Alan Lightman, American physicist

 

In this world, time has three dimensions, like space. Just as an object may move in three perpendicular directions, corresponding to horizontal, vertical, and longitudinal, so an object may participate in three perpendicular futures. 

Each future moves in a different direction of time. Each future is real. 

At every point of decision, the world splits into three worlds, each with the same people, but different fates for those people. In time, there are an infinity of worlds.