Maxwell added a new term to what are now called Maxwell's equations, called the "displacement current," completing them and allowing waves to exist in the theor

Maxwell added a new term to what are now called Maxwell's equations, called the "displacement current," completing them and allowing waves to exist in the theory. Although the symmetries in Maxwell's equations that Lorentz observed were known before Einstein published his paper on special relativity, Einstein was the first to make the bold suggestion of applying them to all matter, not just electrodynamics. In fact, during the period when people believed in the ether, those symmetries in Maxwell's equations were considered flaws in the theory that would be corrected when the properties of the ether became known.