Recently, I was able to see Andromeda for the first time, and it left me wondering about how far away it is. So, here’s what I know.

Andromeda is 2.5 million light years away. That means the light we see has taken 2.5 million years to reach us at about the speed of light. The galaxy is moving towards us, presumably at a speed significantly lower than the speed of light. That would mean the galaxy itself is currently closer than 2.5 million light years away.

My question is, about how far away is Andromeda right now, and how is this distance calculated?