Has the age of the universe changed in 2023?

Question

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.

Answer 1

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.

Answer 2

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.