Book 5, Question 133
Swing and Sand! Why Do Some Clocks Use Swings or Sand?
Some clocks count with something that repeats steadily. A pendulum swings back and forth at a steady pace, and sand in an hourglass runs at a steady pace too. People used many ideas like these to measure time before modern clocks.
From the book
Page from A Million Whys Book 5
More fun facts
- In a grandfather clock, the pendulum swings back and forth at the same rate, and the gears count the swings.
- Each time the pendulum reaches the middle of its swing, the clock ticks and the second hand moves forward.
- A pendulum clock has an escapement, a toothed wheel that moves forward one tooth each time the pendulum finishes a swing.
- If a pendulum's swing were even slightly off, a grandfather clock could end up wrong by a second every ten seconds.
- Once a pendulum is pushed, it takes the same amount of time to swing back to where it started.
Questions kids ask
What is an escapement?
It is a toothed wheel in a pendulum clock that moves one tooth with each swing.