The Colossus of Colliders

By Natalie Angier.

Its 60-mile circumference could embrace Manhattan, Barbados or (almost) Bahrain. Its 2 billion ft. of niobium-titanium wire could encircle the world 16 times. The 150 megawatts of power needed to operate it could light up a city of 15,000. And its price tag of as much as $6 billion could purchase half a dozen new space shuttles. All told, the superconducting supercollider (SSC), a gigantic particle accelerator that the Department of Energy may begin constructing somewhere in the U.S. before the end of the decade, would be the biggest, most elaborate and most ambitious physics project ever undertaken.

Yet what the underground megamachine might accomplish is more boggling still: it would serve as a circular iron-and-steel racetrack for beams of subatomic particles, traveling at fantastic speeds, that would be smashed together in an effort to mimic conditions at the earliest moments of the universe. It would enable physicists to probe fundamental mysteries about the origin of matter and energy and could help them achieve a long-sought goal: to weave the four known forces of nature--electromagnetism, gravity, the weak force (responsible for radioactive decay) and the strong force (which holds atomic nuclei together)--into a single, elegant, grand unified theory. Says Leon Lederman, director of the Fermi National Accelerator Laboratory (Fermilab), the high-energy physics facility near Chicago: "With the SSC, we are bound to make fantastic new discoveries."

At a hearing before a House subcommittee, physicists from the U.S. and Europe last week stressed the importance of the mammoth project for American science. "By building the SSC you will have predominance in this particular field," said Carlo Rubbia, a renowned physicist at the CERN accelerator center near Geneva. His testimony supported the view of Presidential Science Adviser George Keyworth, who earlier this year warned that "it would be a serious blow to U.S. scientific leadership if that facility were built in another country."

Anticipating a federal green light for the collider, 28 states are lobbying to be home to the sprawling complex, which, in addition to generating thousands of jobs, could attract other high-tech businesses to the area. In that respect, says Bob Chandler, city manager of Winnemucca, Nev. (pop. 5,270), one of the contending sites, "it's a hundred times better than the General Motors' Saturn plant."

The supercollider would be still another in a string of new colossal accelerators that seem to be proliferating almost as rapidly as the novel particles they produce. In these machines, electrons or protons (and usually their antimatter counterparts, positrons or antiprotons) are spurred to nearly the speed of light and tremendous energy levels by radio waves and steered on their circular course by magnets. The monumental girth of the new machines stems from limitations in the power of the guiding magnets; bigger circular tracks have gentler curves and thus require less intense magnetic fields to keep the particles on their required path.

At several locations around a track, the particles are either smashed into metallic targets or steered to collide head-on with one another. Most of the new machines opt for the collision technique, which produces more energy. Explains Alvin Tollestrup, a Fermilab physicist: "It's the difference between a semi crashing into a small car and two semis crashing head-on." Some of the tremendous energy of those impacts is fleetingly transformed into strange particles that are thought to have existed in the very first moments of the universe. Before the unstable fragments decay back into energy and more familiar bits of matter, their feathery traces are recorded by detectors.

Those traces have helped physicists to track down more and more members of the large and seemingly limitless bestiary of subatomic particles. Last year, for example, Rubbia shared a Nobel Prize for having discovered, using the CERN super proton-antiproton synchrotron accelerator (SPPS), the W and Z particles. His finding provided proof for a theory that united two of the fundamental forces, electromagnetism and the weak force.

The payoff from the SSC should be even greater. As it is now conceived, the accelerator would generate energies of 40 trillion electron volts, in contrast to the 640 billion electron volts produced by CERN's SPPS accelerator. More impressive still, it would produce collisions 20 times as powerful as the generation of big machines now under construction at CERN, Fermilab and the Stanford Linear Accelerator Center. Whizzing past each other, the SSC's two opposing beams, consisting of closely packed bunches of about 10 billion protons each, would complete about 3,000 laps a second. In four to six places around the ring, the beams would intersect, producing up to 100 million collisions a second. At each collision site, a highly sophisticated detector at least three stories high would be needed to sense and record the impacts, telltale debris and any newly created particles.

The SSC is by no means a certainty. Critics are worried that its cost will drain money from other worthwhile projects, and growing concern about the federal deficit could, at best, delay congressional approval. But many scientists are convinced that the big collider will eventually be built. Says James Cronin, a physicist at the University of Chicago: "If we're serious about finding out about nature, we have to do it."

With reporting by J. Madeleine Nash/Chicago