LHC set to unravel nature's secrets.

The big switch-on of the world's biggest scientific experiment will now take place at the end of this month. Within the year, scientists could be able to tell us whether there are more dimensions of space or perhaps explain what dark matter is made of.

The European particle physics centre in Geneva, CERN, will send the first beam of protons around the 27km tunnel of its new atom smasher, the Large Hadron Collider (LHC). 'For me, this is the most important thing of all, to get the first beam in and to get it circulating with a good lifetime,' project leader Lyn Evans told the EuroScience Open Forum in Barcelona.

Seven to eight weeks after the first beam is switched on, the first collisions will take place. Two beams will race around the tunnel in opposite directions leading to a head-on collision at high energies, a collision that scientists hope will produce subatomic particles never seen before.

'We understand nature at a certain level, there are other things that we merely suspect exist ... The most exciting of all possibilities is that we find something that we did not expect,' Evans said.

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'There are things that could show up immediately; we could be overwhelmed by super-symmetry,' senior CERN scientist Fabiola Gianotti told the meeting. Super-symmetry is a theory in which each particle has a heavier counterpart. It could explain dark matter. But she says it may take six months to a year to make sure that the detectors are working well so it would be at least that long before they could confidently claim any discoveries. 'We would have to be very prudent,' she said.

Lyn's team is currently in the large stages of preparation, which involves cooling the 50 000 tonnes of equipment to just 1.8K above absolute zero, which is colder than it is in outer space. Five of the machines' eight segments are already at the required temperature.

If the LHC used ordinary 'warm' magnets instead of superconductors, the ring would have to be at least 120km in circumference to achieve the same collision energy and it would consume 40 times more electricity.

The LHC was built first and foremost to seek out a subatomic particle called the Higgs Boson. The existence of this would solve the conundrum as to why the photon (which conveys the forces of electromagnetism) has no mass, whereas the W and Z bosons (which are operative in the nuclear forces that cause radioactive decay) do have mass.

It has taken 14 years to build. 'It feels like we are finishing a marathon with a sprint,' Evans said.

The LHC is designed to reach seven times the energies of the currently reigning particle accelerator at the Fermi National Accelerator Laboratory in lllinois, US.