Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > sci.physics.relativity > #452551

Re: Units in spacetime

From Odd Bodkin <bodkinodd@gmail.com>
Newsgroups sci.physics.relativity
Subject Re: Units in spacetime
Date 2018-03-13 22:55 +0000
Organization Aioe.org NNTP Server
Message-ID <p89kt8$1b9i$1@gioia.aioe.org> (permalink)
References <fgpik3F5ps8U1@mid.individual.net> <c9da30bf-feee-4de2-8bd9-e714c0ad3a5e@googlegroups.com> <p88nm5$1ee8$1@gioia.aioe.org> <1_WpC.124337$a15.44105@fx22.am4>

Show all headers | View raw

Paul B. Andersen <relativity@paulba.no> wrote:
> Den 13.03.2018 15.36, skrev Odd Bodkin:
>> Thomas Heger
>>> 
>>> ds²= -(cdt)² + dx² + dy² + dz².
> 
> metric signature (-,+,+,+)
> 
>> 
>> You should be careful here. The formulation of the interval above really
>> only applies to spacelike intervals. For timelike intervals, the interval
>> is written as
>> ds²= (cdt)² - dx² - dy² - dz².
> 
> metric signature (+,-,-,-)
> 
> see:
> https://en.wikipedia.org/wiki/Sign_convention
> 
> You will find that both signatures are used
> in the literature, but it is not common to mix them,
> the same metric is used for both time-like and space-like intervals.
> 
> Misner & Thorne & Wheeler: "Gravitation"  use (-,+,+,+)
> Carroll: "Spacetime and Geometry" use (-,+,+,+)
> d'Inverno: "Introducing Einstein's Relativiy" use (+,-,-,-)
> Taylor & Wheeler: "Spacetime Physics" use (+,-,-,-)
> 
> With the signature (-,+,+,+) a positive space time interval s^2
> will be space like, s = sqrt(s^2), while a negative s^2 will be 
> time-like,  \tau = sqrt(-s^2/c^2).
> 
> With the signature (+,-,-,-) a negative space time interval s^2
> will be space like, s = sqrt(-s^2), while a positive s^2 will be 
> time-like,  \tau = sqrt(s^2/c^2).
> 
> 

Agreed. And notice what -s^2 looks like when expressed in components in
flat space. 

