“An American physicist, David Bohm, devised a radical alternative at midcentury, visualizing “pilot waves” that guide every particle, an attempt to eliminate the wave-particle duality. For a long time, he was mainly lambasted or ignored, but variants of the Bohmian interpretation have supporters today. Other interpretations rely on “hidden variables” to account for quantities presumed to exist behind the curtain. Perhaps the most popular lately — certainly the most talked about — is the “many-worlds interpretation”: Every quantum event is a fork in the road, and one way to escape the difficulties is to imagine, mathematically speaking, that each fork creates a new universe.”