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25/04/2007

To the Big Bang and back

As the Large Hadron Collider at CERN prepares to go into action, astrophysicist and author Ulrich Woelk takes us on a journey to the origin of things

In his novel "The Enigma of Arrival" the Trinidad-born writer and Nobel Prize laureate V.S. Naipaul describes a wanderer searching for a homeland. During long, quiet walks through Wiltshire near the famous Stonehenge monument, he familiarises himself with the landscape and the people who live off it. With time his eye for detail sharpens and the "flat wet fields with the ditches" become "water meadows" and "wet meadows" and the low smooth hills in the background, beyond the river, "downs".



CMS Higgs-event. All images courtesy CERN.


Stonehenge
– always in the peripheral vision of Naipaul's wanderer – is one of the oldest monuments of mankind. The blocks of stone in circular formation still have historians and hobby anthropologists puzzling. It seems to have been used for ritualistic purposes as well as the observation of the sky. Erected at a time when the quest for knowledge had yet to be separated from the worship of nature, Stonehenge is an enduring symbol of both: the longing for a holistic experience of our existence as much as the desire to record its conditions analytically.

The main stones of Stonehenge function as astronomical markings. They make it possible to determine the day of the solstice or to predict the lunar eclipse. The circle of stones, once erected to honour the gods, is also one of the first instruments for extracting God from the heavens by revealing his mathematical characteristics. It is not the higher powers that determine the movement of the stars, but cycles determined by laws of nature that were first discovered thousands of years later by Johannes Kepler. Stonehenge was a sort of world computer of the megalith culture.

So the tradition of erecting circles on the earth to track down natural forces is nothing new. Ring geometries represent a prominent construction principle of physical order: that of the orbits. Planets circle the sun, the moon the earth, electrons the atomic core. Moreover, circles make ideal running circuits if one needs to get atomic particles to move rapidly and collide with each other to try to determine the innermost structure of matter from the post-collision ruins.



Overall view of the LHC experiments


Which brings us to the largest ring that mankind has ever inscribed into the face of the earth, on the Swiss-French border near Geneva. Underground, 27 or so kilometres of the acceleration tunnel of CERN (Conseil Europeen pour la Recherche Nucleaire, today Organisation Europeenne pour la Recherche Nucleaire) wind through the rock. And this year, a gigantic research machine with the name of LHC, Large Hadron Collider, will go into operation there. (See computer animation of the LHC in action.)

The old desire to understand the world at its innermost has entered increasingly microscopic dimensions in the past hundred years. The discovery of the atom was followed by the discovery of the atomic nucleus which turned out to be a cluster of nucleons – protons and neutrons. But that was not the end of the all structures. On closer inspection, the nucleons turned out to be conglomerates of particles made of quarks and gluons.

And there are many answers to the question of how much longer this Russian-doll game will continue. If one is to be absolutely honest, none is reliable, although at least there is a fascinatingly stringent basic system, from whose hat all the currently known subatomic particles can be pulled: the Standard Model of elementary particle physics. It knows six quarks and three leptons (with their respective anti-particles and neutrinos) as well as four bosons which mediate the forces between particles. All these particles and their combinations – christened with nice little names like Charm, Pion and Kaon – are well defined within the model, whose clairvoyant powers border on the magical. And yet particle physicists are not entirely satisfied with their construction kit, because it has a few gaps in it which prevent them from sleeping at night.



Installation of the muon chambers in the UX5 cavern


The sorest point is that to this day, gravity, that primal cosmic force which defines the universe as a whole, has been impossible to fit into this energy system of elementary particles. Why – and this is the greatest puzzle of theoretical physics – do particles have a mass at all, or more trivially still, a weight? It is precisely this property of matter, which in everyday life seems the first and most natural that is the most puzzling in terms of physics. The hope is that the LHC will help clarify why gravity is so inexorably fundamental.

The answer to this and a string of other elementary questions in particle physics lies on the far side of an energy boundary which has never been crossed in any experiment to date. The LHC will literally take physicists to a new world, and, as with any expedition into new territory, there is a host of complicated theories dealing with what lies in store for the travelling researchers. They have names like Higgs mechanism and supersymmetry and are the brainchildren of formal considerations as well as the dictates of mathematical consistency.

Yet all these theories amount to something like a landscape painted with nothing more than suggestions and finger-pointing. It's little more than a hypothesis of forms and colours, as long as it is not verified with a comparison with reality. And this is where the LHC comes in: to draw aside a further curtain concealing the innermost secrets of the world, and contrast the theoretical representation with the original picture of reality.

