Wouldn't the gravitational limits of different star systems appear as such bubbles?
As a mathematical model, yes, but as a visual one, no. All we would perceive would be the intersections between the bubble we are in and the adjacent ones as a contour map.
an assumption going all the way back to Aristotle, really – is that space is continuous and infinitely divisible, so that any distance could be chopped up into even smaller distances. But Hogan questions whether that is really true.
Inspired by Mathis, I have made an experiment that proves something related to that chunkiness. Namely that the change of direction of motion cannot be continuous. In other words: the direction of motion cannot change more frequently than some minimum distance (or time) ...or the direction has to stay constant for a certain minimum distance.