btw the mathpages indeed have some of the most thoughtful commentary on relativity available on the internet the author of the mathpages is an executive of a major corporation and prizes his anonymity back a few years ago when i was helping don koks find a backup editor for the usenet physics faq i was able to do a whois on the site to identify the owner and unsuccessfully tried to recruit him for faq duties shortly afterwards it no longer was possible to get any useful whois information