The Hollow Moon hypothesis says that moon is hollow, an old abandoned alien spacecraft. This was said based on few observations. (CC BY-SA4.0) license link: https://creativecommons.org/licenses/by-sa/4.0/ about image: Cutaway illustration of an alien base in a hollow Moon derivative work: Bromley86 File:Revolving space station (artwork).jpg: Mrazvan22 File:Geodesic1.jpg: DavidLevinson File:Full moon.jpeg, File:12- Foot Free-Flight Tunnel (5277460737).jpg: NASA File:OV1-8 PASCOMSAT_Gridsphere.jpg: U.S. Air Forc Michael Vasin and Alexander Scherbakov were the first to put out this theory. large moon craters which are assumed to be formed by meteor impact were found to be too shallow with a flat or convex bottom. They said that small meteors were making cup shaped hole in the rocky surface of the moon while large meteors are going though this Rocky layer but stop after hitting something hard like a metallic covering/armor. After the Apollo mission seismometers were ...