Gravitational Lensing : Eddington Experiment

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

  1. The God Valued Senior Member

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    Pseudoscience will always be unsupported, it becomes mainstream as soon as it is supported. isn't it ?

    The point is anything contrary to established, can be named anything from pure BS to Pseudoscience. There is no fun in discussing whatever is established, real learning comes only when we dig deeper and argue....Its quite likely that we get BS at the end, but something may come out of such discussions, say, some hidden gem of a paper, you never know.
     
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  3. origin Trump is the best argument against a democracy. Valued Senior Member

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    You need to learn what is established first before you can move on. You are not well versed in what is established so you need to further your education if you want to discuss future directions in physics. If you make proposals without having the background knowledge then you are pretty much guaranteed to be discussing pseudoscience.
     
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  5. hansda Valued Senior Member

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    Is the "reality" a function of model/theory? Consider the reality of a mass falling under gravity. Will this reality change in Newtonian model or GR or in any other model?
     
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  7. Schmelzer Valued Senior Member

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    If the stone falls, it is, of course, a real stone, real matter, which is falling, and this stone is, of course, model-independent.

    But already if we describe this event in words, and even more in our theories, we use models of this reality. And these models are no longer reality itself, but only something theory-dependent. So they are different in NT and GR. Reality remains unchanged, our ideas about what the reality is change.
     
  8. hansda Valued Senior Member

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    If the stone is a reality, it is model-independent. Similarly if spacetime is a reality, it also should be model-independent.
     
  9. Schmelzer Valued Senior Member

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    The stone itself is reality. But if we use the word "stone" to describe this thing, we already use a model, and, therefore, something which is not model-independent. And what the meaning of the word "stone" is, is quite different for different people.

    There is some reality out there. But the concept of "spacetime" is part of a model of reality related with GR. So its model-dependence is a triviality.

    Of course, every particular model hopes that it describes reality correctly. But this does not change the fact that it is a model, and its parts are, therefore, model-dependent.
     
  10. hansda Valued Senior Member

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    CORRECT.

    The word "stone" is not a model but a name given to the 'reality of stone' for its proper identification. The name "stone" is neither model-dependent nor model-independent because it is only a word.

    The meaning of the word "stone" is the 'reality of stone'. This meaning is not different for different people. This meaning is same for all the people.

    What is 'some reality'? It can not be 'some real and some unreal'. It has to be either 'fully real' or 'fully unreal'.

    "Spacetime" can not be 'partly real'. Either it is 'fully real' or 'fully model'.

    You mean "spacetime" is model-independent?

    CORRECT.

    You mean "spacetime" is model-dependent?
     
  11. Schmelzer Valued Senior Member

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    But what is the meaning of this name? What is the critical minimal size which makes the difference between a stone and a grain of sand? How hard it has to be for being a stone instead a clod of earth? What is the material of a stone? Behind the word "stone" is the meaning of this word, and this meaning is theory, a theory about reality.
    The meaning of пиздец is 'reality of пиздец'? Certainly not. This sentence does not give you any information about the meaning of пиздец. The meaning of пиздец is very different for different people, believe me.
    Another try: There is something out there which really exists, independent of my wishes and my observation and so on.
    Spacetime is a name for some particular aspects of reality in some model of reality known as GR.

    There are other models of reality, known as spacetime interpretations of alternative metric theories of reality, which share the meaning of "spacetime" with GR. So, in some aspects it is model-independent - there are different models using the same spacetime concept. Other models of reality allow the use of "spacetime" but give it a different meaning. So, from point of view of an ether interpretation, "spacetime" would be something comparable with "history": It is not assumed that history actually exists, reality is (at least for non-fatalists) something different from history. So, in this larger class the meaning of "spacetime" is already model-dependent. And there is another class where "spacetime" simply does not have any meaning at all.
     
  12. The God Valued Senior Member

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    This argument holds good for those who support the mainstream without really understanding what it is. Many posters here do not understand the correct interpretation of established and still take a position of supporter of mainstream.
     
