# Clocks

From shadows on a sundial to water clocks, pendulums and quartz, clocks are anything that repeats steadily. Since 1967 the second has been defined by the vibration of caesium atoms, which makes the best clocks agree to within a second over many millions of years.

Connects to:
- [Time](https://mapideas.org/i/time)
- [Day, month, year](https://mapideas.org/i/ti_daymonthyear)
- [Time and motion](https://mapideas.org/i/ti_relativity)
- [What is a moment?](https://mapideas.org/i/q_time_moment)
- [How accurate can a clock be?](https://mapideas.org/i/q_time_clock)
- [How sure can a date be?](https://mapideas.org/i/q_hist_date)

Sources:
- [Wikipedia: Atomic clock](https://en.wikipedia.org/wiki/Atomic_clock)
- [Wikipedia: History of timekeeping devices](https://en.wikipedia.org/wiki/History_of_timekeeping_devices)

Source: https://mapideas.org/i/ti_clocks · open on the map: https://mapideas.org/#ti_clocks