Amid a quiet patch of prairie 35 miles southwest of Chicago, scientists at the controls of the world's biggest machine are preparing to set off the world's biggest manmade collision.

But the smashup will not ruffle so much as a feather on the sandhill cranes and trumpeter swans who live nearby.

The soundless and all-but-invisible collision will occur when researchers at Fermi National Accelerator Laboratory here send atomic particles whizzing in opposite directions around a circular magnetic racetrack four miles long to smash headlong into each other.

Each set of particles will be accelerated on repeated passes around the track until they reach 1 trillion electron volts (Tev), about the highest controlled energy level ever imparted by humans to matter.

The particles will be traveling near the speed of light -- 186,000 miles per second. When they collide, the combined energy level will be 2 Tev, the highest achieved to date in such an accelerator.

In atomic-physics terms, the collision may be the equivalent of the Bicentennial fireworks on the Mall. And, like fireworks anywhere, it may light up observers' faces with delight and surprise as they participate in something ephemeral and stirring.

But no one will really see the collision. For one thing, the accelerator is mostly contained in a tunnel buried beneath the prairie. Little can be seen of its universe of sensors, pumps, cables, helium tanks, computers and high-voltage electrical lines that web along a thin-walled, hollow pipe surrounded by immensely powerful magnets.

The pipe is the racetrack, and the magnets keep the particles on it by exerting confining forces around the edge of the track.

The collision will take place inside a special, closed 2,400-ton chamber that Fermi engineers and scientists are installing now. The particles are subatomic, among the smallest known bits of material and hardly accessible to the human eye.

When they collide, they will shower the chamber with even smaller fractions of matter. Using batteries of sensitive instruments, the scientists will be looking at these fractional entities to see if the collision has jarred loose some of the subatomic forces that hold atoms together.

The higher the energy in the colliding particles, the higher the possibility that some of these key particles of force will be knocked into the open, where they may be detected by Fermi's sensors.

Physicists are seeking perhaps as many as three dozen of these particles in their efforts to comprehend the basic forces -- the quarks, gluons, W particles, Z particles and other phenomena -- that hold the universe together. This is the frontier of atomic physics and, fittingly for a prairie facility, Fermi is on it.

Its efforts are part of a national drive to seize the lead in particle physics from the West Europeans, who forged ahead in the last decade and have set the pace of subatomic discovery ever since. Last year two Europeans won the Nobel Prize in physics for discovering new subatomic particles. They did their work at an accelerator in Europe called CERN.

While physicists remain unshakably gentlemanly about it, the rivalry is genuine.

"There's absolutely no doubt we'd like to go right past them," said a Fermi official when asked about CERN's achievements.

To achieve that, much of Fermi's staff of 2,200 is rushing to add a second racetrack to the tunnel, just below the first track. The new track, due to be completed this summer, will be coupled with the old track to achieve simultaneous acceleration of particles in opposite directions to 1 Tev each, so that the collision will occur at 2 Tev, the force necessary to shake out the force particles.

"We believe the physics are so exciting, we are pushing very, very hard right now," said Dr. Bruce Chrisman, associate director of Fermilab.

But this is not the only race. A new contest is shaping up to build an accelerator 10 times more powerful than Fermi, which now is the most powerful anywhere. A coalition of builders, bankers and politicians is lobbying to locate the new accelerator in Illinois. Small wonder: The project carries a $2 billion to $3 billion federal price tag and would mean new construction jobs and a sure place at the forefront of U.S. science for years.

In Springfield, Gov. James R. Thompson wants the legislature to vote $7 million to begin acquiring land for the gigantic racetrack this monster will require -- from 60 to 120 miles long. But several other states are hardly standing still. Texas is preparing a $200 million commitment if the so-called superconducting, super collider is built in the Lone Star state. A decision is many months away.

Meanwhile, out here on the edge of Chicago's outermost suburbs, Fermi physicists pursue the edges of atomic reality on a small patch of prairie.