IF ALL goes well, on 10 September a lone beam of protons will complete the first lap around the world鈥檚 most powerful particle accelerator, the Large Hadron Collider (LHC) at the CERN laboratory near Geneva in Switzerland. The trip round the 27-kilometre ring, which straddles the border with France, will take just 90 microseconds. Though the world will not end as some doomsayers have predicted, the event will rank as a monumental milestone.
The LHC is to physics what the Apollo programme was to space exploration. It is a massive technological achievement that promises to open up new vistas on our understanding of the universe. Protons will accelerate in a vacuum that is 10 times stronger than that on the surface of the moon. The 9300 magnets that will steer these protons contain enough superconducting filaments to stretch to the sun and back five times over. And the superconductors are cooled to 1.9 kelvin, making the LHC colder than outer space (see 鈥淯ltimate machine鈥�).
And that鈥檚 just the accelerator. Four giant detectors, built to study collisions between protons, have also pushed technological and engineering boundaries. The ATLAS detector will take 90 million measurements 600 million times a second.
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To achieve these superlatives has called for global cooperation on an unprecedented scale; no one company, institution or country could have made it happen. Some 6000 scientists from hundreds of institutions in more than 55 countries work on the LHC experiments, not counting the hundreds of theorists who have made an industry out of speculating on what the particle collisions will throw up. The giant feet on which the CMS detector is mounted were made in Pakistan, its vast framework was built in China, and the particle detectors that sit like a set of Russian dolls inside it came from another 36 countries.
鈥淲hatever the LHC鈥檚 findings, physics and cosmology are in for an exciting time over the next few years鈥�
Don鈥檛 expect the LHC and its experiments to work straight away. This is uncharted territory for the physicists accelerating the protons and for those sifting through the debris of the collisions. It will take weeks, probably months, to iron out the problems that a project on this scale brings. Yet no one doubts that they will manage it.
When the discoveries do start trickling in, a year or so from now, what can we expect? The LHC鈥檚 primary target is the as yet unseen Higgs boson, known by some as the 鈥淕od particle鈥�. It is a crucial missing piece of the standard model of particle physics, which encapsulates our best theories of the basic building blocks of matter and the forces between them. The Higgs is the entity that explains how those building blocks acquire mass.
As the LHC picks up steam it could also reveal other particles, perhaps some that lie outside even the fertile imaginations of theorists. Such findings promise to rule in or rule out various models of reality鈥檚 fundamental nature, from the standard model to supersymmetry and compositeness. More widely, the LHC should give us clues about the big bang, the nature of dark matter and the fate of the universe鈥檚 antimatter (see 鈥淧ower up鈥�). It should also provide new leads to perhaps the most intractable task facing physicists today: bridging the chasm between quantum theory and relativity.
Of course, the LHC may find no new particles. This would be a disastrous setback for those physicists already campaigning for the next great machine, the International Linear Collider. Yet it would also represent perhaps the most profound of all discoveries: it would mean that our understanding of matter and forces has been on the wrong track for decades. Rearranging the jigsaw of the standard model so that it could be completed without any new pieces would be a truly challenging task.
Whatever the LHC鈥檚 findings, physics and cosmology are in for plenty of excitement over the next few years. In a world where proposed scientific research stands little chance of funding unless it has a practical purpose 鈥� more wealth, perhaps, or better health 鈥� it is refreshing to see an experiment on such a grand scale intended solely for the pursuit of knowledge. It is difficult to imagine that this knowledge, fundamental as it is, will not lead to practical applications, but for now at least the LHC鈥檚 greatest promise is to improve our understanding of the universe and our place in it.
The Large Hadron Collider 鈥� find out more about the world鈥檚 biggest experiment in our cutting-edge special report.
