|Andromeda and Milky Way are the largest galaxies in the Local group. ref|
The distance from us to the nearest galaxy Andromeda is estimated at about 2.5 million light years.
So how near is 2.5m ly? Could we go there or have visitors from there here upon Earth?
Let us try to understand the distance in terms of time it would travel there and back at light speed.
If we were to broadcast today 25 May 2012 a radio signal towards Andromeda and if someone out there would catch our signal, figure out exactly from where it came and kindly immediately responds to our signal with an identical radio signal, a kind of inter-galactic "ping", we would have that response back in our receivers clear and loud 25 May 5002012 AD.
How long period of time is that?
One point of reference is the fact that humans have existed on planet Earth as a distinct species approximately that time - 5002012 years take or leave some. Evolutionary biologists are estimating that according to the DNA records we humans were separated from chimpanzees in Africa about five million years ago.
Such a point of reference gives some perspective to astronomic distances and dates.