hollow Earth Theories: A List of References"
• U.S. Geological Survey, "The Science of Earthquakes"
• U.S. Geological Survey, "P-wave and S-wave paths through the earth"

Operations note

This is relatively safe because it is strongly fictionalized, but the scientific rebuttal can become technical. Simple explanations of seismic evidence are appropriate.