One of the oldest mysteries of theoretical thought is the question: What is time?
Immanuel Kant defined time and space as “pure intuitions.” We see time as inextricably related to matter and motion. Without matter and space [matter and motion], we have no way to measure the passing of time. Time, it seems, is always in motion. It can never be stopped.
Historically, we have measured the passing of time with various material objects: the sundial, which displays the movement of shadows across its face; the sand pouring through the hourglass; the hands moved by gears within a watch and the minute and hour hands moving around a circle of numbers. I think of staring at a large wall clock and watching the sweeping motion of the second hand. I look at twelve on the dial and wait for the second hand to pass it. My eyes glance below to the number six, and I know that the second hand has not reached it yet, but as the hand sweeps towards the bottom of the face, I get the sensation of time moving so swiftly toward the future at number six. Then, instantly, the second hand is past it, and what a moment ago was future now lies in the past. Sometimes when I experiment with such exercises, I want to call for the clock to stop. But it will not stop — it cannot stop. As the axiom declares, “Time marches on.”