A17-mile-long circular tunnel lies beneath the French-Swiss border just outside Geneva. Parts of it are more than 500 feet below ground. The tunnel houses the Large Hadron Collider (LHC), the most powerful particle collider on the planet.
Shortly after beginning operations last fall, the LHC's cooling system sprang a leak that shut it down. When operations begin again later this year, scientists will smash particles together to see what happens when they collide. Some people think those collisions will reveal the deepest secrets of the universe. Others believe the whole idea is a $15 billion boondoggle, and a tiny minority believe the collider could produce a black hole that will swallow the Earth.
In his recent book, Paul Halpern, a physics professor at Philadelphia's University of the Sciences, lays out the case for the collider. He argues convincingly against both the economic (you're wasting money) and doomsday (you're going to destroy the Earth) lines of reasoning.
He begins by explaining how the collider will work when it is restarted. First, an electric field will accelerate protons -- positively charged subatomic particles -- to almost the speed of light. About 15,000 magnets cooled to minus 456 degrees Fahrenheit will steer them through the 11,245 revolutions they make though the tunnel every second. When two protons traveling at those speeds in opposite directions collide, they release a lot of energy. According to Einstein's famous equation E = mc2, mass and energy are interconvertible. So some of their energy will be converted into mass in the form of new particles. And the higher the energy of the colliding particles, then the heavier the particle that can be created in the collision.
Keeping terms straight
Halpern leads into the LHC story by reviewing the history of particle physics. He begins with the brilliant New Zealand physicist Ernest Rutherford, who was, Halpern says, "the first to split open the atom." Intertwined with the stories of scientists are the stories of the colliders that make modern particle physics possible.
This is not light reading. Particle accelerators are usually referred to by acronym (SLAC for Stanford Linear Accelerator, for instance). Halpern is careful to define his acronyms, but most readers will have a difficult time remembering what they all mean. Almost as confusing are the particles themselves: quarks, kaons, muons and so forth. There are so many that even scientists working in this field refer to them as the "particle zoo."
None of this nomenclatural confusion is Halpern's fault. It is the nature of his subject. And behind the disconcerting language lies the fascinating story of science's long struggle to understand what the universe is made of. After examining the results of millions of particle collisions, physicists thought by 1967 that they knew all the animals in the zoo, even if they had not directly detected them. That body of knowledge became known as the Standard Model of particle physics.
At the time the Standard Model was proposed, it predicted the existence of four particles that had not been detected. Soon after, more powerful accelerators enabled scientists to find three of them. Their properties were exactly what the Standard Model predicted. The fourth particle is the Higgs boson. It has never been observed because, up to now, no accelerator was powerful enough to create it.
The Higgs is a crucial component of the Standard Model because of one important quality: It bestows mass on other particles. Its status is such, Halpern writes, that it "has acquired the nickname the 'God' particle ... the holy grail of contemporary physics."
Finding the Higgs is one of the main goals of scientists at the LHC. If they do find it, their observations could confirm the Standard Model or cast it into the failed-theory trash can. Of course every scientific experiment is a roll of the dice, and the results could be a total surprise. Other, unsuspected, particles might be found. Or hidden dimensions, as predicted by string theory. The LHC has the potential to affirm or revise science's most fundamental theories about the universe. And like any scientific project this big, it has attracted Cassandras.
Fear of the hole
Walter Wagner is a physicist and the head of a group that aims to stop operations at the LHC. He worries that the high energies generated in the collider could produce microscopic black holes. Under certain conditions, one could be captured by the Earth's gravity. Then, like the Blob of horror movie fame, it would consume more and more material, grow bigger and bigger, and ... Well, you get the idea. The black hole would be the end of the LHC and everything else on Earth.
Working scientists at the collider chuckle at such predictions. But CERN -- the European consortium that operates the collider -- cannot, and does not, take them lightly. The consortium has released detailed reports showing why microscopic black holes pose no threat to Earth or anything else. The carefully reasoned science is enough to convince most people but to sway diehard prophets of doom, CERN has a trump card. The Earth, it points out, is already being hit by far more energetic particles than the LHC could possibly produce. Billions and billions of high-powered cosmic rays have bombarded Earth since it formed - and continue to do so. So far no microscopic black holes have devoured the planet.
While fear of black holes is not a good reason to oppose the LHC, the economic argument carries some weight. The money spent on the LHC may be wasted. It might not produce any worthwhile, results. However, some people thought that about Rutherford's experiment, too, and it led to nuclear medicine: the MRIs, CT scans, and radiation therapies that so many of us depend on.
In any case, a lot of very smart, hardworking scientists are betting a good part of their careers that the LHC will reveal important and useful information about the nature of matter. And digging out that knowledge is what scientists have always done and what they are supposed to do.
