Gravity: The why and the how:

Discussion in 'Astronomy, Exobiology, & Cosmology' started by paddoboy, Oct 24, 2015.

  1. paddoboy Valued Senior Member

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  3. paddoboy Valued Senior Member

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    Well then if my assertions are incorrect, so are the assertions of my reputable links above supporting what I have said from the likes of Professors Thorne and Hamilton. You call that pop science?
    And of course if they are wrong, why are you unable to supply a link supporting your own assertions?
    You are continually asked that but refuse to give any.
     
    Last edited: Nov 16, 2015
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  5. paddoboy Valued Senior Member

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    Another interesting scientific paper......
    http://arxiv.org/ftp/arxiv/papers/0806/0806.1176.pdf
    Abstract:
    The modern notion of a black-hole singularity is considered with reference to the Schwarzchild solution to Einstein’s field equations of general relativity. A brief derivation of both the original and the modern line elements is given. The argument is put forward that the singularity occurring within the Schwarzchild line element, that has been associated with the radius of the black-hole event horizon, is in fact merely a mathematical occurrence, and does not exist physically. The real aim here, however, is to attempt to open up the whole problem, draw some conclusions but finally to urge everyone to consider the points raised with no preconceived opinions and then come to their own final conclusion.
    Some interesting notes from this paper.
    NOTE: Page 4:
    "However, stars of mass greater than approximately 3M, were thought to contract indefinitely, since the force of gravity would overwhelm all other forces".

    The paper in its near entirety is devoted to discussing the Singularity and the nature of such a beast.
    NOTE: Page 12:
    "An adequate explanation of what a ‘singularity’ in physical space, or space-time, is does not seem to exist. It is described as the point at which the curvature of space-time becomes infinite and the known laws of physics break down but, in reality, it seems that a singularity within general relativity is exactly the same as a singularity within any other theory - meaningless as a physical entity. This is not to say that general relativity is incorrect due to the existence of this singularity within the mathematics of the theory but, rather, that the existence of these singularities demonstrates possible limits to Einstein’s theory, and that some deductions from that theory, following work carried out in the 1950s and 60s, may be in error. Hence, as was suggested earlier, it seems sensible for this entire area to be viewed again without any preconceived ideas as to the final answer. Only in this way will satisfactory answers emerge and physics be allowed to progress safely in pursuit of the truth".
     
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  7. paddoboy Valued Senior Member

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    Here's another paper:
    http://arxiv.org/pdf/1201.3660.pdf
    At 3:1 it says...........
    A black hole is born: The Oppenheimer-Snyder-Datt model:

    "To understand the final state of collapse for a massive star, we need to trace the time evolution of the system or its dynamical progression using the Einstein equations of gravity. The star shrinks under the force of its own gravity, which comes to dominate other basic interactions of nature such as the weak and strong nuclear forces that typically provided the outwards pressure to balance the pull of gravity".
     
  8. brucep Valued Senior Member

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    That author is a clueless crank with respect to the science of black holes. Everybody knows the coordinates
    dr/(1-2M/r)^1/2 don't exist for r=2M. That doesn't mean a light like boundary doesn't exist at some real coordinates. The rest is downhill for this author.
     
  9. paddoboy Valued Senior Member

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    The point of the paper brucep was to highlight the accepted knowledge that inside the BH,s EH, gravity overcomes all other forces. A point that our friend "the god" is unable to accept despite at least half a dozen references.
    Yet even a similar crank as he is, [as you pointed out] has at least that much right.
    I know you have him on ignore, but his denial of accepted mainstream cosmology is good for a belly laugh.

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  10. brucep Valued Senior Member

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    The author is a person that thinks he figured out r=2M is a coordinate singularity. He thinks the objects are better described by the Newtonian physics of the dark star. The text is juvenile and full of holes.
     
  11. The God Valued Senior Member

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    No doubt you are shaddy character, abyssmally low morality.
     
  12. paddoboy Valued Senior Member

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    All you need to do is support what you claim. Is that so hard?
     
  13. Farsight

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    What's going on here?

    I wrote an article on black holes a couple of years ago when I was blogging for Delingpole. See Science on Sundays with John Duffield: Black Holes

    "...Optical clocks go slower when they’re lower because the space down there is different to the space up here. They call it gravitational time dilation, but it’s just the light going slower when it’s lower, so the clocks go slower too. How much slower? Have a google on infinite gravitational time dilation. What pops up time and time again? Yes, black holes. Remember those parallel-mirror light-clocks at different elevations? Gravitational time dilation is said to go infinite at the black hole event horizon. So an optical clock at the event horizon doesn’t tick at all. And if it doesn’t tick, it can only be because the light isn’t moving. Because the speed of light at the event horizon is zero. That’s why your laser beam doesn’t get out of the black hole. Not because of some mystic curvature, or because the sky’s falling in, but because at that location the speed of light is zero, zip, zilch. The light isn’t moving, so it doesn’t go up and it doesn’t get out because it is effectively “frozen”. Did you know that black holes were originally called frozen stars? If you google on frozen star Oppenheimer you can find references to this. However if you google on frozen star and follow the links, what comes up is black hole along with a point singularity. It’s like history has been rewritten. It’s like the original “frozen star” has been airbrushed away, and replaced with something else. Something stupid. See the picture below? ..."
     
