Sunfall

by Jim Al-Khalili

  Marc and Qiang had flown out to Antarctica to witness the experiment at first hand. It was the most nervous Marc had felt in his life. If this test had failed that would most likely have spelled the end of the Project.

  The chosen spot for the dark-matter beams to converge, just south of the Kraul Mountains in the Norwegian dependency of Queen Maud Land, was a remote enough site, yet close enough to the British Halley Research Station eighty kilometres away to be carefully monitored from a safe distance.

  After a twenty-four-hour delay due to a security breach at J-PARC, the three labs had fired their dark-matter bursts into the ground. When the pulses met, a split second later and thousands of kilometres away, they created a burst of energy so great it vaporized a volume of the remaining Antarctic ice, leaving behind a lake of hot, but rapidly cooling water three kilometres wide and two hundred metres deep. Under normal circumstances, such devastation would have horrified environmentalists, but these were not normal circumstances. Marc found himself wondering whether Oppenheimer, Fermi and the rest of the gang on the Manhattan Project had experienced the same feelings of awe and dread at such pure, unleashed power, as they gazed out at the first mushroom cloud in the New Mexico desert a century ago. The difference now was that, unlike the Manhattan Project, this test was meant to save humankind rather than incinerate it.

  And yet he had to remind himself that this test had been with just three dark-matter beams rather than the eight he and Qiang were proposing, not to mention the fact that they had been operating at a fraction of the intensity that could be achieved, and which would ultimately be needed when the time came.

  Marc’s thoughts were interrupted when the lights dimmed, and he heard a familiar voice over the PA system. Despite the importance of the event, proceedings began just as all CERN conferences had done for some years past: with a welcoming address from the lab’s Mind. The holographic human avatar representing the AI that controlled every aspect of the vast laboratory complex was, in contrast, simple and understated. The original programmers had created it in the stately image of a woman with white hair tied efficiently in a bun at the back of her head. Those listening to her without the use of the universal translators would hear her speak softly in English with a hint of an Italian accent. It was said that this was a deliberate nod by the programmers to the laboratory’s first female director, Fabiola Gianotti. They had even given it her name. The real Dr Gianotti had retired several years ago but still came to the lab regularly. Marc had once asked her what she thought of the avatar created in her image.

  ‘I’m very flattered,’ she’d replied. ‘If only it had been around when I was director. I could have taken longer holidays and left it in charge. It knows far more about how to run CERN than I ever did.’

  Like everyone else in the room, Marc now saw the Mind’s avatar in augmented reality and listened as Fabiola gave a brief introduction to the lab.

  ‘Many of you will know that CERN was conceived in the late 1940s as a laboratory to be shared by many nations when particle physics research became too expensive for any one country to pursue alone. So, it is fitting that today it is the centre of operations for a new type of experiment – one that involves a truly worldwide collaboration between eight laboratories spread around the globe. Many of you will know that we have this type of connectivity in science already, with our largest radio telescopes linked together to effectively act as a single Earth-sized telescope to look deeper into space, but humankind has never attempted something as audacious as Project Odin.’

  As the Mind went on to introduce Qiang and invite him to present the latest test results, Marc’s attention drifted once again. The great human technological achievements of the past, such as the space exploration programmes to the Moon in the 1960s and Mars in the 2030s, had been driven by nothing more than national pride and economic supremacy; this current race against time was different. Unlike with the Moon and Mars programmes, failure now quite literally wasn’t an option.

  Sitting there, only half listening to Qiang describing the results of the Antarctic test, he felt a sudden unexpected surge of panic. This entire project really was quite insane. He tried to recall the confidence and excitement he’d experienced during that weekend of feverish activity in his New York hotel room, when the two men had conceived the plan. But despite their calculations being checked and verified by hundreds of other scientists, he now felt more nervous than ever.

