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this is my first post in this community and I am not entirely sure if it is appropriate. I am not an educated physicist, just an ethusiastic person trying to understand the universe. So I apologise if this is not the right place or form to ask this question, if so, I would appreciate directions.

As far as I come to understand, it is clear that space itself expands, meaning that the distance between i.e. our Sun and other stars grows larger while this objects themselves do not move (that much) through spacetime. Now what I dont understand: If this is happening, why does the space between all things that exist not expand at the same rate, so that I, as an observer, would not be able to noice it at all?

Let me try to picture it: The space between Sun and Alpha Centauri expands, fine. What is about the space between me and my desk? Between the molecules / atoms / smallest parts of matter that my body and my eyes are made of and so on? Why do Earth, Sun and Alpha Centauri not grow with the same rate as the space between them grows, so that in the end the effect would even itself out to the eyes of an observer? Or is there a force that keeps me and my desk at the same distance, woking against the force of expanding space? If so, what force is that?

This is the best that I can do to explain my question, I hope it is understandable enough. I really hope someone can help me understanding this, because it really gives me a headache.

Qmechanic
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Thomas
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    Does this answer your question? Why does space expansion not expand matter? or https://physics.stackexchange.com/q/258479/ – ProfRob Jan 28 '21 at 20:05
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    @ProfRob Yes, it does, thank you! I did not find the right words for the search function to find this, so thanks for helping me out. – Thomas Jan 28 '21 at 20:07
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    As the top answer to the linked question explains, the space between the Sun and Alpha Centauri isn't expanding. The force of expansion is quite weak, so it's easily overwhelmed by gravity (and other forces) on distance scales smaller than a cluster of galaxies. – PM 2Ring Jan 28 '21 at 20:10
  • @PM2Ring: I was not aware of this, thanks for pointing it out. – Thomas Jan 28 '21 at 20:13
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    No worries. But even if you had two rocks separated by 4.4 lightyears (4.16×10¹⁶ metres, roughly the distance from here to Alpha Centauri) sitting in the middle of a great void, millions of lightyears from anything else, the expansion rate between them would be a little under 0.1 metres per second, which is pretty hard to notice. ;) – PM 2Ring Jan 28 '21 at 20:23

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