iso
PHVSICS OF TUE IMPOSSIBLE
efficient. Only a tiny fraction of the uranium is turned into energy. But
if an antimatter bomb could be constructed, it would convert 100 percent of its mass into energy, making it far more efficient than a nuclear
bomb. (More precisely, about 50 percent of the matter in an antimatter bomb would be turned into usable explosive energy; the rest
would be carried away in the form of undetectable particles called
neutrinos.)
Antimatter has long been the focus of intense speculation. Although an antimatter bomb does not exist, physicists have been able to
use their powerful atom smashers to create minute quantities of antimatter for study.
PRODUCING ANTI-ATOMS AND
ANTI-CHEMISTRY
At the beginning of the twentieth century, physicists realized that the
atom consisted of charged subatomic particles with electrons (with a
negative charge) circulating around a tiny nucleus (with a positive
charge). The nucleus, in turn, consisted of protons (which carried the
positive charge) and neutrons (which were electrically neutral).
So it came as quite a shock in the 1930s when physicists realized
that for every particle there is a twin, an antiparticle, but with an opposite charge. The first antiparticle to be discovered was the antielectron (called the positron), which has a positive charge. The positron is
identical to the electron in every way, except that it carries the opposite charge. It was first discovered in photographs of cosmic rays taken
in a cloud chamber. (Positron tracks are quite easy to see in a cloud
chamber. When placed in a powerful magnetic field, they bend in the
opposite direction from ordinary electrons. In fact, I photographed
such antimatter tracks while I was in high school.)
In 1955 the particle accelerator at the University of California at
Berkeley, the Bevatron, produced the first antiproton. As expected, it is
identical to the proton except that it has a negative charge. This means
that, in principle, one can create anti-atoms (with positrons circulating
PHVSICS OF TUE IMPOSSIBLE
efficient. Only a tiny fraction of the uranium is turned into energy. But
if an antimatter bomb could be constructed, it would convert 100 percent of its mass into energy, making it far more efficient than a nuclear
bomb. (More precisely, about 50 percent of the matter in an antimatter bomb would be turned into usable explosive energy; the rest
would be carried away in the form of undetectable particles called
neutrinos.)
Antimatter has long been the focus of intense speculation. Although an antimatter bomb does not exist, physicists have been able to
use their powerful atom smashers to create minute quantities of antimatter for study.
PRODUCING ANTI-ATOMS AND
ANTI-CHEMISTRY
At the beginning of the twentieth century, physicists realized that the
atom consisted of charged subatomic particles with electrons (with a
negative charge) circulating around a tiny nucleus (with a positive
charge). The nucleus, in turn, consisted of protons (which carried the
positive charge) and neutrons (which were electrically neutral).
So it came as quite a shock in the 1930s when physicists realized
that for every particle there is a twin, an antiparticle, but with an opposite charge. The first antiparticle to be discovered was the antielectron (called the positron), which has a positive charge. The positron is
identical to the electron in every way, except that it carries the opposite charge. It was first discovered in photographs of cosmic rays taken
in a cloud chamber. (Positron tracks are quite easy to see in a cloud
chamber. When placed in a powerful magnetic field, they bend in the
opposite direction from ordinary electrons. In fact, I photographed
such antimatter tracks while I was in high school.)
In 1955 the particle accelerator at the University of California at
Berkeley, the Bevatron, produced the first antiproton. As expected, it is
identical to the proton except that it has a negative charge. This means
that, in principle, one can create anti-atoms (with positrons circulating