this post was submitted on 02 Oct 2023
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No. Local attractive forces, like gravity, especially those at the atomic level, overpower the expansion for tightly coupled systems. So the earth isn't expanding, and neither are the people on it. I don't recall exactly what scale it kicks in at, but there is a good chance it's not even affecting the distance between planets in a system. Most likely it only plays a role in inter-planetary-systems and larger. Ie, stars get further apart from each other.
Edit. This explains it better https://www.astronomy.com/science/does-the-space-inside-an-atom-expand-with-the-universe/
That says that the expansion really only applies to the space between galaxies. In anything smaller than that, gravity still overpowers the expensive forces. Making it far weaker than I initially thought.
It's at a much, much larger scale** than that
our local group is collapsing in on itself, and it's ~10M lightyears in diameter.
** talking about length scales only makes sense in reference to the specifics
two bananas separated by 10M lightyears, with no other matter nearby, would (I'm guessing) be expanded away, but a cluster of galaxies will not.
Using a banana for scale really made this so much better. :)
Yeah, finally I can imagine the vastness of space. Thank you, bananas!
Wouldn't it cause some sort of force locally at the atomic level all the same even for tightly coupled systems? They shouldn't feel the expansion as it is not a force from my understanding but just growth of space itself. But for example wouldn't the orbit around an atom be off just so slightly that it would need to expend some level of energy to correct for lack of better word.
Or do we think this does happen but the amount is so small that we can not measure it experimentally in any way.
My understanding is that it does exert a force everywhere, even locally. It's just so incredibly weak that other local forces dominate and overpower it. Take the classic example of expansion as ants on a balloon as it's inflated. The expansion wants to pull them apart, but if they were tied to each other by thread, the thread would be stronger and they would stay together. The thread represents the inter molecular forces. Also remember that the expansion force is in every direction, without an origin, so from an atom's perspective the force seems to push outward,not from the side, so there would be no "offset".