I was a bit lose with my language when I said "distant galaxies don't exist anymore", but that was a really interesting correction so I'm glad I said that! A lot of the stuff about simultaneousness I was already aware of, but it's still nice to read. And I knew nothing about the efficiency of galaxies. It's kinda crazy to think that galaxies survive for so long.

I have been thinking about this more since my post, and the concept and a "here and now" is really messing with my head. If I could instantly teleport to this distant galaxy, what would I see? Probably nothing. The galaxy might exist, but it will have moved, a lot, in the time it has taken for its light to reach us. So in this sense I am kinda applying my own sense of "now" in an effort to see the universe as it is in my "now" rather than looking back in time. Which I appreciate is absurd. I might as well visualise it from the timeless photon's pov, which flattens everything and renders distance irrelevant.

I'm still mulling this over.

Although, one more thing. Heat death isn't inevitable. You just told me that the universe has changed its rate of expansion over time. Why would we assume the rate of expansion to play nice with us in the future if it hasn't in the past? We still don't know why it expands. We just make up concepts like dark energy and hope to one day understand what we actually mean by that. So just because it might look like heat death is inevitable, well observers in the very early universe would probably have expected heat death much sooner and are probably surprised to see that things calmed down a bit.