Around the world, sightings of strange flying objects and mysterious lights in the sky have been reported. Could these UFOs be signs of intelligent life outside our planet, or are they just natural or man-made phenomena?

Different cultures call it different things: Bigfoot, Sasquatch, Abominable Snowman and Yeti, but they're all talking about the same phenomenon and the descriptions are similar: large, hair-covered creatures that walk upright like humans.