Why is the distance between stars expressed in light years?
Answer:
The Sun is nearly 150,000,000 kilometres (150 million km) away from the Earth. The next nearest star is Alpha Centauri. It is at a distance of about 40,000,000,000,000 km from the Earth. Such large distances cannot be expressed conveniently in kilometres. Thus, the unit light year is used. One light year is the distance travelled by light in one year.