From: mlfasf@comcast.net   
      
   On 4/6/22 12:22 PM, Richard Livingston wrote:   
   >   
   > What myself and others have been trying to get you (Mike Fontenot)   
   > to understand is that the acceleration of the observer does not actually   
   > change anything about the distant twin.   
      
   It's not clear what that statement even MEANS.  Obviously, the distant   
   twin (she) doesn't suddenly feel like she's getting younger.  At each   
   instant in her life, her brain is in a state that is different from all   
   of her other brain states.  Nothing can change those states.  But the   
   accelerating observer DOES conclude that she instantaneously gets   
   younger when he instantaneously changes his velocity in the direction   
   away from her.  And so, FOR HIM, she ACTUALLY gets younger.   All   
   perpetually-inertial observers disagree with him about her getting   
   younger when he instantaneously changes his velocity, but they also all   
   disagree among themselves about what her current age is when the   
   accelerating observer changes his velocity.  And FOR EACH OF THEM, she   
   ACTUALLY has the current age they compute.  That's just the way special   
   relativity IS ... different observers disagree, they all think they are   
   right, and none of them is wrong!   
      
   What is really new, though, in my latest results, is the fact that the   
   accelerating observer can assemble an array of clocks (and attending   
   "helper friends" (HF's)), which give him a "NOW" that extends throughout   
   all space (analogous to what Einstein did for inertial observers).  And   
   THAT guarantees that the accelerating observer's conclusions about the   
   home twin's age are fully MEANINGFUL to him.  His conclusions agree with   
   the CMIF simultaneity method, which means that the CMIF simultaneity   
   method is the only correct simultaneity method.   
      
   [[Mod. note -- I think you're mistaken in a couple of places:   
      
   1. An accelerating obserer ("he") does not (or to be pedantic, should   
      not, if he is doing physics correctly) conclude that the distant twin   
      ("she") instantaneously gets younger when he instantaneously changes   
      his velocity in the direction away from her.  Rather he concludes   
      that her age coordinate in inertial reference frame #2 (after his   
      velocity change) < her age coordinate in inertial reference frame #1   
      (before his velocity change).  But these are two DIFFERENT inertial   
      reference frames, with DIFFERENT time coordinates.  Attributing   
      physical meaning to a comparison between DIFFERENT inertial frame's   
      time coordinates is no more valid than (say) attributing physical   
      meaning to the difference between 2022 (the current year on Earth   
      in the Gregorian calendar) and 4720 (the current year on Earth in   
      the Chinese calendar).  If I install new calendar software on my   
      computer, I don't suddenly get 4720-2022 years younger or older for   
      any sensible meaning of "younger" or "older". :)   
      
   2. What does it mean to say a time coordinate is "physically meaningful"?   
      I would argue that it means that you can write the laws of physics   
      in a sensible form in terms of that time coordinate.  So, what would   
      (say) Newton's 2nd law look like using the CMIF time coordinate of   
      an accelerating observer?  Ick, not nice at all.  Or how about Maxwell's   
      equations?  Or even something very simple like the radioactive decay   
      law   
        N_atoms(t) = N_atoms(0) * exp(-lambda*t)   
      for a fixed lambda.  Again, not nice at all if "t" on the left-hand   
      side and "t" on the right-hand-side are the time coordinate of different   
      inertial frames.   
      
      The fact that these and other laws of physics don't have a sensible   
      form when written in a mixture of different time coordinates (such   
      as CMIF times for accelerating observers) is, I would argue, prima   
      facie evidence that such a mixture of time coordinates is *not*   
      physically meaningful.   
      
   3. You write that "the CMIF simultaneity method is the only correct   
      simultaneity method".  But this begs the question of how to define   
      "correct".  There are other ways of doing distant clock synchronization   
      which differ from Einstein synchronization (e.g., slow (adiabatic)   
      clock transport, which gives a different synchronization result   
      for each choice of the inertial reference frame in which the clock   
      transport is "slow").   
      
   	[That is, suppose we are at (fixed) position A in some inertial   
   	reference frame F0, and set a (gedanken) ideal clock M to match   
   	our A clock.  Then we transport M at velocity v << c to some   
   	other (fixed) position B a distance d away in this same inertial   
   	reference frame F0.  This takes a time d/v.  Since M's Lorentz   
   	time Lorentz time dialation factor is quadratic in v (for v << c),   
   	the accumulated time dialation effect on effect on M's clock   
   	by the time M arrives at B is linear in v, and hence can be   
   	made arbitrarily small by choosing v small enough (and waiting   
   	long enough for M to arrive at B).  Then when M (eventually)   
   	arrives at B, we set B's clock to M's reading.   
      
   	This defines the "slow clock transport" clock synchronization   
   	scheme.   
      
   	The interesting -- and slightly counterintuitive -- thing is   
   	that if we observe this entire process from some other inertial   
   	reference frame F1 which is moving (along the A-B direction)   
   	with respect to our original inertial reference frame F0, and   
   	use F1's definition of "slow motion", then it turns out that   
   	we'll get a *different* clock synchronization.]   
      
      Can you point to a law of physics which specifically picks out   
      Einstein synchronization as "correct" and other synchronizations   
      as "incorrect"?  If not, what basis do we have for saying that   
      one of these is "correct".   
      
   -- jt]]   
      
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