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If everything in the universe is slowly drifting away how soon before we see signs of this?Maybe we’ve already registered things at the visible edge of the universe disappearing. If not will, it ever be possible?

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  • $\begingroup$ Hope you don't mind. I edited your tags to get better attention to your question at hand. $\endgroup$ – docscience Mar 4 '20 at 1:42
  • $\begingroup$ @docscience thank you $\endgroup$ – Bill Alsept Mar 4 '20 at 1:45
  • $\begingroup$ Time that light takes to come to us from the horizon equals the age of the universe. So we “see” things at the horizon as they were shortly after the Big Bang when there were no stars yet. Thus we cannot ”see” an accelerating galaxy crossing the horizon redshifted. Instead we would see its creation in reverse, so to us it would appear “uncollapsing” into a primordial cloud of hydrogen and disappearing into CMB, according to the mainstream cosmological model. $\endgroup$ – safesphere Mar 4 '20 at 5:46
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    $\begingroup$ I point to the fact that for a certain epoch new things enter into our visible / observable universe, too. $\endgroup$ – Alchimista Mar 4 '20 at 9:37
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Wikipedia's article on the Observable Universe give an answer for this question.

As the universe's expansion is accelerating, all currently observable objects will eventually appear to freeze in time, while emitting progressively redder and fainter light. For instance, objects with the current redshift z from 5 to 10 will remain observable for no more than 4–6 billion years. In addition, light emitted by objects currently situated beyond a certain comoving distance (currently about 19 billion parsecs) will never reach Earth.

So yes, we will eventually (in fact already are) seeing things disappearing.

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  • $\begingroup$ Thanks for the answer but is Wikipedia saying observable objects will all eventually freeze or disappear?? At the end you say we already are seeing things disappear. What do you mean by this? Anything specific? $\endgroup$ – Bill Alsept Mar 4 '20 at 3:09
  • $\begingroup$ @BillAlsept they'll eventually disappear in the sense that we can no longer see them. As for things that are already disappearing: remember the timescale is very long (4-6 billion years). Things are certainly moving out of our observable universe, just we are not likely to be aware of them (since they are too dim to see). $\endgroup$ – Allure Mar 4 '20 at 3:30
  • $\begingroup$ I kind of figured that about the time scale but what about current objects admitting progressively redder light? Has a current observable object ever had its red shift verified and then later tested again to show an additional red shift? Is 100 years enough to show even a fraction of a wavelength difference? How many years would it take between compared measurements to confirm? $\endgroup$ – Bill Alsept Mar 4 '20 at 3:46
  • $\begingroup$ @BillAlsept I don't know, but intuitively I'd guess any variation will be vanishingly small. $\endgroup$ – Allure Mar 4 '20 at 3:51
  • $\begingroup$ see pursuit.unimelb.edu.au/articles/a-galaxy-very-far-far-away $\endgroup$ – anna v Mar 4 '20 at 5:59

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