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Re: What is mass?

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kefischer wrote:

> […] Thomas 'PointedEars' Lahn […] wrote:
>>> GR *assumes* the equivalence of both types
>>
>> Because it can be *demonstrated*.  Read on the elevator experiment:
>> Without additional information, you cannot tell whether you are far away
>> from a source of gravity or in free fall, and you cannot tell whether you
>> are accelerating or near a source of gravity.
> 
>        Big error there, either you are accelerating,
> like in a rocket ship, or you are on the surface
> of a gravitating body like Earth.

The error is yours.

You can also be accelerated on the surface of a gravitating body like Earth.  
For example, when you push the throttle pedal or the brake pedal of an 
automobile with a running motor (and no other brakes engaged) your motion is 
accelerated relative to the surface: in a fixed time interval you move 
either more or less distance than in the interval before; the *magnitude* of 
your velocity changes.

And if you are turning with the car, the car is accelerated towards the 
centroid of the corresponding curve (which causes you to be seemingly pushed 
away from it) even if your (non-zero) speed remained constant; the 
*direction* of the car’s velocity changes (and you, otherwise in inertial 
motion, are forced to comply, not being in inertial motion anymore then).

In fact, your motion is accelerated in the frame of reference of an extra-
terrestrial observer even if you stand still on the surface of the Earth, 
because the Earth is rotating about its axis *and* revolving around the Sun.

Velocity is the change of position in a certain time interval:

  v⃗ = dr⃗∕dt

Acceleration is the change of velocity in a certain time interval:

  a⃗ = dv⃗∕dt = d²r⃗∕dt²
 
>        All motion in free space is inertial motion
> with no acceleration felt.

Wrong.  If you hit the thrusters of a rocketship, you are accelerating (your 
velocity changes); ask astronauts whether they feel that.  And ask yourself 
why they are training in large centrifuges.


PointedEars
-- 
I heard that entropy isn't what it used to be.

(from: WolframAlpha)

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Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-26 08:35 +0200
  Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-26 12:23 +0000
    Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 09:07 -0400
      Re: What is mass? Fabian Russell <root@localhost.localdomain> - 2015-09-26 18:18 +0000
        Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 14:45 -0400
          Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-26 19:49 +0000
            Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 16:38 -0400
              Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-26 21:35 +0000
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 18:44 -0400
                Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-26 22:57 +0000
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 19:06 -0400
                Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-26 23:18 +0000
                Re: What is mass? pnalsing@gmail.com - 2015-09-26 16:23 -0700
                Re: What is mass? pnalsing@gmail.com - 2015-09-26 16:42 -0700
                Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-27 00:21 +0000
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 21:24 -0400
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 21:32 -0400
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-27 01:20 -0400
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 19:42 -0400
                Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-27 00:22 +0000
                Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 21:29 -0400
                Re: What is mass? Kent Beeler <kenbee@jefffast.au> - 2015-09-27 10:33 +0000
        Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 14:57 -0400
  Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 13:09 -0400
    Re: What is mass? Jimmie Wynne <jimmwyn@metermap.org> - 2015-09-26 17:25 +0000
      Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 14:40 -0400
    Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-26 21:42 +0200
      Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-26 16:35 -0400
        Re: What is mass? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-09-27 13:48 +0200
          Re: What is mass? kefischer <emoneyjoe@iglou.com> - 2015-09-27 11:59 -0400

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