The future of particle physics in the United States has never been as imperiled as it is now, says economist Harold Shapiro, president emeritus of Princeton University. Failure to act, he says, could mean missing out on opportunities to answer some of the most profound questions about the nature of time, space and the origins of the universe.

Shapiro, who led a diverse committee of particle physicists, other academics and business leaders that last month reported on its 18-month examination of the state of elementary particle physics in the United States, spoke at Schwartz Auditorium on May 8. Ritchie Patterson, Cornell professor of physics, is a member of the committee.

The committee's report, "Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics," describes a field at a turning point: on the brink of profound new insights, but facing decline in the United States as funding stagnates and research at major facilities winds down.

It's a new and alarming situation, said Shapiro. Historically, the United States has been a leader in particle physics research, with important discoveries coming out of particle accelerators like the Stanford Linear Accelerator Center (SLAC), the Cornell Electron-positron Storage Ring (CESR), Brookhaven National Laboratory and the world's most powerful particle accelerator, the Tevatron at Fermilab in Illinois. But operations for particle physics at SLAC's accelerator, the Tevatron and CESR are all slated to end over the next decade (CESR will continue to work as an X-ray source and testing facility), leaving researchers with drastically reduced opportunities for research in the United States and potentially leading to a brain drain as promising young physicists move abroad -- particularly to Europe and Japan.

The future of the field, researchers agree, lies largely in two not-yet-built accelerators that will operate at the terascale (at energies measured in teraelectron volts, or 1 trillion volts). The first, the Large Hadron Collider (LHC), will open at the European Centre for Nuclear Research (CERN) in Geneva, Switzerland, in 2007, with the capacity to directly observe theoretical particles like the Higgs boson, which is thought to give other particles their mass. The second, the proposed International Linear Accelerator (ILC), would take the discoveries of the LHC further, allowing researchers to probe the nature of such particles in depth.

The ILC is anything but a certainty. Still in the earliest planning stages, it has a daunting price tag (many billions of dollars), no chosen location and little public awareness. But Shapiro -- who admits he came into the process a skeptic -- said he's now convinced that mounting a successful bid to build the ILC in the United States is vital to the country's continued scientific progress.

Rallying excitement and support for the ILC will be tough, but, Shapiro said, "The committee felt that terascale physics was the area that had the greatest potential for discovery and for piquing people's curiosity. If you think about the vitality of the scientific community, this is central. It would be a crime to step away from this field."

Patterson, who also is involved with the LHC, is just as emphatic. "The LHC will be fabulous for discovering that new things are going on," Patterson said. But because it will operate by colliding protons, whose components (quarks and gluons) can carry any fraction of the [proton's] momentum, there will always be too few constraints in the system to allow researchers to reconstruct a full picture of what's going on.

To get the full picture, Patterson said, researchers need the additional capabilities of the ILC. "With ILC it's electrons, so you know to a gnat's eyelash what the energy of the colliding particles is. And that gives you more constraints."

The concept for the linear accelerator was first proposed in 1965 by Maury Tigner, director of Cornell's Laboratory of Elementary Particle Physics. Cornell has a huge stake in the ILC, with Patterson and other researchers heavily involved in its design and implementation.

But the public has a stake in the ILC too, Patterson added. America's future role in particle physics could depend on it.

"It could be great," she said, "or it could die."