How does a clock measure something we can't see?
The Counting Trick
How does a clock measure something we can't see?
You've never seen time, touched it, or caught it in a jar. Yet right now, a clock on the wall is measuring it — tick, tick, tick — as surely as a ruler measures your height. How does it pull off this trick?
Here's the secret: clocks don't actually measure time itself. They measure change. Time is just our name for the fact that things happen, one after another — your heart beats, the sun moves across the sky, water drips from a faucet. A clock's job is to count a change that happens over and over, as regularly as possible.
