The standard model overview ii
The Standard Model is the accepted picture of particle physics. It describes the fundamental particles, the forces between them and the ways that they combine to make other particles. Although many of the particle names seem new and peculiar, the Standard Model provides a remarkably simple model. It says that all normal matter is:
  • made of the first generation of two families of fundamental particles - leptons and quarks (table 1)
  • held together (or apart) by four main forces (table 2)
Particles
Forces
Family Particle Forces
felt
quark up

Down
gravity
e-mag
strong
weak
lepton electron

neutrino
(elec)
gravity
weak
Force Has effect on
gravity anything with mass
electromagnetic anything with charge
strong nuclear quarks & therefore protons and neutrons
weak force all fundamental particles
Table 1. Table 2
Nucleon Quarks Representation
proton up

up

down
Quark composition of proton
neutron Up

Down

Down
Quark composition of proton
Rollover sequence showing how matter is built up from fundamental particles
Rollover sequence showing how matter is built up from fundamental particles
Rollover sequence showing how matter is built up from fundamental particles
Table 3
The up and down quarks combine in triplets to make protons and neutrons (Table 3). They fuse together and pick up electrons to make atoms. Atoms bind to make molecules, which may form into cells, organs and living creatures.
Family matters
The leptons and quarks are different from each other in a number of ways. Most notably:
  • leptons can exist on their own whereas quarks only exist in combination with other quarks making hadrons
  • quarks feel the strong nuclear force and leptons do not.
Is it really that easy?
Although normal matter is made of only these four fundamental particles, the full standard model includes more particles. Each of the families has four more particles and every particle has an associated anti-particle. The extra quarks combine with each other and with anti-quarks to make many new hadrons. However, apart from protons and neutrons, all the hadrons are very unstable and decay within a hundredth of a second and do not form part of normal matter. Nevertheless, these particles and the quarks that make them are important to physicists to help them form a complete picture and find unifying theories.
The full Standard Model with all the generations
M6e
You can find out about the Standard Model by following one of these routed through this e_source.
The model History The story of
the Universe
The story so far
  • Everything in the Universe is either matter or radiation
  • Scientists are always trying to find simple ways of modelling matter and the way it behaves