Astronomers use light years to measure distances in space because space is so massive and distances so far that conventional numbering is inadequate and unmanageable. One light year is a distance measurement equivalent to six trillion miles.
Scientists use the light year instead of astronomical units to measure the distance between stars because the distance between stars is very large and the use of light year is more efficient to express large distances. Measurement in light year is also easy to understand. The use of astronomical units is not practical. A light-year is the distance traveled by light in one year in an empty space. 1 light year = 9.4605284 × 10^12 kilometers.
