The world of science has two Sean Carrolls. One is an evolutionary biologist. The other is a cosmologist and theoretical physicist, an expert on time and the early moments of the universe. As it happened, the physicist stopped by the offices of The New York Times on a recent March morning. Dr. Carroll, a 43-year-old research professor at the California Institute of Technology, had come to New York for an appearance on "The Colbert Report." He was in town promoting his meditation on the physics of time, a trade book with the clever title "From Eternity to Here."