The Gaia space telescope is not just create the ultimate star map of the Milky Way. It is also showing us our galaxy's past and how it will change in the future.

The Sky at Night team takes a look at the history of astrometry and meets the scientists now able to prove that change is the only constant in the universe.

Chris and Maggie dive into the archives to discover how the hunt for extra-terrestrial life in the universe has been reported by the BBC over six decades. Such luminaries as Patrick Moore, Arthur C. Clarke, Carl Sagan, James Burke and Alan Whicker discuss the eternal question of whether we are alone. The story of how the BBC has covered advancements in this scientific field is told from the birth of radio astronomy in the 1960s to the discovery of the first planets outside of our own solar system in the 1990s, and right up to probes exploring our neighbouring planets in the present day. There are also some rather more offbeat claims of UFO sightings, alien abductions and accounts of humanoid-like beings that supposedly live on Venus.