Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.Extraterrestrial hypothesis, Unidentified flying object, Extraterrestrial life, Extrasolar planet, Spacecraft, The Day the Earth Stood Still (1951 film), The War of the Worlds (1953 film), Earth vs. the Flying Saucers, Forbidden Planet, American Astronomical Society, American Institute of Aeronautics and Astronautics, American Association for the Advancement of Science, UFO conspiracy theory, Flying saucer, Project Blue Book