A field equation is an equation in a physical theory that describes how a fundamental force (or a combination of such forces) interacts with matter. The four fundamental forces are the gravitational force, the electromagnetic force, the strong nuclear force and the weak nuclear force. Theoretical physics attempts to understand the world by making a model of reality, used for rationalizing, explaining, predicting physical phenomena through a physical theory. There are three types of theories in physics; mainstream theories, proposed theories and fringe theories. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... Matter is anything that has mass and occupies space. ... This article covers the physics of gravitation. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ...

Before the theory of quantum mechanics was fully developed, there were two known field theories, namely gravitation and electromagnetism —these two are sometimes referred to as classical field theories, as they were formulated before the advent of quantum mechanics, and hence do not take into account quantum phenomena. Fig. ... This article covers the physics of gravitation. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ...

The first field theory was Newton's theory of gravitation, which described gravity as obeying an inverse square law. This was very useful in describing the motion of planets around the Sun. This theory is now superceded by Einstein's theory of general relativity. The field equations of gravitation are Einstein's field equations which describe gravity as a 'curvature' of spacetime produced by the existence of matter. Field theory (mathematics), the theory of the algebraic concept of field. ... Two-dimensional visualisation of space-time distortion. ...

The electromagnetic force is best described by Maxwell's theory of electromagnetism. The field equations of classical electromagnetism are Maxwell's equations which describe how electromagnetic fields are produced from charged particles. Classical electromagnetism is a theory of electromagnetism that was developed over the course of the 19th century, most prominently by James Clerk Maxwell. ... Maxwells equations are the set of four equations, attributed to James Clerk Maxwell, that describe the behavior of both the electric and magnetic fields, as well as their interactions with matter. ...

Modern field equations tend to be tensor equations.