From: fortunati.luigi@gmail.com   
      
   Jens Schweikhardt il 06/01/2025 16:01:29 ha scritto:   
   > Luigi Fortunati  wrote   
   > 	in :   
   > [...]   
   > # But then, why do two extraordinarily different systems like the Earth's   
   > # mass (6*10^24kg) generate the force of 90kg-weight on my body (mass   
   > # 90kg) and my body generates the *same* opposing force of -90kg-weight   
   > # on the Earth?   
   >   
   > Asking "why" in physics usually means "is there a more elementary   
   > explanantion?"   
   >   
   > Do you accept   
   >   
   >     F = G*m1*m2/r^2     (1)   
   >   
   > as an empirical observation?   
      
   The formula (1) has proven itself very well but has failed a bit on the   
   precession of the perihelion of Mercury's orbit and, *much* more so, on   
   the motion of the peripheral stars of our galaxy, which forces us to   
   imagine unobtainable dark matter and energy.   
      
   So it is reliable but not perfect.   
      
   > Indeed, nobody has ever measured the effect of your body's gravitational   
   > force on the Earth. The orders of magnitude for the respective   
   > accelerations are too different.   
      
   Exactly, we know perfectly well the gravitational force of the Earth on   
   me but we do not know at all my gravitational force on Earth.   
      
   And I find it very difficult to imagine and accept that the   
   gravitational force of the miserable mass of my body could exert a   
   force of 90kg-weight on the Earth or on any other body.   
      
   The real problem with formula (1) is that it concerns only one total   
   force that acts between the masses m1 and m2, without distinguishing   
   how much force m1 exerts on m2 and how much m2 exerts on m1.   
      
   This was remedied by accepting Newton's third law as valid.   
      
   > Verification of that formula is only   
   > technically feasible for large pairs of masses, say Earth/Moon or   
   > Sun/Jupiter by observing both bodies in orbit around their barycenter.   
      
   This is not true.   
      
   How can we verify a formula in which there are masses that no one has   
   ever measured? How much is the mass of the Earth, the Moon, Jupiter and   
   the Sun?   
      
   Do you know them? No.   
      
   You cannot know them exactly because no one has ever measured them   
   directly.   
      
   We can only assume that we have certain masses by deriving them   
   indirectly through formula (1) and, thus, we verify the validity of a   
   formula using values taken from the formula itself!   
      
   > This requires each body being subject to equal but opposite forces.   
      
   No, the opposite forces are equal only when the rotation occurs around   
   the midpoint and not when it occurs around a centre of rotation that is   
   closer to one mass than the other.   
      
   > The answer could be "because the masses in (1) appear without preference   
   > for either." Or "because multiplication is commutative". Or "because   
   > when (1) is written in vector notation, the force vectors have the same   
   > magnitude, but opposing direction when the masses are exchanged."   
      
   These are not proofs.   
      
   So far, we have accepted the equality between the action of m1 on m2   
   and that of m2 on m1, counting on the validity of Newton's third law,   
   which I have shown to be invalid.   
      
   I repeat: the claim that my miserable gravitational force can attract   
   the Earth with the same force (90kg-weight) with which the Earth   
   attracts me (as the equality between action and reaction claims) is   
   unacceptable!   
      
   Regards,   
   Luigi   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)