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It's my understanding that in a few billion years, clusters of galaxies won't be able to directly observe one another due to the expansion of spacetime overcoming gravity between those clusters. However, it is also my understanding that spacetime in the local gravity clusters is "less" expanded due to, well, the presence of powerful gravitational forces holding spacetime together locally.

Specifically, I'm wondering if perturbations in space-time due to gravity might be detectable by finding areas of perhaps "less expanded" spacetime along the edges of the gravitational local group of the local galaxy cluster?

Let's speak purely theoretically, and ask the question of whether or not there will be some kind of stored information that a perfect observer might glean from the rate of expansion of spacetime along the edges of the gravitational local group.

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How do you differentiate between observation, detection, and interaction? – Asher Sep 2 '15 at 22:24
In the end, they're all the same, but it's a question of WHAT you are observing/interacting with/detecting. You might not be able to directly observe (via electromagnetic radiation) a remote galaxy due to spacetime expansion becoming too fast to allow for the passage of spacetime... Which actually answers my question in the negative, I think. Since gravity (as far as we know) also operates according to the universal constant, any effects it have will also cease to operate as soon as the remote galaxies become unobservable. At that point, the galactic local group will be the only actor. – Laereom Sep 9 '15 at 21:08

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