What is a light year?
The term is familiar, but what exactly is a light year? Contrary to what many think, a light year is actually a measurement of distance, not time. Specifically, a light year is the distance that light travels in one year. Considering light travels at 186,282 miles per second – and nothing travels faster than the speed of light – one light year equals 5.8 trillion miles. Similar units of astronomical measurement include a light minute and light second – the distance light travels in one minute or one second. Equivalents: 1 light year=5,865,696,000,000 miles 1 light minute=11,176,920 miles 1 light second=186,282 miles To keep numbers manageable, the measurement of a light year is necessary for astronomers in describing the enormous distances between the stars and galaxies of the universe. Proxima Centauri, the closest star to Earth other than the Sun, is 4.2 light years away. The most distant celestial body visible to the naked eye is the Triangulum Galaxy, almost 2.6 million light years
A light year is a way of measuring distance. That doesn’t make much sense because “light year” contains the word “year,” which is normally a unit of time. Even so, light years measure distance. You are used to measuring distances in either inches/feet/miles or centimeters/meters/kilometers, depending on where you live. You know how long a foot or a meter is — you are comfortable with these units because you use them every day. Same thing with miles and kilometers — these are nice, human increments of distance. When astronomers use their telescopes to look at stars, things are different. The distances are gigantic. For example, the closest star to Earth (besides our sun) is something like 24,000,000,000,000 miles (38,000,000,000,000 kilometers) away. That’s the closest star. There are stars that are billions of times farther away than that. When you start talking about those kinds of distan
