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|    sci.physics.relativity    |    The theory of relativity    |    225,861 messages    |
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|    Message 225,417 of 225,861    |
|    Thomas 'PointedEars' Lahn to All    |
|    Re: Galaxies don't fly apart because the    |
|    28 Jan 26 23:23:31    |
      XPost: sci.math       From: PointedEars@web.de              The 'nym-shifting troll trolled as "Wayne Timerbaev":       > Paul B. Andersen wrote:       >> Den 28.01.2026 20:04, skrev Paul B. Andersen:       >>> Hint: d²v/dt² = 10 m/s²       >>       >> Should be:       >> Hint: dv/dt = 10 m/s²       >       > idiot, you have to put the time in it, to find the speed, wrt the place       > the time is starting, if not offset.              Since the acceleration is the time derivative of velocity, from the       fundamental theorem of calculus follows that, if the motion is along a       straight line, the speed is obtained by integration of the magnitude of the       acceleration over time:               v(t) = ∫ dt [dv/dt](t) = ∫ dt a(t).              If the acceleration is constant over time, too, the integral is trivial to       calculate:               v(t) = ∫ dt a = a ∫ dt = a t + C; C = const. (wrt. t)              One can see then that the constant of integration is C = v(0).              But that is precisely the point that Paul B. Andersen was making, and that       the 'nym-shifting troll here missed:              The initial speed is unknown as well as the time t = 0 at which the       acceleration began; moreover, the initial speed depends on the choice of       rest frame as all speeds are (measured) relative (to something else). So it       is not possible to tell the speed of an object merely from the magnitude of       its (proper) acceleration.              --       PointedEars              Twitter: @PointedEars2       Please do not cc me. / Bitte keine Kopien per E-Mail.              --- SoupGate-Win32 v1.05        * Origin: you cannot sedate... all the things you hate (1:229/2)    |
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