€4bn atom smasher is on hunt for dark matter
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, Prof Rolf Heuer, director general of Cern, the European Organisation for Nuclear Research, said: "Congratulations. Thanks everyone ... now the hard work starts."
Currently the £3.74bn 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 astounded the world with the discovery of the Higgs boson, an elementary particle that gives other particles mass. However, a glitch had delayed the restart of the LHC after an upgrade.
Now the scientists have their sights set on an even more exotic trophy - dark matter, the invisible, undetectable material that makes up 84pc of matter in the universe and binds galaxies together, yet whose nature is unknown.