Tired of tired light

Challenges to the age of the universe play into a sinister narrative about science

I was in Canada over the weekend, traveling through Toronto, Ottawa, and Niagara Falls visiting family. While I was near the University of Ottawa, I saw that Joe Rogan had shared an article on a paper that claimed the universe was 26.7 billion years old, not the 13.8 billion that we have been told.

This created a lot of drama in the twittersphere as astrophysicists fought to control the narrative against the likes of Rogan and Elon Musk. The paper, published in the Monthly Notices of the Royal Astronomical Society by an adjunct professor, Raj Gupta, at the University of Ottawa, used a theory that combined the expansion of the universe with the tired light theory to try to account for the early formation of galaxies that we are seeing in the images from the JWST.

Quite a few journals would have (and perhaps did) reject this paper on the grounds that the tired light theory has been debunked. Combining it with an expanding universe model helps a bit but not too much.

The age of the universe comes from studying the Cosmic Microwave Background in minute detail. Since this is the earliest light we can see, it has been redshifted by the maximum amount. (See my previous newsletter for an explanation of redshift.) Both observations and models say that redshift is linearly correlated with time and so by precisely measuring redshift, we can determine how old the CMB is. Models let us work backwards from there to the time when the universe began: the Big Bang.

This means that, technically, we only know how old the CMB is, and we can determine how old many objects are that came after the CMB such as the oldest stars and galaxies. We cannot see back to the start of the universe, so at that point our models take over to complete the picture.

The primary model we use, the Lambda-CDM model, combines dark energy as a cosmological constant, Lambda, and “cold” (meaning made of massive particles, not radiation) dark matter with Einstein’s theory of general relativity. Two more assumptions complete it: one is based on the Copernican principle that we do not have a special place in the universe so the universe should be the same in every direction, the isotropic assumption, and the other is based on the distribution of matter, which we believe is the same everywhere, the homogeneous assumption.

This model has excellent agreement with observations and so it makes sense to use it to work back to determine the age of the universe. In truth, however, we only know when the observable universe started expanding in the way it does now. We believe this happened at the end of a period called inflation, and at that time the observable universe would have been some finite size anywhere between a grain of sand to a couple football fields. The universe as a whole, beyond what is observable, is assumed to be infinite so doesn’t have a meaningful definition of size.

This model accounts for most of what we see in the universe.

A tired light model suggests that redshift, on the other hand, comes from light hitting stuff on the way to us. So, rather than simply stretching out because of general relativity, which happens when a fixed amount of light energy lives in an expanding spacetime, it is actually losing energy to other matter and fields in the universe.

Tired light theories have three big problems with them:

• They do not explain what we see in the CMB. The CMB has a particular temperature curve called a “blackbody” curve. In fact, it is the most perfect blackbody radiation curve ever observed. When we observe this curve, we see that the CMB matches theory exactly. This is a consequence of a fixed amount of light energy in the universe losing density as the universe expands. In other words, if you put a very hot blackbody, which is just something that emits thermal radiation and is non-reflective (meaning it is black), in a space time that is expanding, the blackbody curves approaches that of a cooler blackbody. If, on the other hand, you put a blackbody in a universe that is not expanding and just siphon off energy from the radiation, causing redshift, then you don’t get a cooler blackbody curve, you get a warped blackbody curve. The tired light theory would predict that the CMB’s blackbody curve should be shifted to account for the light transferring energy to something else in the universe. We do not see that.

• They cannot explain why we are able to resolve distant objects so well. If you send a beam of light and it interacts with matter along the way, you would see some kind of blurring or warping of the light. Even the most transparent medium will blur objects seen through it. The tired light theory is effectively saying that light is passing through a kind of medium and so should make things look blurry. Since we can see galaxies to billions of light years, it is unlikely there is any medium in between.

• Einstein’s general relativity tells us that in an expanding universe, the further away an event is, the slower it will appear to happen. That doesn’t mean it is actually happening slower. It is consequence of the expansion of the universe. We observe this time dilation of type 1a supernovae (they literally happen in slow motion). Type 1a supernovae are a kind of supernova that has a standard brightness. We use them to determine how far away things are without using redshift, and they are really important for measuring the Hubble constant, the speed at which the universe is expanding. Tired light would not account for the time dilation.

