A clarification of something in Michael Donnelly's 28 September post in which he pointed out the crucial distinction between the nature of electromagnetic waves and sound waves, namely, that they are, respectively, transverse waves that can travel through a vacuum, and longitudinal waves that require a material medium.
Michael wrote: > But what about space? We now think of space as a vacuum, > but back then they reasoned that outer space must have a fluid medium, > which they speculatively called "the aether". This theory was dispelled > when they realized that the wave nature of light didn't require a fluid > medium for its transmission (because photons are particles with a "wavy > nature", if you will). In fact it was the publication of Einstein's special theory of relativity (1905), which repudiated the Newtonian notion of absolute time, that was the key historical event leading to the concept of the ether being dispensed with. See John Stachel, "1905 and all that": http://www.uio.no/studier/emner/matnat/fys/FYS-MEK1110/v05/nature2005spesia l.pdf http://tinyurl.com/3x7n8o For a considerably more detailed historical account, see Stachel's "How Did Einstein Discover Relativity?" http://www.aip.org/history/einstein/essay-einstein-relativity.htm Allen Esterson Former lecturer, Science Department Southwark College, London http://www.esterson.org ---
