`  == Relativity ==  Hi, ED.  Thanks for providing those references.  I'm sorry these conversations have gotten so combative-probably both sides could be more cooperative.  You clearly know a lot about physics, and there's no reason to doubt you're an experienced researcher, so I think these disagreements must be somehow based on misunderstandings.  Since there are some subtle issues being discussed, maybe everyone's just butting heads because of miscommunications.  Thanks again for the references-they help immensely.  I don't have any of those texts on hand, but I can look them up tomorrow, and I do have a few others.  After reviewing Resnick/Halliday/Krane, French, Goldstein, and Marion Thornton, one in particular (Marion-Thornton) seems to describe the relevant issues clearly.  First of all, in the section on Newtonian mechanics, it mentions ``Galilean invariance`` and the ``principle of Newtonian relativity.``  Then, in the chapter on special relativity, we find  The basis of relativity theory is contained in two postulates.  but shortly thereafter,  Postulate I, which Einstein called the ``principle of relativity,`` is the fundamental basis for the theory of relativity.  Postulate II, the law of propagation of light, follows from Postulate I if we accept, as Einstein did, that Maxwell's equations are fundamental laws of physics.  So I think these disagreements have been based on an issue of perspective.  If one knows nothing except the principle of relativity, then the second postulate is necessary-indeed, since Newtonian mechanics satisfies the principle of relativity, that principle alone can't lead to SR.  That's why Einstein included the 2nd postulate.  However, if we accept E&M;, or the fact that massive particles don't accelarate linearly forever with a constant force (mentioned by French), or indeed any of the abounding evidence that there's a ``speed limit`` in the universe, then the full structure of SR can be derived from only the principle of relativity.  Do you think that's a reasonable understanding of things?  If so, maybe we can all work together to find a way to explain things in the article.  I'd be happy to discuss things further.  Regards,   `