Sean Carroll is a physicist and author. He received his Ph.D. from Harvard in 1993, and is now on the faculty at the California Institute of Technology, where his research focuses on fundamental physics and cosmology. Carroll is the author of "From Eternity to Here: The Quest for the Ultimate Theory of Time," and "Spacetime and Geometry: An Introduction to General Relativity," as well as his latest book, "The Particle at the End of the Universe." He has written for Discover, Scientific American, New Scientist, and other publications. His blog Cosmic Variance is hosted by Discover magazine, and he has been featured on television shows such as The Colbert Report, National Geographic's Known Universe, and Through the Wormhole with Morgan Freeman.