What Are the Different Kinds of Forces in Physics?

Modern physics recognizes four fundamental types of interaction between particles: the strong force, the weak force, electromagnetism and gravity. Each force acts in a distinct way over distance, and all operate at different energy values.

The strong force is a residual effect of the color force carried by particles called gluons. Protons are made from smaller particles called quarks, which have a quality known as color. Quarks with different colors are held together by gluons, with the side effect that protons adhere to each other despite their mutually-repulsive positive charges.

The strong force is thus strong enough to overcome electromagnetic repulsion over distances equivalent to the diameter of an atomic nucleus. The weak force is about 10^-16 the strength of the strong force and works to change one type of quark into another. It governs the emission of radiation from a decaying atom, and it is responsible for the buildup of heavy atomic nuclei. The weak force is carried by a type of particle called a boson and works over ranges of 0.1 percent of the diameter of a single proton.

Electromagnetism is familiar to most people, if only because it works over potentially infinite range and is carried by photons. Gravity is, by far, the weakest force, but it also works over infinite distance and is always attractive, so its effects compound with mass and proximity. Gravity is the major force shaping large systems, such as galaxies.