Do alien civilisations exist? When will ET phone home?
In the second part of our alien double bill, Hannah and Adam boldly go in search of intelligence. They may be some time.
What will aliens look like? Where should we look for them? And what are the chances of finding complex life in the cosmos?
Featuring astronomer Seth Shostak from the SETI Institute in California, exoplanet hunter Sara Rugheimer from the University of St Andrews and zoologist Matthew Cobb from Manchester University,
Presenters: Hannah Fry, Adam Rutherford Producer: Michelle Martin.