Light-Year

space · astronomy · distance · light

Light travels fast. Light moves at about 186,000 miles per second in space, which is the fastest thing in the whole universe. Nothing can go faster than light.

It measures distance. Even though it has the word 'year' in it, a light-year is actually a distance measurement, not a measure of time. It tells us how far light travels in one year.

Super huge distances. One light-year equals about 5.88 trillion miles. That's so far that if you tried to drive it in a car, it would take millions of years to get there.

Stars are light-years away. When astronomers say a star is four light-years away, it means the light from that star takes four years to reach Earth. So we're actually seeing what that star looked like four years ago.

Official space measurement. The International Astronomical Union decided exactly how long a light-year should be so that all scientists around the world use the same measurement when talking about space distances.