STEPHEN HAWKING held the position of Lucasian Professor of Mathematics at the University of Cambridge for thirty years; his other books for the general reader include the essay collection Black Holes and Baby Universes and The Universe in a Nutshell. Physicist LEONARD MLODINOW, his collaborator for this new edition, has taught at Cal Tech, written for Star Trek: The Next Generation, and is the author of Euclid's Window and Feynman's Rainbow and the co-author of the children's book series The Kids of Einstein Elementary.