The Large Electron–Positron collider was switched on in 1989

On this day thirty years ago, the Large Electron–Positron collider (LEP) saw its first collisions. Designed to study the recently discovered W and Z bosons, and to look for signs of the Higgs boson, it was a remarkable machine in many ways.

When LEP was switched on in 1989, it was the largest scientific instrument ever made. It was proposed in the late 1970s and it took over 20 million work-hours for the machine to be realised. Between 1983 and 1988 LEP was the largest civil-engineering project in Europe.

After eleven years of fruitful research, including helping determine that there are only three generations of neutrinos, the accelerator was decommissioned in 2000. However, its legacy lives on: LEP’s 27-km tunnel was reused to house the Large Hadron Collider (LHC). Now, as particle physicists discuss an update to the European Strategy of Particle Physics and plan an accelerator that will eventually supersede the LHC, LEP is an important reminder of the long-term nature of pursuing fundamental knowledge.

This short video tells the story of LEP, from planning and construction to its invaluable research outputs: