In this exclusive Kindle Singles Interview, celebrated physicist and author Brian Greene (The Elegant Universe, The Fabric of the Cosmos) discusses the origins of string theory, Einstein's cosmological misstep, how to picture the nothingness of empty space, the triumph of the Higgs boson, and how a baseball hanging from the ceiling by a piece of chewing gum became a pivotal moment in his scientific career. Greene, who recently launched World Science U, which offers free online science courses, explains what it is that's so "elegant" about string theory while lamenting the possible limits of what dogs (and by implication humans) can ever hope to understand about the universe. The interview was conducted by Rivka Galchen, an acclaimed fiction writer and journalist, named by The New Yorker as one of 20 Writers Under 40. Cover design by Adil Dara Kim.