Time is one of the least understood aspects of our universe. We know it exists yet we have trouble grasping exactly what it is. Time can be viewed in two ways, it is a manmade concept used as a tool to describe to explain the sequence of events, comparing the durations and intervals between them.

Time is one of the fundamental quantities which also includes distance, velocity, mass, momentum, energy, and weight and thanks to the work of Einstein and others we know time also makes up the very fabric of our Universe.

Here are ten facts you may or may not have known about time.

10. Time is not a constant; time is relative to different observers. The only constant in the Universe is the speed of light which means no matter how fast you are travelling the speed of light will remain the same although time will slow down.

9. Time can be described as a dimension and along with the other three dimensions we are aware of (up/down, left/right and forward/backward) forms a four dimensional ‘space-time’.

8. Time always moves forward yet many theoretical physicists believe that backwards time travel could be possible.

7. Gravity can warp space-time making time slow down the stronger the gravitational force. Experiments with atomic clocks show the higher above sea level they are (and therefore under less gravitational influence) the faster they run (although the difference is very small).

6. As the speed of light is the only constant in the Universe no matter how fast you travel, light will always seem to be the same speed, this is because time will slow down. A journey at close to the speed of light may seem like a few seconds for a traveler but to an observer it would have taken thousands of years.

5. Time has not always existed. Time started with the big bang and will end if the Universe does.

4. Time can be perceived differently by our brains depending on our activities. A boring day will ‘drag’ on whilst if we are enjoying ourselves time will seem to ‘fly’, this phenomenon is referred to as ‘temporal illusion’ by psychologists.

3. Time appears to accelerate the older we get. Some (including Stephen Hawking) suggest the reason for this is that when we are ten years old a year is a tenth of our whole life and seems a long time, yet for a sixty-year-old a year is just a 60th of their life and therefore perceived as a shorter period.

2. Some modern atomic clocks are so accurate they can lose less than a second in 400 million years.

1. A universal time scale has been developed called UTC (Coordinated Universal Time) which is based on the time told by atomic clocks but compensates for the minute slowing of the Earth’s rotation (caused by the gravity of the Moon) by adding Leap Seconds every year to prevent day from creeping into night (albeit in a millennia or two).

Thanks to atomic clocks and UTC time computer networks all over the world can receive a UTC time source over the Internet, via a national radio transmission or through the GPS network. A NTP server (Network Time Protocol) can synchronise all devices on a network to that time.