Once upon a time, in the days of sundials and pendulum clocks, people needed a way to agree on the time. For instance, if my watch says 11:13 and your watch says 1:32, who’s right?
One way to coordinate time in a city or a sea port was a time ball placed somewhere highly visible. People could use the ball to set their pocket watches, and use their pocket watches to set their other clocks.
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