In the summer of 1984, Michael Salamon and Steve Ahlen went looking for antimatter in the cosmos the old-fashioned, low-budget way. Salamon, who was then at the University of California at Berkeley, and Ahlen, who was at Indiana University, bootlegged some spare cash from a previous experiment and used it to wire up an antimatter detector--a superconducting magnet and some elaborate electronics. They rigged the contraption to sit on a shelflike structure hanging from a high-altitude balloon. The balloon was capable of rising up to 130,000 feet, where it would be above the bulk of the atmosphere and could capture unimpeded the cosmic rays that rain continuously from the heavens. After a few years building the detector and then a month of 18-hour days readying the equipment for its mission, Salamon and Ahlen launched the balloon from Prince Albert, Saskatchewan, on August 13, 1987. It rose to its heavenly altitude above the stratosphere, floated serenely for 12 hours, and then, like a dying duck, plummeted to Earth in the Canadian wilderness.
When we finally found it, says Salamon, it took a hell of a time to get it out. We had to bulldoze some of the forest so a helicopter could get in and fly the payload out. But then the helicopter couldn’t pick it up, because the payload had impaled itself on the trunks of trees it had knocked down. We had to disassemble the support structure. It then took Salamon and Ahlen three months to analyze the data, which came up empty in any case. They had detected no sign of cosmic antimatter. That didn’t mean it wasn’t there, only that their experiment wasn’t sensitive enough to find it.
While Salamon and Ahlen thrashed around upper Saskatchewan, Samuel C. C. Ting was in Switzerland, establishing the largest experimental physics collaboration in the world--a $350 million, 600-physicist experiment known as L-3, which studies the collisions of elementary particles--at the European Organization for Nuclear Research, a laboratory known by its French acronym, CERN. Ting, who shared a Nobel Prize in 1976 and who has been described as the George Patton of high-energy physics, is a consummate experimentalist. But the experiment he was putting together in 1987 represented the twilight of his career, which was slowly being done in by the complex politics of the world’s most expensive pursuit of pure knowledge. By 1993, Ting would be looking for a way to do one more interesting experiment, as he put it, before he retired.
So it was that one of the most renowned practitioners of big science teamed up with a couple of inveterate low-budget astrophysicists to go searching for antimatter. Now Ting, Ahlen, Salamon, and a few dozen collaborators have convinced NASA to conduct the most thorough antimatter search ever. The $20 million experiment will fly first on a space shuttle in April 1998 and then for three years on the International Space Station Alpha, beginning in 2001. It should establish once and for all whether half the universe is made of antimatter, or whether matter, the stuff we’re made of, is all there is.
The search for antimatter has nothing to do with the paradox of dark matter, which is the roughly 80 percent of the universe that’s obviously there but isn’t emitting visible light and so cannot be seen. Ting and his collaborators are concerned instead with the 50 percent of the universe that isn’t there at all--the half that should be made of antimatter. Quantum mechanics dictates that matter can arise from pure energy, that elementary particles can pop into existence from a vacuum, provided that they do so in such a way that various fundamental quantities, such as electric charge and momentum, are conserved. This happened on a large scale during the Big Bang, when the universe began, and it’s been happening on a much smaller scale ever since.
