Difference Between Matter And Antimatter
Matter. One of the fundamental problems in the history of science is the definition of matter. Although we can offer no final judgment, matter may be defined as the basic “stuff” making up the objects of daily experience. We can also say that matter fills space, that it moves, and that it has mass and inertia. But like all scientific concepts, the concept of matter has undergone numerous transformations. Philosophers, theologians, alchemists, and physical scientists have contrasted matter with form, mind, soul, motion, and force. In a sense, contemporary science has not escaped this dualistic tradition: inasmuch as matter can be converted into energy (and energy into matter), the physical world is now described as matter-energy.
Since antiquity, matter has been conceived to be composed of ever smaller and simpler units. One of the many units devised in antiquity was the atom, from the Greek atomos, meaning “indivisible.” Today an atom is understood to be the simplest unit of an element (for example, oxygen) that can combine with the simplest units of other elements (such as hydrogen) to create a molecule. Atoms are the major components of an element; molecules are the smallest particles that still possess the characteristics of an element or compound; compounds consist of more than one kind of atom. One molecule of the familiar chemical compound H2O (water), for example, is made up of two atoms of hydrogen (H) and one atom of oxygen (O).
Antimatter, the name for material consisting of antiparticles. The importance of antimatter has resulted from the discovery that antiparticles exist and from the possibility, at least in principle, that there are atoms made up of antiparticles.
Ordinary matter has an atomic structure composed of light negative electrons surrounding a heavy nucleus containing positive protons and neutrons, which have zero charge. For each of these particles there is an antiparticle. Antimatter would have positive electrons surrounding nuclei containing antineutrons and negatively charged antiprotons.
A union of a particle and its antiparticle results in their mutual annihilation. Their rest-mass energy is converted to the rest-mass energy of other particles or to kinetic energy. For instance, when a positron forms a brief union with an electron, the two of them disappear and two X rays normally shoot out in opposite directions. These X rays share the total rest-mass energy of the electron-positron pair. When a proton-antiproton pair is annihilated, mesons are emitted. These mesons rapidly decay to electrons, massless neutrinos, and X rays.