antimatter

In physics, form of matter in which most of the attributes (such as electrical charge, magnetic moment, and spin) of elementary particles are reversed. These antiparticles can be created in particle accelerators, such as those at CERN in Geneva, Switzerland, and at Fermilab in the USA. In 1996 physicists at CERN created the first atoms of antimatter: nine atoms of antihydrogen survived for 40 nanoseconds (40 billionths of a second).

The Alpha Magnetic Spectrometer was flown on the space shuttle Discovery in June 1998, searching unsuccessfully for antihelium and measuring the energy spectra of positrons and antiprotons. A successor experiment is planned for the International Space Station.