Robert and Brian Greene discuss what's beyond the horizon of our universe, what you might wear in infinite universes with finite pairs of designer shoes, and why the Universe and swiss cheese have more in common than you think.

 Have you wondered if there is another you out there? Somewhere? Sitting in the same chair, reading the same blog post, wearing the same clothes and thinking the same thoughts? Well, Brian Greene says there must be one. Or two. Or lots and lots and lots and lots and... Why? You ask, well listen to Greene's argument in this week's podcast.

We are still furiously working on Season 5, so while you wait we bring you today's podcast of a conversation between Robert Krulwich and Brian Greene, physics and mathematics professor and director of the Institute of Strings, Cosmology, and Astroparticle Physics at Columbia University. The interview is part of a series called 'Giants of Science' hosted by venerable New York institution, the 92nd St Y.

PLEASE NOTE: Our apologies, there's some noise at the end of the recording, please don't be alarmed! It's us, not you.

You can see a video of Brian talking about string theory here.