Talk:Observable universe

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The content of Large-scale structure of the cosmos was merged into Observable universe. The former page's history now serves to provide attribution for that content in the latter page, and it must not be deleted as long as the latter page exists. For the discussion at that location, see its talk page.

What is the verifiability of the "In an inflationary universe, there could be as many as 10^100 stars?

Earlier, the Wikipedia article says there are about 10^24 stars in the observable universe. In one place, it says the total universe, using a specific modal, could have 10^100 stars. The total universe would be much larger than the observable universe, but that much difference seems insane. That would be like taking all the stars in the observable universe and putting it to the power of three. When I looked at the source, I found it was from a research paper published in 2020. Do I have a valid concern? AFanOfTheWanderingInnNumber25 (talk) 23:10, 21 September 2025 (UTC)[reply]

You would have a valid concern if that is what the article said. However, the article talks about an "inflationary universe", not the total universe. The total universe may be infinite for all we know.

To be honest the cited article is making a puzzling analysis, that based on RNA statistical analysis life may not exist in the observable universe but may exist in an unobservable universe derived from imagining an initial condition before inflation. I reworded it, take a look. Johnjbarton (talk) 03:24, 22 September 2025 (UTC)[reply]

Check the relevant section of the paper [1]. The argument is, if the universe underwent inflation, and inflation increased the size of the universe by at least 60 e-folds (which is e⁶⁰), then the universe is at least that much bigger than the observable universe. The author further argues that if you want to have no fine tuning, then you need about twice as many e-folds as the minimum. That's where the number came from, and it's not that surprising it's so large, since the size of the universe increases exponentially during inflation. I cannot get the exact number quoted in the paper, but it's in the same ballpark. Banedon (talk) 23:54, 22 September 2025 (UTC)[reply]

I think the original is better (and I reverted). If it's still unclear one could also write e.g. "If cosmic inflation occurred and the universe expanded by >60 e-folds, then the universe could contain over 10¹⁰⁰ stars". Banedon (talk) 00:03, 23 September 2025 (UTC)[reply]

Well I don't see what is significantly different from my version but ok fine. Johnjbarton (talk) 00:06, 23 September 2025 (UTC)[reply]

What is the topic here?

As far as I am concerned this article is about the cosmological term "observable universe". However a bunch of the later material here is "things that can be observed in the universe", which as far as I can tell should all be in Universe. Am I right? Johnjbarton (talk) 19:32, 27 September 2025 (UTC)[reply]