Naipaul – the homeless wanderer looking for a homeland – shudders at the sight of the Celtic landscape. A herd of cows reminds him vividly of the labels on the condensed-milk tins of his childhood: "on a sunny day, and especially if at the top of the slope some of the cattle stood against the sky, there was a corner of my fantasy in which I felt that some minute, remote yearning ... had been satisfied, and I was in the original of that condensed-milk label."



CMS inner detector assembled in a clean room

Perhaps it is inappropriate or disrespectful to compare brilliant intellectual achievements such as the Higgs Mechanism or the concept of supersymmetry with a condensed-milk label. But at the end of the day, physicists are looking for this Naipaulian moment of fulfilment – that's the goal of all their sober and rational work. The label is complete, the only thing missing is the "sunny day" of the experiment. Physicists are idealists in the truest sense of the word. They believe in the truth of their mathematical images. And in their innermost selves, they believe that Nature won't leave them high and dry, and will be calculable in the end.

It is still not certain, however, whether Nature will be good enough to reward the enormous experimental effort at the base of the Alps with new knowledge. Most calculations predict a particle that will attribute mass to things: the Higgs-Boson. It should be netted by the LHC. If it's not, however (so much realism must be allowed despite the general idealism), there is a sort of theoretical Plan B, which relocates the hugely important tiny particle to even higher energy dimensions. There it could never be hunted down, however. At least not as long as humanity refrains from building an even bigger particle accelerator in a supranational effort - which seems anything but likely at present.

So the disappointment could be huge. The operation of the LHC will consequently also give a lesson on the fate of scientific theories. In the worst case, the experiments could remain fruitless over a broad front, revealing no trace in the hall-sized detectors of the LHC of either the Higgs-Boson or the super-symmetrical particles so important for cosmology like photinos and neutralinos. What then?



View of A side ATLAS cavern

In social terms, the physicists at the LHC are in a schizophrenic position. Pressure to justify their investigations publicly is greater than ever. To the scrutinising eye of a financially squeezed society, carrying out research into the tiniest particles with the largest imaginable expense seems increasingly questionable. And if nothing, or merely inessential results, are found on the far side of the energy border when it's broken by the LHC, politicians and governments will be hardly jumping up and down to invest more funds for even larger experiments. On the other hand, you can't order nature to subordinate herself to political or economic interests. Whether Higgs-Boson exists or not is not a question of ideological opportunities, but simply of finding the truth.

That may sound laughable, or even childish. The assumption that there is an objective reality is an outdated philosophical standpoint. But as the operating basis for all natural scientific research, it has stood up to every test. The needles of measuring instruments swing when something in nature causes them to do so! And physicists will always see in the entirety of all needle movements a pointer to the inner constitution of the material world. They can't help it. In the final analysis, it doesn't make a whit of difference if you're predicting an eclipse of the moon or the existence of Higgs-Boson. The first was no doubt just as tricky for a priest of the Neolithic era as the second is for a theoretical physicist today. The installation at Stonehenge is a Stone Age image of the objective workings of the heavenly mechanism - even if many people presumably see things differently.

We can never know what awaits us when we start out on a journey - be it physical or intellectual. "New to the valley," writes Naipaul, "I had seen everything as a kind of perfection, perfectly evolved. But I had hardly begun to look, the land and its look had hardly begun to shape itself about me, when things began to change. And I had fallen back on old ideas... to fight the distress I felt at everything - a death, a fence, a departure - that undid or altered or threatened the perfection I had found."



View of the CMS detector in the surface hall at Cessy


Whether the landscape of natural laws is perfect we do not know. Physicists are local researchers. Ultimately they take reality as it is - they just want to know why it is as it is. But that is a question only God can answer. Or - with a bit of luck - the LHC.

In any event, the energy relationships to be created at CERN correspond to the state of the entire universe around one ten-trillionth of a second after the big bang (so according to what we know it's not a simulation of creation - that happened around ten to the power of minus twenty seconds earlier). Whether such an investigation into our material origin can have any significance for us is hard to say. The Copernican Revolution is only attaining its full potential impact today, with the development of missile and satellite technology. And if the point were to benefit from practical applications, you could save yourself the theoretical energy, because no one lives four hundred years.

As a Naipaul reader, however, one comes to the conclusion that life is less a matter of being in the world, and much more a matter of arriving in it, of looking about. Theories are one thing, experience is another. Behind the energy frontier the LHC will transcend is a terra incognita, and that's quite somwthing in our fully mapped-out world. The arrival there will be enigmatic - and we should enjoy it. Because it could be the researchers in Geneva are setting out on the last journey to the origins of things for a long time to come.

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This article originally appeared in German in Die Welt on March 24, 2007.

Ulrich Woelk (born 1960) worked as a theoretical astro-physicist before becoming a writer. He has written a number of novels, one of them "Die Letzte Vorstellung" 2002 (the last performance) was made into a film
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Translation: lp, jab.
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