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Re: Meditations about the force

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Luigi Fortunati wrote:

> From the previous examples, is it fair to say that force is manifested
> exclusively when there is a resistance that opposes and never when
> every form of resistance is lacking?

In the classical sense: Yes.  Other “forces” are only apparent forces.

For example (as we are in .relativity), general relativity postulates that 
the gravitational force (short: gravity) is an illusion, only an *apparent* 
force, too:

A body only "feels" its own weight due to gravity because there is a real 
force in the opposite direction, the repulsive electromagnetic force between 
the equally charged particles of matter (and because of the Pauli exclusion 
principle in more extreme cases), that *prevents* that body from continuing 
its motion along a spacetime geodesic.  If that resistance disappears, so do 
all effects of weight (weightlessness).

Einstein realized this in ca. 1911 when he considered a person in an 
elevator (“elevator experiment”): One in an elevator that is falling freely 
in a gravitational field, compared to one in an elevator that is far away 
from any source of gravity.  Likewise, a person in an elevator at rest in a 
gravitational field compared to a person in an "upwards" accelerated 
elevator far away from any source of gravity.  He realized that these two 
situations are physically equivalent, respectively: there is no experiment 
with which the person in the elevator can tell the difference.

<http://www.einstein-online.info/spotlights/equivalence_principle>

(It took him 5 more years to work out the complex mathematics to describe 
this properly: the [Einstein] field equations [EFEs].)

Prof. Brian Greene gives an excellent made-for-laymen summary and 
demonstration of this in “The Late Show with Stephen Colbert”:

<https://www.youtube.com/watch?v=0jjFjC30-4A>
 
-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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Meditations about the force Luigi Fortunati <fortunati.luigi@gmail.com> - 2017-08-15 17:50 +0200
  Re: Meditations about the force Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-16 01:34 +0200
    Re: Meditations about the force mlwozniak@wp.pl - 2017-08-15 23:34 -0700
      Re: Meditations about the force Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-19 12:52 +0200
        Re: Meditations about the force Séverin Thibault <ruud@bwiu.ei> - 2017-08-19 11:04 +0000
        Re: Meditations about the force mlwozniak@wp.pl - 2017-08-19 10:43 -0700
    Re: Meditations about the force Luigi Fortunati <fortunati.luigi@gmail.com> - 2017-08-18 10:10 +0200
      Re: Meditations about the force mlwozniak@wp.pl - 2017-08-18 01:32 -0700
      Re: Meditations about the force Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-08-18 15:06 +0200
      Re: Meditations about the force Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-18 15:56 +0200
        Re: Meditations about the force mlwozniak@wp.pl - 2017-08-18 07:06 -0700
      Re: Meditations about the force "Paul B. Andersen" <relativity@paulba.no> - 2017-08-19 14:00 +0200
        Re: Meditations about the force Luigi Fortunati <fortunati.luigi@gmail.com> - 2017-08-19 17:45 +0200
          Re: Meditations about the force Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-19 21:28 +0200
        Re: Meditations about the force mlwozniak@wp.pl - 2017-08-19 10:44 -0700
        Re: Meditations about the force Thomas Heger <ttt_heg@web.de> - 2017-08-19 20:19 +0200
          Re: Meditations about the force Séverin Thibault <ruud@bwiu.ei> - 2017-08-19 19:56 +0000
            Re: Meditations about the force Séverin Thibault <ruud@bwiu.ei> - 2017-08-19 20:00 +0000

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