Has planet earth ever had a close encounter with aliens? In this Naked Science - Close Encounters documentary Eric Meyers looks into this possibility and attempts to answer how it could have been done given the immense distances they would have needed to travel to get here.
If unidentified flying objects did come from space, how could they have travelled to earth? And how could they survive in our atmosphere? We talk to leading physicists and astrophysicists about the viability of interstellar travel and whether worm holes and warp drives could make it possible. Or perhaps extra-terrestrials will send tiny self-replicating nanobots to explore our Earth?