How far away is the Andromeda galaxy?

We say that the Andromeda galaxy is “relatively nearby” because most galaxies are much farther away; in fact, Andromeda is the nearest large galaxy to our own (several dozen small galaxies are closer). Still, on human terms it is very far away! Its distance is about 2.5 million light-years away, which means that light takes about 2.5 million years to travel the distance from Andromeda to us. Therefore, the photo of Andromeda actually shows what it looked like about 2.5 million years ago.

In the same way, if someone in the Andromeda galaxy used a super telescope to look at Earth today, they would see Earth as it looked 2.5 million years ago, which is long before our ancestors discovered fire or built any structures.