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?

Morgan Freeman produces hosts and narrates this exploration of the greatest mysteries of the universe. The four forces governing our universe are phenomenally finely tuned, so finely that it had led many to the conclusion that someone, or something, must have calibrated them: an alien gameseter who's created our world as the ultimate SIM game for his own amusement.

Sagan discusses the story of the Heike crab and artificial selection of crabs resembling samurai warriors, as an opening into a larger discussion of evolution through natural selection (and the pitfalls of intelligent design). Among the topics are the development of life on the Cosmic Calendar and the Cambrian explosion; the function of DNA in growth; genetic replication, repairs, and mutation; the common biochemistry of terrestrial organisms; the creation of the molecules of life in the Miller-Urey experiment; and speculation on alien life (such as life in Jupiter's clouds). In the Cosmos Update ten years later, Sagan remarks on RNA also controlling chemical reactions and reproducing itself and the different roles of comets (potentially carrying organic molecules or causing the Cretaceous–Paleogene extinction event).

Chris Lintott and Maggie Aderin-Pocock report on the reaction to the dramatic announcement of the discovery of phosphine gas in the clouds of Venus, a gas that could be a sign of life. Venus remains an inhospitable and unlikely host. But if not Venus, where in the solar system is the best place to look for alien life? Chris and Maggie investigate the latest missions to Mars and the icy moons of Jupiter and Saturn. Away from the search for life, Pete Lawrencepreviews the best meteor showers of the year.

When a mysterious cigar-shaped object is spotted tumbling through our solar system, experts race to uncover it's true nature. The object, nicknamed Oumuamua, meaning 'a messenger that reaches out from the distant past' in Hawaiian, was discovered by the Pan-STARRS 1 telescope in Hawaii. Since its discovery, scientists have been at odds to explain its unusual features and precise origins, with researchers first calling it a comet and then an asteroid before finally deeming it the first of its kind: a new class of 'interstellar objects.'
A recent paper by researchers at the Harvard Smithsonian Center for Astrophysics raises the possibility that the elongated dark-red object, which is 10 times as long as it is wide and travelling at speeds of 196,000 mph, might have an 'artificial origin.' The theory is based on the object's 'excess acceleration,' or its unexpected boost in speed as it travelled through and ultimately out of our solar system.

We are living in a new golden age of exploration. Planet hunters are searching far beyond our solar system and they are actually finding new worlds orbiting other suns. Thousands of these alien worlds have already been found, but this is the story of perhaps the greatest discovery yet, a star 40 light-years away with seven Earth-sized planets: Trappist-1.
This new discovery of seven alien Earth-like planets in a faraway solar system is a major milestone in our hunt for extraterrestrial life, and experts investigate the secrets of Trappist -1's mysterious worlds to reveal if we're truly alone in the universe.