How does a clock tell time?

A clock always knows how late it is. It never gets tired and never forgets. But a clock cannot really “see” time. So how does it count the hours so well?

A clock counts steady beats

The secret is that a clock has a part that beats at a perfectly steady rhythm — like a tiny, never-stopping drum.

In an old clock, this part is a swinging weight called a pendulum. It swings back and forth, tick-tock, always taking the same amount of time for each swing. In a modern watch, a tiny crystal buzzes super fast inside, thousands of times every second, always at the same speed.

Gears turn beats into hands

Counting beats is not enough — we need to see the time. That job goes to little toothed wheels called gears.

The gears take all those fast beats and turn them, step by step, into slow movement for the hands. They are set up so cleverly that one hand creeps around once an hour, and another sweeps around once a minute.

Each gear turns the next, slower and slower, until the hands move at exactly the right speed.

Always the same speed

Because the beats never change, the hands never rush or drag. That is why a good clock is right today, tomorrow, and next year.

Wonder fact: The most accurate clocks of all are atomic clocks. They would lose less than one second in millions of years!