Key collider facts

When the 27km long circular tunnel at CERN was excavated, between Lake Geneva and the Jura mountain range, the two ends met up with just one centimetre of error.

The tunnel has its own fire brigade. They are trained in abseiling techniques as well as dealing with chemical and radiation hazards.

At full power, trillions of protons will race around the LHC accelerator ring 11,245 times a second, travelling at 99.999 per cent of the speed of light. Six hundred million collisions will take place every second as the protons smash into each other.

When two beams of protons collide, they will generate temperatures more than 100,000 times hotter than the heart of the sun.

At the centre of the accelerator is a vacuum as empty as interplanetary space in which the proton beams travel. The internal pressure of the LHC is 10-13 atm, 10 times less than the pressure on the moon.

Movement is governed by 9,300 ultra-powerful magnets which work at temperatures so cold no life could exist. They are precooled to minus 193.2C using 10,080 tonnes of liquid nitrogen, before they are filled with nearly 60 tonnes of liquid helium to bring them down to minus 271.3C.

Each proton moves at such speed that it contains the equivalent energy of a family car travelling at 1,056mph.

The collisions are designed to produce particles whose existence has so far only been theorised about, including the Higgs boson, the main focus of its search, which was first postulated in 1964 and has been dubbed the "God particle".

Other products of the collisions could include extra dimensions, "strangelets", which may or may not exist, and micro black holes, the objects at the centre of fears the accelerator could end the world.

The accelerator is powered by a vast amount of electricity, with the magnets connected by superconductors. The cable they use would stretch round the equator 6.8 times.

The data recorded by each of the big experiments at the LHC will fill 100,000 DVDs every year.

CERN, which runs the accelerator, estimates that one per cent of data recorded will be useful.

A special Radio 4 episode of Dr Who spin-off Torchwood is being produced by the BBC to mark the LHC's switch-on.