String theory was originally proposed as a relatively modest attempt to explain some features of strongly-interacting particles, but before too long developed into an ambitious attempt to unite all the forces of nature into a single theory. The great thing about physics is that your theories don't always go where you want them to, and string theory has had some twists and turns along the way. One major challenge facing the theory is the fact that there are many different ways to connect the deep principles of the theory to the specifics of a four-dimensional world; all of these may actually exist out there in the world, in the form of a cosmological multiverse. Brian Greene is an accomplished string theorist as well as one of the world's most successful popularizers and advocates for science. We talk about string theory, its cosmological puzzles and promises, and what the future might hold. (For more general string theory background, check out Episode 18 with Clifford Johnson.) Support Mindscape on Patreon or Paypal. Brian Greene received his doctorate from Oxford University, and is currently a professor of Physics and Mathematics at Columbia University. His research includes foundational work on topology change, mirror symmetry, and the compactification of extra dimensions. He is the author of several best-selling books, including The Elegant Universe and The Fabric of the Cosmos, both of which were made into TV specials for NOVA. He and Tracy Day are co-founders of the World Science Festival. Web site Publications from InSpire Wikipedia page Amazon author page Twitter TV Documentaries TED talk on string theory World Science Festival