How can we accurately measure distances in space?

Question

I just can’t comprehend how we can tell that something is 500 light years away. Or how we know that a galaxy is 100 light years wide.

In: 0

Answer 1

There are various methods used in conjunction. This is called “[cosmic distance ladder](https://en.wikipedia.org/wiki/Cosmic_distance_ladder)”. As others have said, parallax is one of the methods, light redshift is another, but there are many more.

The main problem is to have a reliable method that is common enough to be widely used, but also for them to overlap, so we can count on others when the method becomes unreliable.