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Light Year in Miles

The Trifid Nebula.  Credit:  ESO

The Trifid Nebula. Credit: ESO

Astronomers measure large distances in light years. 1 light year is the distance that light can travel in a single year, and it’s an enormous number. Most of us are metric, but for those of you still working in the imperial system, let’s work out how far a light year is in miles.

The speed of light is 299,792,458 meters/second. That’s the same as 186,282 miles per second. And a year has 31,556,926 seconds.

So to figure out how far 1 lightyear is in miles, you just multiply the speed of light in miles x the length of a year in seconds.

186,282 miles/second x 31,556,926 seconds

This gives you your final answer. 1 light year in miles is 5.88 x 1012 miles. And if you don’t know scientific notation, that’s 5,880,000,000,000 miles. Or 5.88 trillion miles.

We have written many articles about the speed of light for Universe Today. Here’s an article about how gravity also moves at the speed of light, but how high energy gamma rays actually move slower than the speed of light.

Here’s a cool calculator that lets you convert light years to miles.

We have recorded an episode of Astronomy Cast detailing how astronomers measure distance in the Universe. Check it out here – Episode 10: Measuring Distance in the Universe.


Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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