Still curious? Read more: Keeping track of time
What's the time Mr Wolf?
Time is so important to our lives, and there are many ways to measure it.
The caesium atom
The most precise way to measure time is using an atomic clock—the clocks that the internet and satellites depend on to work properly.
An atomic second is calculated by exciting the outermost electron in a caesium atom, then measuring the oscillations of the energy it emits as it goes back to its normal state. One atomic second = 9 192 631 770 (!) oscillations.
Lunar calendars are calculated by observing changes in the appearance of the moon—the period between full moons was the basis for many early calendars. To this day, lunar calendars are still used by different cultures around the world.
Many Indigenous communities measure time by observing changes in plant or animal behaviour. Often these changes help predict food availability or weather patterns.