When I was young, I stayed at my neighbor’s house. They had a grandfather clock. Between the tick and the tock of the pendulum, I lay awake thinking about the perverse nature of time. Mr. O’Donnell is gone now. His wife Barbara, now in her nineties, greets me with her cane when I go back to visit.

We watch our loved ones age and die, and we assume that an external entity called time is responsible for the crime. But experiments increasingly cast doubt on the existence of time as we know it. In fact, the reality of time has long been questioned by philosophers and physicists. When we speak of time, we’re usually referring to change. But change isn’t the same thing as time.

To measure anything’s position precisely is to ‘lock in’ on one static frame of its motion, as in a film. Conversely, as soon as you observe movement, you can’t isolate a frame, because motion is the summation of many frames. Sharpness in one parameter induces blurriness in the other. Consider a film of a flying arrow that stops on a single frame. The pause enables you to know the position of the arrow with great accuracy: it’s […]