Sean CarrollSean Carroll, Ph.D., is a theoretical physicist at the California Institute of Technology. After receiving his doctorate from Harvard University, he pursued his research at the Massachusetts Institute of Technology, the Institute for Theoretical Physcs in Santa Barbara, and the University of Chicago. He has published papers on dark matter and dark energy, the physics of extra dimensions, and alternative theories of gravity as well as the graduate-level textbook Spacetime and Geometry. Sean is one of the founders of the group blog cosmicvariance.com, named one of the five top science blogs by Nature. Read More Read Less