Strong interaction. In particle physics, the strong interaction (also called the strong force, strong nuclear force, nuclear strong force or color force) is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation.
At atomic scale, it is about 100 times stronger than electromagnetism, which in turn is orders of magnitude stronger than the weak force interaction and gravitation. It ensures the stability of ordinary matter, in confining the elementary particles quarks into hadrons such as the proton and neutron, the largest components of the mass of ordinary matter. Furthermore, most of the mass-energy of a common proton or neutron is in the form of the strong force field energy; the individual quarks provide only about 1% of the mass-energy of a proton. In the context of binding protons and neutrons together to form atoms, the strong interaction is called the nuclear force (or residual strong force). Weak interaction.
In particle physics, the weak interaction is the mechanism responsible for the weak force or weak nuclear force, one of the four fundamental interactions of nature, alongside the strong interaction, electromagnetism, and gravitation.
The weak interaction is responsible for both the radioactive decay and nuclear fusion of subatomic particles. The theory of the weak interaction is sometimes called quantum flavordynamics (QFD), in analogy with the terms QCD and QED, but in practice the term is rarely used because the weak force is best understood in terms of electro-weak theory (EWT). Electromagnetism. Gravitation. Gravitation, or gravity, is a natural phenomenon by which all physical bodies attract each other.
It is most commonly recognized and experienced as the agent that gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height. During the grand unification epoch, gravity separated from the electronuclear force.