Earlier this summer, an article by Eric Lerner put the dominant theory about the origin of the universe into question. On October 1st, at the HowTheLightGetsIn festival in London, Lerner took part in a live debate on “Cosmology and the Big Bust”, alongside theoretical physicist Julian Barbour and astrophysicist Claudia Maraston. Their exchanges shed light on the cracks of the theory concerning inflation, dark matter, and dark energy, as well as on the nature of scientific revolutions, and ultimately on why the Big Bang theory isn’t going anywhere any time soon.
In the beginning, there was chaos. At least that’s according to Hesiod’s Theogony, a poem about the creation of the cosmos thought to be articulated around the 8th century BC. Stories about the origin of the universe probably go further back than even that, but it’s safe to say that for at least three millennia humans have been positing hypotheses about how the world we see around us today came into existence. The Big Bang is the latest of these hypotheses, and while most physicists will be quick to protest that there is a huge difference between ancient myth and scientific theory, not everyone agrees.
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There are those, like Sabine Hossenfelder, who think that physics will probably never be able to tell us how the universe came about and argue that we should think of the Big Bang theory as little more than another creation myth. And then there is Eric Lerner. The author of a recent article “The Big Bang Didn’t Happen” that went viral, Lerner articulated a challenge to the current scientific consensus in cosmology that caused quite a stir. On October 1st, at the HowTheLightGetsIn festival in London, Lerner took part in a debate with theoretical physicist Julian Barbour and astrophysicist Claudia Maraston, putting some challenges to the Big Bang theory to the test, in front of a live audience. Despite the explosiveness of the topic, the debate was civil, even if heated.
In Karl Popper’s terms, Lerner thinks the Big Bang theory has been falsified – it has made predictions, and observation has contradicted them – therefore, the theory needs to be rejected.
For Lerner, science is all about predictions, and according to him, the Big Bang theory has systematically failed to make accurate predictions. Instead, it has required constant adjustment and the postulating of auxiliary hypotheses like inflation – the theorised extremely rapid expansion of the universe in its very early moments – and mysterious (and yet unobserved) entities like dark matter and dark energy, in order to help the theory fit the increasingly recalcitrant observations. In Karl Popper’s terms, Lerner thinks the Big Bang theory has been falsified – it has made predictions, and observation has contradicted them – therefore, the theory needs to be rejected. The latest piece of evidence that Lerner believed contradicts the Big Bang Theory comes from the hauntingly beautiful images of the James Webb Telescope. What these images seem to show is that the most distant galaxies that we have now been able to witness are a lot smaller than we would expect to see under the Big Bang framework.
Maraston added that as an astrophysicist who studies the light spectrum of distant galaxies, she believes some data from the James Webb Telescope are not robust and were published prematurely.
Claudia Maraston, a professor of Astrophysics at the University of Portsmouth, defended the Big Bang theory by laying out the key observations that she sees as supporting it. First, there is the phenomenon of cosmic microwave background radiation, known as CMB. This is the weak electromagnetic radiation which seems to be observed, in whichever direction we look in the sky. Cosmologists have taken this to be a remnant of the actual Big Bang event, a fossil if you like of the creation of the universe. Second, Maraston argued, the Big Bang is very good at predicting the abundance of primordial elements in the universe, in particular Helium, which we find in the oldest stars. Finally, the Big Bang theory seems to be the best explanation for what Hubble first observed – that the light from distant galaxies is shifted towards the red end of the spectrum. This redshift has been interpreted to be caused by the Doppler effect – what happens to electromagnetic waves when the objects emitting them are moving away from us – and in turn that has been interpreted as evidence that the universe is expanding.
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Maraston added that as an astrophysicist who studies the light spectrum of distant galaxies, she believes the data from the James Webb Telescope suggesting that the most distant observed galaxies are not the size or age that we would expect them to be, under the Big Bang theory, are not robust and were published prematurely.
Barbour famously declared that he thought the idea of an expanding universe “stinks!”
Julian Barbour, best known for his idiosyncratic views on time, declared to be more on the side of Maraston than Lerner when it came to the Big Bang, but with one big caveat: Barbour doesn’t buy the idea that the universe is expanding. In fact, in an exchange with the astronomer Royal, Martin Rees, Barbour famously declared that he thought the idea of an expanding universe “stinks!” Martin Rees, by Barbour’s own telling, wasn’t impressed. The main reason for Barbour’s reluctance to accept the idea of an expanding universe is conceptual. Size is always relative: we can only tell whether an object is big or small, or in fact expanding, by reference to the fixed size of another object. But when it comes to the entire universe, there is no fixed object outside it we can compare it to, so the very idea of an expanding universe doesn’t seem to make sense. Instead, Barbour suggested, we should think of the universe as changing shape – that we would be able to detect as observers within the universe. Even if Barbour didn’t want to align himself with Lerner, it sounded like his view of a shape-changing universe is closer to Lerner’s suggestion that the universe is evolving, not expanding. Indeed, Barbour has recently put forward the idea that the universe is acquiring complexity and order with time. That sounds rather close to evolution.