  Still, what choice did the world have? Secretly, a small part of him was hoping that someone else would come up with a better plan – one for which the chances of success were higher and where failure would not mean the end of the world. At least if something went wrong and one of the beams did in fact miss the intended rendezvous spot deep in the Earth’s molten core, he wouldn’t have too long to blame himself for destroying the planet.

  Loud applause dragged him back to the here and now. Qiang had finished his short presentation and was returning to his seat. It was time. Standing, Marc waited for a second or two, trying to calm himself and collect his thoughts. He was conscious of hundreds of pairs of eyes burning into the back of his skull as he made his way to the stage. Pausing at the lectern to pick up the holo-control pad, Professor Marc Bruckner turned to face his audience and smiled.

  ‘Ladies and gentlemen,’ he began, ‘I’m aware that many of you are not scientists and will therefore not appreciate the subtler details of dark-matter physics, particle decay pathways and the role of superconducting bending magnets. In any case, the documentation you have all been given lays this out in clearer detail than I am able to do.’

  A murmur of light-hearted approval rippled through the audience, which would have come mainly from the non-scientists.

  ‘As you know, ODIN stands for Octangular Directional Ignition with Neutralinos. This means eight beams of neutralinos, the particles of dark matter, all directed into the core of the planet from different points on the surface. But as you have just heard from Professor Lee, we currently have only three accelerator laboratories capable of producing these particles at sufficiently high energy and intensity.’

  He wondered how what he was about to say would be received. After the tragedy in Texas, they had needed to come up with a revised plan. Many in the audience would now be hearing the new details for the first time.

  He clicked the pad in his hand and a giant three-dimensional globe appeared suspended in the air in front of him, slowly rotating. Created by several holo-projectors around the stage, the bottom of the sphere hovered a metre above the ground, but its top almost reached the roof of the auditorium seven metres above the stage.

  Marc walked across from the podium to stand in the centre of the projection, so that the globe’s South Pole cut through his midriff. And because his eyeline coincided with the southern oceans, as the Earth spun he looked out at the audience through a blue translucent wall. He was aware that his actions might seem overly theatrical, but he had a practical reason for positioning himself inside the hologram. With a click of the pad in his hand, three bright lights lit up at the appropriate locations on the surface of the globe, depicting the sites of the only three labs capable of producing beams of dark matter.

  He continued, ‘The challenge is how to turn three beams into eight, each one aimed into the Earth’s core from a different location.

  ‘Those further five locations have now been identified. They were chosen for two reasons. The first is of course their strategic location on the surface of the planet. The second is that they all have much of the infrastructure that is needed already. You see, we won’t be building five new dark-matter accelerators. Instead, we’re using the beams from the three we already have, only we’re splitting them up.’

  As he spoke, he clicked his pad and five new lights appeared on the globe.

  ‘All we need …’ He paused to give the audience the chance to realize he’d meant those three words sardonically. This time the ripple of laughter came from the other physicists, who knew only too
well the immense scale of the task. ‘… All we need … are giant superconducting magnets to bend the particle beams fired from the three main labs downward into the ground.’

  A subdued buzz spread around the auditorium as people leaned in to each other, whispering, pointing at the globe. Marc began warming to his task.

  ‘For example, the beam produced here at CERN will be split into three: one heading to the north coast of Norway in the Arctic Circle …’ A red line lit up, joining the light that marked Geneva to another in the far north. It traced a perfect straight path that passed below the surface of the Earth instead of following its curvature above ground. ‘… a second to the deserts of Jordan just outside Amman, and a third to Cape Town in South Africa.’ Two more bright lines appeared, radiating out from CERN.

  A few people clapped enthusiastically, and then, feeling self-conscious, stopped again.

  ‘Across in America, the Fermilab beam will be split in two: one heading straight down to the core directly beneath the lab and the other sent south to the Andean Plateau in Peru.

  ‘Finally, the Japanese beam will also split into three, one directly down and the other two to facilities located on Big Island, Hawaii, and Dunedin in the south of New Zealand.

