• Skip to primary navigation
  • Skip to main content
  • Skip to footer
Zippy Facts Logo

Zippy Facts

Interesting Random Facts

  • Animals
  • Culture
  • Firsts
  • Food
  • Geography
  • Health
  • History
  • Inventions
  • Language
  • Mythology
  • Odds
  • People
  • Religion
  • Science
  • Space
  • Universe
  • World
You are here: Home / Universe / What Is a Light Year?

What Is a Light Year?

March 25, 2020 by Karen Hill

A light-year may appear to be a measure of time, but it’s actually a measure of distance. A light-year is the distance that light would travel during the course of one earth year.

Light travels at the speed of about 186,282 miles per second! And there are a little more than 31.5 million seconds in a year. Multiplying these two numbers together, we find that light travels about 5,880,000,000,000 miles in a year, almost six trillion miles. So we say that this distance is equal to one light-year.

The first man to figure out the speed of light, and the distance it travels in a year, was a Danish scientist named Olaus Roemer. In 1676, Roemer observed the movements of one of Jupiter’s moons.

He found that sunlight bouncing off that moon reached Earth later when our planet was on the opposite side of the sun from Jupiter than it did when Earth and Jupiter were on the same side of the sun. The difference in time was about 17 minutes, or 1,000 seconds.

This means that it took light 1,000 seconds to travel across the diameter of Earth’s orbit around the sun. Since Roemer knew that this distance is about 186 million miles, it was easy to figure out that light traveled at a speed of 186,000 miles per second. And at that speed, it would travel about six trillion miles in a year.

In our century, scientists found that the exact speed of light is 186,282 miles per second, just about what Roemer found 300 years ago!

Related Facts

  • Where Did the Term "Leap Year" For Every Fourth Year Come From and How Long is a Leap Year?
  • What Is a Light Year and How Long Does the Light From Our Closest Star Alpha Centauri Take To Reach Earth?
  • What Is Light Made Of, Where Does Light Come From, and Why Is Light a Type of Electromagnetic Radiation?
  • How are Thousand-Year-Old Eggs made and Where do Thousand Year Old Eggs come from?
  • How far is a "Roddenberry" and how much shorter is it than a light year?
  • Why Is Light White and How Do You Separate Light Into the Various Colors of the Spectrum?

Filed Under: Universe

About Karen Hill

Karen Hill is a freelance writer, editor, and columnist. Born in New York, her work has appeared in the Examiner, Yahoo News, Buzzfeed, among others.

Previous Post: « What Is a Fiord?
Next Post: What Are Infrared and Ultraviolet Lights? »

Footer

Follow

  • Facebook
  • Flickr
  • GitHub
  • Google+
  • Instagram
  • LinkedIn
  • Medium
  • Pinterest
  • StumbleUpon
  • Tumblr
  • Twitter
  • YouTube

Categories

Accomplishments Animals Culture Firsts Food Geography Health History Inventions Language Mythology Odds People Religion Science Space Universe World Your Body

About

Zippy Facts empowers the world by serving educational content that is accessible to everyone.

A tribute to growing up, zippyfacts.com showcases interesting and unusual facts about the world.

Our mission is to use technology to facilitate knowledge transfer and sharing.

Copyright © 2021 Zippy Facts

  • About Us
  • Contact
  • Privacy Policy