Scientists have successfully restarted the Large Hadron Collider (LHC), the most powerful atom-smasher ever
built, hoping to enter a new realm of physics and make history for the second time.
Two beams of particles travelling a whisker below the speed of light were sent flying in opposite directions through the LHC's 27 kilometres of circular underground tunnels straddling the Swiss-French border.
Amid scenes of jubilation in the LHC control room, Professor Rolf Heuer, director general of Cern, the European Organisation for Nuclear Research, said: "Congratulations. Thank you very much everyone... now the hard work starts."
Currently the 3.74 billion machine is running at a low "injection" energy of 450 giga-electron volts (GeV). In June, the energy level will be ramped up to a record-breaking 13 tera-electron volts (TeV) and experiments probing the fundamental building blocks of the universe can begin.
Two years ago the LHC team, which includes a number of British physicists, astounded the world with the discovery of the Higgs boson, an elementary particle that gives other particles mass.
Now the scientists have their sights set on an even more exotic trophy - dark matter, the invisible, undetectable material that makes up 84 per cent of matter in the universe and binds galaxies together yet whose nature is unknown.
With a beam energy of 13 TeV - almost twice that which produced the Higgs boson - it is conceivable that the LHC will capture dark matter, marking a leap forward in our understanding of the universe.
A technical hitch had delayed the restart of the LHC after a two year re-fit and upgrade.
An electrical short circuit prompted fears that operations could be put back weeks or even months. However, engineers quickly located the problem - a small piece of metal debris - and removed it.
As tension built during the final minutes before the restart, Frederick Bordry, Cern's director for accelerators and technology, handed out Easter eggs to staff in the LHC control room.
The particles of protons, the "hearts" of atoms, travel round the LHC at just three metres per second below the speed of light.
When experiments begin they will be smashed together in four giant detectors located around the beam ring, sparking the creation of new particles and hopefully opening up a new era in physics.
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