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I teach high school physics and physical science. I was going through the definitions of theory and law when a couple of my students (of different periods) asked about some recent development that suggests the universe isn't 13.8 billion years old. One student was saying 32 billion, but he wasn't confident in that figure but completely disagreed with 13.8 billion years.

Has there been any recent or semi-recent developments on the age of the universe? OR is there an uptick in misinformation about the Big Bang, akin to the Flat Earth movement or antivax? I'm wondering if there's some tiktok thing going around that's confusing the kids. My initial Googling has not suggested any issues.

Another possibility I can think of is that they are confusing age of the universe with some of the other issues with the Big Bang Theory like Baryon Asymmetry, Dark Energy/Matter, and the flatness of the universe.

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    $\begingroup$ Incidentally, 13.8+32=45.8 and the comoving distance to the edge of the observable universe is 46.6 billion light-years. $\endgroup$
    – PM 2Ring
    Commented Aug 26, 2023 at 8:04
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    $\begingroup$ It's not a "Tiktok thing" (lol) but 2023 You-Tube videos they are referencing...videos about the new space telescope JTWS & discrepancies about the dating of the universe supposedly found. $\endgroup$ Commented Aug 26, 2023 at 9:13
  • $\begingroup$ The question, as it currently stands, does not correspond to some of the answers and comments on it. PSE is an English language site, and, in English, place names are capitalized. When "universe" is not capitalized, it means "everything", and the only model I know of that may correspond to the JWST data on that basis is Penrose's "Conformal Cyclic Cosmology", which provides for a possibly past- and future-infinite number of iterations. Inflationary models of, say, multiple "bubble universes" (each of which would be considered to be "the Universe" by its inhabitants) require a multiverse. $\endgroup$
    – Edouard
    Commented Aug 27, 2023 at 19:26
  • $\begingroup$ The bubble universes of Guth's inflationary model, for instance, would be causally separated from each other EXCEPT during the "bubble collisions" that he has felt to be a possibility. I think these pedantic-sounding details are serious enough to require an edit by the question's OP, not by myself, as the OP might be able to question his students as to their awareness of these considerations, which might vary with their independent reading. $\endgroup$
    – Edouard
    Commented Aug 27, 2023 at 19:38

2 Answers 2

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The consensus view among cosmologists is that the age of the Universe is approximately 13.8 billion years old. This has not changed.

There was a recent paper claiming the Universe is approximately 26.7 billion years old, but there are good reasons to be skeptical. For example, the model proposes a "tired light" model where photons intrinsically lose energy as they travel, in addition to the redshift they experience from the Universe's expansion. While this fits some data such as supernova light curves, it does not fit all data, such as thermal fluctuations in the CMB. Suffice to say, the alternative "tired light" model used in this paper is not widely accepted.

An interesting modern controversy about the Hubble constant (related to the age of the Universe) that you may want to teach is the so-called Hubble tension, in which two different methods to measure the Hubble constant give different values, which are more than 5 sigma way from each other (meaning the chance that statistical uncertainties in the observations would be large enough to explain the difference is less than one in 3.5 million -- or in other words, there's a very good chance that something is wrong with the assumptions being made). One method is to use the distance ladder to measure distances to Type 1a supernova and use the luminosity distance to measure the "local expansion," and gets an answer of around $73 \pm 1 {\rm km\ s^{-1}\ Mpc^{-1}}$. The other method is to infer the Hubble constant by measuring cosmological parameters in the early Universe using the CMB and evolving those forward using the standard cosmological model, and gets an answer of around $67.5 \pm 0.5 {\rm km\ s^{-1}\ Mpc^{-1}}$. This tension has gotten worse over the past several years as the error bars have shrunk and the mean values have drifted away from each other, and explaining why these two methods disagree is now a major open problem in cosmology. It is unclear whether the final explanation will involve an error in one or both methods, or some new physics that needs to be added to the standard cosmological model. However, this controversy would change the age of the Universe by a few percent, not a factor of 2.

