What is length?Length is a measure of distance. The length of something is the distance between its two ends. Small length is called short and big length is called long. For two or three dimensional things, length is usually the longest side or edge.
InputAstronomical Unit is roughly the distance from Earth to the Sun. The actual distance varies as Earth orbits the Sun. However, since 2012 it has been defined as exactly 149 597 870 700 meters.
Light-year is a unit of length used to express astronomical distances and is exactly equal to 9 460 730 472 580 800 meters.