By Paul Rincon
Science reporter, BBC News
Scientists have hailed a successful switch-on for an enormous experiment which will recreate the conditions a few moments after the Big Bang.
They have now fired two beams of particles called protons around the 27km-long tunnel which houses the Large Hadron Collider (LHC).
The £5bn machine on the Swiss-French border is designed to smash protons together with cataclysmic force.
Scientists hope it will shed light on fundamental questions in physics.
The first – clockwise – beam completed its first circuit of the underground tunnel at just before 0930 BST. The second – anti-clockwise – beam successfully circled the ring after 1400 BST.
The beams have not yet been run continuously. So far, they have been stopped, or “dumped”, after just a few circuits.
By Wednesday evening, engineers hope to inject clockwise and anti-clockwise protons again, but this time they will “close the orbit”, letting the beams run continuously for a few seconds each.
Cern has not yet announced when it plans to carry out the first collisions, but the BBC understands that low-energy collisions could happen in the next few days. This will allow engineers to calibrate instruments, but will not produce data of scientific interest.
“There it is,” project leader Lyn Evans said when the beam completed its lap. There were cheers in the control room when engineers heard of the successful test.
He added later: “We had a very good start-up.”The LHC is arguably the most complicated and ambitious experiment ever built; the project has been hit by cost overruns, equipment trouble and construction problems. The switch-on itself is two years late.
The collider is operated by the European Organization for Nuclear Research – better known by its French acronym Cern.
The vast circular tunnel – the “ring” – which runs under the French-Swiss border contains more than 1,000 cylindrical magnets arranged end-to-end.
The magnets are there to steer the beam – made up of particles called protons – around this 27km-long ring.
Eventually, two proton beams will be steered in opposite directions around the LHC at close to the speed of light, completing about 11,000 laps each second.
At allotted points around the tunnel, the beams will cross paths, smashing together near four massive “detectors” that monitor the collisions for interesting events.
Scientists are hoping that new sub-atomic particles will emerge, revealing fundamental insights into the nature of the cosmos.
The Fear of Black Hole for which many people opposed the test: