Watch NOVA Season 5 Episode 7 Online

NOVA investigates the theories of von Daniken and others that the Earth has been visited by intelligent beings from outer space. Among claims examined are: that the building techniques used in the Great Pyramid of Cheops are so advanced that only an extraterrestrial intelligence could have built it; and that the engraved stones of Palenque in Mexico depict an ancient astronaut at the controls of a space rocket.