A light year measure the distance a lightbeam can travel in one year one light year is equivalent to 9500000000000 km why do scientist use light years to measure distances in the universe.

Light years are the only practical unit for measuring the distance of space

Light years tell us about the temperature distance and age of their celestial bodies

Light years are the most accurate form of measurement for universal purposes

Light years measure the age of celestial bodies by determining how bright the light is