# Dоes everything in the univеrsе еxpand unifоrmly?

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So we know that the univеrse is expanding at an incrеasing pace, and the gаlaxies are moving away from each other. My question is, does everything expаnd uniformly? For example, is the distance between me and the cоmputer in front of me expanding at the same rate as the distance between the neighboring galaxies?

And if not, then is there a certain limit where – I would assume – the grаvitational pull between two objects gets below some threshold (I would assume it would get below some level of the dark matter expansion force) that distance between them starts expanding?

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No, something x light years away from you is going to move slower then something 2x light years away.

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>For example, is the distance between me and the cоmputer in front of me expanding at the same rate as the distance between the neighboring galaxies?

Attempting to expand, yes. Succeeding? No

The underlying fabric of space seems to be expanding very slowly. In deep space it’s about 2 um/second per kilometer of distance (70 km/s/Mpc in useful distances)

This slow expansion isn’t pulling that hard so within object the electromagnetic force greatly overwhelms it, and even across the width of a galaxy it’s overwhelmed by the relatively weak gravity holding everything together

Expansion has a far bigger impact on the distance between galactic clusters than anything you can hold

Space near matter isn’t expanding. It’s intergalactic space that’s expanding. It’s like if you put a balloon in another balloon and blew the second one up. The first one isn’t expanding. The balloon around it is.

Gravity and the other forces overcome whatever is causing the expansion of the universe at an intergalactic scale, so matter remains near each other.

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The distance between you and the computer is not expanding at all. That applies even on larger scales: Inside galaxies and galaxy clusters, gravity has stopped the expansion of space. Only space between the galaxy clusters is expanding.

> then is there a certain limit where – I would assume – the grаvitational pull between two objects gets below some threshold (I would assume it would get below some level of the dark matter expansion force) that distance between them starts expanding?

Exactly. The technical term is “gravitationally bound”, and the threshold is generally at the level of galaxy clusters, i.e. groups of several galaxies close to each other.

The way space expands is similar to stretching a rubber band. But think about it like this you have a 2D grid increase the distance between the squares on the grid by the same amount around its neighbours and fill the gaps. So more distant things travel faster away from each other as there is more space stretching between them. But space itself apart from the acceleration is uniform and because of that it scales with distance. Yes space does expand between you and your computer just like between distant galaxies but distant galaxies have a lot more space to stretch between them. The rate of expansion is however not too big so things that are close enough and so gravitationally bound together quite strongly overcome the stretching stay together while space stretches through them. Clusters like our the Local Group will remain bound together. But clusters themselves will drift apart.