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Re: The Necessity Alternate Theories

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Odd Bodkin wrote:

> In general relativity, motion is inertial and worldlines are locally
> straight.

Hmmm.  I think it is only safe to say that in GR _spacetime_ is locally 
_flat_.

> "Motion in spacetime" is an oxymoron.

In light of current events, one cannot resist to exclaim:

“You’re just not thinking fourth-dimensionally!”

;-)

Motion is generally characterized by a change of coordinates in a suitable 
frame of reference.

The trivial motion in spacetime, where there are four coordinates, three 
spatial and one temporal, is to do nothing, thereby following along a time-
like world line of maximum proper time, a geodesic:

Then your 3 spatial coordinates in spacetime, x₁, x₂, and x₃ – your 
(3-)position – in a suitable frame of reference (e.g., the surface of Terra 
on which you are standing/sitting/lying), do not change, but your one other, 
temporal coordinate t changes continuously (which you can observe by looking 
at a working, co-moving watch/clock, and if you wait a really long time, by 
observing your hair and nails growing, and yourself aging).  (The proper 
time interval for uniform motion in spacetime is

   ∆τ = √((∆t²) – (∆x_i)²∕c²).

As a result of not moving spatially,

  ∆x_i = 0,

so that the proper time interval between arbitrary events on that curve is 
maximal.  [Using Landau/Lifshitz signature convention, and Einstein 
summation convention.])

See also:

<https://en.wikipedia.org/wiki/Four-velocity> (describes the rate of change 
of four-position, i.e. motion, in spacetime);

<https://en.wikipedia.org/wiki/World_line#Usage_in_physics> pp. (describes 
the [two] possibilities for motion in spacetime).

Also, STFW for peer-reviewed papers and physics books on motion in different 
kinds of space(-)time, such as 
<http://scitation.aip.org/content/aip/journal/jmp/56/3/10.1063/1.4913882> 
and 
<https://books.google.com/books?id=DCLUBwAAQBAJ&pg=PA14&dq=motion+%22in+spacetime%22&hl=de&sa=X&ved=0CDQQ6wEwA2oVChMInrXiss2zyAIViMcUCh0jHwbQ#v=onepage&q=motion%20%22in%20spacetime%22&f=false>


PointedEars
-- 
Q: What did the female magnet say to the male magnet?  
A: From the back, I found you repulsive, but from the front
   I find myself very attracted to you.
(from: WolframAlpha)

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The Necessity Alternate Theories kefischer <emoneyjoe@iglou.com> - 2015-10-08 13:01 -0400
  Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-08 17:09 +0000
  Re: The Necessity Alternate Theories Odd Bodkin <bodkinodd@gmail.com> - 2015-10-08 13:30 -0500
    Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-08 22:45 +0200
      Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-08 22:58 +0200
        Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-08 21:56 +0000
          Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-09 06:39 +0200
            Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-09 10:59 +0000
              Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-09 20:29 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-09 18:44 +0000
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 09:40 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 12:08 +0000
                Re: The Necessity Alternate Theories paparios <paparios@gmail.com> - 2015-10-10 05:25 -0700
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 12:37 +0000
                Re: The Necessity Alternate Theories Maciej Woźniak <mlwozniak@wp.pl> - 2015-10-10 14:54 +0200
                Re: The Necessity Alternate Theories paparios <paparios@gmail.com> - 2015-10-10 06:02 -0700
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 17:49 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 16:08 +0000
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 18:13 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 16:16 +0000
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 19:08 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 18:02 +0000
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 20:17 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 18:37 +0000
                Re: The Necessity Alternate Theories Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-10-10 20:54 +0200
                Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-10 19:00 +0000
                Re: The Necessity Alternate Theories benj <nobody@gmail.com> - 2015-10-10 16:40 -0400
                Re: The Necessity Alternate Theories underante <underante@yahoo.com> - 2015-10-09 15:31 -0700
  Re: The Necessity Alternate Theories kefischer <emoneyjoe@iglou.com> - 2015-10-09 02:42 -0400
    Re: The Necessity Alternate Theories Natalina Nazvarova <natana42@hotmail.com> - 2015-10-09 11:44 +0000
      Re: The Necessity Alternate Theories kefischer <emoneyjoe@iglou.com> - 2015-10-09 08:00 -0400

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