Using the moon solely, one can get a good accuracy of time evolution. Hours can be measured using a "moonlight dial", days can be estimated through moon phases, as well as months thanks to the inclination of the lunar orbit relative to Earth's equatorial plane.

Of course the observation of celestial bodies is still very useful, but considering a solar system as a clock dial would be more complicated than accurate. From one extreme to another, the physical properties of nature also allow for incredibly precise time measurement.

Going from the moon clock to the atomic clock was truly a revolution.

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DrNo

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Sunday, October 15 2017