A light-year is the distance that light travels in one year in a vacuum. It is a unit of length used primarily in astronomy to express vast distances between celestial objects.
- In terms of exact measurements, one light-year equals about 9.46 trillion kilometers (9.461 × 10¹⁵ meters) or approximately 5.88 trillion miles
- Light travels at a speed of roughly 300,000 kilometers per second (186,000 miles per second), and in one year (365.25 days), it covers this enormous distance
- To put it in perspective, the nearest star to the Sun, Proxima Centauri, is about 4.2 light-years away, meaning its light takes a bit over four years to reach Earth
Thus, a light-year is a measure of distance, not time, representing how far light can travel over the span of one Earth year.
