From: relativity@paulba.no   
      
   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!   
   Of course "mass" is the mass of an object.   
   and E = mc² is the energy content of the mass of an object.   
      
   It is quite common to write things like:   
      "Let the speed of the mass m be v".   
   Everybody will understand that m is the mass of an object.   
   And so do you. So why the nit-picking ?   
   This is a post in a Usenet group, not a scientific paper.   
      
   Back to the subject:   
      
   The mass of an objects is invariant, and so is the energy   
   content of the object.   
   The E in the equation E = mc² is invariant, which means   
   that it is independent of the speed of the object.   
      
   It makes no sense to call E = mc² "the *rest* energy of   
   _an object_ whose mass is m."   
      
   The energy of a moving object with mass m is:   
      E = γmc² = mc² + (γ-1)mc²   
   The term mc² is the invariant energy content of the object with mass m,   
   the term (γ-1)mc² is the kinetic energy of the object with mass m.   
      
   The energy content E = mc² of the object with mass m   
   is a property of the object with mass m.   
      
   But a frame dependent entity like kinetic energy or relative speed   
   is not a property of the moving object.   
   They are properties of the relationship between the object   
   and a frame of reference.   
      
   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.   
      
   (Note however that in the fission where the two   
   nuclei and 3 neutrons are moving away from each other   
   in such a way that momentum is conserved, the _sum_   
   of their kinetic energies is invariant.)   
      
   -------   
      
   >> m = m₁-m₂= 3.089167695E-28 kg has disappeared because it is converted to   
   >> kinetic energy which is not mass.   
   Quote out of context:   
      
   Before the fission the mass of the U-235 nucleus + 1 neutron   
   is: m₁ = 3.919748214E-25 kg   
      
   After the fission the mass of the Ba-141 and Kr-92 nuclei +   
   3 neutrons is: m₂ = 3.916659047E-25 kg.   
      
   So the mass isn't conserved, Δm = m₁-m₂= 3.089167695E-28 kg   
      
   >   
   > 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   
      
   I say that the mass Δm lost from the U-235 nucleus is converted   
   to kinetic energy  of the two nuclei and 3 neutrons.   
      
   You are free to choose your wording.   
      
   --   
   Paul   
      
   https://paulba.no/   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)