Plato has Socrates describe a group of people who have lived chained to the wall of a cave all of their lives, facing a blank wall. The people watch shadows projected on the wall from objects passing in front of a fire behind them, and give names to these shadows.
In mid-1947, a United States Army Air Forces balloon crashed at a ranch near Roswell, New Mexico. Following wide initial interest in the crashed “flying disc”, the US military stated that it was merely a conventional weather balloon. Interest subsequently waned until the late 1970s, when ufologists began promoting a variety of increasingly elaborate conspiracy theories, claiming that one or more alien spacecraft had crash-landed and that the extraterrestrial occupants had been recovered by the military, which then engaged in a cover-up.
In the 1990s, the US military published two reports disclosing the true nature of the crashed object: a nuclear test surveillance balloon from Project Mogul.
