WATCH THIS SPACE

Nov 27
5 min read

While we were all distracted (with the internet and war or more recently social media and pandemics or the collapse of traditional media and the takeover of TikTok and ChatGPT and ladies on OnlyFans and fellows talking into a microphone in their bedroom earning more than leading actors and elite athletes) our understanding of the universe, most appropriately, seemingly sprung a whole bunch of leaks.

Starting roughly around 1998 our best model of cosmology, that branch of astrophysics concerning itself with the universe at its largest scales, has been something given the obscurifying acronym ΛCDM (lambda cold dark matter). But since the adoption of ΛCDM, particularly over the last decade, a slew of new tools and techniques arrived for your friendly neighbourhood physics nerds. They figured out how and finally built an observatory to detect gravitational waves, developed new ways to gather and process light and better map the universe, and you might recall the James Webb Space Telescope, Hubble’s predecessor, being completed, launched, reaching its final destination, and beaming back novel images. All that has really paid off.

Turns out each of those tricks and treats and those deploying and exploiting their outputs have been very busy — busy breaking everything we thought we knew about what the universe is composed of, how it should behave, and as a result its origins. That sounds like a lot. And it is. This couldn’t be a more exciting time.

From around 2010 cosmological observations started getting a little weird. More and more papers showed up describing observations with descriptions and titles like “A Giant Arch on the Sky”, “A giant ring-like structure”, and “New data support the existence of a Great Wall”. What they were seeing were clusters, rings, and unimaginably huge walls of galaxies and quasars spanning as much as 10 billion light-years, making these structures by far the largest conglomerations ever observed. (For scale, our solar system is roughly two light years across, our own Milky Way Galaxy is 100,000, and the whole of the cosmos perhaps 93 billion light years or so.) Obviously, a structure spanning 10% of the observable universe is quite the thing. None of that had been seen before and was not anticipated by any theories.

These observations and others (showing there are vast voids between ever-larger structures, like galaxy superclusters and web-like supercluster filaments) suggested a real problem with our current understanding. That’s because foundational to cosmology is the principle that the universe cannot be arbitrarily large and, at least at scale, zoomed out enough, it must be homogenous, effectively a uniform soup. Though there may be an intricate lattice or fractal-like structure at some level, like the knit of your shirt or sweater or the cells of your skin or a leaf, when observed in its entirety it will have this uniform, or isotropic, nature. Even if you haven’t done any math or physics you’ve probably noticed or been told there is inherent pattern and symmetry to be found. These simplifying symmetries, found in Einstein’s work for example, where there are no seriously exotic locations or directions, make the job of modelling the entire universe possible. As you can imagine, if the cosmos was deeply weird and chaotic no observation we could make would be meaningful or tell us anything about any other part of the universe…

So, those gargantuan structures, rings and walls, raised some eyebrows. Then in 2023, I began hearing of a new set of observations and problems and of cosmology in turmoil. Astrophysicists, as they do, were using their telescopes to attempt to measure the current expansion rate of all that we see out there, what is called the Hubble constant. Many calculations of the Hubble constant have arrived since the discovery of the universe’s expansion. Different observations have always, most annoyingly, yielded different results for what the constant could be. And discrepancies there were commonly believed to be due to the imprecision of the tools used; hence the building of much more powerful and precise instruments. Trouble is, in 2023, new values arrived for the Hubble constant using these remarkably accurate instruments only appeared to further clash with the predictions yielded by the standard model of cosmology, while simultaneously killing the comforting explanation of weak tools. Weirder still, two different techniques were used to perform separate measurements. Both arrived at significantly different results. The universe, it appeared, was giving very different answers to the same question. Most annoyingly, both results were tested and tested again and appeared to be correct while both being incompatible with one another and also violating the standard model we’ve used for generations to make our most accurate predictions. Yowza!

This wasn’t some new theory that failed confirmation through observation but the old theory, so very useful and seemingly robust for so long, appearing to fail confirmation using novel observations. As Dr Poulin-Détolle explained in a publication for France’s National Center for Scientific Research, “That’s very exciting because it could mean that our model of cosmology is incomplete and that we need to consider the possibility of new physics.” A review paper published on the matter (with dozens of authors) offered something just as explicit, “While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model.” So all of this was starting to look like a Galileo or Copernicus moment.

Then the James Webb Space Telescope started offering up its own observations. What it sent back was data on galaxies so bright, massive, and distant they had to have arisen extremely early in the formation of the universe, only 280 million years after the singularity. Other galaxies were similarly observed, and more still are yet to be formally confirmed. If accurate, these observations would, once again, put a crack in what we know about physics as our best estimates to date have predicted galaxy formation not at slightly different timelines but hundreds of millions of years later, around 500 million years. One review came back offering that “...the extremely high stellar mass of GS-z14 remains an outlier when compared to previous measurements of high-redshift galaxies detected by JWST and our numerical models (even after accounting for cosmic variance).” Another problem for these earlier-than-expected galaxies is that researchers showed they contain heavy elements like nitrogen and oxygen. That’s a real problem as the standard model tells us the early universe contained only hydrogen and helium, as heavier elements require the cores of existing stars to be forged, and then those stars need to explode in old age to release those heavier elements. So it seems there had to have been generations of existing stars prior to these too-early galaxies. Only, our current physics doesn’t allow for even a single generation of low-mass stars to have aged enough to produce things like nitrogen in a galaxy just 300 million years old. Wow!

So, watch this space.