From: PointedEars@web.de   
      
   Paul.B.Andersen wrote:   
   ^^^^^^^^^^^^^^^   
   I just noticed that since 2025-12-14, when the "Organization" header field   
   of your postings changed, you also do not have a space in there anymore.   
   Not including a space there may exclude your postings from being read,   
   through real-name filters.   
      
   > Den 06.01.2026 03:04, skrev Thomas 'PointedEars' Lahn:   
   >>> E = mc² is the energy content, or the energy equivalent of   
   >>> the mass m.   
   >>   
   >> The first wording is simply wrong.  E (better: E₀) is the *rest* energy of   
   >> _an object_ whose mass is m.  One can also call that the energy content _of   
   >> that object_ at relative rest (as Einstein did, but this wording is   
   >> obsolete), but NOT "of the mass".  Mass is a quantity, not a object; a   
   >> quantity has no content.   
   >   
   > You are nit-picking again!   
      
   No, to distinguish between the concepts here is vital for a proper   
   understanding.   
      
   > Of course "mass" is the mass of an object.   
   > and E = mc² is the energy content of the mass of an object.   
      
   NOT E = m c², but E₀ = m c², is the _energy_ of an object with mass m at   
   relative rest, its *rest energy*.   
      
   > It is quite common to write things like:   
   >    "Let the speed of the mass m be v".   
      
   Maybe in colloquial or popular-scientific (con)texts; but this is a   
   scientific newsgroup, and it is not only good form but required to be   
   precise here and in this regard.   
      
   > Everybody will understand that m is the mass of an object.   
      
   Irrelevant.  The problem is that *you* do not understand it correctly   
   despite the many explanations and references that I gave (you) already.   
      
   > And so do you. So why the nit-picking ?   
      
   It is not nitpicking, but requiring a clarity of expression to arrive at a   
   proper understanding of a subject.   
      
   > This is a post in a Usenet group, not a scientific paper.   
      
   This is a _scientific_ newsgroup.   
      
   > The mass of an objects is invariant,   
      
   It is _Lorentz_-invariant, NOT invariant /per se/.   
      
   > and so is the energy content of the object.   
      
   No.   
      
   > The E in the equation E = mc² is invariant,   
      
   This pop-cultural equation is *wrong*, as I have pointed out /ad nauseam/.   
      
   > which means that it is independent of the speed of the object.   
      
   /Ex falso quodlibet./   
      
   > It makes no sense to call E = mc² "the *rest* energy of   
   > _an object_ whose mass is m."   
      
   It *does*.  That is what it *is*.  "Rest energy" is the agreed   
   physical/scientific term for that form of energy.   
      
   If there is confusion: "rest" here is not meant as in "and all the rest",   
   but as in "at rest", i.e. "not moving".   
      
   See also:    
      
   > The energy of a moving object with mass m is:   
   >    E = γmc² = mc² + (γ-1)mc²   
      
   That is the *total energy* of *any* object with mass m, including one that   
   is moving in the chosen rest frame (then we have γ > 1).   
      
   [The total energy also includes the potential energy, but coordinates can be   
   chosen such that the latter is zero.]   
      
   > The term mc² is the invariant energy content of the object with mass m,   
      
   One can say that; but as I already pointed out, that wording is both   
   obsolete and imprecise.   
      
   > the term (γ-1)mc² is the kinetic energy of the object with mass m.   
      
   If the potential energy is zero.   
      
   > The energy content E = mc² of the object with mass m   
   > is a property of the object with mass m.   
      
   *No, it is the other way around*: The mass m of an object is a measure of   
   its rest energy or, as Einstein wrote in "Does the Inertia of a Body Depend   
   Upon Its Energy Content?" its "energy content" -- by which he meant "its   
   energy content _at relative rest_":   
      
   ,-   
   |   
   | [...], we are led to the more general conclusion: The mass of a body is a   
   | measure of its energy content; if the energy changes by L, the mass   
   | changes in the same sense by L/9 * 10^20, if the energy is measured in   
   | ergs and the mass in grams.   
      
   [Unfortunately, since the commercialization of the Digital Einstein Papers   
   we are required to refer to archived versions or unofficial   
   translations/copies :-(]   
      
   > But a frame dependent entity   
      
   _quantity_, not entity   
      
   > like kinetic energy or relative speed is not a property of the moving object.   
      
   Self-contradictory.   
      
   > They are properties of the relationship between the object   
   > and a frame of reference.   
      
   /Non sequitur./   
      
   > The kinetic energy which can have any value depending on   
   > the arbitrary choice of frame of reference, is not part   
   > of the energy content of the object.   
      
   That depends on how one defines that.  "Energy content" is an obsolete term   
   to begin with.   
      
   However, if one simply substitutes "total energy" for "energy content", then   
   the total energy of an object depends on the choice of rest frame; and the   
   "energy content" that Einstein means is just that of an object/body (with   
   non-zero mass) *at relative rest* -- in modern terminology, the   
   object's/body's *rest* energy.   
      
   > So the mass isn't conserved, [...]   
      
   There is no and has never been a disagreement among the two of us about that.   
      
   >> Again: NOT the mass is partially converted to kinetic energy, but the rest   
   >> energy E_0 = m c^2 *equivalent to* the mass m.   
   >   
   > Energy before fission:   
   > Energy content of mass m₁: E = m₁c² = 3.522894007E-8 J   
   >   
   > Energy after fission:   
   > Energy content of mass m₂: E  = m₁c²= 3.520117602E-8 J   
   >   
   > The difference is ΔE = m₁c² - m₁c² = Δm⋅c² = 3.089167695E-28 J   
   >   
   > The binding energy holding the nucleons together is   
   > part of the energy content of the mass of the U-235 nucleus.   
   > When the nucleus is split, the binding energy in the Ba-141   
   > and Kr-92 nuclei will be ΔE less. The sum of the kinetic energy   
   > of the two nuclei and 3 neutrons will be ΔE = 3.089167695E-28 J   
      
   You keep missing the point.   
      
   > I say that the mass Δm lost from the U-235 nucleus is converted   
   > to kinetic energy  of the two nuclei and 3 neutrons.   
      
   Which is simply the wrong idea.   
      
   > You are free to choose your wording.   
      
   No, one is NOT free to choose one's wording if one wants to participate in a   
   fruitful scientific discussion.  That is a fundamental misconception.   
   Scientific terms have meaning, and the meaning of certain terms has been   
   agreed upon, like total energy, rest energy, mass, kinetic energy, and   
   potential energy.   
      
   What actually happens here is that rest energy is (partially) converted to   
   other forms of energy.  This is equivalent to a reduction in mass; precisely   
   what Einstein wrote in his paper, and in a sense precisely what he suggested   
   in that paper as an experimental test:   
      
      
   [continued in next message]   
      
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