Gravitational Lensing : Eddington Experiment

Discussion in 'Astronomy, Exobiology, & Cosmology' started by The God, Nov 29, 2015.

  1. paddoboy Valued Senior Member

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    But what are yours? Beyond any high school certificate.
     
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  3. The God Valued Senior Member

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    Thanks, at least you admit that I have high school certificate. But as an omniscient God Do I need one ?
     
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  5. paddoboy Valued Senior Member

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    I'm still flabbergasted that our divine friend could ask such a question which is answered so simply correctly.
    How could anyone participating in an astronomy/cosmology thread, not be able to know what an orbit is, or curved spacetime, or a geodesic!

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    No wonder this has gone on for near fifty pages.

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  7. paddoboy Valued Senior Member

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    I was being kind.... But don't despair.
     
  8. The God Valued Senior Member

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    As I said, you don't understand the import of such complex questions.....it will need some more time, I will educate you..Physbang claiming to be a PHD has also failed so you are quite far off as of now to understand this.
     
  9. paddoboy Valued Senior Member

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    Yet as this forum knows, it's your threads that are being shifted to pseudoscience

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    You are only fooling yourself my friend, but that's easy I would imagine.
     
  10. paddoboy Valued Senior Member

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  11. PhysBang Valued Senior Member

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    This is why I call you a liar: because you lie, and in particular lie about me.

    The "weak field approximation" was discussed, with several links, before you asked your question. All answers were there.
     
  12. hansda Valued Senior Member

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    What do you mean by "metaphysics"? Do you think the concept of spacetime is metaphysical ?
     
  13. PhysBang Valued Senior Member

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    What I mean is that people who use the weak field approximation do not feel that they are using something that represents "what is really going on", so to speak. They use it because they know that it gives them results within an allowed amount of accuracy.

    It is often metaphysics when one asks about the nature of space and time. In this case, I meant that those using the weak field approximation do not feel that the model they are using is a faithful representation of the contents of the physical system and its relationships.
     
  14. hansda Valued Senior Member

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    That means the "Physical reality of spacetime" is not very much well defined.

    Space and time are very much well defined in Physics. I dont think they are metaphysical concept.

    Maybe you are correct because Newtonian model does not work in the strong gravitational field and in the weak gravitational field the concept of "curvature of spacetime" becomes meaningless in terms of its Physical reality.
     
  15. PhysBang Valued Senior Member

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    Not at all. It is extremely well-defined. It's just that its not always useful to go to the greatest lengths in physics to get a useful result.
    You are free to think what you will.
    The curvature does not become meaningless in terms of physical reality. What happens is that it becomes less useful to use it in our calculations than it is to use calculations based on a kludge.
     
  16. hansda Valued Senior Member

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    Can you explain the "physical reality of spacetime" in terms of its curvature, in the "weak field approximation" where it is "flat spacetime" ?
     
  17. PhysBang Valued Senior Member

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    There is no "weak field approximation" in reality. The "weak field approximation" is a useful fiction. It is a technique used for calculating that gives an error, but only a very small error in certain circumstances.
     
  18. brucep Valued Senior Member

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    You need to pay attentoon. Right now I think you're looking for some reason why using weak field analysis isn't the right thing to do regardless the goals of the analysis. Regardless Physbangs attempts to answer your questions?
     
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  19. Schmelzer Valued Senior Member

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    Of course I cannot answer incorrect questions. When do you stop to eat small children?

    There is the possibility that one and the same solution is, in one interpretation, described as a flat spacetime with something which distorts measurements, but in another interpretation as a curved spacetime.

    There is the Newtonian approximation of GR, where a Newtonian potential, which would live in Newtonian theory in a flat spacetime, is used to define a metric which defines a curved spacetime.

    No. In the weak field approximation of GR you have time dilation, in Newtonian mechanics not.
     
  20. The God Valued Senior Member

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    Refer my post #938, you are making false accusations...I did specifically asked you about the point, when you claimed about some point of demarcation sort of between GR and Newtonian.. You are 'the liar' not me, all along you have been tacitly supporting that lensing deflection figure in this thread and countering me, but when you realised that it has incorrect deflection value from GR perspective, you backed out..and started claiming that you never said so..You still have to answer on your PhD specialization ? James felt that you never claimed.
     
  21. The God Valued Senior Member

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    That what I was maintaining all along that Newtonian Universal Gravity is conceptually different from so called Newtonian Gravity in GR (Approximation of GR).....

    I am yet to see the exact application of GR maths, its approximation everywhere. Orbital Motion - Approximation, Mercury precession - Approximation, Lensing - Approximation, Schwarzschild Solution - Approximation (Assumption of non spinning etc). Gravity - Approximation (simply because effect of multiple bodies on a test particle is a hopeless situation mathematically in GR).

    So, what is so elegant about GR ?
     
  22. Schmelzer Valued Senior Member

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    Nobody cares much about exact solution. If people talk about elegance, they talk about aspects of mathematical beauty which have nothing to do with the existence of exact solutions. It is more about the nice thing that the equation for moving particles is exactly the same mathematics than the equation for geodesics in a metric. This is something mathematicians like a lot - mathematical connections between completely different things.
     
  23. PhysBang Valued Senior Member

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    OK, so you are lying again. Why you feel the need to lie specifically about me so often I do not know, but please stop.
    Yeah: they are different theories, so one need only look at their different content to find a demarcation between them. If you do not understand this, then how can you hope to understand any physics.
    I supported the idea that one can have a straight line in GR. I don't care what picture you used.
    My credentials do not matter because I am not making an argument from my authority. I was merely being conversational with another poster. You like to talk about your own authority and attack others rather than address significant points.
    Every. Physics. Application. Is. An. Approximation.
     
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