From: relativity@paulba.no   
      
   Den 07.10.2025 10:05, skrev Thomas Heger:   
   > Am Sonntag000005, 05.10.2025 um 12:38 schrieb Paul B. Andersen:   
   >> Den 05.10.2025 11:00, skrev Thomas Heger:   
   >>> Am Samstag000004, 04.10.2025 um 20:39 schrieb Paul B. Andersen:   
   >>>> Den 02.10.2025 09:52, skrev Thomas Heger:   
   >>>>>   
   >>>>> The universe has actually no time, because time is a LOCAL measure.   
   >>>>>   
   >>>>> Your local time will always point into the future, but only into   
   >>>>> your LOCAL future!   
   >>>>>   
   >>>>> Other observers in other locations have a local future, too, but   
   >>>>> that can actually be your past.   
   >>>>>   
   >>>> You are on the Earth and I am on the Moon.   
   >>>>   
   >>>> Can you give an example where my local future is yor local past?   
   >>>>   
   >>>> (Or vice versa if you prefer.)   
   >>>   
   >>> Not, because the distance between Moon and Earth is real valued.   
   >>>   
   >>> If you turn the axis of time upside down, this would be an 'imaginary   
   >>> rotation'.   
   >>>   
   >>> This would be a valid timeline, too, but in world, which is made from   
   >>> anti-matter.   
   >>>   
   >>> Such an 'anti-world' would be perfectly normal, though only for anti-   
   >>> beings living there.   
   >>>   
   >>> But we couldn't go there, because contact to anti-matter would make   
   >>> us detonate instantly.   
   >>>   
   >>>   
   >>> TH   
   >>   
   >> So if my local future were your local past, then the world   
   >> would explode?   
   >   
   > No, you would.   
   >   
   OK.   
   Since you are not trying to defend your statement:   
      
     "Other observers in other locations have a local future,   
      too, but that can actually be your past."   
      
   . . you must have realised that it is meaningless nonsense.   
      
   BTW, you have still not responded to the following:   
      
   Does that mean that you have understood Einstein's   
   definition of simultaneity?   
   Or are you unable to read and understand it?   
      
   Please read it, and if you find a logical error in   
   Einst5ein's derivation,  please point it out.   
      
   -----------------------------------   
      
   quote from § 1. Definition of Simultaneity   
   -------------------------------------------   
   |  we establish   
   |  by definition that the “time” required by light to travel   
   |  from A to B equals the “time” it requires to travel from   
   |  B to A."   
      
   So in SR the speed of light is isotropic c by definition.   
      
   This is a definition of simultaneity, se below.   
      
   That two clocks are synchronous means that they   
   simultaneously show the same.   
   (This is the definition of "synchronous".)   
      
   Einstein made 'an imaginary physical experiment':   
   (a _thought experiment_)   
      
   quote from § 1. Definition of Simultaneity   
   -------------------------------------------   
   | "Let a ray of light start at the “A time” tA from A towards B,   
   | let it at the “B time” tB be reflected at B in the direction   
   | of A, and arrive again at A at the “A time” t′A."   
      
   tA is the time shown by the clock at A when the ray leave A.   
   tB is the time shown by the clock at B when the ray hits B.   
   t'A is the time shown by the clock at A when the reflected   
        ray hits A.   
      
   In a thought experiment measurements can be made with   
   infinite precision, and we can sit at our desks and analyse it.   
      
   The transit time is d/c where d is the distance between A and B.   
   Let clock B be F ahead of clock A, where F is between 0 and   
   a long time.   
      
   We then have: tB  = tA + d/c + F   
   and:          t'A = tB + d/c - F   
      
   so:  (tB - tA)  = d/c + F   
         (t'A - tB) = d/c - F   
      
   If (tB - tA) = (t'A - tB)  then (d/c + F) = (d/c - F),   
   which is true only if F = 0,   
   the clocks simultaneously show the same.   
      
   This means:   
      
       TB = (TA + d/c)   
     When clock B shows TB clock A simultaneously   
     shows (TA + d/c), which is the same.   
      
       t'A = (tB + d/c)   
     When clock A shows t'A clock B simultaneously   
     shows (tB + d/c), which is the same.   
      
      
   Thus:   
     In accordance with definition the two clocks are synchronous if   
          tB − tA = t′A − tB.   
      
   This is a logical consequence of the postulates of SR   
   and that the speed of light is isotropic.   
      
   Einstein's definition of simultaneity is mathematically   
   consistent.   
      
   This doesn't say anything about whether or not SR's   
   predictions are in accordance with measurements.   
   Only real experiments can do that.   
      
      
   --   
   Paul   
      
   https://paulba.no/   
      
   --- SoupGate-Win32 v1.05   
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