It would be more correct to say that distant galaxies appear than to say they disappear. Based upon the accepted big band theory, there are galaxies that formed early in the universe from which light has not yet reached us, but that will reach us in the future. On the other hand, accelerating expansion of the universe could prevent light emitted after a certain time from a galaxy currently visible to never reach us; however, increasingly red-shifted, ever dimmer light from such a galaxy will continue to be observed.
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