Light-Year

astronomy · space · distance · light

Light travels fast. Light moves at about 300,000 kilometers every single second. That's fast enough to go around Earth seven times in just one second!

A giant measuring stick. A light-year measures distance, not time. It's the distance light travels in one whole year, which comes out to about 9.46 trillion kilometers.

Stars are far away. The closest star to Earth (besides the Sun) is about 4.2 light-years away. This means the light we see from that star today actually left it 4.2 years ago!

Impossibly huge distances. Our galaxy is about 100,000 light-years across. Even our fastest spaceships would take millions of years to travel that far.

Looking back in time. When you look at distant stars and galaxies, you're actually seeing light that traveled to Earth for years, decades, or even millions of years.