Give Me a Crash Course In ... the Cern reboot
The Large Hadron Collider, the world’s most powerful particle smasher, has just started up again after a two-year shutdown for repairs and improvements
The Large Hadron Collider (LHC) creates beams of particles and speeds them up to almost the speed of light before letting them crash into one another. Photograph: Cern/PA Wire
Why are people talking about something called Cern? Cern is Europe’s nuclear research centre based on the French-Swiss border. It is the home of the Large Hadron Collider, LHC, the world’s biggest and most powerful particle smasher, and it has just started up again after a two-year shutdown for improvements and repairs. What is a particle smasher? The LHC creates beams of particles and speeds them up to almost the speed of light before letting them crash into one another. The high-speed collisions in turn kick off more shortlived particles that the scientists can detect using big experiments.
That sounds kind of stupid, why would you bother doing such a thing? It gives the scientists huge amounts of information that helps explain what matter is made of. It also helps them find explanations for why the universe is shaped the way it is and how matter formed after the Big Bang.
You are talking about the smallest of things, subatomic particles, and the biggest of things, the universe. How can particle smashing do both? It is all about physics and the forces that hold matter and the universe together. Scientists have devised a “theory of everything”, one that identifies all of the various sub-atomic particles and how they are connected by four different kinds of forces. You need the huge energies created by particle smashing to reveal the smaller constituent parts such as quarks and bosons.
How does the LHC work? It has to do with energy. In the LHC, which is a 27km-long ring (left) built underground beneath the French-Swiss border, powerful superconducting magnets guide packets of particles around the ring, some travelling clockwise and others anticlockwise. The particles collide when near huge detector experiments, most of them bigger than a house and weighing hundreds of tonnes. Before the LHC was shut down for repairs in 2013 it was reaching energies of eight trillion electron volts (8TeV), a measure of energy used by particle physicists. During this run they will push collision energies up 62 per cent to 13 TeV.
So more is more when it comes to colliders? Yes. They increase the energy of the protons and stepping up the energy lets them capture more information. Increasing the energy to 8TeV is what allowed Cern to first detect the existence of the Higgs Boson in July 2012 and then confirm it by March 2013. It took a long time because detection events were rare, but Higgs detection events will increase when the LHC runs at 13TeV.
I have heard of the Higgs Boson. The Higgs particle was the final missing puzzle piece in the theory of everything and this is why the physicists were so excited when it was confirmed. Before that, the Higgs was only a mathematical calculation. But the LHC was able to confirm it because the experiments can see it.
So what comes next? The LHC will be operating at unprecedented energy levels so the scientists have no idea what might emerge, but that of course is the reason why humans pursue difficult tasks – for the joy of discovery.