Why is CERN's Large Hadron Collider Running Again?

The Large Hadron Collider (LHC) was restarted in early April 2015, after having been switched off for the last two years during a major renovation which ultimately cost £100 million.

The so-called 'God Particle'

The machine, situated underground below the border between Switzerland and France, is known, even among non-scientists, for proving the existence of the Higgs boson, or Higgs particle, in July 2012.  The somewhat controversial soubriquet 'God's Particle', helped to attract the interest of the popular media and consequently the general public. In 2013 the Nobel Prize in Physics was awarded jointly to François Englert and Peter Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles''.

So why, after two years 'off-line', is it being restarted and what other secrets of our universe might it unlock next? Well, the reason the particle collider was shut down was to allow work to almost double its energy levels.

Dark Matter

The machine is currently running at a low 'injection' energy of 450 giga-electron volts (GeV), but in June this year it will increase to a record-breaking 13 tera-electron volts (TeV). To put this into relative context it was running at 7 TeV when it managed to detect the Higgs boson. Physicists are now aiming to see the mysterious named hypothetical 'dark matter' for the first time. Dark matter makes up more than 80% of, well, everything really – but it has not been detected directly, making it one of the greatest mysteries in modern astrophysics. If physicists at CERN could detect dark matter, it would represent a truly giant leap for mankind's understanding of our universe.

Other Possibilities

As well as dark matter, the team is hoping to discover more Higgs bosons and other particles which have never been detected before – and perhaps uncover the existence of extra dimensions. Such a discovery could explain why gravity is weaker than theoretical models would predict.

Patience is a virtue....

Every physicist will acknowledge that they work in a field where truly significant developments are rare, with many years passing between major discoveries or even hypotheses. It took 50 years for the Higgs boson to be discovered and 20 years to build the LHC. It may not have taken long for it to allow for discovery of the Higgs boson, but there is of course no guarantee of it unlocking the secrets of dark matter any time soon. Cern spokesman Arnaud Marsollier said: ''If something interesting appears in this new window we will see it. It might be two months from now or two years, we're not able to say........it will be running at least until 2035, so we can be patient.”'

Something truly monumental may be discovered soon – but the chances are that it will be years rather than months.