How does a clock keep time?
The Counting Game
How does a clock keep time?
You glance at a clock and it tells you: 3:47. Four minutes later, it says 3:51. How does it know? How does a little machine sitting on your wall keep perfect track of something invisible — time itself?
Here's the secret: a clock doesn't actually "know" what time it is. It just counts. It counts something that happens over and over, at exactly the same speed, and uses that rhythm to measure time. Your heartbeat does about 70 beats per minute. A clock needs something way more reliable than that.
