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Electromagnetism as one of the fundamental forces of nature. Early on, electricity and magnetism were studied separately and regarded as separate phenomena. Hans Christian Ursa discovered that the two were related. Electric currents give rise to magnetism. Michael Faraday discovered a converse that magnetism could induce electric currents, and James Clerk Maxwell put the whole thing together in a unified theory of electromagnetism. Maxwell's equations further indicated that electromagnetic waves existed, and the experiments of Heinrich Hertz confirmed this, making radio possible. Maxwell also postulated correctly that light was a form of electromagnetic waves, thus making Olive optics a branch of electromagnetism. Radio waves differ from light only in that the wavelength of the former is much longer than the latter. Albert Einstein showed that the magnetic field derives through the relativistic motion of the electric field, and thus magnetism is merely a side effect of electricity. The modern theoretical treatment of electromagnetism is like a quantum field in quantum ielectrodynamics.