The most complex scientific experiment ever undertaken, the Large Hadron Collider (LHC) will accelerate sub-atomic particles to nearly the speed of light and then smash them together, with the aim of filling gaps in our understanding of the cosmos.
It may also determine the outcome of novel theories about space-time: does another dimension -- or dimensions -- exist in parallel to our own?
After nearly two decades and six billion Swiss francs (3.76 billion euros, 5.46 billion dollars), an army of 5,000 scientists, engineers and technicians drawn from nearly three dozen countries have brought the mammoth project close to fruition.
At 9:30 a.m. (0730 GMT) on Wednesday, the first protons will be injected into a 27-kilometre (16.9-mile) ring-shaped tunnel, straddling the Swiss-French border at the headquarters of the European Organisation for Nuclear Research (CERN).
Whizzed to within a millionth of a percent of the speed of the light, the particles will be the first step in a long-term experiment to smash sub-atomic components together, briefly generating temperatures 100,000 times hotter than the Sun in a microscopic space.
Analysts will then pore over the wreckage in the search for fundamental particles.
"We will be entering into a new territory of physics," said Peter Jenni, spokesman for ATLAS -- one of four gargantuan laboratories installed on the ring where a swathe of delicate detectors will spot the collisions.
"Wednesday is a very major milestone."
The LHC is massively-muscled machine compared to its CERN predecessor, the Large Electron-Positron (LEP) collider, and an ageing accelerator at the legendary Fermilab in Illinois.
It has the power to smash protons or ions -- particles known as hadrons -- together at a whopping 14 teraelectron volts (TeV), seven times the record held by Fermilab's Tevatron.
The leviathan scale of the project is neatly juxtaposed by its goal, which is to explore the infinitely small.
Physicists have long puzzled over how particles acquire mass.
In 1964, a British physicist, Peter Higgs, came up with this idea: there must exist a background field that would act rather like treacle.
Particles passing through it would acquire mass by being dragged through a mediator, which theoreticians dubbed the Higgs Boson.
The standard quip about the Higgs is that it is the "God Particle" -- it is everywhere but remains frustratingly elusive.
French physicist Yves Sacquin says that heroic work by the LEP and Fermilab has narrowed down the energy range at which the devious critter is likely to spotted.
Given the LHC's capabilities, "there's a very strong probability that it will be detected," he said.
Some experts are also hopeful about an early LHC breakthrough on the question of supersymmetry.
The supersymmetry theory goes way beyond even the Higgs. It postulates that particles in the Standard Model have related, but more massive, counterparts.
Such particles could explain the unsettling discovery of recent years that visible matter only accounts for some four percent of the Universe. Enigmatic phenomena called dark matter and dark energy account for the rest.
CERN Director General Robert Aymar is confident the massive experiment will yield a correspondingly big breakthrough in penetrating these mysteries.
"It is certain that the LHC will yield the identity and understanding of this dark matter," he said in a video statement.
CERN has had to launch a PR campaign aimed at reassuring the public that the LHC will not create black holes that could engulf the planet or an unpleasant hypothetical particle called a strangelet that would turn the Earth into a lump of goo.
It has commissioned a panel to verify its calculations that such risks are, by any reasonable thinking, impossible, and France too has carried out its own safety probe.
Either way, the end of the world will not happen on Wednesday, for the simple reason that the LHC will not generate any collisions that day.
These will probably be initiated "in a few weeks" as part of a phased programme to commission the LHC, testing its equipment and evaluating work procedures before cranking it up to full strength, said Jenni.
Looking at the daily mountain of data that will have to be analysed, "it will take weeks or months before one can really hope to start discovering something new," he cautioned.
"The LHC is more than a machine. It is the intellectual quest of our age," the British weekly New Scientist said in this week's issue.
"With luck... today's physics textbooks will start to look out of date by the end of 2009."
World's biggest atom-smasher: Mission profile
Following is a mission profile of the Large Hadron Collider (LHC), the world's biggest atom-smasher, which is due to start operations on Wednesday:
- Hunt for the HIGGS BOSON, a theorised particle that would explain why other particles have mass. Confirming the Higgs would fill a huge gap in the so-called Standard Model, the theory that summarises our present knowledge of particles. Over the years, scientists have whittled down the ranges of mass that the Higgs is likely to have. But they have lacked a machine capable of generating collisions powerful enough to to confirm whether this so-called God particle really does exist.
