For decades some have suspected that there might be others out there, intelligent beings capable of communicating with us, even visiting our world. It might sound like science fiction, but today scientists from across the globe are scouring the universe for signals from extraterrestrials. Horizon obtained exclusive access to film researchers at the Green Bank Telescope searching for radio signals from Tabby's Star, a star so mysterious that some scientists believe it might be surrounded by a Dyson Sphere, a vast energy collector built by advanced aliens.

Discoveries of new planets have revealed countless worlds much stranger than Earth. Some of these strange worlds don’t have stars; others are made out of diamonds. Will we ever find a planet like Earth, or are these distant worlds stranger than fiction?

Mark Oliver Everett, singer of the band EELS, on his quest to get to know his later father, quantum physicist Hugh Everett III, who invented the Many Worlds theory. The film follows Mark on his journey across America, where he meets old friends and colleagues of his father. Hugh died of a heart attack in his home in 1982, where his body was found by 19-year-old Mark. Even though they had lived in the same house, the two of them were alienated. Only by entering the paradoxical world of quantum mechanics can Mark hope to understand why he was such a stranger to his own father.

Many argue that flying saucers and other extra-terrestrial space ships continuously visit the earth. If that were true, what kinds of technologies would such alien spacecraft require? And do eyewitness reports of UFO sightings jibe with modern theories of how interstellar travel might be possible? Authors, astronomers and theoretical physicists weigh in with the blueprints for inertia-canceling devices, nuclear-powered craft, antimatter propulsion systems and even warp drives. Based on Einstein's theories and countless scientific studies, we'll find out how these visitors might bridge the vast distances between the stars. And if they could survive such hazardous journeys, are they flesh and blood or intelligent machines?

Ancient Aliens explores the controversial theory that extraterrestrials have visited Earth for millions of years. From the age of the dinosaurs to ancient Egypt, from early cave drawings to continued mass sightings. In this episode researchers discuss the possibility that the great technological developments made by inventor Nikola Tesla were inspired by extraterrestrials

20 years ago, two astronomers made a remarkable discovery, one which would change the way we view the universe for ever. A planet outside our solar system, orbiting a distant star - an exoplanet. Since then, we have found worlds where it rains diamonds, ones that boil at 3,000 degrees centigrade and even a world with four suns in its sky. But the big question is - will we ever find another Earth? As we close in on the discovery of the 2,000th planet outside our solar system, or exoplanet, we investigates the techniques that are revealing so much about these alien worlds. The documentary asks if we are really any closer to finding another world like our own - a second Earth.