LHC switch-on in 2008: a billion viewers, no collisions

The Large Hadron Collider first circulated a proton beam on 10 September 2008: at 10:28 local time, after being threaded through the machine sector by sector, a bunch of protons completed a full lap of CERN’s 27-kilometre ring, 100 metres beneath the French–Swiss border. Later that day a beam made it round in the opposite direction too.

One thing many people remember about that day is wrong: nothing collided. “First-beam day” was a routine commissioning step with no collisions or physics results scheduled, and the protons carried less energy than those in the US Tevatron collider then running.

The attention was enormous anyway: an estimated audience of more than a billion people, some 2,500 television broadcasts and 6,000 press articles, and more visits to CERN’s homepage than to NASA’s. Part of the draw was the claim that the machine could create an Earth-swallowing black hole. CERN’s safety assessment, endorsed by the American Physical Society, the UK Institute of Physics and the German Physical Society, concluded the collisions are safe; nature already runs more than 10 million million LHC-like collisions every second, and stars and planets survive.

What happened next:

• 19 September 2008: a faulty splice between two magnets fails during circuit tests, releasing six tonnes of helium and damaging about 400 metres of the machine. Repairs set operations back 14 months.
• November 2009: the beams reach a record 1.18 TeV each.
• 30 March 2010: the physics programme begins, with collisions at 7 TeV.
• 4 July 2012: the ATLAS and CMS experiments announce the Higgs boson.

In its latest run the LHC collided protons at 13.6 TeV, still the world’s most powerful particle accelerator, before a long shutdown for a major upgrade scheduled from July 2026.