The Secret Life of Time

For more than two thousand years, the world’s great minds have argued about the essence of time. Is it finite or infinite? Does it flow like a river or is it granular, proceeding in small bits, like sand trickling through an hourglass? And what is the present? Is now an indivisible instant, a line of vapor between the past and the future? Or is it an instant that can be measured—and, if so, how long is it? And what lies between the instants? “The instant, this strange nature, is something inserted between motion and rest, and it is in no time at all,” Plato remarked in the fourth century B.C.E. “But into it and from it what is moved changes to being at rest, and what is at rest to being moved.”