A Big Bang of Physics

If you are not completely confused by quantum mechanics, you do not understand it.” That vote of non-­confidence comes to us from John Wheeler, one of the great minds of twentieth-­century physics, who died in 2008. The Toronto-based physicist Lee Smolin had many conversations with Wheeler over the years. He remembers Wheeler as a towering intellect, but also someone who spoke “in riddles and paradoxes.” Wheeler once asked Smolin what he would say if he were to find himself at the Pearly Gates and Saint Peter asked, “Why the quantum?” Why, in other words, do we live in a universe described by quantum mechanics — and what does it say about the nature of reality? “Much of my life,” Smolin writes in his new book, “has been spent searching for a satisfying answer to that question.”

Quantum mechanics, born in the early decades of the last century, has left the greatest thinkers scratching their heads. Wheeler was just one of many who found the theory discombobulating...