PX156 - E2 - forces

• an exchange of quantum numbers between two particles, mostly, but not always, carried by a force particle
• each force only interacts with particles carrying the specific charge that the force can 'see'

gravity

• responsible for large scale structure of the universe
• acts between masses

electromagnetic

• responsible for all the everyday interactions that can be seen around
• interacts with anything with an electric charge
• the force carrier is the photon
• photons only see '+' and '-' electric charges

weak force

• destroys stuff - responsible for fission, radioactive decay
• interacts with 'weak isospin', there are two types of this
• the force carriers are: $W^{\pm }$ and $Z^0$ bosons
• the fact that there are three force carriers arises from the splitting of weak and electromagnetic forces

strong force

• builds stuff - binds particles/nucleons/nuclei together
• interacts with the 'colour' charge: red, green, and blue