Light Years

Space is huge, so scientists need a big way to measure distances. They use something called a light year. A light year is not a unit of time. It is a unit of distance. It measures how far light can travel in one year.

How Fast Is Light?

Light travels faster than anything else in the universe. It moves at about 186,000 miles every second. That is so fast it could go around Earth seven times in one second. In one year, light travels about 6 trillion miles. That is a lot of zeros.

Looking Back in Time

When we look at stars, we see them as they were long ago. The light we see has been traveling to us for years. Some stars are so far away that their light takes thousands of years to reach Earth. So we are looking back in time. The star might not even exist anymore.

Fun Facts

• The nearest star after the Sun is about 4 light years away.
• Our galaxy is about 100,000 light years wide.
• Sunlight takes 8 minutes to reach Earth.

Did You Know?

The James Webb Space Telescope can see galaxies over 13 billion light years away.