Talk:Observable universe

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Recent reverts[edit]

hey Banedon! I reverted addition of several sentences backed by Siegel's blog as unencyclopedic. Can you please tell me how is this valuable for the article? It looks like a poorly sourced trivia: An interesting occurrence: the future visibility limit is exactly equal to the reachable limit (of 18 billion light-years) added to the current visibility limit (of 46 billion light-years). This no coincidence; the light that will ultimately reach us is right at that reachable limit today, after journeying 46 billion light-years since the Big Bang. Someday far in the future, it will arrive at our eyes. Artem.G (talk) 07:13, 2 April 2023 (UTC)[reply]

I don't understand what you mean. The size of the observable universe changes over time. The quote you give explains how the size of the observable universe as well as the size of the reachable universe changes in the future. This article is on the observable universe. Banedon (talk) 14:23, 2 April 2023 (UTC)[reply]

An interesting occurrence, Someday far in the future, it will arrive at our eyes. doesn't sound like an encyclopedic article, but more like attention-grabbing journalistic piece. Aren't there any better sources from real papers, not from a blog? (even if this blog is by an expert, it's not peer reviewed and thus not entirely reliable) And it should be rewritten anyway, even if you think the sources are acceptable. I'm mostly away for this and the next week, but will ping some users who can have an opinion on this: Praemonitus, XOR'easter, Serendipodous. Artem.G (talk) 06:46, 3 April 2023 (UTC)[reply]

That's the sort of thing which should be cited to an introductory cosmology book, not a random blog post. (If the only place that a topic is discussed is in a random blog post, then we have to wonder whether it deserves including here.) Also, it needs to be written, not copied. XOR'easter (talk) 11:12, 3 April 2023 (UTC)[reply]

This is the kind of thing that won't show up in the research literature, because the math is well-known and the results depend on parameters. Like, let's say you have an equation x + y = 10. You can't say what x and y are because the system is unconstrained, but once you experimentally measure one, the theory tells you the value for the other. That's what we have here. Depending on the amount of dark energy & matter in the universe, the reachable limit will vary, same as the visibility limit of the future. You could find papers on how much dark energy & matter there is (c.f. Planck), but not what the reachable/visible limit will be. Banedon (talk) 02:05, 4 April 2023 (UTC)[reply]

As far as I understand, the expansion of the universe means that the farther reaches of the universe will never be able to reach our eyes. Serendi ^podous 09:29, 3 April 2023 (UTC)[reply]

Well if we can already see it, then light from those regions is already able to reach our eyes. It's just that as the universe expands, the size of the observable universe changes; what we can currently see might not be visible in the future. Banedon (talk) 01:56, 4 April 2023 (UTC)[reply]

I think this is trivial calculation for those are the expert in the field. I could not find introductory book written about it yet, but here is a simple Astronomy paper explain the math the relation ship between the size"reachable/affected universe" with future size of observable universe. Sorry for copy paste of the article, I'm not very articulate in English language. I think one can write down as equation a+b=c. The value of a and c already well source in this article, the value of b (reachable universe) is always overshadow by observable universe article in search engine result. Thus my effort to highlighting it in wikipedia page J.X (talk) 12:52, 4 April 2023 (UTC)[reply]

Astute readers will notice that the radius of the affectable universe (16.5 billion light years) and that of the observable universe (46.4 billion light years) sum to the greatest distance light can travel (62.9 billion light years). This is not a coincidence, but a fundamental fact of our universe. J.X (talk) 12:56, 4 April 2023 (UTC)[reply]

What actually is at the center of the observable universe?[edit]

Is it right to say that the earth has an observable universe? Isn't it rather the case that each identifiable region of spacetime has a unique observable universe centered on it? EDMM2 (talk) 17:31, 31 January 2024 (UTC)[reply]