-- 
Odd Bodkin — Maker of fine toys, tools, tables

Back to sci.physics.relativity | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-13 10:06 +0100
  Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-13 07:15 -0700
    Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-13 14:36 +0000
      Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-13 07:51 -0700
        Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-13 08:34 -0700
      Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-13 09:20 -0700
        Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-13 16:27 +0000
          Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-13 16:28 +0000
          Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-13 09:45 -0700
            Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-13 18:39 +0100
              Re: Units in spacetime Térov Balónky <iytn@yeicenlw.ik> - 2018-03-13 17:49 +0000
                Re: Units in spacetime Térov Balónky <iytn@yeicenlw.ik> - 2018-03-13 17:49 +0000
                Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-14 13:54 +0100
                Re: Units in spacetime Térov Balónky <iytn@yeicenlw.ik> - 2018-03-14 16:02 +0000
                Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-14 21:47 +0100
            Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-13 18:02 +0000
              Re: Units in spacetime Térov Balónky <iytn@yeicenlw.ik> - 2018-03-13 18:12 +0000
      Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-13 22:00 +0100
        Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-13 22:55 +0000
          Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-14 09:19 -0700
            Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-14 09:32 -0700
              Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-14 09:52 -0700
            Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-14 18:07 +0000
              Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-14 12:03 -0700
              Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-14 13:18 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-14 21:38 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-14 16:27 -0700
                Re: Units in spacetime Python <python@python.invalid> - 2018-03-15 01:05 +0100
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-15 03:52 +0000
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-14 23:10 -0700
                Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-15 00:16 -0700
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-15 11:55 +0000
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-15 14:40 +0100
                Re: Units in spacetime Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-03-15 16:02 +0100
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-15 15:20 +0000
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-15 09:49 -0700
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-15 19:49 +0000
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-15 11:26 +0100
                Re: Units in spacetime mlwozniak@wp.pl - 2018-03-15 04:03 -0700
                Re: Units in spacetime Keith Stein <keithstein111@gmail.com> - 2018-03-15 15:50 +0000
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-15 21:15 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-15 10:30 -0700
                Re: Units in spacetime Python <python@python.invalid> - 2018-03-15 18:32 +0100
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-15 19:51 +0000
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-15 20:56 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-15 23:20 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-16 10:11 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-18 22:25 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-19 09:17 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-19 10:36 -0700
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-19 17:57 +0000
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-19 11:16 -0700
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-19 18:43 +0000
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-19 13:02 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-19 21:24 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-20 09:32 -0700
                Re: Units in spacetime Python <python@python.invalid> - 2018-03-20 17:40 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-20 09:55 -0700
                Re: Units in spacetime Dirk Van de moortel <dirkvandemoortel@notmail.com> - 2018-03-20 18:25 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-20 14:21 -0700
                Re: Units in spacetime Dirk Van de moortel <dirkvandemoortel@notmail.com> - 2018-03-20 22:57 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-20 16:00 -0700
                Re: Units in spacetime Darryl Fletcher <lu@ewiwwe.tt> - 2018-03-20 23:38 +0000
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-22 14:01 +0100
                Re: Units in spacetime Koobee Wublee <koobee.wublee@gmail.com> - 2018-03-22 13:45 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-27 20:18 +0200
                Re: Units in spacetime xip1415926@gmail.com - 2018-03-27 14:40 -0700
                Re: Units in spacetime xip1415926@gmail.com - 2018-03-26 07:38 -0700
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-27 19:53 +0200
                Re: Units in spacetime xip1415926@gmail.com - 2018-03-27 12:21 -0700
                Re: Units in spacetime Tom Roberts <tjroberts137@sbcglobal.net> - 2018-03-27 16:47 -0400
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-28 09:34 +0200
                Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-20 21:12 +0100
                Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-16 10:32 +0100
                Re: Units in spacetime "Paul B. Andersen" <relativity@paulba.no> - 2018-03-16 12:33 +0100
                Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-17 21:29 +0100
                Re: Units in spacetime Odd Bodkin <bodkinodd@gmail.com> - 2018-03-14 20:51 +0000
                Re: Units in spacetime "David (Kronos Prime) Fuller" <fuller.david@hotmail.com> - 2018-03-20 15:41 -0700
            Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-15 14:04 +0100
              Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-15 20:10 +0100
      Re: Units in spacetime Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-03-22 05:57 +0100
        Re: Units in spacetime Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2018-03-27 19:57 +0200
  Re: Units in spacetime numbernumber1964@gmail.com - 2018-03-20 13:49 -0700
    Re: Units in spacetime Keith Stein <keithstein111@gmail.com> - 2018-03-21 07:26 +0000
  Re: Units in spacetime numbernumber1964@gmail.com - 2018-03-22 15:28 -0700
    Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-23 09:57 +0100
      Re: Units in spacetime xip1415926@gmail.com - 2018-03-25 18:54 -0700
  Re: Units in spacetime numbernumber1964@gmail.com - 2018-03-23 10:48 -0700
    Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-25 19:03 +0200
      Re: Units in spacetime xip1415926@gmail.com - 2018-03-26 06:39 -0700
        Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-03-26 21:43 +0200
  Re: Units in spacetime Keith Stein <keithstein111@gmail.com> - 2018-03-30 11:00 +0100
    Re: Units in spacetime Will Bos <sllu@wsws.sb> - 2018-03-30 10:52 +0000
      Re: Units in spacetime Will Bos <sllu@wsws.sb> - 2018-03-30 11:02 +0000
    Re: Units in spacetime Thomas Heger <ttt_heg@web.de> - 2018-04-03 06:45 +0200

csiph-web