  13. The God Valued Senior Member

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    The Einstein GR equations do not take into consideration the motion of object, why ? Probably because it is insignificant or probably because the gravitational system is locked (like planets etc are locked with Sun in our solar system), so the motion of entire solar system does not really matter while discussing warping of spacetime around sun.

    But this neglecting of translational motion of massive object (lensing system) poses a question for Gravitational Lensing...it may not be so significant for Sun (background light hardly takes anytime to cover the sun), but for a massive galaxy this is significant. The light follows the null geodesic, as soon as the Massive Galaxy moves, the null geodesic which was being followed by photon changes, and it is quite possible that depending on the span of Galaxy (lensing) the background lensed star (or quasar) light takes many many light years to cover this span, during this period how does photon manages to hop on and hop off the geodesics. It cannot. This issue will not arise if we let the light follow background flat space......
     
  14. origin Trump is the best argument against a democracy. Valued Senior Member

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    A layman supporting the mainstream only makes sense. A layman trying to present new theories when they do not even understand the current theories is just foolishness and a waste of time.
     
    paddoboy likes this.
  15. The God Valued Senior Member

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    ...It is not the prereq that to propose something different you must know the existing one. It helps to know. But it is prereq to know about something before supporting it, otherwise it is falsehood in legal terms and crowd mentality in general parlance.
     
  16. hansda Valued Senior Member

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    Can you explain the reality, which is named as spacetime.

    Space is a reality. 'Time as indicated by a clock' is reality. If you think the 'reality of spacetime' is some reality, combining the 'reality of space' and 'reality of time'; then 'reality of space' is that it can curve but in 'reality of time' it can not curve. In 'reality of time' it can only dilate or slowdown. So, in reality "curvature of spacetime" essentially becomes "curvature of space". This "curvature of space" can be observed in 'strong gravity field' as in gravitational lensing. But in 'weak gravity field' no "curvature of space" can be observed.
     
    Last edited: Feb 9, 2016
  17. The God Valued Senior Member

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    At the outset I wish to state that I am not in for this spacetime stuff, but I must state you are mixing up. Spacetime curvature is not the spatial space curvature. Period.

    Curvature of anything materialistic has got nothing to do with time, unless its shape is changing over the time. So if we treat spacetime curvature with the curvature of the space, then time becomes irrelevant once the warping has been created in the space by massive object (GR equations do not consider translational motion of massive object), and this warping is not going to change as long as stress energy tensor remains same.

    Actually Einstein got carried away, during his period of GR (1905 till 1915...1919) minkowski spacetime was in vogue, and spatial space still had some relevance thanks to Newtonian Gravity. The Gravity induced motion can be in line only, so if he had focussed only on geodesics or worldlines, then it would have been kind of improvization over Newtonian only, so to put his theory on high pedestal and to cover the cosmological aspect of space expansion he liked and continued the idea with the curved spacetime, which is absolutely redundant.

    See it from this point of view also....photon follows null geodesic (follows curved spacetime as per GR), a particle with speed 0.7c (or any speed > Escape Velocity around that object) follows a curved geodesic which has higher curvature, so curvature of this path is dependent on the initial velocity of the particle under Gravitational influence. Suggesting that this curvature business is nothing but the path followed by an object when exposed to Gravitational field.

    At the best If I were to keep the concept of spacetime alive, then I would call it the 'mesh of the null geodecis' around an object, there will be infinite such null geodesics which can be defined by the direction and position of the photon at any given instant. The complete set of these geodesics will be my 'null spacetime'. It has no observational import, not even required to define the motion of a particle.
     
  18. hansda Valued Senior Member

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    Dont go into the math of spacetime. Just think in terms of reality. Curvature of spacetime can be thought of as curvature of space and curvature of time. Curvature of space, we can think of. But can we think of curvature of time? So, in reality curvature of spacetime becomes curvature of space.



