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Newtonian gravity vs. general relativity (was: Milky Way's Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us)

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jamesl51165@gmail.com wrote:

> On Saturday, February 6, 2016 at 9:20:18 AM UTC-8, Thomas 'PointedEars'
> Lahn wrote:

It’s attribution *line*, _not_ attribution novel.

>> > The levels of orbital motion for the Earth are easy to pin point...
>> > We orbit the center of the Sun's gravity.
>  Gravity is a force (field); it has no center.
> 
> So Newton was wrong in his math?

He was certainly not quite right, as Einstein, among others, showed.  
Newton’s theory of gravity works only approximately for objects with non-
zero mass, and it does not work at all for photons which have zero mass (we 
observe that massive bodies are bending light).

But it is your invention that Newton said “center of gravity”.

> When did this happen?

Between the years 1907 and 1919 inclusive.  Einstein started work on what he 
later called “(the) general (theory of) relativity” (GR) after he postulated 
what he later called “(the) special (theory of) relativity” in 1905.  He 
publicly presented the corrected field equations of GR in 1915, which 
finally gained widespread laymen acceptance (after being accepted within the 
scientific community at the latest when Einstein showed that his new theory 
could very precisely predict Mercury’s perihelion precession – which 
Newton’s theory could not) with Eddington’s observations related to the 
solar eclipse of 1919.

<https://en.wikipedia.org/wiki/History_of_general_relativity>

> They say gravity drops off inward to a zero.

Who says that about which object?

> If this is true then there is the center of the Earth
> and it's gravity center.

You are confusing terminology here, at best.

>> > We orbit the Milky Way gravity center.
>> 
>> Given that Sol's mass dominates the Sol System (99.86 % of the Sol
>> System's total mass comes from that star), it would be only correct to
>> say that Sol or the Sol System orbit the Milky Way barycenter.  So do
>> other star systems in the Milky Way.
> 
> The solar system whole has a center that orbits the center of the milky
> way.

The Sol System has a center _of mass_ that orbits the center _of mass_ of 
the Milky Way.

> Again Newton is accepted on the account of this truth...

Nonsense.

> Einstein adopted a center of field for his contractile curvature...

No, he did not.  That a field could have a center is only your invention.  
And “contractile curvature” is not even wrong.

A field is a description of a mathematical space that assigns a value to 
each point of that space.  If the values are vectors, each of which has a 
direction and a magnitude, then that field is called a vector field.  If the 
value is just a number, then the field is called a scalar field; consider, 
for example, the temperatures measured across a room.  If the value is a 
tensor… you get the picture.

<https://en.wikipedia.org/wiki/Field_(physics)>

The gravitational field of Newtonian gravity is a vector field: the 
gravitational acceleration (and thus the force of gravity) on a test 
particle (with non-zero mass) has a different direction and magnitude in 
each point in the vicinity of a point particle (with non-zero mass).

IIUC, in GR the gravitational field is described as a tensor field where 
each point of spacetime is assigned a tensor describing the spacetime 
curvature at that point corresponding to the energy/mass density, stress, 
and momentum at that point.  Gravity is reduced to a fictional force, and 
the motion of objects is determined by the curvature of spacetime, and
vice-versa, instead.

<https://en.wikipedia.org/wiki/Gravitational_potential#General_relativity>

Please do not quote signatures, and anything else, unless you refer to them.
And get a real name.


PointedEars
-- 
Q: What did the nuclear physicist post on the laboratory door
   when he went camping?  
A: 'Gone fission'.
(from: WolframAlpha)

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Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us jamesl51165@gmail.com - 2016-01-23 12:56 -0800
  Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us jamesl51165@gmail.com - 2016-02-05 12:34 -0800
    Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us shan <shan@enterapps.org> - 2016-02-05 22:12 +0000
      Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us John Gogo <jfgogo22@yahoo.com> - 2016-02-05 14:19 -0800
        Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us shan <shan@enterapps.org> - 2016-02-05 22:40 +0000
          Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us jamesl51165@gmail.com - 2016-02-05 14:54 -0800
            Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 18:20 +0100
              Re: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us jamesl51165@gmail.com - 2016-02-06 10:07 -0800
                Newtonian gravity vs. general relativity (was: Milky Way's  Kinetic Energy in Our orbiting arm; this motion we share with the larger that is together with us) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 21:58 +0100

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