by Harry Cliff
Even so, we are still talking huge sums of money at a time when the world is facing an unprecedented economic and health crisis. Making the case to spend billions on what might be regarded as a big toy for physicists could easily come across as arrogant or at the very least extraordinarily tone-deaf. Indeed, there is ample warning from history about the perils of such megaprojects. Under the desert near Fort Worth, Texas, are more than 20 kilometers of abandoned tunnels, dug for the Superconducting Super Collider, a 90-kilometer machine that would have reached three times the energy of the LHC. Driven partly by concerns over its ballooning budget, the U.S. Congress canceled the project in 1993 after more than $2 billion had already been spent, a blow from which American high-energy physics has never really recovered.
I haven’t gotten into the whole “why particle physics is good for you” argument so far, because that’s not the story I’m telling. However, if there is to be another generation of colliders, physicists now need to fully engage with making the wider case to the general public, beyond the excitement of finding out more about the world we live in. A persuasive argument can be made. First of all, these large high-tech projects invariably generate spin-off technologies that find broad applications, perhaps the best example of which is the World Wide Web, developed by Tim Berners-Lee at CERN as a way to share information between physicists and then given away to the world for nothing. The Web alone has paid for CERN many, many times over. Likewise, superconducting magnets developed for accelerators have found their way into hospitals in the form of MRI machines. Another argument is the inspiration provided by projects like the LHC, with a majority of physics students citing the excitement of particle physics and astronomy as the reasons they went into the subject, most of whom will eventually end up applying their skills in other areas of the economy. And finally, we shouldn’t ignore the possibility of one day making use of the fundamental knowledge itself. When J. J. Thomson discovered the electron in 1897, it was regarded as a mere scientist’s plaything, and yet today almost all our technology relies on a deep understanding of electrons. Such applications often come long after the fundamental knowledge and are inherently unpredictable, but when they do come, they can be transformative. As ATLAS physicist Jon Butterworth mused, who’s to say we won’t one day be able to fly across the universe on an interstellar Higgs drive?
That said, just from a scientific perspective it’s more than reasonable to ask whether two giant colliders are a good use of €26 billion. Could that money be better spent on other, smaller projects? Maybe, but this kind of assumes that if we weren’t going to spend €26 billion on colliders, we’d get to spend it on other areas of fundamental research. Unfortunately, that isn’t really how the world works. CERN has been uniquely successful in persuading governments to commit resources to fundamental research for decades now, partly thanks to its many successes but also because of the international prestige that comes from being part of a world-leading scientific organization. The idea that if CERN shut up shop its budget would get redistributed to other areas of research is seriously naïve. In the end it really comes down to whether you think trying to answer these big questions is worth the price tag when balanced against the other potential benefits.
A scientific argument that’s been made against these machines is that there is no reason to expect them to find any new particles. The people behind the LHC promised that we’d discover supersymmetry and dark matter, and yet, so far at least, they haven’t delivered. Or so the argument goes. When I put this to Nima, I could sense his blood rising; I could only imagine the reactions of his fellow passengers on the train bound for New York as he grew increasingly animated.
“That, I think, is an especially dumb argument. It comes from people who got into particle physics because they wanted to see some new bumps in a plot and go to Stockholm or something. And that’s what they thought particle physics was about. And they say, look, it’s even built into the name of the goddam subject! This is just the honest truth. For me that was not the attraction of the subject at all, it made it feel a bit like chemistry, and I sucked very badly at chemistry. And you know, all these particles, all these funny names, were actually a barrier to me that I had to overcome. But of course, what got me into it is you get this most amazing view of the deep workings of the laws of nature. That’s what it’s really about!
“There’s this cognitive dissonance,” he continued. “People like me will go around saying this is the most amazing period in physics for a hundred years and then there are other people going, ‘Oh my god, it’s so depressing, we’ve only seen the Higgs and nothing else.’ And it can be confusing to hear these two different things. Like, am I on drugs? Or are they on drugs? My attitude is that this is a great time, we know that there’s some ninety-degree turn in the trajectory of the subject. I think it’s a ninety-degree turn into the most profound place we’ve been in a hundred years; other people might think it’s a ninety-degree turn into darkness and death. And the people who think that should do something else with their lives.”
Decades from now, if a future collider discovered supersymmetry or perhaps found that the Higgs is really made of smaller things, the long march of reductionism would go on. Once again, we would have understood more about the world by looking deeper. However, bizarrely perhaps, the most exciting outcome of all would be if these giant machines found nothing at all. No supersymmetry, no extra dimensions, just the plain old fundamental Higgs boson. Reductionism would have failed, forcing a radical rethink of our entire approach to understanding the world we live in. You might wonder, why not just ask a theorist to assume that we find nothing new and then figure out how to deal with that? The problem is, you can’t start a revolution without knowing for damn sure that the old regime needs overthrowing. Or as Nima put it as he jumped into a cab at Penn Station, “You need experiment to turn your entire fucking world upside down.”
