Quote:
Originally Posted by renormalised
If the spacetime dough disappears, so do the raisins 
In their answer, the galaxies will begin to fall towards one another, yes, but only if they're both still under the influence of their mutual gravities. If that mutual attraction is less than the Hubble flow for the distance between them, both will eventually get caught up in the flow and start to recede, despite of initially moving together (or not at all, if not under their mutual gravitational influence i.e. too far away). It's only when two or more galaxies are under the influence of their mutual gravitational fields, like the Milky Way and Andromeda, that the local Hubble flow becomes negligible in comparison to their gravitational connection and as far as the flow is concerned they're considered to be one object. |
Its off topic a bit, but seeing as you brought it up, what/where is the evidence that Andromeda and the Milky Way are actually within range to be significantly gravitationally attracted ? (I know it smells a bit like GIEC (Giant Intergalactic Eddy Currents) but what the hell ? ... its been that kind of week !).
Of course other than GIEC, there's another possibility ... (early universe inertia although, perhaps this would imply co-incident paths which couldn't have happened with Inflation ?).
Wondering ... Cheers