Fundamental interaction

Standard Model of Elementary Particles

Particle overview

Fundamental interactions, also known as fundamental forces, are the interactions in physical systems that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to modern physics: gravitational force, electromagnetic force, strong nuclear force (also known as the strong interaction), and the weak nuclear force (or weak interaction). These forces govern how particles and objects interact with one another on every scale, from subatomic particles to galaxies.

Overview

Each of the four fundamental interactions has unique characteristics and plays a crucial role in the universe's structure and dynamics.

Gravitational Force

The gravitational force is the weakest of the four forces but has an infinite range. It is always attractive and acts between any two pieces of matter in the universe due to their mass. The modern theory of gravity, general relativity, describes gravity not as a force but as a consequence of the curvature of spacetime caused by mass and energy.

Electromagnetic Force

The electromagnetic force is responsible for the interactions between charged particles. It is mediated by photons and is much stronger than gravity but decreases rapidly with distance. This force includes all electromagnetic phenomena, governed by the laws of quantum electrodynamics.

Strong Nuclear Force

The strong nuclear force is the strongest of the four fundamental interactions. It acts between quarks and gluons, the fundamental particles that make up protons and neutrons. This force holds the nucleus of an atom together, overcoming the electromagnetic repulsion between protons. It has a very short range, acting only over distances on the order of nucleons.

Weak Nuclear Force

The weak nuclear force is responsible for processes such as beta decay in nuclear physics. It has a very short range and is weaker than both the strong force and electromagnetic force but plays a crucial role in the nuclear reactions that power the sun and, consequently, in the synthesis of elements in stars.

Unified Theories

Physicists have long sought to develop a unified theory that would describe all four fundamental interactions within a single framework. The electroweak theory, which unifies the electromagnetic force and the weak nuclear force, represents a significant step towards this goal. Efforts to include the strong force in a Grand Unified Theory (GUT) and to incorporate gravity in a theory of everything (TOE), such as string theory or quantum gravity, are ongoing areas of research.

Implications

Understanding the fundamental interactions is crucial for many areas of physics and cosmology, including the study of the early universe, the structure and evolution of stars, the properties of elementary particles, and the development of new technologies based on quantum and nuclear physics.