Talk:Initial singularity

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Traditional Model, First Sentence

Why is the second reference shown here? It shows neither specific descriptions of how general relativity's predictions fail nor broader criticism of the idea that the singularity was infinitely dense. Also, the first reference is simply an introduction to the Big Bounce unrelated to the criticism stated in the first sentence. This should be at least remedied by an additional sentence following the first that clarifies that the Big Bounce is an example of the mathematical model of an infinitely dense singularity being criticized (supported by the first reference). In my opinion it would be better if a more "blanket" reference of criticism was found or the first sentence removed entirely. Section 8.6 of [1] is adequate for a reference here. The Big Bounce is not prevailing criticism but rather an alternative that has been disregarded. — Preceding unsigned comment added by Nathan Vercaemert (talk) 17:58, 11 April 2024 (UTC)[reply]

[1] http://ndl.ethernet.edu.et/bitstream/123456789/34642/1/Tai%20L.%20Chow.pdf

Validity of traditional model

I'm told that the concept of a body containing all mass, energy, and spacetime in the Universe would be compressed to an infinitely dense point is dead wrong, that it's misleading pop-science and doesn't reflect the views of professional cosmologists. Thoughts on this?Docsavage20 (talk) 01:55, 19 January 2018 (UTC)[reply]

If you have a reliable source on the subject, then it may well warrant inclusion in the article. But until then, it can't be included because it's original research. 96.28.39.103 (talk) 11:27, 27 March 2018 (UTC)[reply]

Grumble. There is some patently wrong stuff here that is included with no reliable references. Why is it that getting rid of it needs reliable references? Anyhow, here are a few, starting with one of the "bibles" on this topic: "We must therefore exclude this point from the space-time manifold, as no known physical laws could be valid here." (Hawking & Ellis, Cambridge U. Press 1973, p. 137). "From a mathematical point of view, S=0 describes a spacetime singularity. If we compute the components of [the Riemann tensor] and construct invariants out of these [...], these invariants diverge as S tends to 0. It is therefore meaningless to talk of a spacetime geometry at S=0." (Narlikar, Cambridge U. Press 1993, pp. 117-118.) "Because the density rises without limit as t->0, the mass within any sphere today (even the size of our present horizon) was once packed into an arbitrarily small volume. Nevertheless, this does not justify the 'primaeval atom' terminology unless the universe is closed. The mass of an open universe is infinite: however far back we run the clock, there is infinitely more mass outside a given volume than inside it." (Peacock, Cambridge U. Press 1999, p. 86.) In light of these, and similar statements in just about every decent introductory text on physical cosmology (though usually with little or no emphasis, as the student is supposed to know already from elementary calculus that when a function is singular at some value of the independent variable, that value is excluded from its domain) I strongly recommend revising the present article to reflect the actual science, not the pop-science version (I'm willing to consider doing it, but I do not wish to find myself engaged in a silly edit war.) vttoth (talk) 21:21, 21 February 2019 (UTC)[reply]

Second paragraph in alternative theories should probably be removed. Has no / improper citations, is poorly written, may or may not be sensible (probably isn't) — Preceding unsigned comment added by 68.175.134.62 (talk) 18:29, 4 April 2020 (UTC)[reply]

Traditional model

The section titled "traditional model" doesn't actually describe what the traditional model is... Could a physicist rectify this? Furius (talk) 20:17, 30 May 2023 (UTC)[reply]

Article is based on incorrect unreliable sources.

Multiple reliable sources on cosmology point out that the "singularity" is a mathematical artifact. For example see page 305:

Peacock, J. A. (1998-12-28). Cosmological Physics (1 ed.). Cambridge University Press. doi:10.1017/cbo9780511804533. ISBN 978-0-521-41072-4.

