THE most powerful atom-smasher ever built could make some bizarre discoveries, such as invisible matter or extra dimensions in space, after it is switched on in August.
But some critics fear the Large Hadron Collider could exceed physicists’ wildest conjectures: Will it spawn a black hole that could swallow Earth? Or spit out particles that could turn the planet into a hot dead clump?
Ridiculous, say scientists at the EU Organisation for Nuclear Research, known by its French initials CERN — some of whom have been working for a generation on the $5.8 billion (€3.7bn) collider, or LHC.
“Obviously, the world will not end when the LHC switches on,” said project leader Lyn Evans.
The collider consists of a ring of supercooled magnets 27km in circumference attached to barrel-shaped detectors. The ring, which straddles the French and Swiss border, is 100m underground.
Scientists plan to hunt for signs of the invisible “dark matter” and “dark energy” that make up more than 96% of the universe, and hope to glimpse the elusive Higgs boson, a so-far undiscovered particle thought to give matter its mass.
The collider could find evidence of extra dimensions, a boon for superstring theory, which holds that quarks, the particles that make up atoms, are infinitesimal vibrating strings.
The safety of the collider, which will generate energies seven times higher than its most powerful rival, at Fermilab near Chicago, has been debated for years. The physicist Martin Rees has estimated the chance of an accelerator producing a global catastrophe at one in 50 million.
By contrast, a CERN team this month issued a report concluding there is “no conceivable danger” of a cataclysmic event.
Critics of the LHC filed a lawsuit in a Hawaiian court in March seeking to block its startup, alleging there was “a significant risk that ... operation of the Collider may have unintended consequences which could ultimately result in the destruction of our planet”.
One of the plaintiffs, Walter L Wagner, a physicist and lawyer, said CERN’s safety report, released on June 20, “has several major flaws”.
And last week, US Justice Department lawyers representing the Department of Energy and the National Science Foundation filed a motion to dismiss the case.
The agencies have contributed $531 million to building the collider, and the NSF has agreed to pay $87m of its annual operating costs.
The lawyers said “there is no basis for any conceivable threat” from black holes or other objects the LHC might produce. A hearing on the motion is expected in late July or August.
CERN scientists point out that cosmic rays have been bombarding the earth, and triggering collisions similar to those planned for the collider, since the solar system formed 4.5 billion years ago.
“The LHC is only going to reproduce what nature does every second, what it has been doing for billions of years,” said John Ellis, a British theoretical physicist at CERN.
Critics have said the collisions caused by accelerators could be more hazardous than those of cosmic rays.
Both may produce micro black holes, subatomic versions of cosmic black holes — collapsed stars whose gravity fields are so powerful that they can suck in planets and other stars.
But micro black holes produced by cosmic ray collisions would likely be travelling so fast they would pass harmlessly through the earth.
Micro black holes produced by a collider, the sceptics theorise, would move more slowly and might be trapped inside the earth’s gravitational field.
Ellis said critics assume the collider will create micro black holes, which he called unlikely. And even if they appeared, he said, they would instantly evaporate, as predicted by the British physicist Stephen Hawking.
As for strangelets, CERN scientists point out that they have never been proven to exist. They said that even if these particles formed inside the collider they would quickly break down.
When the LHC is finally at full power, two beams of protons will race around the huge ring 11,000 times a second in opposite directions. They will travel in two tubes about the width of fire hoses, speeding through a vacuum that is colder and emptier than outer space.
Their trajectory will be curved by supercooled magnets — to guide the beams around the rings and prevent the packets of protons from cutting through the surrounding magnets.
The paths of these beams will cross, and a few of the protons in them will collide, at a series of cylindrical detectors along the ring. The two largest detectors are essentially huge digital cameras, each weighing thousands of tons, capable of taking millions of snapshots a second.
Each year the detectors will generate 15 petabytes of data, the equivalent of a stack of CDs 20km tall. The data will require a high speed global network of computers for analysis.
“There is a huge army of scientists who know what they are talking about and are sleeping quite soundly as far as concerns the LHC,” said project leader Evans.
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