  ‘Once the beams from the labs reach the six remote locations, powerful magnets will bend them downwards, aiming them into the ground.’

  As he spoke new red lines appeared around him pointing radially inwards from each location, to meet at the centre of the hologram at a point high above his head.

  He now stepped back out of the holo image. ‘As you can see, the eight beams,’ he indicated back to the red spokes of light inside the sphere, ‘two from the existing facilities and the other six from the new locations, all meet in a single spot in the Earth’s core.’

  Marc paused to join the audience in admiring the image. ‘I could stop here and just ask you to wish us luck. But since I have you as a captive audience I feel I should share with you the really cool stuff.’

  He looked out across the auditorium. There was a mixture of admiration and concentration on the sea of faces in front of him. His own earlier anxiety and pessimism about the Project had evaporated and his missionary zeal was filling him with a reassuring belief that this could really work. Marc Bruckner had spent his entire adult life testing and prodding the laws of nature. Now was the chance to put his years of study and research to the ultimate test.

  He caught sight of Aguda sitting in the front row. The geologist’s stony expression contrasted with the animated features of those around him.

  Oh well, can’t please everyone. For some reason his eyes drifted across to where Peter Hogan was sitting, but he found it impossible to read the man’s blank expression, which he found somewhat unnerving. To counter his unease, he quickly glanced up at Sarah, who gave him a reassuring nod of encouragement. He took a deep breath.

  ‘You see, ladies and gentlemen, for the magnets to bend the trajectories of our beams from their original direction so that they enter the ground, the particles need to know the magnets are there and react to them, right?

  ‘Yes, I know that sounds obvious. But, as I hope you all know by now, dark matter doesn’t feel the presence of normal matter, by which I mean it’s not affected by the electromagnetic force. So, just as dark matter passes through normal matter as if it weren’t there, it will also be oblivious to the presence of the magnets, regardless of how powerful those magnets are.’

  The background murmuring began afresh as many in the audience suddenly understood what seemed to be a fundamental flaw in the scheme.

  Marc took a couple of steps closer to the front of the stage. ‘So, here’s the plan. We don’t make beams of neutralinos, the usual dark-matter particles, to begin with, but heavier versions of them. These are called, somewhat unimaginatively I’m afraid, heavy neutralinos. Think of them as the normal neutralinos’ overweight and short-lived cousins. Beams of these heavy particles will be created in all three accelerators, surviving just long enough, if produced at the right energy, to travel out to the six magnets.

  ‘Then, just as they arrive at the magnets, and rather like Cinderella’s coach at midnight, each of them transforms into yet another type of particle called a chargino.’

  There was a smattering of laughter at this and Marc acknowledged it with good grace. ‘Yes, I know, it sounds like I’m just making this stuff up as I go along, but I promise you I didn’t invent these names.

  ‘What’s important,’ he continued after the audience had settled, ‘is that these charginos, as their name suggests, have an electric charge, which means they will be bent downwards by the magnets, but they too live for such a short time that they will almost immediately transform – we say decay – into the light neutralinos that we want. This step is crucial.’

  Marc knew that the better the job he made of explaining things now, the easier his life would be in the press conference later. So, he ploughed on. ‘The point is that the solid ground will appear to the charginos as just that: solid. If they don’t transform in time to neutralinos they will be stopped dead in their tracks. This is because their electric charge interacts with the atoms that make up the stuff of the planet. Luckily for us, these charginos transform very quickly back into neutralinos. Once they do, it will be as though the earth suddenly becomes transparent again and they continue on their path unobstructed, but this time in their new direction towards the core.

  ‘The eight neutralino beams travel downwards until they meet, slamming together in the mother of all bangs. The energy this produces in the planet’s liquid core will be a hundred million times greater than the burst that melted that chunk of Antarctica. We’ve calculated – that is, Professor Lee and I have calculated …’ Marc nodded towards Qiang. ‘… that this would be enough to create a seismic pulse that kick-starts the Earth’s inner dynamo, and switches the magnetosphere back on.’

