Why science?
It’s hard to remember a single moment that turned me on to science, but like a lot of small children, I was fascinated by dinosaurs and tried to drag my parents up to the Natural History Museum as often as I could. Aged about six, I wanted to be a palaeontologist, which was probably the longest word I knew at the time. Another moment came at secondary school when we started to learn about atoms and how the orbits of electrons explained the properties of the chemical elements. I found that idea, that all these radically different materials emerged from rearrangements of tiny constituents, electrifying. That’s still what excites me about physics today – that you can explain all the richness of the world around us in terms of a tiny number of basic building blocks interacting through a small number of forces, all following remarkably simple laws.
There’s another aspect too – science is a source of optimism. Science progresses, our knowledge deepens, our understanding grows, as does the frontier of our ignorance. Not only that, but scientific understanding allows us to achieve things we never could have imagined without it. It’s the most powerful tool humans have for understanding and controlling the world around us. At a time when it feels like we’re going backwards in a lot of ways, the fact that science continues to advance is a source of hope.
Why are anomalies important to science?
Isaac Asimov, the American science fiction author, once wrote that ‘the most exciting phrase to hear in science isn’t “Eureka!” (I found it!) but “that’s funny...”’. We tend to have this romantic idea that breakthroughs in science come from flashes of inspiration, like the myth of Newton seeing an apple fall from a tree and inventing his law of gravitation or Archimedes jumping out of the bath, but many of the biggest advances have come from small niggling effects in experiments, that could have all too easily have been dismissed.
A great example of this is the evidence that finally clinched the Big Bang as the correct theory of the universe. In 1963-64 two radio astronomers, Arno Penzias and Robert Wilson, were plagued by a low-level microwave noise in the antenna that they were trying to use to make astronomical observations. After eliminating a catalogue of possible causes, including famously evicting two pigeons that had taken up roost in their instrument and cleaning up ‘the white dielectric material’ that they left behind, they eventually discovered that the noise that was spoiling their measurements was in fact the faded light from the fireball of the Big Bang. It was their dogged pursuit of this irritating microwave buzz that led to what was arguably the most profound realisation in the history of science – that the universe had a beginning.
Stories like this crop up again and again through the history of physics. Our modern theory of particles and forces was founded on the basis of an anomaly in the spectrum of hydrogen. The first evidence for Einstein’s general theory of relativity came from a minute anomaly in the orbit of Mercury around the Sun. Of course, more often than not, anomalies have a mundane explanation, but occasionally they give us the key to a new view of nature. That’s what makes them so fascinating and exciting.
Which current anomaly has the most potential to create a paradigm shift?
Of the five big anomalies I discuss in Space Oddities, I find the disagreement over how fast the universe is expanding the most compelling. This anomaly is known as the ‘Hubble tension’ in cosmology, and essentially boils down to the fact that when astronomers measure the expansion rate of space by observing distant galaxies, they get a significantly different result to what is predicted. These predictions are based on the measured properties of the early universe deduced from the cosmic microwave background, the faded light from the fireball of the Big Bang, projected forward to the present day using the standard cosmological model.
The fact that this anomaly has persisted for over a decade comes from multiple different measurements, and is, statically speaking at least, very significant makes it challenging to explain as a missed bias in either the measurements or the prediction. That said, there is still a healthy debate between different teams over the crucial issue of how you measure distances to galaxies, and just a month or so ago a new study using the James Webb Space Telescope came out that cast some doubt on the anomaly. But if I was forced to put my money on an anomaly panning out, it’d be that one.
If the Hubble tension is the real deal, then it’s potentially telling us several things about the universe at once, perhaps that dark energy varies with time, that dark matter has its own set of forces or even that our theory of gravity needs revision. Any of these would have an enormous impact on the way we think about the universe and its history.
The description of the LHCb anomalies and how they turned out to be due to incorrectly filtering out misleading signals is fascinating - but it makes you think, can we know for certain that any modern particle physics result is not due to a failure to rule out misleading signals?
I’d turn this around and say that way the mistake was discovered and corrected is actually a reason why we can trust particle physics results. It shows that science is a self-correcting process. That when mistakes are made, they are invariably found out one way or another and then fixed.
We went through this rollercoaster on LHCb were for a long while we were seeing evidence that beauty quarks were decaying in ways that cannot be explained by the standard model of particle physics. The implications were huge, as if confirmed the results would have implied the existence of a new fundamental force. Several different results seemed to confirm this until, to our horror, we gradually realised that there was a background process that was biasing the results. However, to the credit of my colleagues, they didn’t hide the mistake and worked incredibly hard to put out a corrected result that the community could have confidence in.
However, let’s imagine that we hadn’t found the mistake, or that we’d been unscrupulous so-and-sos and hidden it. Well, rightly, the community would never have fully believed that a new force had been discovered until other experiments had verified it, and when that happened the truth would have outed anyway. That’s why there are two big general-purpose detectors at the Large Hadron Collider – they exist to cross-check each other. One of the crucial facts that convinced the world that the Higgs boson really was discovered in 2012 was that two independent experiments saw the same particle at the same energy.
Ultimately, any discovery needs verification. And even when mistakes are made, you always learn from them, whether that’s how to perform certain kinds of experiments or the correct way to carry out theoretical calculations. My undergraduate physics tutor used to have a card above his desk that read, ‘I’ve learned so much from my mistakes, I think I’ll make another’.
Is there still a chance for the LHC to produce results that change the standard model, or have its limits been reached?
There’s definitely a very good chance that the LHC will still find something from beyond the standard model. By 2029, the collider will have gotten a major upgrade to dramatically increase the rate it collides protons, meaning that the rate we accumulate data will increase enormously. This will make it possible to eke out ever rarer or more subtle signals that could have been missed so far. What’s more, physicists are constantly coming up with new ways to look at the existing data to spy signals that might be hiding in the data.
However, even in the absence of new physics, by the time the LHC switches off some time in the early 2040s it will have left an enormous legacy in terms of understanding the standard model itself. There are still many phenomena predicted by our current theory that we don’t fully understand. For instance, we don’t actually know whether the Higgs boson discovered in 2012 is really the bog-standard model Higgs or perhaps something more exotic. The LHC will continue to put the Higgs under the microscope over the next decade and a half giving us a much clearer picture of this all important particle. At the same time, we’re constantly learning more about the properties of the known particles and discovering new phenomena associated with the strong force, like tetraquarks and pentaquarks, or probing the super-heated liquid known as ‘quark-gluon plasma’ that filled the very early universe. The LHC still has a lot to teach us.
Interview by Brian Clegg - See all of Brian's online articles or subscribe to a digest free here
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