The upper and lower sixth-form Physics sets enjoyed a three-day visit to Switzerland this February in order to take a tour of the world’s foremost particle physics laboratory at CERN, near Geneva. Here, many different experiments are carried out to learn more about the fundamental particles that make up the universe, and the forces that make matter behave in the way it does.

The largest and perhaps most important experiment at CERN is the Large Hadron Collider (LHC). With construction nearing completion, it is an underground circular tunnel of diameter 8.6km, containing an evacuated tube along with powerful electromagnets and electric “accelerating cavities”. Its purpose is to accelerate nuclear particles to speeds well above 99% of the speed of light.

Atoms are made up of a nucleus containing protons and neutrons, surrounded by a cloud of lighter electrons. Unlike its predecessor (the Large Electron Positron collider), the LHC will be accelerating nuclear particles – both protons and their antimatter counterparts, as well as entire nuclei. The LHC can give every one of the hundred billion lead (as in the metal) nuclei in its beam kinetic energy equivalent to that of a speeding hornet. This may not sound like all that much but when packed into such a small space, it is an incredible amount of energy.

Due to Einstein’s famous relation E=mc², energy and mass can be interchanged. When the nuclei or protons/antiprotons are made to collide with each other, a portion of their enormous kinetic energy is converted into mass. This mass takes the form of rare and interesting particles. The vast majority of these particles “decay” very quickly into ordinary matter again, but before they do so they can be observed by enormous detectors hich are built around the tube at the point of collision. By observing the new particles and how they behave, physicists can test and refine theories about how the universe operates.

On our trip we were privileged to visit the ALICE detector, which is the largest of the four detectors that are to be installed around the LHC. It is difficult to convey the magnitude of this engineering feat but ALICE is the size of a large house and every part of it is precision engineered, from the millions of detecting wires and complex microelectronics to the cryogenic cooling system for its superconducting magnets. We were also given an interesting lecture on some of the details involved in particle experiments, during which student Fergus Noble raised some remarkable questions on fluid dynamics.

Before coming home we also had a chance to visit Geneva’s historical old town including St Peter’s cathedral; and some lower-speed but more painful collisions were involved when we attempted ice skating!