Groups > sci.physics.relativity > #471283

Re: Ectoplasm

From	moroney@world.std.spaamtrap.com (Michael Moroney)
Newsgroups	sci.physics.relativity
Subject	Re: Ectoplasm
Date	2018-09-10 17:05 +0000
Organization	The World : www.TheWorld.com : Since 1989
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Keith Stein <keithstein111@gmail.com> writes:

>On 10/09/2018 13:07, Michael Moroney wrote:

>> The only problem with that is that Maxwell's Equations just
>> come up with the speed of light = constant. Never constant
>> relative to anything, just the same constant everywhere.
>> Part of the motivation for Einstein's SR later, which raised
>> the speed of light=c to all inertial observers to a postulate.

>Clearly you have never read Maxwell's "Treatise on Electricity
>and Magnetism", Michael. If you had you would surely know that
>Maxwell did NOT come up with the speed of light = constant, but
>rather a speed which depended on the electric permitivity and
>magnetic permeability OF THE MEDIUM. Not only did he NOT
>introduce the constants epsilon0 and mu0, but it is obvious
>that he would have reject such concepts, since the final
>chapter of his famous Treatise is headed "A MEDIUM NECESSARY".

The modern Maxwell's Equations (modified by Heaviside, Hertz and others)
have two forms: an unwieldy form where you essentially have to account for
every single charge and current but applies to all situations, and a
simpler/integral form where materials of a bulk form have a displacement
field D replacing the electric field E, and the H magnetizing field
replacing the magnet field B. The difference between D and E is D contains
a permittivity of a material which is E_r*E_0, and H is B divided by the
magnetic permeability mu of the material, which is mu_r*mu_0.

The first form does not involve materials (except as a whole bunch of
charges/currents that have to be accounted for) and produces the vacuum
speed of light c=1/sqrt(mu_0*E_0). The second form can produce the speed
of light in a material with permittivity E_r*E_0 and permeability
mu_r*mu_0.

Maxwell did not know E_0 and mu_0 individually, but he did know their
product, and noticed that 1/square root of it was very close to the known
speed of light. This is why Maxwell suggested light was electromagnetic
radiation. The product E_0*mu_0 was discovered in an 1855 experiment by
Weber and Kohlrausch.

In empty space (no charges, no currents, no materials) the first form is
used and E_0*mu_0 is constant, so the speed of light c=1/sqrt(E_0*mu_0) is
also constant.  It does not (cannot) depend on the velocity of anything
since in empty space there is nothing there to move!

Thread

Ectoplasm xip1415926@gmail.com - 2018-09-08 09:37 -0700
  Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 09:51 +0100
    Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 10:12 +0100
      Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-10 12:07 +0000
        Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 13:32 +0100
          Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-10 17:05 +0000
            Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 18:42 +0100
              Re: Ectoplasm Odd Bodkin <bodkinodd@gmail.com> - 2018-09-10 17:53 +0000
                Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 19:16 +0100
                Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-10 18:27 +0000
                Re: Ectoplasm "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2018-09-10 12:23 -0700
                Re: Ectoplasm Odd Bodkin <bodkinodd@gmail.com> - 2018-09-10 19:27 +0000
                Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-11 08:16 +0100
                Re: Ectoplasm Odd Bodkin <bodkinodd@gmail.com> - 2018-09-11 11:52 +0000
                Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-11 14:54 +0100
                Re: Ectoplasm (Whoops! Typos eh!) Keith Stein <keithstein111@gmail.com> - 2018-09-11 16:00 +0100
                Re: Ectoplasm (Whoops! Typos eh!) xip1415926@gmail.com - 2018-09-11 08:27 -0700
                Re: Ectoplasm ( and Epistemology and Einstein's Nefarious Practices.) Keith Stein <keithstein111@gmail.com> - 2018-09-11 16:57 +0100
                Re: Ectoplasm Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-16 08:56 -0500
                Re: Ectoplasm xip1415926@gmail.com - 2018-09-16 12:48 -0700
                Re: Ectoplasm xip1415926@gmail.com - 2018-09-16 13:01 -0700
                Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-17 18:38 +0100
                Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-17 18:04 +0000
                Re: Ectoplasm Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-17 14:00 -0500
                Re: Ectoplasm "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2018-09-17 20:59 -0700
                Re: Ectoplasm "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2018-09-17 21:16 -0700
                Re: Ectoplasm "Ross A. Finlayson" <ross.finlayson@gmail.com> - 2018-09-23 20:07 -0700
              Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-10 18:16 +0000
                Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-11 07:52 +0100
                Re: Ectoplasm moroney@world.std.spaamtrap.com (Michael Moroney) - 2018-09-11 12:01 +0000
            Re: Ectoplasm Thomas Heger <ttt_heg@web.de> - 2018-09-14 21:16 +0200
              Re: Ectoplasm Thomas Heger <ttt_heg@web.de> - 2018-09-16 20:23 +0200
      Re: Ectoplasm xip1415926@gmail.com - 2018-09-10 07:03 -0700
      Re: Ectoplasm Tom Roberts <tjroberts137@sbcglobal.net> - 2018-09-10 09:39 -0500
        Re: Ectoplasm Keith Stein <keithstein111@gmail.com> - 2018-09-10 16:18 +0100
        Re: Ectoplasm Wilbur Foley <boue@eywffl.uf> - 2018-09-10 17:07 +0000
  Re: Ectoplasm (or History and Foundations of the LT) Keith Stein <keithstein111@gmail.com> - 2018-09-13 16:24 +0100
    Re: Ectoplasm (or History and Foundations of the LT) xip1415926@gmail.com - 2018-09-14 03:45 -0700

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