The light-year for measuring distances
The huge distances and sizes in the Universe require an adapted unit: the light-year.
It is the distance travelled by light in one year, at the speed of 300 000 kilometers per second.
At this breathtaking velocity, light goes 7 times around the Earth in one second. It also runs in one second from the Moon to Earth.
And it requires no less than 8 minutes for light to cover the 150 million kilometers which separate the Sun from our planet Earth.