Light Year

The Light Year is a way of measuring distance - and not time as you might think from the name.

It is the distance that light travels in one year.

You may not think that light takes any time at all to travel - after all, there is no pause after you turn on a light switch, but that is because it travels very fast.

In fact, it moves 300,000 km every second. That is more than 7 times around the Earth in a single second!

Therefore, a light year is a very long way and very useful for measuring the huge distances between stars and galaxies.

Looking back in time

Of course, because light takes so long to travel between stars and galaxies, when you look at very distant objects, you are actually looking back in time!

Astronomers use this to look at the history of stars and even the whole Universe.