The world's largest atom smasher was poised to start a new era of science today, colliding beams of protons to learn more about the make-up of the universe and its smallest particles.
Dubbed the world's largest scientific experiment, the €7.5bn Large Hadron Collider holds the promise of revealing details about theoretical particles and microforces, scientists say.
Two beams of protons began 11 days ago to speed at high energy in opposite directions around the 17-mile tunnel under the Swiss-French border in Geneva.
The beams have been pushed to 3.5 trillion electron volts, the highest energy achieved by any physics accelerator - some three times greater than the previous record.
The European Organisation for Nuclear Research, or CERN, plans today to start trying to use the powerful superconducting magnets to force the two beams to cross, creating collisions and showers of particles. They could be successful immediately, but such huge machines can be so tricky to run that it could take days.
The beams will be packed with hundreds of billions of protons, but the particles are so tiny that few will collide at each crossing.
Steve Myers, CERN's director for accelerators and technology, describes the challenge of lining up the beams as being akin to "firing needles across the Atlantic and getting them to collide half way".
The collisions will come over the objections of some people who fear they could eventually imperil Earth by creating micro black holes - sub-atomic versions of collapsed stars whose gravity is so strong they can suck in planets and other stars.
CERN and many scientists dismiss any threat to Earth or people on it, saying that any such holes would be so weak that they would vanish almost instantly without causing any damage.
The collider has been running smoothly since November when it was restarted following extensive repairs. It soon eclipsed the next largest accelerator - the Tevatron at Fermilab near Chicago - pushing its energy to 1.18 trillion electron volts, or TeV. Tevatron operates at 0.98 TeV.
The Large Hadron Collider was launched with great fanfare on September 10, 2008, but was sidetracked nine days later when a badly-soldered electrical splice overheated, causing extensive damage to the massive magnets and other parts of the collider some 300 feet below the ground.
It cost €30m to repair and improve the machine so that it could be used again at the end of November. Since then the collider has performed almost flawlessly, giving scientists valuable data in the four-week run before Christmas.
The extra energy in Geneva is expected to reveal even more about the unanswered questions of particle physics, such as the existence of antimatter and the search for the Higgs boson, a hypothetical particle that scientists think gives mass to other particles and thus to other objects and creatures in the universe.
Scientists hope also to approach on a tiny scale what happened in the first split seconds after the Big Bang, which they believe was the creation of the universe some 14 billion years ago.
Rolf-Dieter Heuer, the director-general of CERN, has said it is likely to take months before any scientific discoveries are made, partly because computers will have to sort through massive amounts of data produced by the collisions.
Mr Heuer said researchers hoped by the end of this year to make discoveries into the dark matter that scientists believe comprises 26% of the universe. The better understood visible matter makes up only 4% of the universe.
Dark matter has been theorised by scientists to account for missing mass and bent light in far-away galaxies. Scientists believe it makes galaxies spin faster.
A separate entity called "dark energy", making up the remaining 70% of the universe, is believed to be linked to the vacuum that is evenly distributed in space and time. It is believed to accelerate the expansion of the universe.
Other possible candidates for discovery are hidden dimensions of space and time.
Physicists have used smaller, room-temperature colliders for decades to study the atom.
They once thought protons and neutrons were the smallest components of the atom's nucleus, but the colliders showed that they were made of quarks and gluons and that there were other forces and particles.