Units of measure

The universe is so big that the typical units of measure that we use
on Earth to calculate distances (kilometers, miles,…) are too small.
Because of this we use:

Astronomical units (AU): It is equivalent to the average distance
from the Earth to the Sun. About 150 million km. Generally used to
measure distances within the Solar System.

Light year. Distances in space are so vast that they are measured in
light years – the distance that light travels in a year. Light travels at
a speed of roughly 300 000 km per second. A light year is therefore
about 9 500 000 000 000 km