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Author Topic: Does Einstein create the real General relativity ??  (Read 17290 times)

Offline parakorn

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Re: Does Einstein create the real General relativity ??
« Reply #25 on: 30/08/2014 15:08:39 »
May be we had out from our first topic of this discussion so I think that we should back to our topic about Einstein and his Gravitational theory. PMB you want me to find the evidence about Einstein theory of space time curvature I will show you
my evidence
   first http://en.wikisource.org/wiki/Translation:The_Field_Equations_of_Gravitation [nofollow] the field equation of gravitatinal of General Relativity in 1915 Einstein wrote that "I have shown in two recently published reports,[1] how one can arrive at field equations of gravitation, that are in agreement with the postulate of general relativity, i.e. which in their general form are covariant in respect to arbitrary substitutions of space-time variables".
   We obtain the ten general covariant equations of the gravitational field in spaces, in which "matter" is absent, by putting
G_{im}=0   (2)
These equations can be formed in a simpler way, when one choses the reference system so that \sqrt{-g}=1. Then S_{im} vanishes due to (1b), so that one obtains instead of (2)
R_{im}=\sum\limits _{l}\frac{\partial\Gamma_{im}^{l}}{\partial x_{l}}+\sum\limits _{\rho l}\Gamma_{i\rho}^{l}\Gamma_{ml}^{\rho}=0   (3)
\sqrt{-g}=1   (3a)
Here we put
\Gamma_{im}^{l}=-\left\{ {im\atop l}\right\}    (4)
which magnitudes we will denote as the "components" of the gravitational field.
If "matter" exists in the considered space, then its energy tensor appears on the right hand side of (2) or (3). We put
G_{im}=-\varkappa\left(T_{im}-\frac{1}{2}g_{im}T\right)
   Second in Einstein book http://en.wikisource.org/wiki/Relativity:_The_Special_and_General_Theory/Part_III#Section_32_-_The_Structure_of_Space_According_to_the_General_Theory_of_Relativity [nofollow] Einstein said that " According to the general theory of relativity, the geometrical properties of space are not independent, but they are determined by matter. Thus we can draw conclusions about the geometrical structure of the universe only if we base our considerations on the state of the matter as being something that is known." That mean the curvature of space can explain by the appear of matter.
  In third evidence is about Einstein field equation in The meaning of relativity paper http://en.wikisource.org/wiki/The_Meaning_of_Relativity/Lecture_4 [nofollow]
R_{\mu\nu} - \frac{1}{2}g_{\mu\nu}R = -\kappa T_{\mu\nu}. In the left hand side show the Einstein tensor that have Ricci tensor to explain about the curvature of space and in right side show about mass and energy tensor
  All of these were the evidence about matter can cause of the curvature of space time.
If you said that Einstein version of general relativity wasn't relate with space time curvature I think you are wrong but if you said that Einstein version of general relativity wasn't relate with Tidal force.I will agree with you because The tidal force conect with general relativity was the modern view of general relativity not Einstein general relativity. I haven't seen in any paper of Einstein general relativity that he write about tidal force
 

Offline parakorn

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Re: Does Einstein create the real General relativity ??
« Reply #26 on: 30/08/2014 15:10:57 »
I can't post the equation here who can help me please.
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #27 on: 30/08/2014 15:14:05 »
There is a difference between the curvature of the trajectory and the inherent geometry of the field causing the curvature. They will both be parabolic but will differ due to the geometry of the masses involved.
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #28 on: 30/08/2014 15:57:56 »
I'm afraid some of what you read about is just rubbish, Jeffrey.

Probably some of the work I am attempting is too. I am open to learning more.
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #29 on: 30/08/2014 16:24:32 »
Quote from: parakorn
May be we had out from our first topic of this discussion so I think that we should back to our topic about Einstein and his Gravitational theory. PMB you want me to find the evidence about Einstein theory of space time curvature I will show you
my evidence ..
You can't merely toss out a page of text and say "This is where Einstein said this is true". You have to post the exact sentence and what about that sentence makes you correct and me wrong. Watch. That's what I'll do with your "evidence"

Einstein wrote
Quote
Here we put

\Gamma_{im}^{l}=-\left\{ {im\atop l}\right\}  (4)

which magnitudes we will denote as the "components" of the gravitational field.
which is exactly what my paper says. Here's an example of a gravitational field which has flat spacetime but for which the "components" of the gravitational field are not zero - http://home.comcast.net/~peter.m.brown/gr/uniform_force.htm

I gave that example in my paper but you ignored it. Why did you ignore it?

