system
Given the following post, respond as if you're commenting on Reddit:
human
If space is "expanding" are the ratios of distances conserved?

From my very limited understanding of space I am under the impression that objects in space are not "moving apart" but rather space itself is getting "bigger" (if that makes any sense). My question is that if the latter is true does that mean that ratio of the distances between, let's say, earth and the center of the milky way and from the milky way center to the next nearest galaxy center will remain the same in the next million years or are different parts of space "expanding" at different rates?
gpt
If you look at an atom, say, the forces holding the atom together are far far far stronger than the tiny effective force of the space expanding between the electrons an nucleons. So the size of the atom never changes. Same goes for our solar system, and even our galaxy. It is only when we zoom out and start looking at the distances between galaxies that the expansion of space begins  to compete with the gravitational force, and the actual distances between galaxies grows with time. So overall, the ratios are not conserved. But for "small" things actual sizes of objects don't even change at all.