How can they show us the passage of time? And how is it so exact?
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Clocks take advantage of one of two phenomena, depending on the type of clock.
1) Pendulums. The time it takes a pendulum to swing back and forth is a function of the length of the pendulum, and gravity. It doesn’t matter if the pendulum is making wide fast swings, or short slow swings, it still takes the same pendulum the same amount of time to swing back and forth. So in something like a grandfather clock, you design the pendulum so that its swing lasts one second, you use some machinery to make the pendulum swing fairly low friction (so that it will swing for a long time without needing to be reset,) and that’s your mechanism for keeping time.
2) Crystals. If you apply a small amount of electricity to a quartz crystal, it vibrates. And the vibration is at an extremely precise frequency. So any electric clock, be it in your watch or your phone or whatever, uses a tiny battery and a quartz crystal as its mechanism for keeping time.
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