The Forces Of Nature
Forces of Nature
Forces of Nature

Particle physicists know of four basic forces in nature, that govern the interaction between matter and energy.

(1) THE GRAVITATIONAL INTERACTION. Gravity attracts all matter but is too weak to have significant effects at a subatomic scales.

(2) THE ELECTROMAGNETIC INTERACTION. This plays an important role in the forces between charged particles and is responsible for the phenomenon of electromagnetism.

(3) THE STRONG INTERACTION. It is this force that binds atomic nuclei together and stops them flying apart due to the mutual repulsion of their protons and is the dominant interaction in reactions and decays of most of the fundamental particles. However, leptons to not experience the strong force.

(4) THE WEAK INTERACTION. The weak interaction is a force that is involved in nuclear beta decay and other radioactive processes. All particles experience the weak interaction.

Gravity and the electromagnetic interaction have an unlimited range which is mainly why they are so familiar in everyday life. The strong force has a range no larger than that of an atomic nucleus, and the weak much less than this are not observed directly.

The relative strength of a force decides the time scale over which it can act. If two particles are brought together so that any of these four forces can act in an interction, then because of its lesser strength, the weak force requires a longer time to cause a particle decay or reaction than the strong force. The characteristic time is a measure of how long the force needs to act to produce an effect. The lifetime of a particle decay process is often a clue to the type of interaction going on with strong forces acting for much shorter characteristic times (~10-23s) than the others.

Fundamental particles can interact with each other through any of these four forces. All of them can interact through the gravitational and weak forces only leptons interact with the strong force. When two particles interact through the strong force then we can often neglect the effects of the weak and the electromagneticforces in decay processes since because of their relative strengths, these effects are much smaller. The gravitational force is far too small to be any consequence in particle reactions and decay.

InteractionStrength (relative to Strong)Range/mCharacteristic Time
Electromagnetic10-2~infinite10-14 - 10-20s
Weak10-610-1810-8 - 10-13s

All hadrons (baryons and mesons) feel the strong force and all particles feel the gravitational and weak forces.


Forces of Nature
Further Forces of Nature
Particle Physics-Forces of Nature
Fundamental Forces of Nature