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Over an unusually hot, sunny weekend as the summer of 2019 gave way to autumn, CERN threw open its doors to the general public. In just two days, more than 75,000 people thronged to see the giant experiments of the Large Hadron Collider, sometimes queuing for several hours in the baking sun for a chance to take a trip underground. Dressed, rather fetchingly I thought, in a bright blue high-viz jacket, luminous orange T-shirt, and the obligatory hard hat, I took group after group down the 100-meter lift shaft to stand beneath the towering LHCb experiment. While it probably wasn’t obvious to the visitors peering into the confusing jumble of multicolored metalwork, most of the detector was missing.
When the LHC switched off for its second long shutdown at the end of 2018, my collaborators on LHCb began a two-year project to more or less completely replace the experiment. When the LHC restarts again (we hope in 2022), the upgraded LHCb experiment will be able to record data at forty times its previous rate, allowing us to home in on ever-rarer processes. As I write this, the anomalies in how beauty quarks decay that have caused so much excitement over the past few years are still there, and early in 2020, some of my colleagues released a result that seems to show that they were strengthening. It’s still too early to say which way things will go, whether the anomalies will fade away or whether we will soon have convincing evidence of new quantum fields beyond the standard model. But the LHCb upgrade will give us the crucial data we need. There is a chance, albeit an uncertain one, that a major step forward in our understanding of matter is on the horizon.
We’re living in a golden age of physics and cosmology, where experiments and observatories that would have been almost unimaginable just a few decades ago are teaching us more and more about the universe we live in. As I write this, the team at Borexino under the Gran Sasso mountains have just announced that against all odds they’ve snared their final great prize: neutrinos produced by the carbon-nitrogen-oxygen cycle that cooks protons into helium at the center of the Sun, filling in yet another part of the story of m
atter’s origins.
The future is bright. Over the coming decades new gravitational wave observatories, telescopes on Earth and in space, dark matter detectors deep underground, precision laboratory experiments, and gigantic neutrino observatories will come online. No one can say what they’ll find—experimental physics is exploration—but there will surely be surprises. In my own field, the LHC has a decade and a half still to run, and thousands of physicists will continue to determinedly scour the trillions upon trillions of collisions in the hope of finding clues that may lead us to the next layer of reality.
Reading popular science books and watching documentaries as a kid growing up in the 1990s, I got the sense that physics was hurtling toward a dramatic climax. That after a century of revolutionary discoveries and ever-more-unified theories, physicists were on the brink of finding the ultimate theory of the universe. Huge progress has been made since then, and yet Einstein’s dream has if anything drifted further out of reach.
Perhaps it was hubris. The 1970s and 80s was a time of miracles: forces were unified, predictions spectacularly verified, and beautiful new mathematical structures uncovered. Perhaps all that success made people think that we were ready to jump from the standard model all the way to a theory of everything. In any case, it hasn’t turned out that way. Today we can explore physics at incredible energies of around 10,000 GeV in the lab, but the Planck scale is a thousand trillion times higher than that. To think that we could leap from the solid ground of experimental evidence fifteen orders of magnitude into an unexplored world of quantum gravity in a single bound seems to have been premature, to say the least.
Will we ever learn how to make our apple pie from scratch? Quantum mechanics and gravity seem to be telling us that the moment the universe began—when gravity, space, time, and the quantum fields of nature were all united—might be inherently unknowable. But that’s no reason to get downhearted—the opposite in fact. We have come a very long way in our understanding of the basic ingredients of matter and their cosmic origins. But we have a very, very long way to go yet before we reach the Planck scale. Putting aside dreams of a final theory, there are many big mysteries left to solve that are closer at hand. What the hell is dark matter? How did matter survive annihilation during the big bang? Can we explain the weirdness of the Higgs field? Science thrives on such mysteries, and these are all questions that we have a chance of answering in the coming years.
When I spoke to Nima, he said that the biggest bottleneck to building the next generation of colliders isn’t the money, or persuading politicians or the public, nor is it the formidable engineering challenges. The biggest bottleneck is whether there is a generation of young people who are willing to devote their lives to understanding the Higgs boson. Among the many groups of eager visitors whom my colleagues and I showed around LHCb that weekend were dozens and dozens of teenagers who had given up their free time to squeeze into a lift with some berk in a hard hat and spend an hour or more gawping at bits of scientific equipment. I came away from the weekend feeling pretty optimistic for the future. Someday, years from now, perhaps one of those young people will find themselves sitting nervously in an early morning run meeting as the Future Circular Collider prepares to fire up for the first time.
If so, they will be part of a story that stretches back centuries, the story of how we have gradually understood the building blocks of matter and their origins. It’s a story that I fell in love with as a curious teenager and have never stopped being thrilled by. Beyond the incredible discoveries—and who could help but be seduced by the idea that we are made of stuff forged inside stars and in the heat of the big bang—is the fact that thousands of people, across time and cultures, working in different fields, all with their own dreams, strengths, weaknesses, and egos, have slowly built on the achievements of those who came before and led us to an ever-deeper understanding of the world we all share. Most of them never knew one another and were struggling with their own small part of the puzzle, and yet somehow they wove one tapestry, one story, which as far as I’m concerned, at least, is the greatest ever told.
