Area 51 is a top secret military base in Nevada that has long been the subject of conspiracy theories about testing of captured alien spacecraft and studying extraterrestrials. In reality, it was established in 1955 as a site for testing secret military aircraft like the U-2 spy plane. While its secret activities have fueled speculation, the base is simply used for classified defense research and development projects, not studying aliens, though the government keeps most of its activities hidden from the public.