**A light year is a measurement of distance that signifies how far light travels in one year.** The speed of light is 186,000 miles per second or 671 million miles per hour.

Determining how long it takes to travel one light year depends in part on the speed of the observer. If the observer is traveling at the speed of light, then by definition it takes one year. As an example, it takes 1.3 seconds for light to travel from the Earth to the moon and eight hours for a space shuttle to make the same trip. The star Proximasad Centauri is 4.23 light years away from the Earth's solar system. The Voyager 1 spacecraft has covered 1/600th of a light year since its launch in 1977, traveling at approximately 38,000 miles per hour. At that speed, it will reach Proxima Centauri in 80,000 years.