Picture a peaceful sunlit view of the countryside northwest of Geneva extending to the Jura mountain range in the distance.
Strange bunches of green and yellow lights emerge from a small area alongside the Route de Meyrin and move in opposite directions around a vast ring stretching between the airport runway in the foreground and the slopes of the Jura.
The Controller starts pressing buttons: as the Sun dims, more and more lights enter the ring to join the circulating bunches.
The next button is pressed, activating the green and yellow bunches which move faster and faster through fields and forests, across roads and streams, accompanied by a humming sound, its pitch increasing with the increasing speed.
The Controller presses the final button: suddenly brilliant tracks of chattering sparks burst from four points along the ring as yellow and green lights collide. Eventually the lights grow dim and the sparks disappear.
The Controller then travels in time to the year 2005: now the lights are red; bunches so numerous that they fill the ring, travelling at a pace even more furious than before, creating larger and more numerous bursts of light when they collide.
Above: Filling the LHC ring with particles
The coloured lights represent different particles circulating and colliding 100 m underground at CERN, the European centre for particle physics near Geneva. They are part of a new "hands on" exhibit at the Science Museum, which has been designed and built by the High Energy Particle Physics Group of the Department of Physics and Astronomy at University College London. It has been funded by a grant from PPARC, the Particle Physics and Astronomy Research Council, under their Small Awards Scheme for public understanding of science.
The demonstration invites you to become Controller and see how LEP, the Large Electron Positron collider at CERN operates. The green lights represent electrons in the machine, the yellow lights positrons. The exhibit also gives a view of what is in store for the future, when the LHC, or Large Hadron Collider has been built in the same tunnel. This machine will collide high energy protons (the red lights).
The exhibit has proved very popular. In the first 2 years almost 50,000 people pressed the "start" button, more than 30,000 completed the correct sequence of buttons to operate the LEP collider, and nearly all of those went on to control the LHC. So, why not get down there at the next opportunity - take your family too - and have a go at "driving" the world's biggest scientific instrument!
More pictures of particle physics fans operating the collidor at the Science Museum:
Accelerating particles in the LHC ring prior to collision
Accelerating particle bunches in the LEP ring
