Time is something we all use throughout our lives, although many of us probably don’t think about how it work – we just get on with it!
Us humans divide time up into small chunks, like hours and minutes and seconds; or into bigger chunks, like days, weeks, months and years. And we measure time by looking at clocks or watches or calendars.
Animals and plants and other creatures also measure time but they don’t use clocks – they rely on the amount of light to tell if it’s day or night, and they sense more gradual changes in the seasons.
Time-travel, or the ability to move backwards or forwards through time, is an idea that pops up in stories and films. But could it actually happen?
We measure time by the movement of our planet around the Sun. The Earth travels around the Sun on a oval-shaped path (called an ‘orbit’) and it takes one year to make a complete journey. The Earth also spins around as it travels on its orbit. Sometimes the part of Earth you live on will be pointing towards the Sun and sometimes it will be pointing away. It takes one Earth day to do a complete spin (and we call the light time ‘day’ and the dark time ‘night’).
You might like to read my answer to why does the sun rise? to find out more about how the Earth moves around the Sun.
Because the Earth spins, it doesn’t make sense for us to all have the same clock time. When I’m having my lunch in the UK, people in Australia are getting ready for bed! So we have a system of ‘time zones‘ around the world. And this means that wherever we are, our morning starts from sunrise (when our place on Earth starts to point towards the Sun) and our evening finishes at sunset (when our part of the Earth has turned away from the Sun).
If you go from one time zone to another, you will have to change your watch. And you will have travelled through time! If you travel all the way around the world in one go, you will cross the international date line and you may travel forward or back in time by a whole day in just a few seconds! One man managed to have the longest ever birthday by travelling around the world across lots of time zones!
So, it might not be exactly like in the science fiction stories but it is possible to time travel (a little bit) just by travelling around our world!