Quote from: parakorn
All of these were the evidence about matter can cause of the curvature of space.
Just as I though. You're not reading what I'm posting carefully enough. In reply #3 I wrote
Quote
The article only refers to the interpretation of how the term "gravitational field" is defined.
I never anywhere claimed that gravity can't curve spacetime. And we've been talking about this in many posts. Do you not understand the difference between a gravitational field with and without tidal forces in it? The gravitational field around the earth has tidal forces while a uniform gravitational field such as though found in this page
http://home.comcast.net/~peter.m.brown/gr/grav_cavity.htm has zero tidal forces inside the cavity illustrated in the diagram.

Quote from: parakorn
If you said that Einstein version of general relativity wasn't relate with space time curvature I think you are wrong ...
I never said such a thing.

Quote from: parakorn
I haven't seen in any paper of Einstein general relativity that he write about tidal force
He didn't use the term but it's there in principle. The Riemann tensor in GR is merely the relativistic version of the tidal force tensor from Newtonian gravity. Tidal forces and spacetime curvature are merely two ways of saying the same thing.

See Black Holes and Time Warps by Kip Thorne page 111. After the author discusses the crossing of two paths of falling objects the author writes
Quote
Thus, Einstein and Newton, with their very different viewpoints on the nature of space and time, give different names to the agent that causes the crossing. Einstein calls it spacetime curvature; Newton called it tidal gravity. But there is just one agent acting. Therefore, spacetime curvature and tidal gravity must be precisely the same thing, expressed in different languages.

I don't see how you could have missed that since its prominently written on page 3 in the Introduction.

It's quite clear to me that you didn't read my paper very carefully at all.
 

Offline parakorn

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Re: Does Einstein create the real General relativity ??
« Reply #30 on: 01/09/2014 16:38:00 »
   OK may be I didn't understand your paper or I didn't read your article clearly.May be you can to simplify about the different between Einstein General Relativity and Modern General Relativity in the easy word for me. Sorry for I didn't read your article clearly and sorry if this reply disturb you.  Thank you
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #31 on: 01/09/2014 17:11:51 »
Quote from: parakorn
   OK may be I didn't understand your paper or I didn't read your article clearly.May be you can to simplify about the different between Einstein General Relativity and Modern General Relativity in the easy word for me. Sorry for I didn't read your article clearly and sorry if this reply disturb you.  Thank you
Okay. Thanks. And I'd like to compliment you on being able to notice that you might have made a mistake and then be able to correct it and then move on. That's one of the cherished traits in physics that I admire in a person who's discussing physics. :)

Einstein defined gravity such that it's locally equivalent to an accelerating frame of reference. The weak equivalence principle states that at uniform gravitational field is equivalent to a uniformly accelerating frame of reference.

If you're in a flat spacetime then, regardless of what frame of reference (system of coordinates) you're using the Riemann tensor will be zero. There is no gravitational field in this frame. Now transform to a uniformly accelerating frame of reference. In that frame there is a uniform gravitational field. If you read page 9 in my paper you'll see this
Quote
In the year following the completion and publication of the general theory of relativity Einstein published the review article The Foundation of the General Theory of Relativity in 1916. The statement

"It will be seen from these reflections that in pursuing the general theory of relativity we shall be led to a theory of gravitation, since we are able to “produce” a gravitational field merely by changing the system of coordinates."
Others didn't like this notion since it seemed too odd for people to grasp. I.e. How can you create a gravitational field merely by changing to an accelerating frame of reference.  Since they knew that there's no kind of accelerating frame of reference that will mimic tidal gradients (which is dictated by spacetime curvature) they decided to think of a "real" gravitational field as being determined the presence of spacetime curvature. However that has a lot of problems because even some experts will claim that the gravitational force is replaced by spacetime curvature since one has nothing to do with the other in some instances, e.g. like the uniform gravitational field. I've seen most people not understand that a uniform gravitational field has no spacetime curvature because they think of gravity as being spacetime curvature and where ever there's a gravitational force there's spacetime curvature, which is wrong. I saw a guy publish a paper in the American Journal of Physics claim that a uniform gravitational field (which is flat - by definition) claim to have proved that it's curved. He made an error in his assumption of what the proper acceleration should be of a particle. Since he got a curved spacetime it should have told him that it was the wrong answer but since he assumed that gravitational fields have spacetime curvature then he made no mistake. See how these problems can arise because of not using Einstein's definition? His definition is how we think of gravity.