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    $\begingroup$ Gupta's paper starts with a metric whose "most significant difference from the standard FLRW metric is that the $g_{00}$ metric coefficient is time dependent (Gomide & Oehara 1981)." This is physically meaningless: you can substitute $\frac{dt}{du} du$ for $dt$ and get any $g_{00}$ coefficient you want. He's using some kind of modified gravity, but Gomide & Uehara made the same mistake without that excuse. At the least, this suggests the paper wasn't adequately reviewed. Also "Uehara" is misspelled... $\endgroup$
    – benrg
    Commented Aug 26, 2023 at 5:41
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    $\begingroup$ I don't think they have considered how their model fits supernova light curves. All they have done is fitted the published redshift vs peak magnitude relationship for supernovae. Tired light would not explain why the light curves of higher redshift supernovae are dilated/extended by a factor $(1+z)$ and I see no discussion of this in the paper. $\endgroup$
    – ProfRob
    Commented Aug 26, 2023 at 10:43
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I suspect your student's $32$ billion year value comes from the estimated proper distance to GN-z$11$, which was discovered in $2015$, with details about it published in a $2016$ paper. In particular, the last sentence of the first paragraph in that Wikipedia article states

Up until the discovery of JADES-GS-z$13$-$0$ in $2022$ by the James Webb Space Telescope, GN-z$11$ was the oldest and most distant known galaxy yet identified in the observable universe, having a spectroscopic redshift of z = $10.957$, which corresponds to a proper distance of approximately $32$ billion light-years ($9.8$ billion parsecs).

Since a light-year is generally defined as the distance that light travels in a vacuum in a year, that would appear to, at first glance, imply the light from GN-z$11$ has been travelling for about $32$ billion years and, thus, the universe must be at least that old. However, regarding the discrepancy of this distance compared to the currently generally believed age of the universe, the next paragraph states

... It is observed as it existed $13.4$ billion years ago, just $400$ million years after the Big Bang; as a result, its distance is sometimes inappropriately reported as $13.4$ billion light-years, its light-travel distance measurement.

Also, as explained in the Comoving and proper distances Wikipedia article, the main cause of the apparent discrepancy is due to the expansion of the universe, which means the distance between the starting point and its current position is actually considerably more than what would normally be expected based on the speed of the light relative to the local region of space it's in at any particular time (thus, for GN-z$11$, this means the universe expansion has caused an about $32-13.4=18.6$ billion light-years increase in distance between where GN-z$11$ was $13.4$ billion years ago and our current position). As well, the article gives the definition

... Proper distance roughly corresponds to where a distant object would be at a specific moment of cosmological time, which can change over time due to the expansion of the universe. ...

Note that there are multiple posts on this site regarding the definition and use of various distance measures in cosmology, such as the proper distance, e.g., there's The difference between comoving and proper distances in defining the observable universe, Difference between physical, proper, and co-moving distances, Proper distance in cosmology, etc.

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    $\begingroup$ It's not clear from the second quote why the first quote doesn't mean the universe is at least 33 million years old. Could you clarify? $\endgroup$ Commented Aug 26, 2023 at 7:43
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    $\begingroup$ @MikaylaEckelCifrese Unfortunately, my knowledge about these issues in cosmology, such as this one, is very limited. Nonetheless, I added some more details, in particular that the expansions of the universe is the main reason for the difference, as well as links to $3$ posts on this site which deal with that issue. I hope that reading what I added, as well as checking at least some of those other references, will appropriately answer your question. $\endgroup$ Commented Aug 26, 2023 at 7:58
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    $\begingroup$ @Mikayla The universe is certainly much older than that! Did you mean 33 billion? Note that we receive CMBR from the last scattering surface which is currently ~45.7 Gly distant. But that distance is magnified by ~1100 due to expansion. So the original separation distance was only ~41.5 Mly, back when the age of the universe was ~379 thousand years. $\endgroup$
    – PM 2Ring
    Commented Aug 26, 2023 at 8:47

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