If you ignore the fact that tired light has other problems, you could argue that the universe is far older than it is because objects are not expanding away as fast as they appear. This means the Hubble constant is much smaller than we think it is. Working backwards, we then get a much older universe that is expanding more slowly.

Why bother with all this?

The main issue is that the JWST has seen galaxies similar in mass to the Milky Way: full of older, red stars, and formed only 500-700 million years after the Big Bang.

As an aside, the oldest object seen so far with a confirmed redshift value of 13.2 is called JADES-GS-Z13-0. It is 33.6 billion light years away. We looking at it only 320 million years after the Big Bang. It has been suggested, but not confirmed that this might be a “dark star” rather than a galaxy, meaning a supermassive star, 1 million times the mass and 10,000 times the diameter of the Sun, formed out of dark matter.

That is certainly worth studying but it isn’t the most shocking one.

We expect to see baby galaxies so early in the universe small with lots of blue stars, not massive galaxies with red stars.

Using images of these ancient galaxies, we can measure both how far away the galaxies are and how heavy and old the stars in them are. A paper studied several such galaxies and found that they have the same mass of the Milky Way, but they are compact blobs with all the stars jammed together. This means that they are 100 times smaller than the Milky Way but have a similar star formation rate.

In other words, they are freaks.

Our models of galaxy formation can’t account for them forming stars that quickly.

In essence, the Gupta paper proposes a new model for the universe as a whole, but this seems premature, especially given (a) that the JWST is finding other galaxies that break or at least challenge our models of galaxy formation that his model wouldn’t address at all and (b) these galaxies are still freaks.

A recent paper out of my alma mater UTexas, for example, found that there are galaxies that have way too many stars in them for their mass. The current theory for how galaxies form is that dark matter forms a halo which mixes up with baryonic matter like hydrogen. Some of the baryons form stars while the rest remains as gas. The big problem with these galaxies is that it looks like all the baryonic matter turned into stars and that doesn’t make a lot of sense. Surely some of it would remain as gases.

What to make of this?

While people will always propose alternatives and modifications to the Lambda-CDM theory, it is premature to throw it out, given the decades of observations that agree with it, merely because we cannot explain some preliminary results from JWST. The data could be imprecise or inaccurate.

Note that some of our data is only from images and galaxies have, after a spectrographic analysis, been found to be much closer, and therefore later in the universe’s history than at first believed. One galaxy, for example, had its redshift first reported to be 16.4 which put put it at 280 million years after the Big Bang, but later it was revised to 4.9, which means it was more than 1 billion years after.

Besides needing more data, there is a lot we don’t know about the early universe. Maybe things just worked very differently then and we need better theories of galaxy formation.

While it is natural for scientists to challenge existing theories, this has to happen against the backdrop of the existing data. This is just speculation on my part but I feel that the news articles on this paper were shared on social media partly to play into the narrative that scientific consensus is a fiction. It is being used as an example for why warnings over global warming and climate change as well as vaccines and any other recommendation should be treated with contempt. It suggests that, if scientists can simply change their minds about what is true one day, then we don’t have to listen to them.

That is a fundamental misunderstanding of how science works which is that consensus forms because of the preponderance of data such that, anyone who understand how to interpret it, would come to that conclusion. Challenges to central conclusions based on that data tend to fail as this paper will ultimately fail to change any cosmologist’s beliefs about the age of the universe. That there is a forum for such papers to be published, nevertheless, is an indication that science is healthy and that no idea is dismissed out of hand. That is how it should be.

We should be wary of any claims to overthrow decades of research. Even Einstein had to bow to Newton in that he had to show under what circumstances his theory agreed with Newton’s. Likewise, any new theory has to bow to the old.

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Labbé, Ivo, et al. "A population of red candidate massive galaxies~ 600 Myr after the Big Bang." Nature 616.7956 (2023): 266-269.

Boylan-Kolchin, Michael. "Stress testing Λ CDM with high-redshift galaxy candidates." Nature Astronomy (2023): 1-5.