Answer:
Shown from explanation.
Step-by-step explanation:
Light year is the distance light travels in one year and you can calculate that.
Light travels 3× 10^8m in 1 second; so you calculate the number of seconds in 365days and multiply by 3× 10^8m.
Light year was a unit of measure derived by man for expressing planetary distances due to their so huge distance which goes beyond our scale of measure.