James Clerk Maxwell (1831-1879), a Scottish physicist, achieved the "second great unification in physics". He synthesized all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a consistent electromagnetic theory.
Maxwell demonstrated that electric and magnetic fields travel through space in the form of waves and at a constant speed of light. He thought this might not be a coincidence and in 1864 he wrote A Dynamical Theory of the Electromagnetic Field where he first proposed that light was in fact undulations in the same medium that is the cause of magnetic and electric phenomena.
Maxwell is considered the 19th century physicist with the greatest influence on 20th century science. Both particle and wave theories about light had been proposed earlier. Maxwell was inspired by the work of Michael Faraday (1791-1867) who had shown that a magnetic field rotates the plane of polarized light.
Soon after Maxwells publication of 1864, Heinrich Hertz (1857-1894) confirmed the theory experimentally and showed that electromagnetic radio waves behaved like light. This opened the field for today's communication revolution.
In 1853 Maxwell undertook an evangelical conversion having attended Presbyterian and Episcopal services as a youngster. Evangelicals emphasize being born again, have a high regard for Biblical authority and put an emphasis on the death and resurrection of Jesus Christ. As an evangelical he held an anti-positivist position.
Maxwell started out at the University of Edinburgh between 1847-50. He then studied at Cambridge University between 1850-56 after which he got a position at Aberdeen University. The most productive years of his life, after barely having survived a bout of smallpox in 1860, he spent at Kings College, London between 1860-65. He unfortunately died young at 48 in abdominal cancer. He was survived by his wife Katherine whom he married in 1859.
Data from Wikipedia