Clocks have been used for millennia to keep and measure time. Ancient civilizations used sundials and water clocks; since then, there have been candle clocks, incense clocks, hourglasses, mechanical clocks, electric clocks, and atomic clocks. The advent of the wristwatch in the 19th century enabled people to check the time whenever they pleased; today, many of us prefer the convenience of the iPhone.

But the noble clock is more than just a timekeeping device. It also helps to explain our history.