“Everyone would be keen to abandon the theory if there’s a better alternative, nobody’s married to the Big Bang theory.”
Lerner returned to his original, but powerful point: a scientific theory is supposed to make predictions about observations we haven’t made yet, and if those predictions turn out to be wrong, then so much worse for the theory. Going back to the James Webb Telescope images, Lerner argued that the small size of the most distant galaxies the telescope was able to observe is one of those observations that should be enough to refute a central claim of the Big Bang Theory: that the universe is expanding. If the redshift effect we observe in distant galaxies was indeed due to the fact that those galaxies were rapidly receding from us, then, because of the redshift effect after a certain threshold, those distant galaxies would start to appear larger, rather than smaller, to the ones closer to us.
HowTheLightGetsIn, London 2022
Maraston didn’t seem to be moved by this – for her, data can always be put into question. Data can be wrong, or as she put it “model-dependent”, meaning they are already interpreted through the lens of a certain model and therefore can be interpreted differently. In particular, when it comes to the James Webb Telescope images, she argued that measuring the size of galaxies is fiendishly difficult, especially for ones that are so far away “what we are seeing might just be the tip of the iceberg” she said. But perhaps most importantly Maraston argued that, sure, there may be some observational anomalies here and there, and inflation is indeed postulated wihout there being independent evidence of it, but until there is a better alternative, scientists are going to stick to the Big Bang theory. “Everyone would be keen to abandon the theory if there’s a better alternative, nobody’s married to the Big Bang theory.”
Lerner’s complaint that cosmologists are constantly adjusting their theory to meet recalcitrant data isn’t that impactful, that’s what scientists often have done throughout history.
This dispute reminded me of the Karl Popper – Thomas Kuhn disagreement in the philosophy of science. Lerner seems to be playing the role of Popper here, who thought that scientific theories make clear predictions, and once those predictions are shown to be in conflict with observation, the theory needs to be rejected – it has been falsified. Kuhn, however, had an appreciation of the somewhat more complex nature of scientific practice and progress. Kuhn argued that most of the time, when scientists are working within a received paradigm, observations that can seem recalcitrant are explained away in various ways. Sometimes the data itself is questioned, sometimes the auxiliary hypotheses that are needed to make predictions are replaced with others (Popper also acknowledged this), and sometimes new entities or phenomena are postulated to make the theory fit the data. In other words, looking back at the history of science, observation by itself almost never “falsified” a scientific theory, and it certainly didn’t lead scientists to reject it. The process of scientific revolutions, of moving from one scientific theory to the next, is a lot more complicated. So according to this approach, Lerner’s complaint that cosmologists are constantly adjusting their theory to meet recalcitrant data isn’t that impactful, that’s what scientists often have done throughout history.
Kuhn however was also keenly aware that these “excuses” that scientists make for their pet theory, the dominant paradigm of each era, can go too far. The best example of this is the attempt of the ancient astronomer Ptolemy to hold on to the Aristotelian model of the solar system that had Earth at its centre and the rest of the planets, as well as the Sun, revolving around it, despite the data. Even as a number of observations were piling up that were in conflict with the Aristotelian model’s predictions, astronomers didn’t reject it. Instead, they started adjusting it, the most egregious of those adjustments being the postulated epicycles, movements the planets were supposed to be undergoing that would explain why sometimes they appeared to be moving backwards, rather than forwards, in the night sky. What eventually led to the shift to the Copernican model was not new observations, but a collective disillusionment with Ptolemy’s model and the promise that the new theory could overcome some of its problems.
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When I listen to Lerner’s complaints about cosmologists postulating the existence of dark matter, dark energy, and inflation, with little to no independent empirical evidence, just because they make the Big Bang theory cohere with observation, I hear echoes of Ptolemy postulating epicycles to save the geocentric model. But it’s hard to tell from our current vantage point whether that’s just part of the normal working of science or evidence that the Big Bang paradigm has run its course and that a new paradigm is around the corner.
The Big Bang theory was itself the result of a scientific revolution, overthrowing the previous paradigm of the Steady State model, which claimed that the universe had no beginning, will have no end, and that matter was continuously created, forming new stars and galaxies. Perhaps what Lerner is pointing to is the beginning of the end of that Big Bang revolution. Either way, Kuhn was right about the fact that it takes a lot more than pointing to recalcitrant data for scientists to reject a dominant theory: a new, more promising alternative has to be available, and that is yet to be found.
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