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If physics is time reversal invariant, there ought to be white hole complimentarity as well. Imagine a white hole so enormous that it is possible for life to evolve entirely within it for billions of years before emerging to tell their story about the interior of the white hole. Meanwhile, an external observer can observe and keep note of everything in the vicinity of the white hole and what comes out of it. Both observers can meet and compare notes. Can the external observer really claim the white hole interior doesn't exist?

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No one claims that the interior of a white-hole nor black-hole doesn't exist. – Chris Gerig Jul 27 '12 at 10:47
Can you clarify what you are asking? Why would anyone suggest that the interior of a white hole doesn't exist? – John Rennie Jul 27 '12 at 10:52
Ignoring the "doesn't exist" part of the question, the analog here would be that someone inside the white hole can't compare their observations with someone who "fell out" of the white hole, so apparent contradictions in their observations can't be put side by side. The person in the white hole can get no further information about the person outside. – Mitchell Jul 27 '12 at 12:45
Black holes are the same thing as white holes. This has come up a hundred times. Time reversing an equilibrium state is still an equilibrium state. But this suggests strongly that emission from a white hole (at least in the nonrotating neutral state) is entropically forbidden, since it reduces the equilibrated horizon area by more than the entropy of the outgoing stuff. – Ron Maimon Jul 27 '12 at 23:48
Ron's right. Physics isn't time-reversal invariant when you talk about a coarse-grained description (recall the second law of thermodynamics), and black holes are definitely coarse-grained, thermodynamic, high-entropy objects. – Matt Reece Jul 28 '12 at 4:18

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