Brian Cox explains how black holes are formed, Liz Bonnin is at SALT in South Africa, Mark Thompson takes four budding astronomers from the light polluted skies of London to a dark spot, Dara Ó Briain explains the live switch off, UFO's are explained and the team from the University run an animation to show the beginning of the Universe.
Dara and Brian's journey through the night sky continues with a look at black holes, the most mysterious and destructive objects in the whole universe. Liz Bonnin finds out how our galaxy the Milky Way was formed and Mark Thompson investigates the problems that are caused by light pollution.