Massive Physics Experiment

Particle physicists believe they will throw open a new frontier of knowledge on Wednesday when, 100 metres below ground, they switch on a mega-machine crafted to unveil the deepest mysteries of matter.

The most complex scientific experiment ever undertaken, the Large Hadron Collider (LHC) will accelerate sub-atomic particles to nearly the speed of light and then smash them together, with the aim of filling gaps in our understanding of the cosmos.

It may also determine the outcome of novel theories about space-time: does another dimension - or dimensions - exist in parallel to our own?

After nearly two decades and 6 billion Swiss francs ($A6.6 billion), an army of 5,000 scientists, engineers and technicians drawn from nearly three dozen countries have brought the mammoth project close to fruition.

At 9.30am (1730 AEST) on Wednesday, the first protons will be injected into a 27-kilometre ring-shaped tunnel, straddling the Swiss-French border at the headquarters of the European Organisation for Nuclear Research (CERN).

Whizzed to within a millionth of a per cent of the speed of the light, the particles will be the first step in a long-term experiment to smash sub-atomic components together, briefly generating temperatures 100,000 times hotter than the Sun in a microscopic space.

Analysts will then pore over the wreckage in the search for fundamental particles.

"We will be entering into a new territory of physics," said Peter Jenni, spokesman for ATLAS - one of four gargantuan laboratories installed on the ring where a swathe of delicate detectors will spot the collisions.

"Wednesday is a very major milestone."

The LHC is massively-muscled machine compared to its CERN predecessor, the Large Electron-Positron (LEP) collider, and an ageing accelerator at the legendary Fermilab in Illinois.

It has the power to smash protons or ions - particles known as hadrons - together at a whopping 14 teraelectron volts (TeV), seven times the record held by Fermilab's Tevatron.

The leviathan scale of the project is neatly juxtaposed by its goal, which is to explore the infinitely small.

Physicists have long puzzled over how particles acquire mass.

In 1964, a British physicist, Peter Higgs, came up with this idea: there must exist a background field that would act rather like treacle.

Particles passing through it would acquire mass by being dragged through a mediator, which theoreticians dubbed the Higgs Boson.

The standard quip about the Higgs is that it is the "God Particle" - it is everywhere but remains frustratingly elusive.

French physicist Yves Sacquin says that heroic work by the LEP and Fermilab has narrowed down the energy range at which the devious critter is likely to spotted.

Given the LHC's capabilities, "there's a very strong probability that it will be detected," he said.

Some experts are also hopeful about an early LHC breakthrough on the question of supersymmetry.

The supersymmetry theory goes way beyond even the Higgs. It postulates that particles in the Standard Model have related, but more massive, counterparts.

Such particles could explain the unsettling discovery of recent years that visible matter only accounts for some four per cent of the Universe. Enigmatic phenomena called dark matter and dark energy account for the rest.

CERN Director General Robert Aymar is confident the massive experiment will yield a correspondingly big breakthrough in penetrating these mysteries.

"It is certain that the LHC will yield the identity and understanding of this dark matter," he said in a video statement.

CERN has had to launch a PR campaign aimed at reassuring the public that the LHC will not create black holes that could engulf the planet or an unpleasant hypothetical particle called a strangelet that would turn the Earth into a lump of goo.

It has commissioned a panel to verify its calculations that such risks are, by any reasonable thinking, impossible, and France too has carried out its own safety probe.

Either way, the end of the world will not happen on Wednesday, for the simple reason that the LHC will not generate any collisions that day.

These will probably be initiated "in a few weeks" as part of a phased programme to commission the LHC, testing its equipment and evaluating work procedures before cranking it up to full strength, said Jenni.

Looking at the daily mountain of data that will have to be analysed, "it will take weeks or months before one can really hope to start discovering something new," he cautioned.

"The LHC is more than a machine. It is the intellectual quest of our age," the British weekly New Scientist said in this week's issue.

"With luck... today's physics textbooks will start to look out of date by the end of 2009."