Amidst renewed speculation over whether the US has evidence of UFOs, we replay a fascinating chat with Harvard astronomer Avi Loeb about his scientific search for extra-terrestrial life. Plus, we hear about modern history's most daring archaeologists and their biggest discoveries.

Guests:

Avi Loeb, Professor of Science at Harvard University and the Head of the Galileo Project.  

Michael Scott, Professor in Classics and Ancient History at the University of Warwick, broadcaster and author.