5.  The interactions

We work with three fundamental interactions. They are:

            Electromagnetic (associated the exchange of photons between electrically charged particles)

            Weak (associated with the exchange of information between quarks and leptons. Particle physicists describe the exchanges in terms of packets of information called W and Z particles) 

            Strong (associated with the exchange of a kind of charge called 'colour' between quarks. Particle physicists describe the exchanges by saying that colour exchanging particles called 'gluons' pass between quarks) 

The interactions are normally linked to fundamental forces. For example the electromagnetic interaction is linked to the familiar attractions and repulsions associated with electric charge. The weak and the strong interactions are often described as being associated with strong and weak nuclear forces but they don't produce push-pull effects that we experience at a macroscopic level so it is better to think in terms of interactions rather than forces.

Whilst we have listed the electromagnetic and the weak forces separately, it has been shown that they are simply two aspects of a single electroweak force, but it is useful to deal with the interactions of the two aspects separately.

Particle physicists use tools called Feynman vertices to symbolise the three interactions between quarks and leptons.  

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