A light year is a unit of distance used to measure extremely large distances in space. It is defined as the distance that light travels in one year in a vacuum, which is approximately 5.88 trillion miles (9.46 trillion kilometers). The speed of light is about 186,282 miles per second (299,792 kilometers per second), so in one year, light can travel about 5.88 trillion miles. This unit is commonly used in astronomy to express distances between stars and galaxies.
