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Re: What is mass?

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Followups directed to: sci.physics.relativity

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Fabian Russell wrote:

> On Wed, 23 Sep 2015 19:12:18 +0200, Poutnik wrote:
>> cannot be completely wrong equation.
> 
> The equation is wrong because it specifies mass, m, as *the* mass,
> i.e. the definitive mass or the one-and-only mass.

There is only mass.  To answer the question in the Subject header field 
value: Mass is a measure of the energy content of a body at rest in the 
laboratory frame (of reference): E = √(pc)² + (mc²)²) → m = E∕c² for p = 0, 
with p = γmv (relative rest → γ = 1, v = 0).

That is why we build huge machines to *accelerate* subatomar particles close 
to the speed of light in vacuum, and have them collide with each other to 
create particles with a lot of mass and, more recently, to "produce" energy 
through nuclear fusion.
 
> Correctly written, the *inertial* mass must be indicated because,
> as already stated, there are two different "kinds" of mass.

Two terms for the same thing is not how science works.
 
> For some reason, the concepts of inertial mass and gravitational
> mass have been effectively purged from physics,

Because physics is a science.  Superfluous terms are not used in science.  
One uses different terms for different things, the same term for the same 
thing.

> but they are still valid.

Because you say so?

> GR *assumes* the equivalence of both types

Because it can be *demonstrated*.  Read on the elevator experiment: Without 
additional information, you cannot tell whether you are far away from a 
source of gravity or in free fall, and you cannot tell whether you are 
accelerating or near a source of gravity.

(Einstein is often described as a theoretical genius only.  But, in fact, 
the text of his works shows that he was deeply guided by experiment.  And 
there is other evidence: He co-designed and had built an observatory [the 
Einsteinturm in Potsdam, Germany] only for testing GR.  And he would have 
thrown out GR like yesterday’s newspaper if it had given the wrong result 
for the precession of the perihelion of Mercury.  Just as he wrote [in 
German] “then away with the cosmological term” regarding his field equations 
when Hubble’s observations confirmed Lemaître’s theory that the universe was 
in fact not static, but expanding.)

> and perhaps for this reason all textbooks incorrectly mention only a 
> single type of mass.  But, as also mentioned, GR is not yet universally
> established.

In crackpot’s heads, perhaps.  Everywhere else it is, quite literally, 
“universally” established, for example:

- in timekeeping (precise clocks are gauged based on their elevation; it can
  be demonstrated that those at higher elevation tick faster than their
  same-model counterparts at lower elevation)

- in communication (with orbital spacecraft and interplanetary probes);

  * as a special case, in satellite navigation (GPS and alternatives)

  (again, clocks close to a massive body tick slower than those farther away
  from it)

- in astronomy and astrophysics (perihelion precession, gravitational
  lensing, black holes)

- in cosmology (the ΛCDM, or *standard* model of cosmology)


PointedEars
-- 
“Science is empirical: knowing the answer means nothing;
 testing your knowledge means everything.”
   —Dr. Lawrence M. Krauss, theoretical physicist,
    in “A Universe from Nothing” (2009)

