But generally speaking, the answer is 2. That's assuming there's no forces between the two objects.
Space doesn't expand like the outside of a balloon or a rubber sheet - I hate those analogies because they give you the wrong idea.
I'm not aware of any major current theories that say space is quantized, or any theories that have a way of pinpointing a "piece" of space, so the following analogy is flawed. But it should at least point you in the right direction.
Draw a line and put eight dots on it. Draw arrows pointing to the fourth, fifth, and eighth dot. We'll call those dots A, B, and C respectively.
We're going to measure distance by dots. Dots A and B have a distance of 1. Dots A and C have a distance of 4.
Now for each dot, add a new dot before and after it. Measure the distances. Dots A and B now have a distance of 3. Dots A and C now have a distance of 12.
Repeat. Measure the distances. Repeat again. Measure the distances. You'll notice that the distances between the dots you've marked is increasing faster with each repetition, and that the distance between A and C is increasing faster than A and B. An object at any of those points would not be experiencing any force - nothing is pushing or pulling on them - but an observer at any of those points would observe the objects at the other points to be accelerating away from them.
That's sort like how space expands. Of course, space doesn't have "points" as far as we can tell, so there's all kinds of problems with the above analogy, but hopefully it helps.
Things dont fall to the ground because the earth pulls on them. Earth is pulling in the space around it, and those things come with it. See the river model of general relativity for a more thorough explanation.
All of them together are so much stronger it's not even funny. And that's for the "underdense" region that we are in. Not a void, but about half of our galaxy's environment does count as a void.
Gravity wells aren't pulling surrounding space toward their centre. They're only pulling other masses that occupy the surrounding space.
Gravity ensures that structures at the cluster level and below don't expand as the space they're in expands. The space they're in is expanding just like it is everywhere (assuming a cosmological constant) - gravity just holds them together. Which is what I mean when I say matter isn't pinned to space - it just slides through it.
Gravity is too weak to affect distant objects, so we see the effects of the universe's expansion when we look at them.
i will clarify. in the absence of other forces, matter is indeed pinned to the space it is in.
you talk about gravity as if its something distinct from what is driving the expansion of the universe.
we have that model, its what newton proposed.
Regarding being "pinned," that still fails to account for inertia. The idea that there's a specific piece of space that we're stuck to implies there's a rest state at which there is no motion independent of any observer. We know that's not the case.
My original point was that gravity and the other forces that hold us together are so much stronger than whatever is causing expansion that the expansion of space doesn't affect us at small scales. The space we're occupying is expanding. We're not dragged along with it. The Triangulum galaxy doesn't move away from us because gravity keeps the Local Group together. We do see the expansion of space between us and distant objects, but that's because there's no force strong enough to hold those distant objects to us. That's not because we're "pinned" to our location, but because the space between us is getting larger.
In many interpretations of GR it is believed that mass deforms spacetime, but is also influenced by the spacetime it moves through. In the absence of mass, spacetime expands. Carrying along any mass with it. When mass is present this default expansion is overpowered by its influence which causes a contraction. Hence black holes.
Gravity is still colored by classical definitions so most assume its power is unidirectional. However there is a quantitative factor for expansion in the very same Einstein equation which defines GR.
We need to stop thinking of gravity as a force acting on objects, and rather something that acts on spacetime. Many people advocate this but stop at the rubber sheet analogy, which is completely devoid of the idea that the sheet actually moves as well.
Analogy, take two attracted magnets, or two opposing electrodes, and expand the space between them. Things change
The space between the magnets is expanding, just like space everywhere. Assuming the table and magnets are immune to deterioration over time, you can come back after several billion years and the distance between the magnets will have stayed the same. Space expanded, sure, but the stuff occupying the space didn't.
The forces that hold an atom together are significantly stronger than what's holding the two magnets in the example above.