In the pre-industrial age, people only needed to measure years and months to a fair amount of accuracy. The position of the sun in the sky was good enough to break up the day. Timing at the level of fractions of a second was simply not needed.

Eventually, modern industry arose. Fast-moving machines came to dominate human activity, and clocks required hands that could measure seconds. In the current era of digital technology, the timing of electronic circuitry means that millionths or billionths of a second actually matter. None of the high-tech stuff we need, from our phones to our cars, can be controlled or manipulated if we cannot keep close track of it. To make technology work, we need clocks that are faster than the timing of the machines we need to control. For today’s technology, that means we must be able to measure seconds, milliseconds, or even nanoseconds with astonishing accuracy.

Every timekeeping device works via a version of a pendulum. Something must swing back and forth to beat out a basic unit of time. Mechanical clocks used gears and springs. But metal changes shape as it heats or cools, and friction wears down mechanical parts. All of this limits the accuracy of these timekeeping machines. As the speed of human culture climbed higher, it demanded a kind of hyper-fast pendulum that would never wear down.