We use time to order events in the past, present and future. We also use it to make comparisons and measure the speed at which things move.
If you wanted to measure time you could use a watch, clock, hourglass or even a sundial.
A sundial is a tool that uses the position of the Sun to measure time, typically involving a shadow cast across a marked surface.
The use of pendulums to accurately measure time was discovered by Galileo Galilei around 400 years ago. A pendulum is a free swinging weight hanging from a pivot.
There are 60 seconds in a minute, 60 minutes in an hour and 24 hours in a day.
Normal years have 365 days but a Leap year has 366. The Earth takes a little longer than 365 days to go around the Sun so we add an extra day in February every four years (with a few exceptions) to keep calendars and seasons aligned.
10 years is known as a decade, 100 years is known as a century and 1000 years is known as a millennium.
Milliseconds, microseconds and nanoseconds are examples of very small units of time.
Planck time is the name given to the smallest known unit of time. It’s a little confusing but it measures the amount of time it takes light to travel 1 Planck length (a distance so small that it can’t even be measured!).
Scientists believe the moon was used as a form of calendar as far back as 6000 years ago. Calendars have been changing ever since and are very accurate in modern times.
Accurate clocks that measure hours, minutes and seconds have improved with the invention of sundials, water clocks, mechanical clocks, pendulums and hourglasses through to the digital displays and atomic clocks of today.
Many places use daylight saving time (typically by putting clocks forward an hour) for longer daylight in the evenings.
Different parts of the world are located in different time zones. This means that while you are having breakfast in the morning, someone in another part of the world is having dinner.
Theories related to time have been put forward by famous scientists such as Isaac Newton and Albert Einstein. You may have even heard of the term ‘spacetime’, a model in physics that joins space and time together.
In terms of philosophy, time is difficult to define. Scientists and philosophers have disagreed on our understanding of time for many years. Some argue it is a ‘real’ part of the Universe while others argue it is just the way humans think, comparing events and putting them in sequence. It’s a little confusing but fun to think about, what do you think?
Some more questions to get your brain buzzing: Does time have a direction? Did it begin with the Big Bang? Is time travel possible?