    Time does not become irrelevant. Dilation of time is useful in calculating the curvature of space.
     
  19. paddoboy Valued Senior Member

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    Totally agree. If a person is accepted mainstream knowledge and data to illustrate a point, then the revelation of his or hers credentials do not matter in that regard.
    It's the cranks and would be's if they could be's, that see the need to dispute 21st century cosmological data and the accepted interpretations, that need to show what credentials they have.
    Only one on this forum, Schmelzer has done that.
    The rest pretend, obfuscate and spout unsupported nonsense.
    And while our pretentious cranks are allowed to have their opinion, they are certainly not allowed to have their own fabricated maths or facts, as has been shown at different times.
    Bingo! Einstein and SR/GR will never be wrong when applied correctly within their classical zone of applicability.
     
  20. The God Valued Senior Member

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    Good to see you back, hope you are keeping well..
     
  21. The God Valued Senior Member

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    I think I could not point out the context. Once the mass settles and warping gets created, then locally time aspect becomes irrelevant as the curvature on a given point is not going to change as the time flows.
     
  22. paddoboy Valued Senior Member

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    Worth remembering that the many crazy alternative opinions, by the few uncredentialed wannabes that infest this forum, will thankfully never see the light of day.It needs also to be kept in mind that there right to hold an opinion is not being contested: Your beliefs that it be taken seriously is.
    In summing with regards to gravitational lensing......
    It shows that spacetime is indeed curved/warped in the presence of mass, simply by the postulate of light following geodesics in that spacetime.
    Nothing has been shown here or anywhere else that can dispute that fact as supported by the many reputable links that have been given.

    That coupled with the latest direct evidence of not only the existence of gravitational waves, but also further confirming that which most mainstream reputable cosmologists never doubted, that is the evidence for BH's.

    Wasted bandwidth and cyber space denying those facts without any contrary evidence, is just that...wasted bandwidth and cyber space.


    http://www.bbc.com/news/science-environment-35553549

    "It's astonishing; it really is." Jim Hough can't stop repeating the phrase.

    The veteran gravitational wave hunter from Glasgow University has come to the National Press Club in Washington DC to witness the announcement of the first direct detection of ripples in the fabric of space-time caused by the merger of two "intermediate-sized" black holes.

    The numbers look bald on paper, but it's when you try to imagine the scenario being described in those numbers that you rock backwards.

    Imagine two monster black holes spinning down on each other in space. One has a mass which is about 35 times that of our Sun, the other roughly 30. At the moment just before they coalesce, they're turning around each other several tens of times a second. And then, their event horizons merge and they become one - like two soap bubbles in a bath.

    David Reitze, executive director of the Laser Interferometer Gravitational-Wave Observatories (LIGO), described it thus: "Take something about 150km in diameter, and pack 30 times the mass of the Sun into that, and then accelerate it to half the speed of light. Now, take another thing that's 30 times the mass of the Sun, and accelerate that to half the speed of light. And then collide [the two objects] together. That's what we saw here. It's mind boggling."

    In that moment of union, the holes radiate pure energy in the form of gravitational waves, and lose mass equivalent to three times that of our Sun. Energy equals mass times the speed of light, squared. Everyone knows the equation; this is it in action.

    That tremendous release of energy, and the warping of space-time that results, is why the LIGO laboratories have been able to sense it, even though this staggering event occurred about 1.3 billion light-years from Earth.

    A thousand researchers from 80 institutions in 15 countries are celebrating this moment. The excitement this week, building up to the announcement in the US capital, has been palpable. It's easy to see why.
    more at link......
    extract:

    "Although Einstein's equations are famously complicated, they are the simplest equations he could have come up with, given all the constraints he had to satisfy," commented Bernie Schutz from Cardiff University.

    "It is remarkable that nature didn't add in even more complexity. But the equations are what they are, and they're beautiful."
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  23. river Valued Senior Member

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    But these results have yet to be proven that gravity waves is what is proven.
     

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