Light Year Lesson for Kids: Definition & Facts

Instructor: Christie Wild

Christie has taught elementary and middle school, pre-K through 8th grade. She has a bachelor's degree in literature, with a concentration in creative writing.

This lesson explains what a light year is and who helped define it. It also includes several interesting facts about how fast and far you could travel within certain times and distances.

What Is a Light Year?

If you think driving across the nation to go to the beach takes a long time, try flying across the universe! A light year is a unit of measurement that measures the distance light travels in a year.

How far could YOU travel in one year? Well, if you could travel as fast as a light year, you'd travel about 6 trillion miles in a year.

How Long Is a Mile?

From an inch to a foot, these common measurements will give you an idea of how short or long they are in relation to a mile:

  • An inchworm is about an inch long.
  • A foot is 12 inches long.
  • A football field is 300 feet long.
  • One mile is equivalent to 5,230 feet.
  • A trip across the United States is close to 2,800 miles.

If you walked along the widest part of the Earth and traveled its circumference, you would go 24,901 miles! That's not even a tenth of a light year!

Measurements and Zeros

Once you get to 1,000, each major measurement increases by three zeros:

  • 1,000 (thousand)
  • 1,000,000 (million)
  • 1,000,000,000 (billion)
  • 1,000,000,000,000 (trillion)

At one number per second, you could count to:

  • 86,400 in one day
  • 31,536,000 in one year
  • One trillion in 31,710 years

If you wanted to count as fast as a light year, you'd have to count to 186,000 every second!

How Long Does It Take to Reach a Light Year?

Is a light year a measurement of distance, speed, or time? Maybe a little of all three. Technically, it's a measurement of distance as it relates to one year. The distance is so great because the speed is so fast.

If you could travel at the speed of light, you'd go about 6 trillion miles in a year. But if you rode in a super fast jet going 2,000 miles per hour, you'd only go 17,500,000 miles in a year. To go as far as one light year, you'd have to ride in that jet for 571,429 years!

What about a spaceship? A spaceship travels about 17,500 miles per hour. That's a lot faster than a jet! Can a spaceship travel the distance of a light year in a year?

Let's do the math:

  • 17,500 x 24 hours in a day = 420,000 miles per day
  • 420,000 x 365 days in a year = 153,300,000 miles in a year

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