The Time Machine
Aclock does two things: it ticks and it counts the ticks. The clepsydra, or water clock, ticks to the steady drip of water, which, in more advanced devices, drives a set of gears that nudges a pointer along a series of numbers or hash marks, thereby indicating time’s passage.
The clepsydra was in use at least 3,000 years ago, and Roman senators used them to keep their colleagues from talking for too long. (According to Cicero, to “seek the clock” was to request the floor and to “give the clock” was to yield it.) For most of history, though, in most clocks, what ticked was Earth. As the planet rotates on its axis, the sun crosses the sky and casts a moving shadow; cast on a sundial, the shadow indicates where you are in the day.
The pendulum clock, invented in 1656 by Christiaan Huygens, relies on gravity to swing a weight back and forth, which drives a pair of hands around the face of the clock. A tick is simply an oscillation, a steady beat; Earth’s turning provided the rhythm.
In practice, what ticked was the day, the rotational interval from one sunrise to the next. Everything in between — the hours and minutes — was contrived, a man-made way to break up the day into manageable units for us. Now, our days are governed by seconds. They are the currency of modern life, the pennies of our time: ubiquitous and critical in a pinch (like when you just manage to make a train connection).…
From “Why Time Flies: A Mostly Scientific Investigation”