Minkowski Space Time Briefly Revisited

Discussion in 'Physics & Math' started by danshawen, Nov 24, 2014.

  1. Farsight

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    3,492
    They're both true. Take a look at a picture of gravitational potential:

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    CCASA image by AllencMcC, see Wikipedia

    The force of gravity at some location depends on the slope or tilt at that location. It's the first derivative of potential. The tidal force at some location depends on the curvature at that location. It's the second derivative of potential. Now understand this: if there was no curvature at all, this plot would be flat and level. Like a disc. There would be no gravitational field.
     
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  3. Farsight

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    Like you said, I think we're now finished here.
     
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  5. danshawen Valued Senior Member

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    I'm also onboard with most of what he says in this lecture concerning QFT. It is a very comprehensive and detailed theory that shoots down 99.999% of any new weird ideas that come along. But as Godel's incompleteness theorem demands, there will always be that one niggling case that confounds not only the reasoning of its entire structure, but some of the underlying and simplifying assumptions made in order to produce it. God probably does it this way to keep us interested, or perhaps humbled. Good move, big G.

    The holdout is the graviton. You are not going to see something like the graviton in particle physics explained (ever!) because of the disparity of the magnitudes of the forces involved. And this is no small holdout. It's holding you to the surface of this planet. But it doesn't derive of anything you can easily stuff into a collider, and this is the point.

    In coming years, it's going to be a major embarrassment to particle physics and QFT that they missed the idea that not everything that goes on in the universe can be easily captured by taking pictures of what they can conveniently coax into their colliders. The principle of equivalence demands (and this is not a request that can simply be sloughed off) that gravitational mass and inertial mass must be equivalent. Until this issue is resolved, GR and QFT remain very much separate theories. Problems like these are exactly why weird and/or whacky new ideas are occasionally required of finite minds aspiring to understand the big picture.
     
    Last edited: Dec 19, 2014
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  7. danshawen Valued Senior Member

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    I really liked the description of renormalization. It's an idea derived of a precursor of QED and QFT known as Stochastic Electrodynamics (SED), which was also a creation of Feynmann and associates. Before I understood this, renormalization did not make very much sense.

    SED, by the way, agrees well with some of the vacuum field / energy ideas I have mentioned in this thread. I think further development of SED may have been dropped precisely because its predictions could not be tested in a collider, something it's creator would have been particularly opposed to as one of those .001 % wacky and untestable theories.

    Peter Lynds' ideas about time intervals never being =0 or negative can help avoid most infinities related to time (so that renormalization may not be necessary). If space itself actually derives of time, as I have suggested in this thread, the same goes for any distances that would otherwise go to zero as well. At spatiotemporal distances smaller than the Planck length, all energy is virtual, so it would also help to understand exactly what that means.
     
    Last edited: Dec 19, 2014
  8. PhysBang Valued Senior Member

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    2,422
    So when I asked if you could demonstrate this with an example, your answer was, "No."

    I think you've been finished here a long time ago, but you are still running around llike a chicken with your head cut off. Why should we trust that you understand physics when it is clear that you can't do any?
     
  9. OnlyMe Valued Senior Member

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    Farsight, you do understand that the above is a 2D representation, of a 3D anaology, of a 4D theory.., right?

    It may be useful in some limited contexts to convey a simplistic understanding, of spacetime ..., but the way you continually toss it out as if it represents some transcendent example, degrades even that simplistic contribution.

    Do you continually use this and similar simplistic examples because you really believe those you are conversing with are ignorant or is it as others have suggested, you really cannot move beyond that two dimensional understanding?
     
