Scientists seeking the secrets of the universe would like to make a model that shows how all of nature’s forces and particles fit together. It would be nice to do it with Legos. But perhaps a better ...

String theory has so far failed to live up to its promise as a way to unite gravity and quantum mechanics. At the same time, it has blossomed into one of the most useful sets of tools in science.

In 1980, Stephen Hawking gave his first lecture as Lucasian Professor at the University of Cambridge. The lecture was called "Is the end in sight for theoretical physics?" Forty-five years later, ...