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Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime

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On 7/28/17 5:29 AM, shuba wrote:
> Bodkin wrote:
> 
>> "Invariant" is a descriptor applied to a
>> quantity whose VALUE is unchanging.
> 
> I think it is much better defined (especially in a relativistic context) as a quantity independent of frame.
> 
>> An example would be that the momentum in a
>> closed system is invariant.
> 
> The 3-momentum of a particle or center of mass is not an invariant according to my definition above. In your example it is a conserved quantity, that is a quantity whose value (in a particular frame) remains constant over some time evolution of the system.
> 
>> Another example is that invariant mass does not
>> change regardless of the reference frame it's
>> evaluated in.
> 
> Yes, mass is invariant, while 3-momentum and energy are not.
> 
> Logically similar to (m^2 = E^2 - p^2), the covariant derivative (an invariant operator) is a combination of the ordinary derivative and the Christoffel symbol, neither of which are invariant.
> 
> While there is certainly some inconsistency in the use of the terminology, especially in popularizations and introductory material, I believe these definitions (of "invariant" and "conserved") are fairly standard.
> 
> 
>           ---Tim Shuba---
> 

Alright, that's a refinement that is reasonably consistent with what 
I've seen. I've seen "invariant" with the dual meanings I suggested 
(that is, including the synonym of "conserved") and so included both.

-- 
Odd Bodkin -- maker of fine toys, tools, tables

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Apologies - there is NO absolute 'frame', there is an absolute spacetime "Edgar L. Owen" <Edgar@edgarlowen.com> - 2017-07-27 05:00 -0700
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime kenseto <setoken@att.net> - 2017-07-27 05:38 -0700
    Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-07-27 15:06 +0200
  Apologies - there is NO absolute 'frame', there is an absolute spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-07-27 08:16 -0700
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Odd Bodkin <bodkinodd@gmail.com> - 2017-07-27 10:57 -0500
    Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime shuba <thailao2558@gmail.com> - 2017-07-28 03:29 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime mlwozniak@wp.pl - 2017-07-28 03:34 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-07-28 07:34 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Odd Bodkin <bodkinodd@gmail.com> - 2017-07-31 09:00 -0500
    Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-29 07:46 -0500
    Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime "Edgar L. Owen" <Edgar@edgarlowen.com> - 2017-07-29 06:28 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime "Edgar L. Owen" <Edgar@edgarlowen.com> - 2017-07-29 06:49 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-07-29 07:38 -0700
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Odd Bodkin <bodkinodd@gmail.com> - 2017-07-31 09:01 -0500
      Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-31 10:17 -0400
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Ernard Hevalier <adrdo@tarlaab.lr> - 2017-07-27 18:08 +0000
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-07-27 22:50 +0200
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Tom Roberts <tjroberts137@sbcglobal.net> - 2017-07-29 08:14 -0500
    Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime Jeèným Ludnými <hovae@ieuuio.org> - 2017-07-29 16:00 +0000
  Re: Apologies - there is NO absolute 'frame', there is an absolute spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2017-07-29 10:47 -0700

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