I'm working problems on vibrations in crystal lattice for solid state, and a thought occurred to me. Early 20th century and late 19th century scientists supposed an aether for light to pass through. It seemed reasonable at the time - waves travel in a media. However, EM waves are transverse. How did they (or did they?) account for the fact that there were no longitudinal light waves? Another take on the question is this: what material allows transverse but not longitudinal waves? Am I missing something simple?