Why Atomic Clocks Win

The story

Quarky's wristwatch keeps drifting, and he misses the big rocket launch by a whole minute. So he goes looking for the most patient timekeeper in the universe. Inside an atomic clock, tiny cesium atoms hum at exactly the same beat, over and over, forever. Quarky counts along with them: 9,192,631,770 hums make one second, every single time. Springs stretch and pendulums swing differently when it is hot or cold, but atoms never change their tune. That is why atomic clocks run the internet, guide rockets and keep every phone map pointing the right way.