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Re: Gravity needs NO Matter

Cross-posted to 2 groups.

Followups directed to: sci.physics.relativity

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benj wrote in <news:sci.physics.relativity> and <news:sci.physics>:

> On 01/29/2016 12:28 PM, Odd Bodkin wrote:
>> On 1/29/2016 11:22 AM, benj wrote:
>>> In fact mass is the mathematical coefficient between the acceleration
>>> observed in an object and force producing it. It is not even a constant
>>> value except at low velocities.
>> That definition of mass you just described is antiquated and has been
>> out of date for I think about 7 decades.
> 
> Oh gosh, Boinker. How interesting that fashion is SO important in
> science.

Only *you* said “fashion”.

> This is why you always need "authorities" to tell you what is
> "in". I presume you have a nice stubbly growth of hair on your face to
> be like all your Hollywood heros these days!
> 
> So you can't just look at the equation F = ma and notice that m is the
> factor between F and a? Are you REALLY that ignorant? Go back to your
> wooden toys.

You just do not realize that the definition of a “relativistic mass” m_rel 
that increases with relative speed v according to

      E = m_rel c²

  m_rel = γm₀ = m₀∕√(1 − (v∕c)²)

was a rather confusing concept (especially to students) that Einstein 
himself deprecated later.  It is *easier* to consider that what really 
increases with relative speed is the total *energy* that an object has (thus 
the work that it can do, as its kinetic energy must be increased in order to 
put it into relative motion; the total energy in relative motion then also 
called “relativistic energy” as opposed to “rest energy”, its energy in its 
rest frame), so that there is only mass m = m₀ (previously called “rest 
mass”, i.e. the mass of an object in its rest frame), and that the energy–
momentum relation

  E = √((mc²)² + (pc)²),

derived from the norm of the four-momentum P⃗ = (E∕c, p⃗), holds both for 
objects with non-zero (rest) mass and objects with zero (rest) mass such as 
photons, whereas for m > 0 and 0 < v < c

   p = γmv = mv∕√(1 − (v∕c)²),

and for photons (m = 0)

   p = ℎf∕c

(the momentum p and thus the energy of a photon E = ℎf = pc does not depend 
on its speed which is always c, it only depends on the frequency/wavelength 
of the light, in agreement with the observations of the photoelectric 
effect), while for m > 0 and v = 0 it is *still*

   E = mc².

<https://en.wikipedia.org/wiki/Mass_in_special_relativity#Relativistic_mass>

>> Mass is invariant and does not change with velocity, in current usage.
> 
> But the coefficient between Force and acceleration does.

Actually, in special relativity it does not.  What changes is the four-
velocity-dependent four-acceleration:

  F⃗ = dP⃗∕dτ = m A

<https://en.wikipedia.org/wiki/Four-force>

> OR don't you speak math?

Do you?  I have just given you the history and the *equations* underlying 
this definition shift.


Please stop the amok-crossposting.  F'up2 sci.physics.relativity set.


PointedEars
-- 
Q: What did the nuclear physicist post on the laboratory door
   when he went camping?  
A: 'Gone fission'.
(from: WolframAlpha)

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Thread

Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 10:43 +0000
  Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 07:40 -0600
    Re: Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 13:50 +0000
    Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-29 12:22 -0500
      Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 11:28 -0600
        Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-29 13:41 -0500
          Re: Gravity needs NO Matter Odd Bodkin <bodkinodd@gmail.com> - 2016-01-29 13:36 -0600
            Re: Gravity needs NO Matter benj <none@gmail.com> - 2016-01-30 02:30 -0500
          Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-30 14:07 +0100
            Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-30 09:32 -0800
              Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-30 20:19 +0100
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-30 15:37 -0800
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-01-31 18:15 +0100
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-02-06 10:23 -0800
                Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-02-06 11:14 -0800
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 22:24 +0100
                Re: Gravity needs NO Matter Éibhear <eibhear@no-email.net> - 2016-02-06 21:28 +0000
                Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-07 10:00 +0100
            Re: Gravity needs NO Matter Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-01 21:50 +0100
              Re: Gravity needs NO Matter shan <shan@enterapps.org> - 2016-02-05 21:43 +0000
  Re: Gravity needs NO Matter Sam Wormley <swormley1@gmail.com> - 2016-01-29 08:13 -0600
    Re: Gravity needs NO Matter Maciej Woźniak <mlwozniak@wp.pl> - 2016-01-29 16:44 +0100
  Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-29 11:03 -0800
    Re: Gravity needs NO Matter Juan Sebastián <jseb@montserrat.info> - 2016-01-29 19:35 +0000
  Re: Gravity needs NO Matter jamesl51165@gmail.com - 2016-01-29 16:04 -0800

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