From: julio@diegidio.name   
      
   On Sunday, 8 May 2022 at 09:41:41 UTC+2, Luigi Fortunati wrote:   
   > Julio Di Egidio sabato 07/05/2022 alle ore 15:00:52 ha scritto:   
   > >>> A free-falling brick is an inertial frame?   
   > >   
   > > A free-falling brick is *in* "an" inertial frame. Which more precisely   
   > > means that we can find an inertial frame in which the brick is in   
   > > uniform motion, then just a special case is an inertial frame in   
   > > which the brick is at rest, and and even more special case is the   
   > > frame in which the brick is at rest at the origin of space. And we   
   > > might call that last one "the brick's own frame", because there is   
   > > indeed something "privileged" about it as far as that brick is   
   > > concerned: OTOH, though, notice that the fact that the brick is in   
   > > *free-fall* requires no frame to state or verify at all, it's altogether   
   > > a *true* physical property that can be verified *locally*.   
   >   
   > How small must this be "locally"?   
      
   Can I assume the first part is clear now?   
      
   > As small as a brick? A half brick? A tenth of a brick?   
      
   *Local* has a technical definition (do you need me to tell it to   
   you?), just like everything else here, so either you have some   
   serious question starting from that definition, or you should   
   simply get a good introductory course to the matter.  Otherwise   
   I too don't see why you are even allowed to keep posting here.   
      
   Julio   
      
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