Time Reversed Cosmology

One of my favorite authors is Greg Egan, and that's in great part because of how in many stories he starts with known physics, adds a twist, and follows it to its logical conclusion within the story's setting.

A particular idea he's used a few times is the idea that portions of the universe could potentially contain "time-reversed" regions. From our point of view, for instance, a time-reversed star absorbs photons, and if we could observe biological phenomena they would likewise go in reverse. (See e.g., the short story The Hundred Light-Year Diary)

From our point of view, the universe began billions of years ago with the big bang, and as far as I know all present observations are compatible with zero or negative curvature. This apparently gives an infinite amount of time to come in the future, though only a finite portion of that future can support baryonic life like ours.

So what does cosmology look like for the time-reversed universe, and what are their "big problems"? I don't have enough background in basic physics and cosmology to give a really good answer to this question, but here are some things that occur to me:

Entry first conceived on 19 March 2017, 20:16 UTC, last modified on 19 March 2017, 20:16 UTC
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