Editing Special relativity (section)

== Relativity and unifying electromagnetism ==
{{Main|Classical electromagnetism and special relativity|Covariant formulation of classical electromagnetism}}
Theoretical investigation in [[classical electromagnetism]] led to the discovery of wave propagation. Equations generalizing the electromagnetic effects found that finite propagation speed of the '''E''' and '''B''' fields required certain behaviors on charged particles. The general study of moving charges forms the [[Liénard–Wiechert potential]], which is a step towards special relativity.

The Lorentz transformation of the [[electric field]] of a moving charge into a non-moving observer's reference frame results in the appearance of a mathematical term commonly called the [[magnetic field]]. Conversely, the ''magnetic'' field generated by a moving charge disappears and becomes a purely ''electrostatic'' field in a comoving frame of reference. [[Maxwell's equations]] are thus simply an empirical fit to special relativistic effects in a classical model of the Universe. As electric and magnetic fields are reference frame dependent and thus intertwined, one speaks of ''electromagnetic'' fields. Special relativity provides the transformation rules for how an electromagnetic field in one inertial frame appears in another inertial frame.

[[Maxwell's equations]] in the 3D form are already consistent with the physical content of special relativity, although they are easier to manipulate in a [[manifestly covariant]] form, that is, in the language of [[tensor]] calculus.<ref name=Post_1962/>