From: mikko.levanto@iki.fi   
      
   On 20/01/2026 15:54, Paul B. Andersen wrote:   
   > Den 18.01.2026 18:17, skrev Ross Finlayson:   
   >>   
   >> I'm glad that you consider at least one degree of acceleration,   
   >> with respect to velocity, eg dv/dt, yet, there are _infinitely-many_   
   >> higher order derivatives of acceleration, _any one of which_ is   
   >> nominally non-zero given any smoothly changing velocity.   
   >>   
   >>   
   >> Then, you should get to wondering about the equivalence principle,   
   >> and whether's gravity's perceived force of acceleration is really   
   >> equivalent to reaction-mass acceleration, or about how it's not,   
   >> since as lots of physics departments note the equivalency principle   
   >> is violated a lot, just like momentum is lost in the wash in kinematics   
   >> generally.   
   >   
   > You are standing on the floor in a small room   
   > without windows with an accelerometer fixed to the wall.   
   > The accelerometer shows that it is accelerating   
   > in the direction which to you is upwards.   
   >   
   > If the accelerometer shows that the acceleration   
   > is constant 1g, then there is no way you can   
   > decide whether you are stationary at the ground,   
   > or if you are accelerating at 1g in a spaceship.   
   >   
   > If the accelerometer shows that the acceleration   
   > is changing with time, then you know that you are   
   > in a spaceship.   
      
   Depends on how much it changes. On Earth you have small variations   
   from the gravity of Moon and Sun. Sometimes you may have even large   
   variations (of short duration) from earthquakes.   
      
   --   
   Mikko   
      
   --- SoupGate-Win32 v1.05   
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