- Explore SUPERSYMMETRY, the notion that a whole bestiary of related but more massive particles exists beyond those in the Standard Model. Supersymmetry could explain one of the weirdest discoveries of recent years -- that visible matter only accounts for some four percent of the cosmos. Dark matter (23 percent) and dark energy (73 percent) account for the rest. A popular theory is that dark matter comprises supersymmetric particles called neutralinos.
- Investigate the mystery of MATTER AND ANTI-MATTER. When energy transforms into matter, it produces a particle and its mirror image -- called an anti-particle -- which holds the opposite electrical charge. When particles and anti-particles collide, they annihilate each other in a small flash of energy. According to conventional theories of the cosmos, matter and anti-matter should exist in equal amounts, but the puzzle is that anti-matter is rare.
- Replicate the earliest moments after the BIG BANG that created the Universe. At its primal stage, matter existed as a sort of hot, dense soup called quark-gluon plasma. As it cooled, sub-atomic particles called quarks clumped together to form protons and neutrons and other composite particles. The LHC will smash heavy ions together, briefly generating temperatures 100,000 times hotter than the centre of the Sun and freeing quarks from their confinent. The researchers can then see how the liberated quarks aggregate to form ordinary matter.
The CERN atom-smasher: A factfile
Here is a snapshot of the world's biggest atom-smasher, due to start operations on Wednesday at CERN (the European Organisation for Nuclear Research) near Geneva:
-- The Large Hadron Collider (LHC) will accelerate hydrogen protons or lead ions to more than 99.9999 percent of the speed of light. The experiments will take place in a ring-shaped tunnel 27 kilometres (16.9 miles) long and up to 175 metres (568 feet) below the ground. The tunnel stretches out from Swiss territory and into France, looping back into Switzerland.
-- The beams run in parallel in opposite directions. Powerful superconducting magnets then "bend" the beams so that streams of particles collide within four large chambers. The smashups will fleetingly generate temperatures 100,000 hotter than the Sun, replicating the conditions that prevailed just after the "Big Bang" that created the Universe 13.7 billion years ago.
-- Swathing the chambers are detectors which will give a 3-D image of the traces of sub-atomic particles hurled out from the protons' destruction. These traces are then closely analysed in the search for movements, properties or novel particles that could advance our understanding of matter.
-- In top gear, the LHC will generate nearly a billion collisions per second. Above ground, a farm of 3,000 computers, one of the largest in the world, will instantly crunch this number down to about 100 collisions that are of the most interest. The data will then be sent out to a grid of institutions and universities around the world for analysis -- a sort of mini-World Wide Web of its own.
-- The tunnel is the world's largest fridge. The super-magnets are chilled to a temperature as low as -271 degrees Celsius (-456.25 degrees Fahrenheit), which is colder than deep outer space, to help them overcome resistance.
-- The collision chambers are herculean in scale. The biggest, called ATLAS, is 46 metres (149.5 feet) long and 25 metres (81.25 feet) high, or about half the size of the Notre Dame Catheral in Paris. At 7,000 tonnes, ATLAS weighs almost as much as the Eiffel Tower, and has 3,000 kilometres (1,875 miles) of cabling. Nearly 300,000 tonnes of rock were dug to house ATLAS and 50,000 tonnes of concrete were poured. In one year, ATLAS will generate 3,200 terabytes of raw data, equivalent to 160 times the three billion books in the US Library of Congress.
-- In the course of a 10-hour experiment, a beam might travel more than 10 billion kilometres (six billion miles), enough to get to Neptune and back. At full intensity, each beam will have the equivalent energy of a car travelling at 1,600 kilometres (1,000 miles) per hour. The LHC will use up 120 megawatts of power, equal to all the households in the Geneva area.
-- LHC collisions will generate 14 teraelectron volts (TeV), amounting to a high concentration of energy but only at an extraordinarily tiny scale. One TeV is the equivalent energy of motion of a flying mosquito. There is no safety risk, says CERN.
-- The LHC cost 6.03 billion Swiss francs (5.46 billion dollars, 3.9 3.76 billion euros) to build.