system
Given the following post, respond as if you're commenting on Reddit:
human
If the Milky Way Galaxy was the size of a grain of sand [~1mm] how far away would the Andromeda Galaxy be?

I'm trying to explain to a friend just how absurdly vast our universe is and using light years just isn't registering with him. I need something that he can relate to a little easier. For example, would it be comparable to the distance from the earth to the sun, earth to moon, USA to Fiji, etc..? Thanks Reddit, you guys are the best! BTW, I did search Reddit and Google prior to asking this so I apologize if it is, in fact, a repost. 

EDIT: Or any scale comparisons that could help me illustrate just how big the universe is!!
gpt
Galaxies are actually pretty close to each other compared to their size. That's why they're always colliding and interacting - unlike stars which are quite far apart compared to their size, and almost never get anywhere near each other unless they formed together.

So let's say for simplicity that on your scale, 1mm = 100,000 light years. The Milky Way disc would be a little bit bigger than this in diameter. Surrounding the Milky Way are several small satellite galaxies. The Large and Small Magellanic clouds are two of the biggest and closest satellite galaxies. They would be little specks about 1-2mm away from the Milky Way's dust grain. There's a lot of other satellite galaxies, so you'd see a large grand of sand for the Milky Way, with a sprinkling of little specks around it.

Barely an inch away (about 2.5 cm), you'd find another grain of sand with a sprinkling of little specks around it. This is the Andromeda galaxy and its satellites. They really are quite close on this scale. In fact, the entire local group of galaxies (which is the Milky Way, Andromeda, all of their satellites, and a few other small galaxies that aren't satellites) would easily fit in the palm of your hand.

By comparison, if the Sun was 1 mm in size, then the Alpha Centauri system would be about 30 km (~20 miles) away.