Chinese Scholar Yang Jian liang Putting Wrongs to Rights in Astrophysics

in GR, a single particle moving in gavitational field obeys geodesic equation, don't mean the particle cann't have mass, you are too ridiculous. You may go to see the theory of Planet's orbit in GR, know the calculation about Mercury precession in the sun's gravitational field

 

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Only if the charge/mass is completely negligible, or if we're talking about a test charge/mass. In Yang's article it's not made clear this is the case; the text suggests there are real, massive particles moving about.

Indeed, one of us has these confusions. Let's take your post. It clearly doesn't answer the question I posed (and that you quoted). Now tell me, who of us two is the one that's confused?

You don't even seem to understand the importance of a minus-sign difference, so if my "foundation of physics" is too poor, that makes two of us.

That's garbled; can you please rephrase that?

And I suggest you learn the meaning of the word "static".

And I suggest you learn that motion involved movement, and if all things are static, there can be no movement.

So a massive black hole orbiting the sun at Earth's distance would no affect the sun? Because that's what you are claiming.

I see you've failed to understand barycenters. How can you possibly hope to understand GR if you can't even grasp such a simple concept?

 

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As I mentioned to another poster in another thread on another topic
You appear to be playing chess with a pigeon

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Of course, the geodesic equation must return to Newton's law in the weak static gravitational field, and unlike in the past, in Yang Ji-liang 's article, Not only the geodesic equation of low velocity particle is required to return to Newton's theory, but also the geodesic equation of high speed particle is also required to return to the corresponding Newtonian theory. Although the mass of moving particles appeared in Newton's law of gravity, they were eventually eliminated. That is to say, the equation of moving particle's acceleration derived from Newton's theory does not contain particle mass eventually, which is the premise of the comparison between GR and Newton's theory.

 

Of course, the geodesic equation must return to Newton's law in the weak static gravitational field, and unlike in the past, in Yang Ji-liang 's article, Not only the geodesic equation of low velocity particle is required to return to Newton's theory, but also the geodesic equation of high speed particle is also required to return to the corresponding Newtonian theory. Although the mass of moving particles appeared in Newton's law of gravity, they were eventually eliminated. That is to say, the equation of moving particle's acceleration derived from Newton's theory does not contain particle mass eventually, which is the premise of the comparison between GR and Newton's theory.

 

No, that's not the correct elimination of mass. Please re-read my previous post, specifically the massive black hole part.

 

I think it's more like a parrot in this case: heyuhua keep repeating what Yang says (even when that's proven to be wrong), and keeps saying things without understanding them.

 

Can't a charge move in an electrostatic field? similarly, cann't a particle move in a static state's gravitational field? The subject of this study here is the movement of particles in the static gravitational field. This is what we often do. Can you deduce the orbital equation of planets from Newton's law? can you deduce the orbital equation of planets from GR? if you can, You wouldn't have asked these ridiculous questions

 

A charge cannot move if its velocity is zero. Again, re-read the part of Yang's articles where the values of \(U^\mu\) are discussed.

A particle cannot move if its velocity is zero.

1) There are no particles, only a perfect fluid in Yang's universe;
2) There is no movement in Yang's universe.

If you understood what the word "static" means, you wouldn't be giving these ridiculous answers.

 

We should understand that the moving particle here is equivalent to a test particle, which does not participate in the formation of gravitational field, and the particles forming the gravitational field are many other particles at rest. the perfect fluid is the statistical behavior of a large number of particles, its equation of motion is that the divergence of its stress tensor is zero. The motion equation of a single particle is geodesic equation, the two are different.This is the basic assumption that the general relativity is discussed on a single particle.

 

But that's not what Yang is talking about; the term "test particle" is nowhere to be found. The moving particles Yang described clearly are physical particles, with an unrestricted relativistic mass and all. And that's a contradiction with the set-up of Yang's universe.

 

You seem not to understand Yang's paper, In Yang's paper, the first two chapters discuss the motion of particles in Newtonian central gravitational field by using general relativity, and the coupling coefficient in the field equation is reconfirmed by comparison with Newton's results, and there is no cosmological problem at all. The latter chapters are concerned with cosmology and belong to the application of field equation. We really shouldn't be arguing about the mass of moving particle., is it a language barrier?

 

You seem not to understand Yang's paper, In Yang's paper, the first two chapters discuss the motion of particles in Newtonian central gravitational field by using general relativity, and the coupling coefficient in the field equation is reconfirmed by comparison with Newton's results, and there is no cosmological problem at all. The latter chapters are concerned with cosmology and belong to the application of field equation. We really shouldn't be arguing about the mass of moving particle., is it a language barrier?

 

You really need to re-read Yang's articles. Yang isn't deriving these for the general case. Yang's universe contains only a perfect fluid that's stationary (i.e. zero velocity). That means there cannot be any massive particles, nor movement.

But if the first chapters are rubbish, then surely spending time on the later chapters that derive from the first is wasted.

 

universe, universe, universe, why are you always pulling at the universe? now I talking about the central gravitational field but not universe, let's start with the most basic issues, cann't?

 

I'm talking about "universe" because that's what Yang is doing: Yang is setting up a universe with a perfect fluid. I'm sorry that you aren't familiar of this standard terminology, but that's how GR and cosmology are done (in English).

 

your understand is wrong, in Yang's paper, the first two chapters discuss the motion of particles in Newtonian central gravitational field by using general relativity, that is to say, Yang is applying GR to deal with the central gravitational field, and the coupling coefficient in the field equation is reconfirmed by comparison with Newton's results, and don't concern with cosmological questions at all. only in the central gravitational field GR has common langaue with Newton's theory

 

Re-read Yang's articles. Yang is working in a universe where there only is a perfect fluid that is stationary. That is hardly the general case. There is no motion of particles, because:
1) There are no particles in Yang's universe;
2) There is no motion in Yang's universe.

How is this so hard for you to understand?

 

but only Yang's theory, all other cosmology are also the same, galaxies are treated as inmobile, namely there is a following coordinate system, the recession of galaxies is shown through the scale factor

 

That's simply not true; see for example: https://en.wikiversity.org/wiki/Cosmological_simulations

You are mixing up the movement of galaxies and universal expansion. Those are two different things.