Neutrinos, they are very small," wrote John Updike at the beginning of a 1960 poem, "Cosmic Gall." "They have no charge and have no mass / And do not interact at all." At least one of those facts has since been disproved: it was recently discovered that neutrinos have a bit of mass.
But they are very small.
Neutrinos are tiny elementary particles that move through most matter—"Like dustmaids down a drafty hall"—interacting only rarely. Trillions pass through the human body each second. And they're fast: last week a group of physicists, working at the European Center for Nuclear Research, announced that they had clocked a beam of neutrinos at a clip that exceeded the speed of light—a result that, while far from verified, has mind-bending implications, the possibility of time travel not the least of them.
With the closing of the Tevatron, the thrust of Fermi's experimentation shifts to another sort of mystery, for which scientists hope neutrinos will provide a clue: if matter and antimatter existed after the big bang in equal parts, as scientists believe, why is there now a preponderance of matter in the universe?
There are three types of neutrinos, and they're thought to change type as they move. "We think that how it changes types might tell us how, essentially, the world evolved," says Fermi spokesperson Tona Kunz. In the wake of the big bang, "there should've been nothing but free-floating energy. Something weird happened, and like 1 percent flipped up to matter, and that 1 percent difference is what allowed everything in the universe to evolve."
So scientists, here and in Europe, are sending them traveling. Fermi's current neutrino experiments involve shooting a beam of the particles through the earth to greater and greater distances—the lab works with sites at old mines in northern Minnesota and South Dakota—to try and figure out how they change as they travel. The underground component is important: it isolates the neutrinos in the scientists' beams from those that stream out of the sun, which produce enough cosmic noise to obscure experimentation on the earth's surface. A future experiment called "Project X," which will be years in implementing, would create a high-energy beam for use in neutrino experiments; plans are for it to be installed in the old Tevatron tunnel.