A light-year is the distance that light travels in one Earth year. Light moves at about 186,000 miles per second (300,000 kilometers per second), so in one year it covers approximately 5.88 trillion miles (9.46 trillion kilometers)
. To put it simply:
- 1 light-year ≈ 5.88 trillion miles (9.46 trillion km)
- This distance equals how far light travels in 365.25 days (one Julian year) in a vacuum
Astronomers use light-years to measure vast distances in space because conventional units like miles or kilometers become impractical at cosmic scales. For example, the nearest star beyond the Sun, Proxima Centauri, is about 4.2 light-years away, meaning its light takes 4.2 years to reach Earth
. Thus, a light-year is a unit of distance, not time, and it helps us understand the immense scale of the universe.