Johnjbarton (talk) 15:39, 4 April 2025 (UTC)[reply]

Scientific work on cosmological initial singularity

There are a number of scientific articles on this topic which are not covered

Borde, A., & Vilenkin, A. (1996). Singularities in inflationary cosmology: A Review. International Journal of Modern Physics D, 5(06), 813-824.
Guth, A. H. (2007). Eternal inflation and its implications. Journal of Physics A: Mathematical and Theoretical, 40(25), 6811.
Borde, A., Guth, A. H., & Vilenkin, A. (2003). Inflationary spacetimes are incomplete in past directions. Physical review letters, 90(15), 151301.

and I'm sure more. This aspect should be covered but it is challenging to find sources that can be summarized in an encyclopedia. Johnjbarton (talk) 16:54, 2 September 2025 (UTC)[reply]

The article should include a discussion of initial singularities by Hawking and Penrose and a discussion of the Borde–Guth–Vilenkin theorem.--ReyHahn (talk) 08:07, 3 September 2025 (UTC)[reply]

News reports

The news report part is not very encyclopedic and unnecessary. The first example is not even wrong, the only thing we know about the Big Bang is that it was a hot dense state, the singularity is what we are not sure about. ReyHahn (talk) 08:08, 3 September 2025 (UTC)[reply]

As a scientific model we don't agree with a source like

May, Andrew (January 10, 2022). "What Is the Big Bang Theory?". Space. Retrieved 2025-09-02.

which says

"Around 13.7 billion years ago, everything in the entire universe was condensed in an infinitesimally small singularity, a point of infinite denseness and heat."

but it is a point of view and I think a very common one. Readers may see omitting any mention of this as bias. I think this kind of use should be discussed even if it is done in a way completely different from my section on news reports. Johnjbarton (talk) 17:20, 3 September 2025 (UTC)[reply]

That can be discussed it is just unusual to have a "what news says" section. Also what is the issue really? "Condensed into a infinitesimally small singularity" makes no sense, but without quantum gravity there is a predicted singularity nevertheless.--ReyHahn (talk) 17:26, 3 September 2025 (UTC)[reply]

Matt Strassler, an established subject-matter expert, has a blog post

"Did The Universe Really Begin With a Singularity?". Of Particular Significance. March 21, 2014. Retrieved 2025-09-05.

which addresses this media issue, in the paragraph starting "Yet all over the media and all over the web, ... Johnjbarton (talk) 20:41, 5 September 2025 (UTC)[reply]

Intro sentence

We've tried several intro sentences. Now we have

The initial singularity or the Big Bang singularity is a simplified model for cosmogenesis, the origin of the universe, based on extrapolating classical general relativity into a region of large density and energy known as the Big Bang. Extrapolating further leads to a singularity.

but it reads wrong to me. We are extrapolating into an invalid region, one where the physical basis of the Big Bang model is not valid, a region of too large density and too high energy for the classical model to work. So in this sentence what is it that is "known as the Big Bang"? The extrapolation? no. The region? no. What? IDK.

"Big Bang" is widely taken in science articles to mean expansion from initially hot and dense universe. That is the initial condition is hot and dense, not singular. So the extrapolation is not possessed by the Big Bang model, but is an outside feature.

Here is another version

The initial singularity is a simplified model for cosmogenesis, the origin of the universe, based on extrapolating the Big Bang model of cosmology into a region of density and energy where it is known not to be valid. The Big Bang is based on classical general relativity and extrapolating it leads to a singularity.

Johnjbarton (talk) 19:25, 3 September 2025 (UTC)[reply]

There are two things here. Current state of affairs extrapolates in the past to a large dense state known as the Big Bang. That is solid science, extrapolating it further to a singularity (infinitely dense) is what is being discussed in this article. I will take your last version and tweak it again, please be free to edit it back until we agree to some sort of agreement.--ReyHahn (talk) 07:28, 4 September 2025 (UTC)[reply]

Your new version is great, thanks.

Done Johnjbarton (talk) 15:35, 4 September 2025 (UTC)[reply]