This week, we find out what lies beyond the limits of our Universe as we discuss multiverses, higher dimensions, string theory and supersymmetry. We find out how these ideas develop from basic principles and how the LHC can help to confirm, or refute, their existence. In the news, how quartz creates mountain ranges, progesterone excites sperm, and why birds can't help but fly into things. Plus, Meera and Dave find out how to engineer electrons to travel close to the speed of light, and Simon Singh explains how to discover the distance to a far away star.