The Sentinel (short story)

"The Sentinel" by Arthur C. Clarke is a short story about a human astronaut who discovers an ancient, abandoned alien outpost on the Moon. The structure serves as a warning and a sign of earlier extraterrestrial visitors who once visited Earth. The story explores themes of discovery, the possibility of intelligent life beyond Earth, and the implications of contact. Clarke's story is a thoughtful reflection on the search for alien life and how such contact might be understood or interpreted by humans. It served as the basis for his later novel "2001: A Space Odyssey."