Large Hadron Collider II: The Boson Strikes Back
Right now, 100 metres beneath the green fields of the Franco-Swiss border, two beams of proton particles are being hurled into each other around a 27km ring with an energy of 13 trillion electron volts. At various points around the loop, Cern scientists are standing by to... well, just to see what happens.
So what exactly is the second phase of the Large Hadron Collider? Is the wider world at risk of being sucked into an accidental black hole? Could Cern kickstart a second big bang? Or is it all a waste of particles? Here's what you need to know.
What are they doing at the LHC?
This is the second 'run' of Cern's LHC. Between 2008 and 2013, the project made a variety of discoveries by essentially carrying out the scientific equivalent of the childhood act of smashing two HotWheels cars together: one beam of tiny particles was sped around the 27km loop with the equivalent energy of eight trillion electron volts (TeV), with another beam of particles doing exactly the same thing in the opposite direction. Then, in Ghostbusters fashions, the beams were crossed.
By smashing these atoms together, Cern's scientists were hoping to discover more about particle physics by watching the resulting mess.
During the first run at 8 TeV, Cern's scientists made a number of significant discoveries, most notable of which was in identifying the 'God Particle', or Higgs boson - an important discovery for the 'standard model' of particle physics, which helps scientists understand why things have mass. In October 2013, François Englert and Peter W. Higgs were awarded the Nobel Prize in physics "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles".
On 3 June 2015, having lain dormant for 27 months, the LHC has been turned back on to a higher power setting, speeding particles around its loop at 13 TeV - fully 63 percent more energy than before.
Why the two year delay?
The LHC is a very, very expensive undertaking for Cern. Having run for five years, the vast loop needed to be shut down for a variety of repairs to be carried out - which also gave scientists a little breather to go through the vast amount of data collected from the first 'season'.
By turning up the juice, it's hoped that season two of LHC will give further insights into the sub-atomic structures of particles and the general behaviour of how the tiniest building blocks of the universe function. Or, as Cern's director-general elect Fabiola Gianotti put it to the BBC, "a higher energy will allow us to address the great outstanding questions in particle physics".
Sergio Bertolucci, Cern's head of research, was far more poetic about the occasion. He described it in Star Trek terms, stating: "We have the most powerful ship in the world, we have the best crew, now we are ready to go on the next exploration... We are going into a vastly uncharted space and there could be big surprises."
What are they looking for?
By cranking the LHC up to 13 TeV, Cern's scientists are turning on a "data tap": the rate of particle collisions will increase between now and the height of summer, with each collision of proton atoms providing a possible insight into a new sub-atomic building block.
One elusive substance Cern will be keen to find out more about is 'Dark Matter' - a substance that it's thought could make up around 84 percent of the universe. By increasing the power, it's hoped LHC could find some of these previously undetected, 'heavier' particles.
Another theory to be tested is that of 'supersymmetry' - which predicts that every particle has a more massive, undetected partner, which helps to unify nature's forces. So a photon, which carries light, has a photino, a quark has a squark. If you want your brain to go squiffy, you can read more about it on Cern's website here.
Could the LCH end the world?
Short answer: no. The long answer was explored in great detail by Cern and the American Physical Society. Some scientists had posited that if the LHC was looking to recreate conditions apparent at the start of the big bang, with lots of protons flying around at high speeds, it could start something like a black hole, or second big bang, under the French-Swiss border.