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TheLostHippos t1_j18xyaf wrote

Reply to comment by SaiphSDC in in the FAQ it is stated that one proof of the universe's expansion is that "more distant galaxies are packed closer together". What sort of measurements have been made to show this? by DanTheTerrible

Is the reason this tells us its expanding is because the ones farther away are being seen further back in time?

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ersentenza t1_j192xog wrote

Exactly, we are not seeing them as they are now, but as they were back then. So we can observe they were closer in the past.

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SaiphSDC t1_j194gf0 wrote

That is correct.

Distance = time due to the finite speed of light.

So the detail that galaxies far away, and thus in the past, are closer supports the model of an expanding universe.

Especially as this detail is seen in all directions with no variation further supports the expansion model.

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