  10. QuarkHead Remedial Math Student Valued Senior Member

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    I repeat - you quoted some source with apparent approval as saying "gravity is not a force"
    This is at best garbled, at second best plain wrong

    Look, in Newton's theory (using the Poisson eqn) we have simply a scalar potential \(\phi\) such that

    1. \(\phi = k\) (a constant) where there is no field and no source
    2. \(\nabla^2 \phi = 0\) where there is a field but no source \(\nabla^2 \)is the second order Laplace operator defined as div(grad)
    3. \(\nabla^2 \phi = 4\pi k \rho\) where \(\rho\) is the density of the gravitational source

    In GR, the gravitational potential generalizes to the metric tensor whose components are \(g_{jk}\)

    The affine connection \(\gamma_j\,^k\,_l\) is second order in the metric ("potential"), and the contracted (torsion-free symmetric) Ricci tensor \(R_{jk}\) is first order in the connection. It can be shown (with some difficulty I grant) the \(k\) in (1) above is the position invariant Minkowski metric \(\eta_{jk}\) which is diag{-1,1,1,1} and zero elsewhere,

    that (2) above implies \(R_{jk}=0\) in the source-free field

    and that the Einstein field eqns cannot be extracted in any straightforward way from (3), but the analogy, slightly forced in my opinion, can be made.
     
  11. Farsight

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    3,492
    You're just confusing yourself, Quarkhead. As ever you're getting so wrapped up in mathematical abstraction you just aren't understanding the physics. Keep it simple. Place optical clocks throughout a horizontal slice of space through the middle of the Earth. Plot the clock rates to depict gravitational potential. Then understand that those clocks are optical clocks, and the clock rates vary because the speed of light varies. See Einstein saying light curves because the speed of light varies here.
     
  12. QuarkHead Remedial Math Student Valued Senior Member

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    1,740
    I assure you I am not at all confused, and unlike you I not only understand GR pretty well, but accept it as logically closed in its domain of applicability. Your recent posts on Einstein and GR seem to indicate that you do understand GR, you cling to the Newtonian perspective of space and time
    And who, pray, recently introduced first and second order derivatives? I merely pointed out you had the context wrong
    And this is simpler "physics" than understanding differential geometry?

    You know, Farsight, you would be a laugh if you were not so dangerous.
     
  13. Dr_Toad It's green! Valued Senior Member

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    2,527
    Mods, please explain again why permabanning Farsight was a mistake? His only contribution here seems to be the speed at which he can anger people who do understand physics.
     
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  14. OnlyMe Valued Senior Member

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    You keep repeating this Farsight, but I have yet to see you provide any proof! What you are saying is that, it IS the speed of light that governs the optical frequency associated with a specific optical clock.

    While there is evidence that the frequency of an optical clock varies with location. You don't have any proof that the speed of light in vacuum varies under any circumstances... You can only measure it locally.., where the results of your measurements remain constant.

    How you interpret remote observations, is not proof... And neither is how you misinterpret historical comment!
     
  15. PhysBang Valued Senior Member

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    2,422
    You keep saying not to get hung up on the mathematics, but the mathematics is how anything gets done in physics. The only reason to believe GR is because of working through some very complicated mathematics so that we can compare observations to theory.

    So, again, can you show us how to do any physics with these concepts you believe in?
     
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  16. Farsight

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    3,492
    And yet you dismiss the Einstein quotes I give you and ignore the simple explanation.

    Yes I do. Thanks for the compliment.

    I don't. But I do note that Einstein's explanation of gravity is very similar Newton's: "Doth not this aethereal medium in passing out of water, glass, crystal, and other compact and dense bodies in empty spaces, grow denser and denser by degrees, and by that means refract the rays of light not in a point, but by bending them gradually in curve lines?"

    I'm not wrong about this, and it isn't something I've dreamt up. Look it up.

    Yes. And the moot point is that understanding differential geometry doesn't tell you how gravity works. If you beg to differ, start a thread and try to explain how gravity works.

    I'm not dangerous. I talk good physics and give robust references to Einstein and the evidence.
     
