Maxwell's Equations

In words, "(1) electric field diverges from electric charge, an expression of the Coulomb force, (2) there are no isolated magnetic poles, but the Coulomb force acts between the poles of a magnet, (3) electric fields are produced by changing magnetic fields, an expression of Faraday's law of induction, and (4) circulating magnetic fields are produced by changing electric fields and by electric currents." (quotation from EB) The interrelationship between changing electric fields and changing magnetic fields is such that waves of changing electric and magnetic fields propagate through space, producing what we call electromagnetic radiation.

These four equations, first stated together by James Clerk Maxwell in the late 19^th century, form a complete description of electric and magnetic fields and their interaction. Their formulation was a breakthrough in the understanding of light, as they revealed the nature of light--it is really just another portion of the electromagnetic spectrum.

Next article: It's all relative!