Light-year. It’s a measure of distance. And it’s pretty straightforward
– the distance light can travel in a year. But light travels ­fast.
One light-year is about 5.879 trillion miles
or 9.461 trillion kilometers.
So if we have kilometers and miles and inches to measure distance, why do we use light years?
Well, space is big. Like really big.
The nearest star to our solar system – Proxima Centauri – is about
4.2465 light-years away, or 25 trillion miles. And that’s a close star.
So when we start talking about even longer distances, like to other galaxies,
we need bigger units of distance. Cue light-years.
And by the way, it’s not just light-­years. There are also light-seconds,
the distance light can travel in a second, and light-minutes, how far
light travels in a minute. In fact, our Sun is about 8 light-minutes away from Earth,
which means the sunlight you can see right now left the Sun about 8 minutes ago.
Seriously – space is big.