GENEVA — Michelangelo L. Mangano, a respected particle physicist who helped discover the top quark in 1995, now spends most days trying to convince people that his new machine won't destroy the world.
"If it were just crackpots, we could wave them away," the physicist said in an interview at the European Organization for Nuclear Research, known by its French acronym, CERN. "But some are real physicists."
What the critics are in such a lather about is the $8-billion Large Hadron Collider, a massive assemblage of iron, steel and superconducting wire 300 feet underground in a 17-mile-long circular tunnel on the Franco-Swiss border.
The most complex piece of scientific equipment ever built, the collider will send particles crashing into each other at just a wink shy of the speed of light, generating energies more powerful than the sun.
Scientists like Mangano believe that this instrument, when it begins operating as early as this summer, will peer into a looking-glass world that could contain entrances to extra dimensions and super-massive partners of the familiar particles that make up our world. One creature that must be hiding there, the scientists say, is the Higgs particle, one of the most exotic undiscovered objects since the yeti.
Critics think the collider could also spawn a black hole that will swallow Earth.
That could be just an appetizer. Once the collider got going, according to the doomsday scenario, it could gobble up distant stars like a child popping Skittles.
Mangano, who is part of the CERN group studying the safety of the collider, doesn't deny the scant possibility that the collider could yield a mini-black hole.
By smashing protons and lead ions together at energies reaching 14 trillion electron volts, the Large Hadron Collider will dwarf the world's other atom-smashers, including the Fermi National Accelerator Laboratory's mighty Tevatron in Batavia, Ill.
But that energy, Mangano hastened to add, would be concentrated in a space thinner than a human hair. Any black hole would be so tiny that it wouldn't be able to get its teeth around a bit of local chevre cheese, let alone the world.
Still, if a black hole were produced at all, "that would be an extremely spectacular result," he said, a half-smile creeping across his face.
Deep in a dim cavern, UCLA physicist Bob Cousins scrambled onto a catwalk straddling the six-story detector known as the Compact Muon Solenoid, then darted up two flights of stairs to another catwalk, where the guts of the machine materialized out of the half-light.
It looked a little like the inside of a computer suffering from a severe case of gigantism. Plates, shields and pipes jutted everywhere. Thick knots of cable extended from the side like mounds of heavy rope on an 18th century whaling ship.
"This detector was assembled at the surface and lowered in 15 pieces," Cousins said, pointing to a wide opening above the detector that reached to the European sky high above.
The heaviest piece weighed 4 million pounds. It took 10 hours to lower the middle section. At the center of this section is a bulbous extension that makes the behemoth look like the world's biggest television picture tube. This single piece of the collider contains more iron than the Eiffel Tower.
It was all built to probe a beam of particles thinner than a blade of grass.
Decades ago, scientists figured out that atomic nuclei were made up of smaller things than protons and neutrons.
To find those pieces, 20th century physicists came up with an idea that would appeal to most 9-year-old boys with a new toy: "Let's smash it and see what happens."
Early colliders, like the 9-inch cyclotron created at UC Berkeley in 1931, sent particles down a circular drag strip and crashed them into a target to see what flew out.
From there, particle physics exploded. Larger and more sophisticated devices kept packing more energy into the colliding particles, allowing scientists to peer deeper into the guts of the atom.
Protons and neutrons, they found, were made up of even smaller particles, dubbed quarks, which were bound together by another set of particles, called gluons. Gluons were part of a larger family, bosons, each of which carries some form of force. Photons, which make up light, for example, carry the electromagnetic force.
They found a bestiary of particles -- pions, kaons, deltas and other exotically named objects -- that existed beyond an atom's nucleus.
Altogether, scientists found dozens of species of elementary particles, some composed of pieces so tiny that they make an atom look like a sumo wrestler, or a mountain. If a quark measured an inch, an atom would stretch at least 1,000 miles, about the distance from Los Angeles to Denver.
These discoveries enabled physicists to devise a compelling picture of the universe at the subatomic level. Known as the Standard Model, it is considered the most successful scientific theory in history.