Sorry about the title of this, but with 50+ views of my previous message and only one reply, I surmised that I need to be a bit more "punchy" in my delivery. In his book, Relativity, Dr. Einstein tells us that the fact that an organ pipe on a train carriage sounds the same no matter what its orientation (relative to the carriage) is "a powerful argument in favor of the principle of relativity." But I do not think that this is right. Would not the medium of sound (the air in the carriage) be moving in the carriage's inertial frame, and thus at rest with respect to the carriage? And would this not negate any effect of the motion of the carriage on the sound produced by the pipe? Any help here would be greatly appreciated. Perhaps I am missing something here - some subtle effect of motion on the sound waves generated by the organ pipe. I am not trying to comment on the principle of relativity here. I am just saying that I don't think that this experiment can prove or disprove the principle of relativity. Any help?