The results of particle accelerator experiments have led scientist to postulate the existence of three types of forces important in the nucleus: The strong force, the weak force, and the electromagnetic force. These forces are though to account for all types of interaction found in matter. The fourth force found in nature, but not in the nucleus, is the gravitational force. These forces are believed to be generated by the exchange of particles between the interacting pieces of matter. For example, the gravitational force is thought to be carried by particles called gravitons. The electromagnetic force is assumed to be exerted through the exchange of photons. The strong force, not charge related, and only effective at very short distances ( 10-13 cm), is postulated to involve the exchange of particles called gluons. The weak force is 100 times weaker than the strong force and seems to be exerted through the exchange of two types of large particles, the W (has a mass 70 times the proton's mass) and the Z (has a mass 90 times the proton's mass).
The particles discovered have been classified into several categories. Three of the most important classes are as follows:
Each of these main classes also contains antiparticles. For example the electron, which is a Lepton, has an antiparticle called a positron ("electron" with a positive charge).
The world of particle physics appears mysterious and complicated. For example, particle physicists have discovered new properties of matter they call "color", "charm", and "strangeness" and have postulated conservation laws involving these properties. This area of science is extremely important because it should help us to understand the interactions of matter in a more unified way.
Elementary Particles: Leptons and quarks
This page was made by Erik Epp.