* Ian Sample
* September 10, 2008
One of the most significant scientific experiments in history begins today - and it may help unravel the mysteries of the universe.
BENEATH the rural tranquillity of the Geneva countryside, where ramshackle sheds dot the wide-open fields, scientists are getting ready for a trip into the unknown. Here, under 100 metres of rock and sandstone, lies the biggest, most complex machine humans have ever built, and today they will finally get to turn it on.
Scientists involved in a historic 'Big Bang' experiment to begin this week hope it will turn up many surprises about the universe and its origins.
For CERN, the European nuclear research organisation, it will mark the end of a lengthy wait and the beginning of a new era of physics. Over the next 20 years or so, the $9.6 billion machine will direct its formidable power towards some of the most enduring mysteries of the universe.
The machine will search for extra dimensions, which could be curled up into microscopic loops. It might produce "dark matter", the unknown substance that stretches through space like an invisible skeleton. And it will almost certainly discover the elusive Higgs boson, which is better known by its wince-inducing moniker, the God particle.
At least that is the hope. For the machine to work, a dizzying number of electronic circuits, computer-controlled valves, airtight seals and superconducting magnets must all operate in concert.
The machine is called the Large Hadron Collider (LHC), and when working at full tilt it will drive two beams of particles in opposite directions around a 27 kilometre ring at 99.9999991% of the speed of light. Every second each of the beams will complete 11,245 laps of the machine.
At four points around the ring the beams will be steered into head-on collisions, causing the particles to slam into one another with enough energy to recreate in a microcosm the violent fireball conditions that existed one-trillionth of a second after the Big Bang.
Giant detectors will then scrutinise the shower of subatomic debris in the hope of finding something no one has ever seen before. The largest detector, named Atlas, sits in a cavern and is about 45 metres long, more than 25 metres high, and weighs about 7000 tons. It is about half as big as the Notre Dame Cathedral in Paris.
"This is a once-in-a-generation kind of machine, and we really don't know what we will find," says Brian Cox, a physicist at Manchester University who works on Atlas. "It's like going to Mars. You know you're going to find something new, because you're going where no one has been before."
And physicists everywhere will be watching - from control rooms and auditoriums on the scene, or on webcasts. The Fermi National Accelerator Laboratory, or Fermilab, outside Chicago, will even hold a "pyjama party" for staff members and journalists to watch the events live from a remote control room.
But physicists' excitement aside, the awesome power of the LHC has prompted a flurry of alarmist fears that the machine might create a black hole that would swiftly consume the planet. In the run-up to the machine switching on, the laboratory has received a steady stream of calls from people wanting reassurance, or simply asking the scientists to stop. Two attempts to stop the machine through the courts were dismissed. Scientists say far more energetic collisions happen regularly in nature, when cosmic rays strike stray particles in space.
The doomsday claims have also been vigorously rebutted by a series of safety reports and studies, the most recent of which was published last week in The Journal of Physics G: Nuclear and Particle Physics, a peer-reviewed journal.
The director-general of CERN, Robert Aymar, said in a news release: "The LHC is safe, and any suggestion that it might present a risk is pure fiction."
And besides - the beams, for now, will only be circulating, not colliding.
Although CERN has already conducted some basic tests with its machine, today will be the first attempt to get a beam of protons circulating inside it.
"If the beam goes all the way round on the first go, that would be quite amazing. It's never happened in the history of particle colliders," says CERN's James Gillies.
If the test is successful, scientists may try to send the beam around in the opposite direction, though first collisions are not expected until next month. They expect to spend a few months getting to grips with the machine before putting it to work in earnest.
CERN was set up in 1954 by European scientists who had won the ear of government through their nuclear work during World War II, and who recognised that progress in their subject would require equipment too expensive for any single European country to fund.
CERN, therefore, became one of Europe's first joint ventures and now has 20 member states.
The organisation employs about 2500 people. Some 8000 visiting scientists - half of the world's particle physicists - come to CERN for their research. The laboratory sits astride the Franco-Swiss border near Geneva and is famously the birthplace of the World Wide Web.
The LHC is perhaps the most significant milestone in the research organisation's history. It is likely to be the world's premier accelerator for at least the next 15 years.
In The Daily Telegraph, Lord Martin Rees, Astronomer Royal and president of the Royal Society, writes that some scientific challenges are so great that "they demand a massive enterprise, in which thousands of researchers combine their efforts to achieve a common goal".
"This happened in astronomy with the Hubble Telescope, and in biology with the human genome project. And now it is happening in physics," Rees writes. "The Large Hadron Collider ... will be the largest experiment in human history."
The potential for discovery is breathtaking.
"People might think we already know a lot about the way things work, but the wheels are coming off our understanding of the universe. We can confidently say that 95% of the universe is made up of stuff we don't understand," Cox says.
Only 5% of the universe is made of matter scientists understand. A further 25% is so-called "dark matter", which clusters around galaxies, and the remaining 70% is even more enigmatic "dark energy", which drives the expansion of the universe.
In recent weeks, there has been a blitzkrieg of papers and predictions on what might or might not be discovered when protons are accelerated to energies of 7 trillion electron volts - seven times higher than at Fermilab, currently the most powerful particle collider in the world - and smashed together.
One of the first discoveries that could emerge is proof of a theory known as supersymmetry. According to the theory, every particle in the universe has a slightly overweight but invisible twin. One of these, called the neutralino, is a leading candidate for dark matter, and could be made as soon as the machine performs its first collisions. The mysterious dark matter provides the invisible scaffolding of galaxies and the cosmos.
The LHC may also see the emergence of the Higgs boson, which is hypothesised to endow other particles with mass.
Some optimists hope the colliding protons may reveal surprises about the nature of space itself. Theories suggest that space is actually 10-dimensional, or that there may be other entire universes "alongside" ours, like sheets of paper separated by less than a millimetre, but separated forever because they are in different dimensions.
But the world should not hold its breath for exciting news. Most of the effects being sought involve very rare events - maybe only one collision in a billion. Huge volumes of data will need to be collected and sifted before any firm claims emerge. This "big science" entails a style of work ill-suited to mavericks and individualists, but it's an essential complement to the contribution of the swarm of theorists ready to pounce on any novel phenomenon that emerges.
For the 10,000 scientists and engineers involved in the project this is the culmination of more than 20 years of work.
Agencies
LINK
See the live webcast at:
lhc-first-beam.web.cern.ch
