Ether

Because light consists of waves, the belief that all waves must be channeled through a medium (as sound through air or water) led 19th century physicists to construct ether as the medium supporting the propagation of light. However, the Michelson-Morley Experiment showed that if ether existed it could not be observed. It also demonstrated, more generally, that the construct of a physical medium is inessential for research into communication processes. (Krippendorff)