Fundamental interactions

In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four conventionally accepted fundamental interactions—gravitational, electromagnetic, strong, and weak. Each one is described mathematically as a field. The gravitational force is modelled as a continuous classical field. The other three, part of the Standard Model of particle physics, are described as discrete quantum fields, and their interactions are each carried by a quantum, an elementary particle.

The strong and weak interactions have short ranges, producing forces at minuscule, subatomic distances; these forces govern nuclear interactions. The strong interaction, which is carried by the gluon particle, is responsible for the binding of quarks together to form hadrons, such as protons and neutrons. As a residual effect, it creates the nuclear force that binds the latter particles to form atomic nuclei. The weak interaction, which is carried by the W and Z particles, also acts on the nucleus, mediating radioactive decay. The other two, electromagnetism and gravity, produce significant forces at macroscopic scales where the effects can be seen directly in everyday life. The electromagnetic force, carried by the photon, creates electric and magnetic fields, which are responsible for chemical bonding and are used in electrical technology. Electromagnetic forces tend to cancel each other out when large collections of objects are considered, so over the largest distances (on the scale of planets and galaxies), gravity tends to be the dominant force.

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