Re: energy and mass

From	ram@zedat.fu-berlin.de (Stefan Ram)
Newsgroups	sci.physics.relativity, sci.electronics.design
Subject	Re: energy and mass
Date	2026-02-13 10:29 +0000
Organization	Stefan Ram
Message-ID	<photon-20260213110610@ram.dialup.fu-berlin.de> (permalink)
References	(11 earlier) <mass-20260212201526@ram.dialup.fu-berlin.de> <xna4xdit4q.fsf@delorie.com> <photons-20260212222813@ram.dialup.fu-berlin.de> <10mlq9b$h4me$1@gwaiyur.mb-net.net> <xn5x81iets.fsf@delorie.com>

Cross-posted to 2 groups.

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DJ Delorie <dj@delorie.com> wrote or quoted:
>So... a photon moving at speed of light has some
>energy-mass-whatever-equivalent, which is sufficient to warp spacetime.

  Everything has a "stress-energy tensor", including photons.
  (There is a Wikipedia page "Stress-energy tensor")

>That change may cause other photons' paths to "bend"

  That tensor changes the curvature of space-time, which influences
  the paths of everything moving in space-time, including photons.

>                                                     as if gravity were
>a force, regardless of time effects, because it's not a force, it's a
>shape.

  Whether gravity is a force depends on the model. In general
  relativity, it's not a force, but in other fields it's sometimes
  a force. In high-school physics, it certainly is a force.

>I wonder, though, if there were some non-spacetime actual "force"
>between photons (I realize there isn't, but imagine one for a moment).

  Yes, there is photon-photon scattering in QED (virtual charged particle
  loops), but it is a very weak effect that rarely matters in practice.

  Both effects (a photon's stress-energy tensor and photon-photon
  scattering) are very weak and therefore not observable in practice.

>If said force obeyed the usual F=ma, *now* would time dilation come into
>play wrt photons?  Two photons travelling next to each other, from their
>point of view (or any other), how would that force evolve itself over
>"time" ?

  Time dilation does not matter here because everything can be
  described from one single frame of reference (the lab frame)
  while it cannot be described from the "point of view of a photon".

>[*] except if photons move at the speed of light, and "gravity" does
>    too, do photons create gravitational shock waves as they travel?  Or
>    does the distortion just travel happily along with the photon?  Or
>    just behind it?  How could we find out?

  The photon is a quantum of an electromagnetic field; that field
  has a stress-energy tensor; that stress-energy tensor modifies
  the curvature of space-time. But we do not yet have a "theory
  of everything" that describes quanta (such as photons) /and/
  gravitation. Quantum electrodynamics describes quantum effects
  in electrodynamics and general relativity describes gravitation.

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Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 14:55 +0100
  Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 14:58 +0100
  Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-12 07:43 -0800
    Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-12 16:23 +0000
      Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-12 08:44 -0800
        Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-12 17:15 +0000
          Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-13 13:45 +0000
        Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 05:12 +1100
          Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 20:26 +0100
            Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 15:56 +1100
              Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-14 14:17 +0100
            Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-14 13:56 +0100
              Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-14 09:39 -0800
                Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-14 09:40 -0800
      Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 22:08 +0100
        Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-13 10:07 -0800
      Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 22:57 +0100
        Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-13 10:11 -0800
      Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 00:33 +0100
    Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-12 19:39 +0100
      Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-12 11:04 -0800
        Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-12 19:22 +0000
          Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-12 20:16 +0000
          Re: energy and mass DJ Delorie <dj@delorie.com> - 2026-02-12 15:50 -0500
            Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-12 21:29 +0000
              Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 01:12 +0100
                Re: energy and mass DJ Delorie <dj@delorie.com> - 2026-02-12 20:59 -0500
                Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 03:15 +0100
                Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-13 11:27 +0100
                Re: energy and mass DJ Delorie <dj@delorie.com> - 2026-02-13 10:09 -0500
                Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 17:39 +0100
                Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-13 23:40 +0100
                Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-13 10:29 +0000
                Re: energy and mass DJ Delorie <dj@delorie.com> - 2026-02-13 10:21 -0500
                Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 17:34 +0100
              Re: energy and mass ram@zedat.fu-berlin.de (Stefan Ram) - 2026-02-21 15:24 +0000
            Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-12 23:12 +0100
            Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 23:27 +0100
        Re: energy and mass The Starmaker <starmaker@ix.netcom.com> - 2026-02-12 11:28 -0800
        Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-12 22:29 +0100
        Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 05:22 +1100
          Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 19:58 +0100
            Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 07:13 +1100
              Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-14 00:44 +0100
                Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-14 03:52 +0100
                Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-14 21:59 +0100
      Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-13 09:50 -0800
    Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-12 22:03 +0100
      Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-12 23:12 +0100
        Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 05:34 +1100
          Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-13 20:35 +0100
            Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-14 22:57 +0100
          Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-14 21:59 +0100
            Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-15 17:50 +1100
              Re: energy and mass Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2026-02-15 12:47 +0100
                Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-15 23:51 +1100
                Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-15 21:48 +0100
                Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-15 08:13 -0800
                Re: energy and mass nospam@de-ster.demon.nl (J. J. Lodder) - 2026-02-15 21:48 +0100
                Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-15 13:11 -0800
                Re: energy and mass Seymour Dobrov <ouo@yosdm.ru> - 2026-02-15 19:49 +0000
      Re: energy and mass john larkin <jl@glen--canyon.com> - 2026-02-13 10:04 -0800
      Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-13 10:05 -0800
    Re: energy and mass Bill Sloman <bill.sloman@ieee.org> - 2026-02-14 05:00 +1100
      Re: energy and mass Ross Finlayson <ross.a.finlayson@gmail.com> - 2026-02-13 10:19 -0800

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