Like many theoretical physicists, Harvard professor Nima Arkani-Hamed spends a great deal of his time thinking deep thoughts about the nature of the universe and how they correspond with the rules governing the tiniest particles in nature.

A giant tube, part of the Large Hadron Collider in Geneva, where new particles may be revealed. (Courtesy: CERN)

The trouble is, the only agreed upon framework for those rules — the Standard Model of particle physics — has been around for longer than the 34-year-old from Toronto has been alive.

The Standard Model — with its familiar particles like the electron and the photon, and its host of other, less intuitive particles like muons, strange quarks and Higgs bosons — has managed to last for as long as it has because it has proved surprisingly accurate in experiments, and because those same experiments haven't worked on a scale small enough to catch any inconsistencies.

That accuracy will be put to the test, however, when the Large Hadron Collider, or LHC, officially begins operations in November of this year and begins operating at full power in 2008.

Could do for physics what telescope did for astronomy

Made up of two pipes enclosed in superconducting magnets with enough power to direct a proton beam at speeds and energies never before reached, the LHC could do for particle physics what the telescope did for astronomy: lift the veil on a previously unseen world.

Able to detect the presence of particles at a scale of 10 to the power of –17 centimetres, the LHC itself is enormous: the pipes are contained in a 27-kilometre circumference tunnel buried underground near Geneva and the Franco-Swiss border.

The pipes also intersect, allowing the scientists to smash two proton beams — coming from opposite directions — into one another in an effort to create a host of new particles and effects, some predicted by the Standard Model and others belonging to the even more theoretical branches of physics that have since been developed.

When those first protons run into one another, the results could change everything physicists know about the world they study, says Arkani-Hamed.

Scientists 'tense with excitement'

Naturally, he's getting restless.

"It's exciting and tense. It's tense with excitement," Arkani-Hamed told CBC News Online.

The Standard Model

The Standard Model of particle physics explains the interactions of matter with three of the four fundamental forces of nature: electromagnetism, the strong nuclear force (which binds the parts of an nucleus together) and the weak nuclear force (which allows for the radioactive decay of particles). Its collection of particles consists of bosons — which mediate these forces — and fermions, which combine to make up the matter.

Where it comes up short is when dealing with the fourth fundamental force: gravity. Gravity is so weak it can normally be discounted but that's not possible in extreme cases such as the high-energy, small space predicted in the early moments of the Big Bang theory of the universe. In those moments, gravity would have been operating at levels comparable to the other forces. Here the Standard Model takes a bow and exits stage left.

"Since the Standard Model has been developed, it's never been wrong. But for good reason — we haven't gone to the place where theoretically it should break. The place where it should start to break is right now, where we're about to go."

But there is more at stake than a three-decade-old model of the subatomic universe. A host of theories developed since — including supersymmetry, string theory and the multiverse [see the descriptions below] — will also be put to the test.

Each of these has their own elegant mathematical explanations of the subatomic world, but collectively they have all defied efforts to experimentally test them.

Likewise, physicists hoping to better understand how particles interacted at high energies during the first few moment of the Big Bang are looking to the LHC to deepen their understanding of a world that for now lives only in theory.

This lack of experimental data has left physicists at a standstill and helped stifle the public's understanding of the nature of the universe.

Past theories like relativity and quantum physics stretched the limits of the layman's understanding of the universe — but ordinary people could still appreciate the impact in the real world of, say, nuclear fission, and at the same time marvel at the simplicity and even the theological implications of a model of the universe like the Big Bang.

But particle physics has so far proved as elusive to the public as the particles are to the scientists, and a large part of the reason for the confusion and disinterest is the mixed message of competing theories.

At the scales the LHC will be looking at, however, evidence of one or more of these theories could turn up and help shape the future debate of our understanding of the world we live in, said Arkani-Hamed.

"I really think the future of fundamental physics will be predicated one way or another on the results of these experiments," he said.

How the accelerator works

Like the particle accelerator in Chicago at Fermilab, the LHC speeds the protons through a series of superconducting magnets, each of which push them through the pipe and impart greater and greater amounts of energy.

The unusual suspects

In the past 30 years, scientists have worked on a number of theories designed to improve upon and replace the Standard Model. Here's a look at a few of these theories.