  17. PhysBang Valued Senior Member

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    2,422
    Your "simple" explanations are, when they are not obviously contradictory, too simple to be of serious use. You continually refuse (presumably because of your incompetence) to provide explanations of any detail sufficient to do any physics.
    Yes, you are well known for clinging to Newton's alchemy rather than to the physics that Newton produced. Presumably this is because you can't follow Newton's physics.
    One certainly can look up your fantasies, you have left quite a trail on the internet that well documents that you have made most of this up.
    But you claim to understand something that you show no proficiency with. How can we tell if any of your ideas match the details of how gravity actually works if we can't see these details in action?

    Again you lie: you never show us the physics. Please rectify this and show us some physics. Show even one simple example, please.

    Maybe you want to pick one of your past favorites: you can show us the right way to calculate a galaxy rotation curve, unlike all the other physicists in the world that you claim do this incorrectly.
     
  18. QuarkHead Remedial Math Student Valued Senior Member

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    Your dishonesty prevents you from acknowledging that I typo'd, and meant to say you do NOT understand GR

    But now I have refreshed myself with a beer, I see the following circular argument
    So we have (in your own words, don.t try to dissemble) that the gravitational potential comes from variable clock rate/light speed, which is in turn comes from the variable gravitational potential!

    It is well known that GR is a non-linear theory, but this does not mean it admits of circular arguments
     
  19. Farsight

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    3,492
    LOL, I had a laugh at that. Something of a Freudian slip, n'est pas? Note that I answered your question in post #281 at the top of this page. And note that I am not dishonest.

    It obviously wasn't a Heineken, because you've got this wrong. The clock rate/light speed varies because a concentration of energy in the guise of a massive star "conditions" the surrounding space rendering it inhomogeneous, and this effect diminishes with distance. Again, go and read what Einstein said:

    "According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that "empty space" in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gmn), has, I think, finally disposed of the view that space is physically empty. "

    You describe the state of space using the gravitational potentials, and the equatorial light clocks give you a simple intuitive way of plotting the familiar bowling ball depiction of curved spacetime:

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    GNUFDL image by Johnstone, see Wikipedia.

    The circular argument is that your clock goes slower when its lower because spacetime is curved. That's saying your clock goes slower when its lower because your plot of clock rates is curved. It's a nonsense.
     
  20. PhysBang Valued Senior Member

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    2,422
    Everyone knows that you are dishonest. I've personally pointed out dozens of ties that you have either flat out lied or deceived your readers about the nature of your citations. Now you don't even answer my questions, since you can't produce an answer without either outright lying or demonstrating that you can't do any physics.

    I'm quite happy that you continue to ignore my questions, since it demonstrates your deceptive nature and your incompetence.
    Can you walk us through an example with the actual gravitation potentials, or can you only show a picture?

    (We already know the answer: you can't do any physics.)
    Can you demonstrate this in the actually practiced science?
     
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  21. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    2,973
    except it was faraday's work that einstein realized light is a constant and time is the variable.
    can you tell me why it is refereed to as continuum ?
     
  22. krash661 [MK6] transitioning scifi to reality Valued Senior Member

    Messages:
    2,973
    except it was faraday's work that einstein realized light is a constant and time is the variable.
    can you tell me why it is refereed to as continuum ?
     
  23. QuarkHead Remedial Math Student Valued Senior Member

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    1,740
    Actually it is n'est-ce pas
    Where once again, in spite of my repeated requests for clarification you use the term "force of gravity", in spite of your often-repeated mantra that "gravity is not a force".
    Hmm....

    What you vaguely call the "gravitational potentials" I interpret (as Einstein did) as the spacetime metric tensor field. I explained this in a previous post - are you no longer drawing a distinction between space and spacetime?
    Leaving aside I am not sure what you mean by "curved plot of clock rates"..........Only if I agree that MY clock goes slower when I am occupy a spacetime point closer to the source than....er....who, exactly.

    This is equivalent to your earlier unsupportable assertion that, for an observer crossing the event horizon of a black hole, his own clock stops

    Here you deny relativity - clock rates, even stopped vs not-stopped - depend upon the coordinates you use.
     

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