Groups > sci.physics.relativity > #388216

Re: Gravity and light question

From	Poutnik <poutnik4nntp@gmail.com>
Newsgroups	sci.physics.relativity
Subject	Re: Gravity and light question
Date	2016-07-23 07:23 +0200
Organization	Good company
Message-ID	<nmuuvn$vjj$1@dont-email.me> (permalink)
References	(11 earlier) <nmjh16$11f7$1@gioia.aioe.org> <4231954.31r3eYUQgx@PointedEars.de> <XeednXdReMoB2g_KnZ2dnUU7_8zNnZ2d@giganews.com> <nmtpab$10uf$1@gioia.aioe.org> <GJ-dnRQU_7lUeg_KnZ2dnUU7_8xi4p2d@giganews.com>

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Dne 23/07/2016 v 05:43 Tom Roberts napsal(a):
> On 7/22/16 7/22/16   1:40 PM, Ben Wagner wrote:
>> Tom Roberts wrote:

>>> Just LOOK at the equation you wrote above -- the
>>> curvature (LHS) is related to the energy-momentum tensor T. Light clearly
>>> has nonzero T, and thus affects the curvature.
>>
>>  empty space itself has the above nonzero.
> 
> No. Empty space, aka vacuum, had T=0. That's what we mean by "vacuum" (or "empty 
> space").
> 

Hmmm, I am not expert in GR at all, but..

As absolute temperature cannot reach 0K ( The 3rd TD law )
there is always at least very low but nonzero radiation density.

As "Light clearly has nonzero T",
the space cannot have exactly T=0.

But the residual T can be reasonably neglected,
as it is rather mathematical nitpicking.

-- 
Poutnik ( The Pilgrim, Der Wanderer )
Knowledge makes great men humble, but small men arrogant.

Thread

Re: Gravity and light question Odd Bodkin <bodkinodd@gmail.com> - 2016-07-18 16:17 -0500
  Re: Gravity and light question Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-19 06:31 +0200
    Re: Gravity and light question Odd Bodkin <bodkinodd@gmail.com> - 2016-07-22 07:13 -0500
      Re: Gravity and light question Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 15:52 +0200
    Re: Gravity and light question Tom Roberts <tjroberts137@sbcglobal.net> - 2016-07-22 11:19 -0500
      Re: Gravity and light question Ben Wagner <benwa@ubuntusite.org> - 2016-07-22 18:40 +0000
        Re: Gravity and light question Tom Roberts <tjroberts137@sbcglobal.net> - 2016-07-22 22:43 -0500
          Re: Gravity and light question Poutnik <poutnik4nntp@gmail.com> - 2016-07-23 07:23 +0200
            Re: Gravity and light question Poutnik <poutnik4nntp@gmail.com> - 2016-07-23 08:15 +0200
      Re: Gravity and light question Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 15:38 +0200

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