[Michael Barnes]

The Milky Way and Andromeda are going to collide and during that collision, not much is going to touch one and other. Space is vast.

[ZX12R]

The Milky Way and Andromeda are going to collide and during that collision, not much is going to touch one and other. Space is vast.

Like an atom, takes up space, but most of the space is made up of nothing.

[zeugma]

The Milky Way and Andromeda are going to collide and during that collision, not much is going to touch one and other. Space is vast.

True, but the gravitational effects are huge, especially the cores of each galaxy. Of course the time scale of the event puts even the longest slo-mo to shame, but I've seen modeled predictions of the interaction, and it's pretty cool. The merger of the Milky Way and Andromeda will pretty much double the size of our home galaxy as far as mass is concerned.