From: utzoo!decvax!harpo!ihnp4!ihldt!bnp Newsgroups: net.space Title: Einstein's Universe?! Article-I.D.: ihldt.1313 Posted: Mon Feb 7 12:59:40 1983 Received: Wed Feb 9 01:30:29 1983 Reply-To: bnp@ihldt.UUCP (Bruce Peters) This query may be a repeat of an old question, but it has been bothering me for some time so... I have never had a good qualitative understanding of Einstien's' theories of relativity (both special and general), and a friend recommended a book entitled "Einstein's Universe" by Nigel Calder, as a good introduction to the subject. I got a copy from a local library and began reading, but quickly ran into trouble when the author began describing the differences in the Doppler shift mechanisms which apply to light vs. sound. I was hoping that someone on the net could provide a better explanation, or recommend a good book. I can see how in air, the magnitude of a Doppler shift will depend on whether the observer or the source of the sound is moving, but I cannot understand how the two cases can be treated identically for light. I have heard the arguments about the lack of an "either" through which the light moves, but that doesn't seem to explain the mechanism causing the Doppler shift when the observer is moving relative to the source of the light. Please respond by mail, and if other similiar queries appear, I will summarize. Thanks, Bruce Peters BTL - Naperville