Einstein didn't like all that stuff about curvature. That's why he wrote that letter to Max Von Laue saying
Quote
... what characterizes the existence of a gravitational field from the empirical standpoint is the non-vanishing of the components of the affine connection], not the vanishing of the [components of the Riemann tensor]. If one does
not think in such intuitive (anschaulich) ways, one cannot grasp why something like curvature should have anything at all to do with gravitation. In any case, no rational person would have hit upon anything otherwise. The key to the understanding of the equality of gravitational mass and inertial mass would have been missing.

Make sense now? :)
 

Offline JohnDuffield

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Re: Does Einstein create the real General relativity ??
« Reply #32 on: 01/09/2014 18:58:27 »
Perhaps I could back that up with a simplified version? Parakorn, have a look at the depiction of gravitational potential:



The curvature you can see in the depiction relates to the Riemann curvature tensor. But things don't actually fall down because of this. The force of gravity is denoted by the degree of slope, the first derivative of potential. The tidal force or Riemann curvature tensor is denoted by the change in slope, the second derivative of potential.   
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #33 on: 02/09/2014 20:45:30 »
Perhaps I could back that up with a simplified version? Parakorn, have a look at the depiction of gravitational potential:



The curvature you can see in the depiction relates to the Riemann curvature tensor. But things don't actually fall down because of this. The force of gravity is denoted by the degree of slope, the first derivative of potential. The tidal force or Riemann curvature tensor is denoted by the change in slope, the second derivative of potential.   

And of course acceleration is curved in Minkowsi diagrams and shows curvature but unlike gravitation and free-fall a force IS felt.
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #34 on: 03/09/2014 04:04:06 »
Quote from: jeffreyH
And of course acceleration is curved in Minkowsi diagrams and shows curvature ...
What do you mean by "shows curvature"? Suppose you're in a uniformly accelerating frame in flat spacetime. There's acceleration but no curvature. So how does what you say apply in that case?
 

Offline JohnDuffield

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Re: Does Einstein create the real General relativity ??
« Reply #35 on: 03/09/2014 17:10:36 »
Jeffrey, imagine you're standing on a big flat board. You roll a bowling ball across it, and it goes straight. There's no curvature. But now imagine I tilt the big flat board. Now when you roll the bowling ball across it, it curves because of the slope. However the board isn't curved, it's still flat, but it's tilted. Spacetime is like the board, the path of light is like the path of the bowling ball.

Once you've got that just think of the board as being tilted and curved, like something in a skateboard park.   
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #36 on: 03/09/2014 20:16:29 »
Jeffrey, imagine you're standing on a big flat board. You roll a bowling ball across it, and it goes straight. There's no curvature. But now imagine I tilt the big flat board. Now when you roll the bowling ball across it, it curves because of the slope. However the board isn't curved, it's still flat, but it's tilted. Spacetime is like the board, the path of light is like the path of the bowling ball.

Once you've got that just think of the board as being tilted and curved, like something in a skateboard park.
That is a wonderful analogy John! :)
 

Offline JohnDuffield

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Re: Does Einstein create the real General relativity ??
« Reply #37 on: 04/09/2014 09:17:38 »
Thanks Pete. It can be difficult to find a way to make it sound simple.
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #38 on: 04/09/2014 16:09:36 »
Thanks Pete. It can be difficult to find a way to make it sound simple.
Your welcome. Back in the late 90's I came up with the same analogy myself. I set it aside because I'm not 100% sure that there aren't any problems with that analogy. But I still thing its a wonderful one. I just don't use it myself at this point in time.
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #39 on: 04/09/2014 19:53:06 »
Quote from: jeffreyH
And of course acceleration is curved in Minkowsi diagrams and shows curvature ...
What do you mean by "shows curvature"? Suppose you're in a uniformly accelerating frame in flat spacetime. There's acceleration but no curvature. So how does what you say apply in that case?

Have you ever plotted acceleration on a Minkowski diagram?
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #40 on: 04/09/2014 20:04:25 »
Think of a row of horse drawn wagons but instead of horses we have attached ropes. In one situation the ropes are only attached to the furthest wagon and when we pull it it moves independently of the others. Eventually it will touch the wagon in front and ultimately all the wagons will touch and we can pull them all. This compresses the wagons and we can say a force is felt. Now consider that we have ropes attached to all the wagons and can pull them at exactly the same time. Since no compression occurs we can liken this to gravity. Think of it like every particle in a falling mass moving in unison.
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #41 on: 05/09/2014 04:01:45 »
Quote from: jeffreyH
And of course acceleration is curved in Minkowsi diagrams and shows curvature ...
What do you mean by "shows curvature"? Suppose you're in a uniformly accelerating frame in flat spacetime. There's acceleration but no curvature. So how does what you say apply in that case?

