Time facts for kids
To measure time, we can use anything that repeats itself regularly. One example is the start of a new day (as Earth rotates on its axis). Two more are the phases of the moon (as it orbits the Earth), and the seasons of the year (as the Earth orbits the Sun).
Even in ancient times, people developed calendars to keep track of the number of days in a year. They also developed sundials that used the moving shadows cast by the sun through the day to measure times smaller than a day. Today, highly accurate clocks can measure time in less than a billionth of a second. The study of time measurement is known as horology.
Units of time
- 1 millennium = 10 centuries = 100 decades = 200 lustrums = 250 quadrenniums = 333.33 trienniums = 500 bienniums = 1,000 years
- 1 century = 10 decades = 20 lustrums = 25 quadrenniums = 33.33 trienniums = 50 bienniums = 100 years
- 1 decade = 2 lustrums = 2.5 quadrenniums = 3.33 trienniums = 5 bienniums = 10 years
- 1 year = 12 months = 52 weeks = 365 days (366 days in leap years)
- 1 month = 4 weeks = 2 fortnights = 28 to 31 days
- 1 fortnight = 2 weeks = 14 days
- 1 week = 7 days
- 1 day = 24 hours
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- 1 second = SI base unit of time
- 1 millisecond = 1/1,000 second
- 1 microsecond = 1/1,000,000 second
- 1 nanosecond = 1/1,000,000,000 second
- 1 picosecond = 1/1,000,000,000,000 of a second
- 1 femtosecond = 1/1,000,000,000,000,000 of a second
- 1 attosecond = 1/1,000,000,000,000,000,000 of a second
- 1 Planck time = smallest measurable unit of time
Things used to measure time
Images for kids
Horizontal sundial in Taganrog
A contemporary quartz watch, 2007
Views of spacetime along the world line of a rapidly accelerating observer in a relativistic universe. The events ("dots") that pass the two diagonal lines in the bottom half of the image (the past light cone of the observer in the origin) are the events visible to the observer.
Philosopher and psychologist William James
Time Facts for Kids. Kiddle Encyclopedia.