What on earth is this machine?
It is the Large Hadron Collider (LHC), the world’s largest particle
accelerator. Built at the European Organization for Nuclear Research
(CERN) near Geneva and housed within a 17-mile-long underground circular tunnel, the $8 billion project is designed to reproduce the incredibly high energies found in the first trillionth of a second after the Big Bang, which brought our universe into existence. Last week, CERN scientists rejoiced after they activated the collider and successfully propelled a beam of protons around its track. Eventually, the collider will accelerate beams of the tiny subatomic particles in opposite directions and smash them together, at speeds of 99.9999991 percent of the speed of light.
Why are scientists doing this?
“We simply want to understand what the world is made of, and how,” says Jos Engelen, CERN’s chief scientific officer. Over the past century, physicists have gone a long way toward identifying the basic building blocks of the universe. First came the discovery that each atom has a heavy nucleus, consisting of protons and neutrons (collectively known as hadrons), orbited by a matching number of light electrons. But these hadrons were found to be made up of yet smaller particles: quarks, glued together by gluons. In the 1970s, physicists developed the Standard Model, a sort of user’s guide to the subatomic world. The model has successfully predicted subatomic interactions, but it is incomplete: It doesn’t explain how gravity works, and its explanation of mass remains untested.
Where does the Large Hadron Collider fit in?
Discoveries about subatomic particles are made using devices that smash up atoms and examine the resulting subatomic debris. In 1932, Cambridge University scientists John Cockcroft and Ernest Walton first split the atom, using a particle accelerator to fire protons into lithium atoms, producing helium. Since then, bigger and better atom-smashers have confirmed the existence of a whole world of mysterious, and mysteriously named, particles such as the W and Z boson, the charm quark, and the top quark. But earlier colliders are peashooters compared with the LHC.
So what could it discover?
The holy grail is the Higgs boson, named after Edinburgh physicist Peter Higgs. He proposed its existence in 1964 as a solution to the mystery of why matter has mass, and thus exists in a form that allows it to make planets and people, while some phenomena—such as light—do not. Higgs theorized that the universe is pervaded by an invisible, molasses-like field of bosons (the Higgs field). As particles move through this field, bosons stick to some of them, making them more massive, while others, like particles of light (photons), are unaffected. This boson has been sought in every collider since, but to no avail. Locked securely in the atomic nucleus, it theoretically shows itself only at the vast energies that last existed in the moments after the Big Bang. Hence the LHC.
What if they find Higgs boson?
The Higgs boson is so central to modern physics that one Nobel laureate described it as the “God particle.” Finding it would essentially verify the Standard Model and bring scientists closer to a Grand Unified Theory describing all physical phenomena in nature—to “know the mind of God,” in Stephen Hawking’s phrase. Hawking, however, is betting that if the Higgs boson exists, its discovery will have to wait until scientists build an even more powerful accelerator. Higgs himself will be “very puzzled” if it isn’t found. “I will no longer understand what I think I understand,” he declares.
What else might we learn?
The possibilities are virtually limitless. Physicists hope to discover a “jewel box” of new particles; to test a group of theories, such as string theory and supersymmetry, that go beyond the Standard Model; to throw light on “dark matter,” which seems to make up most of the universe but is not visible; even, perhaps, to see evidence of further dimensions. They will also be looking for “mini black holes.” This has fed fears that the LHC is a doomsday machine, creating black holes that could swallow up the Earth. Two amateur physicists, Walter Wagner and Luis Sancho, have even sought a restraining order against the LHC in the U.S. courts. Concerns have also been raised about “strangelets,” objects made of quarks that could turn all matter into “strange matter,” making the world vanish. These worries are widely regarded as coming from science’s lunatic fringe. CERN promises that any black holes will be small, fleeting, and “benign,” and that we are “safe from strangelet-initiated catastrophe.”
Are there any practical implications?
The main purpose of the LHC is knowledge for its own sake. Still, as the world’s premier “blue-skies thinking laboratory,” CERN produces many practical spinoffs. In 1989, Tim Berners-Lee invented the World Wide Web while working there. Civil engineering and superconductor technologies have been pushed to new boundaries for the LHC; imaging techniques developed for the project are now used in hundreds of hospitals. CERN has also created the world’s most powerful computer network, the Grid, to process the staggering amount of data produced by the LHC. The network uses the processing power of research institutes in 33 nations, and the technology is expected to be made publicly available, revolutionizing computing.
Simulating the Big Bang
Employing some 7,000 physicists and engineers from 111 nations, the Large Hadron Collider is a scientific endeavor unlike any the world has ever seen. Its 13-foot-wide tunnel contains two pipes, down which the proton beams are fired. Thousands of superconducting magnets, cooled to minus 465 degrees Fahrenheit by 130 tons of liquid helium, keep the beams on course. Each beam will not only be traveling a hairbreadth off the speed of light, it will have an energy of 7 trillion electron volts—roughly comparable to that of a high-speed train moving at full velocity. Particles will collide at four points, where four vast caverns hold sophisticated detectors. Despite the massive energies involved, the collision shouldn’t be dangerous. Earth is constantly being bombarded by accelerated particles, in the form of cosmic rays from our sun and outside the solar system, and these particles zip along with far more energy than anything inside the LHC. Yet, as The Week went to press, the planet still existed.