Have you ever plotted acceleration on a Minkowski diagram?
There are two ways to address that. What are you referring to when you use the term "Minkowski diagram"? Typically that refers to spacetime diagrams for inertial frames of reference. When you plot an acceleration on such a diagram like I have in figure one here http://home.comcast.net/~peter.m.brown/sr/uniform_accel.htm  then that's a particle moving under a force, not in free fall and having nothing to do with gravity.

However if you have in mind a spacetime diagram of a frame of reference which is accelerating uniformly and plotting the position of a particle in free-fall then that will be a curved trajectory. However the use of the term "Curvature" here refers to the worldline and not the spacetime. The spacetime is still flat. Have you been confusing the curvature of world-lines and the curvature of spacetime all this time, have you?
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #42 on: 05/09/2014 07:15:11 »
Quote from: jeffreyH
And of course acceleration is curved in Minkowsi diagrams and shows curvature ...
What do you mean by "shows curvature"? Suppose you're in a uniformly accelerating frame in flat spacetime. There's acceleration but no curvature. So how does what you say apply in that case?

Have you ever plotted acceleration on a Minkowski diagram?
There are two ways to address that. What are you referring to when you use the term "Minkowski diagram"? Typically that refers to spacetime diagrams for inertial frames of reference. When you plot an acceleration on such a diagram like I have in figure one here http://home.comcast.net/~peter.m.brown/sr/uniform_accel.htm  then that's a particle moving under a force, not in free fall and having nothing to do with gravity.

However if you have in mind a spacetime diagram of a frame of reference which is accelerating uniformly and plotting the position of a particle in free-fall then that will be a curved trajectory. However the use of the term "Curvature" here refers to the worldline and not the spacetime. The spacetime is still flat. Have you been confusing the curvature of world-lines and the curvature of spacetime all this time, have you?

No
 

Offline jeffreyH

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Re: Does Einstein create the real General relativity ??
« Reply #43 on: 05/09/2014 07:22:54 »
We can make acceleration linear by a varying scale on the SPACE and TIME axes. How is that confusing world lines with spacetime. Or are you just trying to make me look inept? Are you?
 

Offline parakorn

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Re: Does Einstein create the real General relativity ??
« Reply #44 on: 10/09/2014 15:55:15 »
A fter I have come back to read the article again and again many time. In my understanding from the article are There are two version of General relativity once is einstein version and another was modern version. In Einstein version there are 2 type of gravitational field 1. uniform gravitational field that can conclude that gravitaty is the same as acceleration that we can create gravitational by changing of the coordinate there is no curvature of space time in this type of gravitational field. 2. Permanent Gravitatinal field is the space time curvature that is the same thing with tidal force. In modern view physicist confuse in 2 type of the field and conclude that  uniform gravitational field is the same thing with curvature of space time.That wrong interpretation. Does I read it correctly or not ???
 

Offline PmbPhy

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Re: Does Einstein create the real General relativity ??
« Reply #45 on: 10/09/2014 16:33:44 »
A fter I have come back to read the article again and again many time. In my understanding from the article are There are two version of General relativity once is einstein version and another was modern version. In Einstein version there are 2 type of gravitational field 1. uniform gravitational field that can conclude that gravitaty is the same as acceleration that we can create gravitational by changing of the coordinate there is no curvature of space time in this type of gravitational field. 2. Permanent Gravitatinal field is the space time curvature that is the same thing with tidal force. In modern view physicist confuse in 2 type of the field and conclude that  uniform gravitational field is the same thing with curvature of space time.That wrong interpretation. Does I read it correctly or not ???
I'm so glad to see that you've got it now. It warms my heart to see that I was able to get through to someone. Thanks for your diligence! :)
 

Offline parakorn

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Re: Does Einstein create the real General relativity ??
« Reply #46 on: 10/09/2014 17:39:15 »
A fter I have come back to read the article again and again many time. In my understanding from the article are There are two version of General relativity once is einstein version and another was modern version. In Einstein version there are 2 type of gravitational field 1. uniform gravitational field that can conclude that gravitaty is the same as acceleration that we can create gravitational by changing of the coordinate there is no curvature of space time in this type of gravitational field. 2. Permanent Gravitatinal field is the space time curvature that is the same thing with tidal force. In modern view physicist confuse in 2 type of the field and conclude that  uniform gravitational field is the same thing with curvature of space time.That wrong interpretation. Does I read it correctly or not ???
I'm so glad to see that you've got it now. It warms my heart to see that I was able to get through to someone. Thanks for your diligence! :)
Thank you  :)
 

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Re: Does Einstein create the real General relativity ??
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