Unified field theory 1820 Hans Christian Ørsted discovered that electric currents exerted forces on magnets, while in 1831, Michael Faraday made the observation that time-varying magnetic fields could induce electric currents. Until then, electricity and magnetism had been thought of as unrelated phenomena. In 1864, Maxwell published his famous paper on a dynamical theory of the electromagnetic field. This was the first example of a theory that was able to encompass previously separate field theories (namely electricity and magnetism) to provide a unifying theory of electromagnetism. By 1905, Albert Einstein had used the constancy of the speed of light in Maxwell's theory to
Unified combatant command unified combatant commands is legally mandated in Title 10, U.S. Code Sections 161–168. The Unified Command Plan (UCP) establishes the missions, command responsibilities, and geographic areas of responsibility of the unified combatant commands. As of May 2018, there are ten unified combatant commands. Six have regional responsibilities, and four have functional responsibilities. Each time the Unified Command Plan is updated, the organization of the combatant commands is reviewed for military efficiency and efficacy, as well as alignment with national policy. Each unified command is led by a combatant commander (CCDR), who is a four-star general or admiral. CCDRs exercise combatant