Series exploring the cosmos. Adam Hart-Davis joins alien hunters at a huge new telescope in California dedicated to receiving the first message from intelligent beings. Janet Sumner investigates a new way to detect life on Mars, using a probe made with living material from Earth. And Adam asks: what if the aliens are listening to us? He finds out how far into the cosmos our ancient broadcasts have travelled.

How do you build a universe? Adam Hart-Davis is 100 metres underground with the team hoping to blast their way back to the Big Bang in the world\'s largest experiment. They are on the trail of tiny particles not seen since space and time began. There is also the story of Prof. Carlos Frenk who has spent decades attempting to make universes in his computer - but has only recently got the recipe right. And there is a team from Scotland who make stomach-churning anti-gravity flights in an attempt to find out how the planets were formed.

Space is a dangerous place, as Adam Hart-Davis discovers when he joins the team in Leicester hunting for the biggest bangs since the Big Bang. He finds that these vast explosions were discovered accidentally by spy satellites. The centre of our own galaxy is revealed as the site of a super-massive black hole 3000 times more massive than the sun which is gobbling up material from all around. Maggie Aderin investigates the asteroid threatening the Earth in thirty years time, and tries out the methods that might be used to save us.

Is there another Earth? Adam Hart-Davis is on the summit of La Palma in the Canary Islands, searching for planets around other suns. He discovers how it is possible to find planets too small to see, and tells the story of how the first ever planet outside our solar system was found - an event that rocked the world of astronomy. Janet Sumner visits the Virtual Planetary Laboratory, where they invent inhabited planets so that astronomers know what to look for.