An explosion in the beam tunnel caused a major setback. Accelerator scientists examine what went wrong and outline how the beam gathers speed, ready for collision

Transcript -- The world's most complicated machine

To mark the re-launch of the Large Hadron Collider, the world's most powerful particle accelerator, this album examines how an accelerator works, why the LHC failed in 2008 and what scientists hope its high-energy collisions will reveal. The audio tracks feature Dr Stephen Serjeant and Dr David Broadhurst from The Open University and Dr Dan Faircloth and Dr Bruce Kennedy from the Science and Technology Facilities Council's Rutherford Appleton Laboratory. They share their passion for this immense machine that will recreate, on a tiny scale, conditions that existed just after the Big Bang. It is hoped the LHC will provide a glimpse of the theoretical Higgs boson and explain the origin of mass. It may also discover a new family of supersymmetric particles and provide an insight into the nature of dark matter. Looking to the future, there is a sneak preview of the LHC upgrade plans, and a particle accelerator of the future, the Next Linear Collider.