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Re: Does Velocity Play A Factor?
Forum List  Follow Ups  Post Message  Back to Thread Topics  In Response To Posted by Zephram Cochrane/">Zephram Cochrane on November 16, 1999 08:15:41 UTC 
: re Riemann tensor not curvature tensor.  The curvature tensor is just another name for the Reimann tensor. Sometimes it's even called the Riemann curvature tensor I am saying that I disagree with that naming. : : re  There is no such tensor so it implies no such thing.  Sure there is. The components of the tidal force tensor are a subset of the components of the curvature tensor. Your can look it up in either MTW or Ohanian. You misread. As I said you may define one if you wish as gmn ; ls but this does not really give you the experienced tidal forces. Thus, even though this is a tensor it is not truly a tidal "acceleration" tensor. It's definitely not a tidal "force" tensor. There is no such thing. And I think you mistake this for gmn , ls which is not the same thing. This is not even a tensor. : : re  : Not under a short enough proper time ...  What's your point? The question was whether velocity affects tidal force  not whether or how tidal effect can be ignored. That's a separate issue. It is the difference between "does distort" and "will distort." I made my point as to how velocity affect tidal force. Reread it. : : re  : again you misunderstand local.  Nope. Don't put words into my mouth. There is a wellestablished criterion in MTW for determining when a region of spacetime can be called locally flat. Loosely speaking  If, within a given amount of time and given a specified precision, no relative acceleration of test objects is detected then that region of spacetime is referred to as "locally flat." The questioner asked about tidal forces. You addressed local aspects, not I. : re  SO what?  What kind of question is this? The so what, is that I never said that I was mearly applying this to point particles. It is that it is easy to see tidal force as with other local accelerations you just mention vanish in a local frame of free fall. I answered the question and then added that whether or not the object was in a local frame of free fall Vs one with external forces played a more important role as to the measurements of tidal forces. You disagreed, before really considering what I just said. This is evident in that your last paragraph here actually agrees with what I actually said. Instead of looking for disagreement where there really isn't one, try to understand what are obviously well informed points of view. Your MTW quote is practically a repetition of what I already said. 

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