What is a light year used to measure?

A light year is a unit of distance that represents how far light travels in one year. Light moves at an incredibly high speed, approximately 299,792 kilometers per second in a vacuum. If you calculate the distance light covers in one year, it amounts to about 9.46 trillion kilometers (or approximately 5.88 trillion miles). This measurement is particularly useful in astronomy for expressing distances on a cosmic scale, such as the distance between stars and galaxies.

The other options do not accurately describe what a light year measures. For instance, it's not simply the distance light travels in an hour, nor does it pertain to the speed or energy of light itself. The definition revolves solely around the distance covered over the span of a year. Understanding this concept is essential for grasping how vast the universe is and the scales involved in space measurements.