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Thread

What is mass? gilber34 <fafa@invalid.com> - 2015-09-23 11:02 -0500
  Re: What is mass? Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-23 18:55 +0200
  Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-23 16:59 +0000
    Re: What is mass? Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-23 19:12 +0200
      Re: What is mass? Poutnik <Poutnik4NNTP@gmail.com> - 2015-09-23 19:17 +0200
      Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-23 17:34 +0000
        Re: What is mass? Poutnik <poutnik4nntp@gmail.com> - 2015-09-23 20:35 +0200
          Re: What is mass? omnilobe@gmail.com - 2015-09-23 12:40 -0700
          Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-23 21:44 +0000
            Re: What is mass? Poutnik <poutnik4nntp@gmail.com> - 2015-09-24 08:50 +0200
              Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-26 22:34 -0700
        Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-26 08:35 +0200
          Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-26 12:35 +0000
            Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-26 15:37 +0200
              Re: What is mass? john <johnsefton288@gmail.com> - 2015-09-26 07:14 -0700
                Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-26 16:17 +0200
          a-hem; m = F/a is also gOOd noTthaTguY <abu.kuanysh05@gmail.com> - 2015-09-26 17:16 -0700
            Re: a-hem; m = F/a is also gOOd Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-27 03:26 +0200
              top-posting is frpowned upon by certain advertizers ... just don't ask them, why not noTthaTguY <abu.kuanysh05@gmail.com> - 2015-09-27 15:53 -0700
                What is mass (was: top-posting is frpowned upon by certain advertizers ... just don't ask them, why not) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-28 17:05 +0200
                a.k.a photonics -- thanks for the tip (pi dollars is gOOd noTthaTguY <abu.kuanysh05@gmail.com> - 2015-09-29 11:28 -0700
                Re: a.k.a photonics -- thanks for the tip (pi dollars is gOOd Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 21:01 +0200
                no skwares in the medium of space noTthaTguY <abu.kuanysh05@gmail.com> - 2015-09-29 19:29 -0700
    Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-23 23:07 -0700
  Re: What is mass? "nuny@bid.nes" <Alien8752@gmail.com> - 2015-09-23 14:01 -0700
    Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-27 23:40 -0700
  Re: What is mass? "reber g=emc^2" <herbertglazier0@gmail.com> - 2015-09-24 13:36 -0700
  Re: What is mass? Yousuf Khan <bbbl67@spammenot.yahoo.com> - 2015-09-28 02:13 -0400
    Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-28 09:27 -0700
      Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 04:31 +0200
        Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-29 00:29 -0700
          Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 13:21 +0200
            Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 13:34 +0200
            Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-29 05:19 -0700
        Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-29 05:40 -0700
          Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 15:11 +0200
            Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-29 06:37 -0700
              Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 16:22 +0200
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-29 07:51 -0700
                Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 18:45 +0200
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-29 11:06 -0700
                Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-29 21:00 +0200
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-09-29 13:47 -0700
                Re: What is mass? "Ma Hipple" <invalid@example.com> - 2015-09-30 07:20 -0700
              Re: What is mass? "Alan Smith" <invalid@example.com> - 2015-09-29 07:33 -0700
          Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-09-30 02:21 -0700
            Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-10-04 19:11 -0700
              Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-10-05 00:39 -0700
                Re: What is mass? noTthaTguY <abu.kuanysh05@gmail.com> - 2015-10-05 18:38 -0700
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-10-05 18:50 -0700
                Re: What is mass? "Eric Smith" <invalid@example.com> - 2015-10-05 20:01 -0700
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-10-05 20:49 -0700
                Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-10-06 03:18 -0700
              Re: What is mass? "Fred Smith" <invalid@example.com> - 2015-10-06 17:41 -0700
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-10-06 19:38 -0700
                Re: What is mass? "Greg Smith" <invalid@example.com> - 2015-10-07 06:59 -0700
                Re: What is mass? gilber34 <fafa@invalid.com> - 2015-10-07 09:03 -0500
                Re: What is mass? "Hank Smith" <invalid@example.com> - 2015-10-07 07:20 -0700
                Re: What is mass? Mahipal <mahipal7638@gmail.com> - 2015-10-07 08:11 -0700
                Re: What is mass? noTthaTguY <abu.kuanysh05@gmail.com> - 2015-10-07 16:07 -0700
                Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-10-08 00:18 -0700
                Re: What is mass? john <johnsefton288@gmail.com> - 2015-10-08 06:15 -0700
                Re: What is mass? "Y.Porat" <y.y.porat@gmail.com> - 2015-10-10 01:11 -0700
                Re: What is mass? noTthaTguY <abu.kuanysh05@gmail.com> - 2015-10-10 16:43 -0700
                Re: What is mass? noTthaTguY <abu.kuanysh05@gmail.com> - 2015-10-08 12:34 -0700

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