Even an object as mundane as an apple pie is deeply rooted in this cosmic drama, and to truly understand it is to understand the universe and our own small part in it. There may be good reasons to think that we will never be able to discover its ultimate origins, but then again, nature has shown an almost infinite capacity to surprise us. As we go on exploring, gazing farther into space and probing deeper into the smallest elements of matter, who can say what new wonders we will find? We have come a long way, but the story isn’t done yet. It is still being written. If we carry on exploring, then perhaps one day we’ll finally find the recipe for our universe.
Skip Notes
*1 The same guy who bet a year’s salary that the Higgs would be found.
*2 Technically what are known as “weakly interacting massive particles” (WIMPs), produced in the fireball of the big bang.
How to Make an Apple Pie from Scratch
Serves eight. Preparation time 13.8 billion years.
Ingredients:
A smidge of spacetime
Six quark fields, six lepton fields
U(1) × SU(2) × SU(3) local symmetries
One Higgs field
Supersymmetry or extra dimensions of space (depending on taste)
Dark matter (not available in shops)
Probably some other stuff
Instructions:
First, invent the universe.
Inflate your initial smidge of spacetime for approximately 10-32 seconds until your universe has grown to around ten trillion trillion times its original size. Take care not to allow inflation to continue for too long or you will just end up with a howling void, spoiling the dish.
After inflating, you should find that your universe’s temperature rises dramatically, creating large numbers of particles and antiparticles. Meanwhile, your U(1), SU(2), and SU(3) local symmetries should automatically produce the electroweak and strong force fields. Allow to continue to expand and cool at a gentler rate for another trillionth of a second.
At this point, begin to switch on the Higgs field, aiming for a value of around 246 GeV. I recommend using supersymmetry or extra dimensions to ensure the field remains stable, otherwise you will find it almost impossible to cook atoms later on. However, if you prefer, you can simply repeat the above instructions approximately a million trillion trillion times until you randomly get it right.
To make matter, try to ensure that the Higgs field switches on unevenly, forming expanding bubbles in your mixture that will preferentially absorb quarks over antiquarks. Meanwhile use sphalerons to convert antiquarks into quarks outside the bubbles. Once your Higgs field has reached the desired consistency you should find that you have more quarks than antiquarks, and also that the electroweak force has separated into electromagnetic and weak forces.
Allow the resulting hot soup of quarks and gluons to continue to expand and cool for a further millionth of a second until it begins to congeal to form protons and neutrons. Allow antimatter and matter to annihilate, leaving only around one ten-billionth of the original amount of matter. Don’t worry, this should be more than enough for the apple pie.
After another two minutes the mixture should have cooled below 1 billion degrees and you can begin making the first elements beyond hydrogen. Your mixture should now consist of about one neutron to every seven protons, plus a fuck-load of photons. Simmer gently at a gradually reducing temperature for about ten minutes, until nuclear fusion results in a mixture of light nuclei: about one part helium to three parts hydrogen, plus a tiny sprinkling of lithium.
Allow the hydrogen-helium mixture to continue to cool for a further 380,000 years, when, all being well, you should notice that the hot fiery mixture becomes transparent as electrons bind to hydrogen and helium nuclei to form the first neutral atoms. You ca
n now leave the warm gases to cool unattended for a further 100 to 250 million years, so time for a nice cup of tea.
Wait over, you can start to form the first stars by collapsing large clouds of hydrogen and helium gas. In their cores, begin by converting hydrogen into helium, then helium into carbon via the triple-alpha process. You may find that these first stars are large enough to continue to fuse all the elements up to iron, which can then be spread through the mixture using supernovae.
For another 9 or so billion years, continue to make larger quantities of heavy elements in subsequent generations of stars, supernovae, and neutron star collisions, until you have a mixture with a good spread of elements from hydrogen all the way up to uranium. From this mixture, form a rocky sphere approximately 13,000 kilometers in diameter and place in the habitable zone of a yellow dwarf star. Make sure the resulting planet has sufficient quantities of hydrogen and oxygen (preferably in the form of water), carbon, and nitrogen.
Now do some biology. To be honest, I’m not at all sure about this next bit. But with a little luck after around 4.5 billion years you should end up with apples, trees, cows, and wheat, plus a few other handy living organisms. Hopefully supermarkets will also have spontaneously evolved by now, so go out and buy:
For the shortcrust pastry
400g all-purpose flour, plus extra for rolling out
2 tbsp. sugar
Pinch of salt
Grated zest of a lemon
250g cold butter, cut into cubes
1 free-range egg beaten with 2 tbsp. cold water
For the filling