  As an afterthought he added, with a theatrical wave of his hands, ‘And that’s how we’re going to save the world.’

  There was wild and enthusiastic applause, even from colleagues who knew the science inside out. A few were standing, and he noticed that Sarah was among them.

  He waited patiently for the applause to die down. When it was quiet again he asked, ‘Right, does anyone have any questions?’

  ‘Excuse me, Professor Bruckner.’ A man in the second row was leaning towards the microphone by his seat. Marc recognized him as a Swiss journalist from Le Temps who had interviewed him a couple of years ago. ‘Could you please explain something to us lesser mortals? How can you know precisely when these different particles transform from one type to the other? From my basic understanding of quantum physics, this is not something you can control.’

  Marc nodded. Unbidden, a famous quote came to him. He had a feeling it was from a Kurt Vonnegut novel, but couldn’t remember the character or what the story was about. It was along the lines of: any scientist who couldn’t explain to an eight-year-old what he was doing was a charlatan.

  ‘You are right, of course, that particles decay according to the rules of quantum mechanics, which state that this takes place at an indeterminate moment. This is not to say that quantum mechanics is an imprecise theory, but rather that Nature herself hasn’t decided when such individual quantum events will happen.’

  The sage-like slow nodding from the journalist suggested to Marc that he was still following, or at least pretending to, so he ploughed on. ‘Quantum mechanics tells us that the world of subatomic particles is a fuzzy one ruled by probability and uncertainty. So, while we cannot control or predict when any given particle will decay, we do know the average lifetime when we have lots of them. So, we produce very many heavy neutralinos in a tight bunch, all travelling at just the right speed, such that most of them will decay just before arrival at the magnet. Of course, some won’t decay until it’s too late and they’ll overshoot the magnet. Those are lost. Others will decay too soon and won’t even reach the magnet because they wi
ll interact with other atoms in the ground or the air and be knocked off their course. But most will make it, transforming just in time for the magnets to do their bending job on them.

  ‘They enter the facilities as a pulse of dark-matter particles travelling through the air, which passes into a sealed beam pipe kept under high vacuum. Only once isolated inside this do they transform into charginos that get bent by the magnets, following an arc within the enclosed, curved pipe that carries them down to the ground.

  ‘And because we know the speed and lifetime of these charginos we can calculate how far they will travel, on average, before they transform back into neutralinos, and so we just have to make sure the beam pipe and the surrounding magnets are high enough above the ground. We’ve calculated that raising them by about a hundred metres would be enough to give most charginos the chance to decay. Only then do they decay back to dark matter again and the pulse passes through the other end of the beam pipe like a phantom and continues down into the earth.’

  He paused to let the information sink in.

  The journalist interjected: ‘But isn’t that quite a tough engineering challenge?’

  Marc laughed. ‘The whole project is something of an engineering challenge.’ A number of people laughed too. ‘But you’re right. And so, there’s an alternative plan that might be easier. The magnets are kept at ground level, but instead we bore a vertical tunnel into the ground, down which the beam pipe of charginos is directed, to give them that extra breathing space. Again, some longer-lived charginos won’t have decayed in time. They hit the sealed end of the beam pipe and are lost.’

  Marc wished he’d been able to give a more traditional seminar to an audience of physicists alone. That way he wouldn’t have had to choose his language carefully and skip so much of the interesting technical detail. For example, he’d conveniently left out the fact that the heavy neutralino beams would decay into a host of other particles besides charginos, like W and Z bosons, which in turn would quickly decay into other more familiar particles like quarks and electrons, all of which would be slamming into the magnets at incredible energy. Hopefully they wouldn’t destroy the electronics before the magnets had served their purpose.