The Plank length thing is just going to add confusion here. Quantum stuff is weird. That's where analogies go to die.
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.
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.