The Standard Model

The standard model is a theory of particle physics that explains the relationship between the elementary particles of matter and the electromagnetic, weak nuclear, and strong nuclear forces. It basically describes what everything in the universe is made of and what keeps it all together. The standard model separates the elementary particles into groups. One group consists of fermions. Fermions are the elementary particles that form matter. The fermions group can be further broken down into quarks and leptons. The basic difference between quarks and leptons is that quarks are always found together forming other particles such as protons and neutrons. Leptons are solitary and do not join together to form other particles. The best known lepton is the electron which surrounds protons and neutrons to form atoms. Another group of elementary particles described in the standard model are the bosons. Bosons are particles that carry the fundamental forces of nature. For example a gluon is a boson that carries the strong nuclear force that holds the nucleus of atoms together. The strong force is propagated by particles exchanging gluons with each other. The other forces of nature are propagated in the same way with particles exchanging bosons with each other. The force of gravity is propagated by a boson called the graviton. The graviton has not been found yet, but physicist can predict its existence through experimentation. String theory suggests that all of the particles in the standard model are vibrating strings and not point particles. String theory also suggests that the standard model is not complete. According to string theory each of the particles in the standard model has a supersymmetric partner particle. These supersymmetric partner particles are predicted to exist by string theory, but have not yet been proven to exist by experimentation.