Physicists firing up atom-smasher

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Scientists have fired the first protons into a 27km-long tunnel at the world's largest particle collider in science's next great step to understand the make-up of the universe.

Project leader Lyn Evans gave the order to send the protons into the $US3.8 billion ($A4.75 billion) Large Hadron Collider (LHC) below the Swiss-French border early Wednesday.

Scientists hope it will provide the necessary power to smash the components of atoms so that they can see how they are made.

The start-up has been eagerly awaited by 9,000 physicists around the world who will conduct experiments.

Some sceptics fear the collisions of protons could eventually imperil Earth. They took the experiment's architects to court in the US and France, believing it could create black holes in which the earth could disappear.

The collision of particles will briefly stoke temperatures 100,000 times hotter than the Sun, fleetingly replicating conditions which prevailed in split-seconds after the "Big Bang" that created the Universe 13.7 billion years ago.

In this primordial soup, novel particles may lurk that will resolve mysteries clouding our understanding of fundamental matter, scientists say.

"This machine will probably bring unexpected results that could turn particle physics on its head," French astrophysicist Hubert Reeves says.

Wednesday's operation kicks off a long and cautious commissioning process, testing equipment and procedures, before experiments begin in several weeks.

When all is ready, the LHC will whiz two parallel beams of protons, one clockwise and the other anticlockwise, around the tunnel.

Superconducting magnets cooled close to absolute zero - the chill of deep space - will then steer the beams so that they converge inside four chambers, like racing cars in a chicane.

Some protons are bound to collide, and subatomic wreckage from the smash will fly into the detectors, leaving a calling-card trace of their identity.

Over the years in which will the LHC will operate, masses of data will spew from these collisions and will be closely scrutinised by universities and laboratories around the world.

The Holy Grail will be finding a particle, called the Higgs Boson after British physicist Peter Higgs, who devised the theory of its existence in 1964.

The "Higgs" would explain how particles acquire mass, and some particles are more massive than others.

The idea is that these particles exist in a sort of invisible background field. Other particles passing through the Higgs field would acquire mass, like feathers passing through treacle.

Another big challenge will be testing the theory of supersymmetry, which postulates that the members of the known bestiary of sub-atomic particles 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.

Before the startup, internet-driven rumours said the LHC would create black holes or a nasty hypothetical particle called a strangelet that would gobble up the planet.

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

Melbourne University physicist Geoff Taylor has led an Australian contingent which designed detectors and shielding as well as software that triggers the collection of information.

Professor Taylor says the experiment's opponents are "completely misguided" in their stance.

"One of the things we are trying to do is create mini-black holes which scientifically would be a magnificent thing and tell us we don't live in three dimensions but that we live in nine or 10 dimensions," Prof Taylor said.

"As soon as you say there is the possibility of creating black holes you have people saying we are going to be swallowed up by black holes.

"That's where the furore has come and it's completely misguided."

Prof Taylor said the results could have a similar outcome as when Copernicus discovered that the earth was not the centre of the universe.

"That changed the whole way we looked at ourselves and realised that everything did not revolve around us - that we were just a part of something much, much bigger," he said.

He said if the experiment showed there were more than the three dimensions - height, width and depth - it could change the way we look at life.

If scientists can verify the existence of the Higgs Boson, it would be a big step in the search for a Grand Unified Theory, which aims to bring together three of the four known fundamental forces: electromagnetism, the strong nuclear force and the weak nuclear force, leaving out only gravity.

"One of the key reasons for building the machine is to find out if (the God Particle) exists," Prof Taylor said.

"The existence of such a particle would give us a whole new view on the structure of the universe."

Cathy Foley, president of the Australian Institute of Physics, said particles would be smashed together at speeds that generate large amounts of energy but when compared to more everyday events they were less impressive.

"Each collision of a pair of protons in the LHC will release an amount of energy comparable to that of two colliding mosquitoes," she said.

"It's like a rice-bubble pop."

Renowned British astrophysicist Stephen Hawking says he has bet $US100 ($A122) that the mega-experiment will not find the elusive particle seen as a holy grail of cosmic science.

"I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of 100 dollars that we won't find the Higgs," said Hawking, whose books including A Brief History of Time have sought to popularise study of stellar physics.

While questioning the likelihood of finding Higgs Bosons, Hawking said the experiment could discover superpartners, particles that would be "supersymmetric partners" to particles already known about.

"Their existence would be a key confirmation of string theory, and they could make up the mysterious dark matter that holds galaxies together," he told the BBC.

"Whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the universe," he added.

Hawking, the 66-year-old Lucasian Professor of Mathematics at Cambridge University, was diagnosed with the muscle-wasting motor neuron disease at the age of 22.

He is in a wheelchair and speaks with the aid of a computer and voice synthesiser.