Supersymmetry: The most natural replacement to the Standard Model, supersymmetry argues that every known particle in the universe has a superpartner. If these superpartners — which have never been detected — exist, it could help explain some of the nagging inconsistencies of the Standard Model. But it would also double the number of particles.

String theory: A leading front-runner in the world of particle physics, string theory reduces the forces and matter of the universe to tiny one-dimensional filaments called strings that vibrate in 10 dimensions. It's considered mathematically elegant but virtually untestable, though physicists in the U.S. have already announced a way to use the LHC to at least prove its non-existence.

The Multiverse: The theory of countless multiple universes dispenses with the esthetic needs of symmetry by surrounding the unique conditions of our world with zillions of universes operating by different rules. Five hundred years ago, Copernicus made everyone in the world feel a little smaller when he presented the view that the Earth rotated around the Sun, and not the other way around. Likewise, this theory shrinks our sense of importance even further, with our universe becoming "just a tiny speck in some giant multiverse," said Arkani-Hamed.

The protons are then smashed into each other, causing them to break apart into other particles. The higher the energy of the accelerator, the more likely the protons will transform into completely different particles.

(The LHC has the higher energies required for some spectacular collisions, with each of the proton beams traveling with seven teraelectron volts of energy. If the proton beam was deviated at this energy so it banged into the surrounding pipe, it would be as if over 100 kilograms of TNT went off, says Arkani-Hamed.)

Every time particles collide and form different particles, they deposit energy. Scientists are then able to figure out which particles were created — even though they can't see them — by the distinct energy patterns left by the particles on material chosen to "catch" these slight changes in energy.

Each material is designed to catch particular particles: an electron or photon would be detected by its energy signature on one material, while protons and neutrons would leave their mark on a different material.

Only exist for tiny fragment of second

But how do they detect a particle that has never been encountered before? If a scientist doesn't intuitively know the energy pattern left by a particle, how can he or she say it was even there?

It's a problem confounded by another unfortunate happenstance of many of the theoretical particles predicted by the Standard Model and theories like supersymmetry: many of them are extremely short-lived.

Arkani-Hamed uses the example of a particle predicted by supersymmetry, called the squark, to explain the difficulties.

"The new particles tend to be ridiculously unstable because they can decay into ordinary particles as quickly as 10 to the minus 27 seconds. So these particles come out and almost instantaneously decay and we never see them," he said.

"They don't come out with a little name card saying, 'I am a superpartner of the quark.' They just have characteristic patterns of decay, and from the characteristics pattern of decays you have to reconstruct what actually happened."

In much the same way two protons could collide and produce any number of combinations of particles, so too can these new particles decay in a variety of ways.

"A squark could decay into a quark and the superpartner of a photon called a photino, or it could decay into a quark and a gluino and then the gluino would decay into something else. It can be a long complicated change until ultimately what you see are ordinary particles."

Could find extra dimensions

Figuring out what actually happened will be an exhaustive process for the two teams of 1,000 scientists who must pore over the data and reconstruct from the energy patterns what might have happened.

Adding to the confusion is the possibility that the detectors might be able to notice something really revolutionary — like the appearance of extra dimensions beyond the four we live in.

Arkani-Hamed said it is possible these might turn up given the high energies of the proton beams and the small scales the LHC will be detecting, and would be noticeable by the disappearance of energy into these dimensions.

It's also possible the protons will hit each other and react in ways that are completely unexpected, he said. But regardless of which theory proves correct, the important thing is scientists have reason to believe something will happen.

It's an occasion long overdue, said Arkani-Hamed, who for the past five years has written papers on everything from the disappearance of gravity through extra dimensions to the possible existence of billions of extra universes.

While his wide-ranging theories earned him a full professorship at Harvard at the age of 30 and the praise of Popular Science magazine — which named him one of its "Brilliant 10" in 2006 — it's an exhausting process to work in all of the fields at the same time.

"Science works best when there are trees of good ideas that then get pruned by experiment," he said.

"It's impossible for us to develop all the ideas for what might be going on simultaneously. We need the prune, we need direction from experiment and that's what we're going to get."

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