Greetings from the Antiworld

Every subatomic particle has its opposite number, but luckily it's not true on a larger scale

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The scene is familiar to fans of Star Trek: with an order from the captain, antimatter fuel is released through a dilithium crystal to annihilate with matter, and the starship Enterprise shoots off at warp speed. "Well, warp speed is pure science fiction," writes author and physicist James Trefil. "So is the dilithium crystal." But antimatter "is another story."

Scientists have known for decades that for every kind of particle--whether the familiar electrons, neutrons or protons, or the more recently discovered quarks and neutrinos--there exists a particle that is its mirror image, identical in mass and amount of charge, but different in at least one crucial way. "If the ordinary particle has a positive electrical charge," explains Trefil, "then the antiparticle's charge will be negative. In some cases, if the particle has a clockwise spin, the antiparticle will have a counterclockwise one." Furthermore, he writes, the rules that govern the world of antiparticles should be pretty much the same as the rules that govern ordinary matter. But when the two worlds come into contact, "all hell breaks loose. The representatives of the anti- and ordinary worlds disappear in an explosion, and their combined mass is replaced by an enormous burst of energy and a cloud of secondary particles."

Recently, scientists found what appears to be a fountain of antiparticles squirting from the center of our galaxy and annihilating furiously with regular matter. And in the past few years, in laboratories in Switzerland and the United States, particle physicists have managed to create the first antiatoms: a single antielectron (or "positron") spinning around a single antiproton to form the simplest antielement: antihydrogen.

Created only in high-energy collisions in laboratories or in space (the fountain of antimatter is thought to come from some violent cosmic event), or released in minuscule quanti ties during radioactive decay (a fact which enables doctors to study the brain using PET, or "positron emission tomography"), antimatter is rare and exotic stuff. Working steadily for several years, the world's largest "antimatter factory" — the Fermi National Accelerator Laboratory outside Chicago — has only produced about a nanogram, which weighs as much as one-millionth of a grain of sand. But even that little bit, our author discovers, has offered scientists insight into the nature of matter, and the history and makeup of our universe. And who knows? Maybe someday, we'll make enough to fly off at warp speed where no one has gone before...

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