ether

In the late nineteenth century, physicists were putting what they thought were the finishing touches on their theoretical description of electricity and magnetism. In the theory, electromagnetic waves traveled through a medium called "luminiferous ether" just as sound waves travel through the air, or the seismic waves that we experience as earthquakes travel through the Earth. The last remaining detail was to detect the ether and understand its properties. In 1887, Albert Michelson and Edward Morley performed an experiment, verified by many others, that demonstrated that light does not travel through ether. The lack of ether was one of many factors leading Einstein to develop special relativity.