The world's largest particle collider passed its first major tests by firing two beams of protons in opposite directions around a 27km underground ring on Wednesday in what scientists hope is the next great step to understanding the makeup of the universe.
The start of the collider was described by scientists from the European Organisation for Nuclear Research, known by its French acronym CERN, as the biggest physics experiment in history using the most complicated scientific instrument ever built.
After a series of trial runs, two white dots flashed on a computer screen at 10:26 a.m. (0826 GMT) indicating that the protons had travelled clockwise along the full length of the US $3.8 billion Large Hadron Collider - described as the biggest physics experiment in history.
Cheers erupted from the assembled scientists, including project leader Lyn Evans, in the collider's control room at the Swiss-French border when the beam completed its lap.
Champagne corks popped in labs as far away as Chicago, where contributing scientists watched the proceedings by satellite.
Five hours later, scientists successfully fired a beam counter clockwise.
Physicists around the world now have much greater power to smash the components of atoms together in attempts to learn about their structure.
Robert Aymar, director-general of the European Organisation for Nuclear Research, congratulated and thanked the assembled scientists in the collider's control room at the Swiss-French border after the second beam completed its circular journey.
The organisation, known by its French acronym CERN, began firing the protons - a type of subatomic particle - around the tunnel in stages less than an hour earlier, with the first beam injection at 9:35 am (0735 GMT).
Eventually two beams will be fired at the same time in opposite directions with the aim of recreating conditions a split second after the big bang, which scientists theorise was the massive explosion that created the universe.
"My first thought was relief," said Evans, who has been working on the project since its inception in 1984. "This is a machine of enormous complexity. Things can go wrong at any time."
He did not want to set a date, but said that he expected scientists would be able to conduct collisions for their experiments "within a few months."
Jrgen Schuhkraft, speaking from the Alice Control Room, was impressed with the enormous achievement of the test beam.
"I think I should also congratulate the machine. We were really not expecting to get the first beam twice after less than one hour because we saw actually the beam even three times around now the detectors and that was really a big feat thanks to the machine," he said.
The collider is designed to push the proton beam close to the speed of light, whizzing 11,000 times a second around the tunnel.
Scientists hope to eventually send two beams of protons through two tubes about the width of fire hoses, speeding through a vacuum that is colder and emptier than outer space.
The paths of these beams will cross, and a few protons will collide.
The collider's two largest detectors - essentially huge digital cameras weighing thousands of tons - are capable of taking millions of snapshots a second.
The supercooled magnets that guide the proton beam heated slightly in the morning's first test, leading to a pause to recool them before trying the opposite direction.
The CERN experiments could reveal more about "dark matter," antimatter and possibly hidden dimensions of space and time.
It could also find evidence of the hypothetical particle - the Higgs boson - which is sometimes called the "God particle" because it is believed to give mass to all other particles, and thus to matter that makes up the universe.
Questioned by reporters in Edinburgh about this prospect, Higgs expressed confidence in his theory.
"I'll be very surprised and disappointed if it turns out not to be so. It would mean that I really no longer understand things which I think I now understand well," he said.
The start of the collider came over the objections of some who feared the collision of protons could eventually imperil the Earth by creating micro-black holes, subatomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.
James Gillies, chief spokesman for CERN dismissed this as nonsense before Wednesday's start.
CERN was backed by leading scientists like Britain's Stephen Hawking who declared the experiments to be absolutely safe.
Gillies said that the most dangerous thing that could happen would be if a beam at full power were to go out of control, and that would only damage the accelerator itself and burrow into the rock around the tunnel.
Nothing of the sort occurred on Wednesday, though the accelerator is still probably a year away from full power.
CERN Particle Physics Scientist James Strait echoed their assurances of safety.
"What we're doing here is done in nature on a regular basis with very high cosmic energy rays that hit the earth on a regular basis at collision energies much higher than we can achieve here, and no black holes yet, and it's been going on for (b) billions of years, so this is very safe," Strait told AP Television.
"We have here what is the biggest, most complicated scientific instrument ever built, combining many accelerators and very complex experiments with which we hope to learn amazing things about how the universe works," he added.
The project organised by the 20 European member nations of CERN has attracted researchers from 80 nations.
Some 1,200 are from the United States, an observer country that contributed 531 (m) million US dollar. Japan, another observer, is a major contributor.
Some scientists have been waiting for 20 years to use the LHC.
The complexity of manufacturing it required groundbreaking advances in the use of supercooled, superconducting equipment.
The 2001 start and 2005 completion dates were pushed back by two years each, and the cost of the construction was 25 percent higher than originally budgeted in 1996, CERN's director-general at the time told The Associated Press.
Smaller colliders have been used for decades to study the makeup of the atom.
Less than 100 years ago scientists thought protons and neutrons were the smallest components of an atom's nucleus, but in stages since then experiments have shown they were made of still smaller quarks and gluons and that there were other forces and particles.
APTN
Listen to RadioLIVE's Marcus Lush on Breakfast speak with David Krofcheck, an Auckland University Researcher who has been involved with the project for eight years.