  14. paddoboy Valued Senior Member

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    Sorry my pseudoscience friend, the speed of light is constant. It does not go slower but is gradually red shifted to infinity.
    It is gravitational time dilation. And if you had anything concrete saying different, you would not be here and would not need to keep buying copies of your own book to give some limited respectability to sale figures.

    Too much rubbish to comment on Farsight. The others giving you a hard time?

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    Let me tell you properly. From any local frame say at the EH, nothing strange happens....everything appears as normal other than for tidal gravity effects. Light will fall into the BH at "c" unless directed radially away where it will literally appear to "hover"forever from that local frame, with the EH apparently chasing it at the same "c"


    But I'm not just full of bluster like you, here's another link/paper.

    http://arxiv.org/pdf/gr-qc/0411060.pdf
    Abstract:
    This paper presents an under-appreciated way to conceptualize stationary black holes, which we call the river model. The river model is mathematically sound, yet simple enough that the basic picture can be understood by non-experts. In the river model, space itself flows like a river through a flat background, while objects move through the river according to the rules of special relativity. In a spherical black hole, the river of space falls into the black hole at the Newtonian escape velocity, hitting the speed of light at the horizon. Inside the horizon, the river flows inward faster than light, carrying everything with it. We show that the river model works also for rotating (Kerr-Newman) black holes, though with a surprising twist. As in the spherical case, the river of space can be regarded as moving through a flat background. However, the river does not spiral inward, as one might have anticipated, but rather falls inward with no azimuthal swirl at all. Instead, the river has at each point not only a velocity but also a rotation, or twist. That is, the river has a Lorentz structure, characterized by six numbers (velocity and rotation), not just three (velocity). As an object moves through the river, it changes its velocity and rotation in response to tidal changes in the velocity and twist of the river along its path. An explicit expression is given for the river field, a six-component bivector field that encodes the velocity and twist of the river at each point, and that encapsulates all the properties of a stationary rotating black hole
     
  15. paddoboy Valued Senior Member

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    Like the proverbial cocky on the biscuit tin, you just aint in it Farsight!
     
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  16. Farsight

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    What are you on about? My book hasn't been on sale for years. I haven't been buying copies to boost the sales figures, ever. There's a few secondhand copies at silly-money prices, but Amazon are a law unto themselves, and it's nothing to do with me. As for the speed of light, see the Einstein digital papers:

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    Nowadays this is generally referred to as the coordinate speed of light. It varies. If it didn't, light wouldn't curve and your pencil wouldn't fall down. At the event horizon, it's zero. And guess what: it can't go lower than that.

    Only that doesn't square with Einstein.

    It's popscience tosh. There is no river of space falling into a black hole. Einstein rejected Gullstrand-Painlevé coordinates for good reason. In general relativity we talk of inhomogeneous space and curved spacetime, not space that's falling down. We do not live in some Chicken-Little world where you pencil falls down because the sky is falling in.
     
  17. paddoboy Valued Senior Member

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    Like I said, the great man would be cringing at the thought of some crank misinterpreting what he has said.
    Let me again make it abundantly clear. The speed of light is a constant: A postulate of SR.
    Guess what? As usual you are wrong. Light does not curve, it simply follows geodesics in curved spacetime, which has also been conclusively evidenced.

    As usual my Chicken Little friend, you have things grossly astray. That's why you are considered a harmless crank...that's why you are banned from so many sites...that's why the only places you are able to evangelize your nonsense, is on public forums such as this.
     
  18. James R Just this guy, you know? Staff Member

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    No valid solution of Einstein's gravitational equations is popscience tosh. The "river" metric is a valid solution. Ergo, not popscience tosh.
     
  19. The God Valued Senior Member

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    river metric ? No, its not. Its a simplified model meant for those who don't want to get into mathematics, suggesting a popuar science representation.

    Prof Hamilton wrote a paper on this too (apart from that link pushed by one particular poster in his every second post on the subject), he was so bemused at the end that he put a self made Q&A section on that paper. Bad, his endorsement got a place in arXive for this paper.

    Its a fantasy kind of representation, fails instantly when we extend that sky is falling at 0.86c even at 1.5EH (photon sphere). On the other hand metric is a well defined mathematical representation of spacetime geometry, nothing to do with ponds or rivers or oceans.
     
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  20. The God Valued Senior Member

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    The difference between the age of father and son is x. The product of x when added with 10 and when subtracted with 10 yields 21. If the 'son' is 18 year old what is the age of father ?

    The above problem can be written mathematically as

    (x+10)(x-10) = 21

    Solving this great mathematical equation gives x = +/- 11, so there are two solutions:

    Father's Age = 18 + 10 = 28 Years
    Father's age = 18 - 10 = 8 Years.

    Father is younger than Son and that too 8 years old. This is a valid solution, I am sure a great mind can see some kind of time travel in this solution, but it has to be discarded, so why can't ridiculous/trivial solutions of great Einstein Gravitational equations be discarded ? Just because we do not know how to discard them?

    Enjoy...
     
    Last edited: Nov 19, 2015
  21. James R Just this guy, you know? Staff Member

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    For non-rotating black holes, it is equivalent to the Schwarzschild metric, is it not? Did you read the paper linked above?
     
  22. The God Valued Senior Member

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    ...............In this paper we have presented a way to conceptualize
    stationary black holes, which we call the river model.
    The river model offers a mental picture of black holes
    which is intuitively appealing, and whose basic elements
    are simple enough that they can be grasped by nonexperts.
    In the river model, space itself flows like a river
    through a flat background, while objects move through
    the river according to the rules of special relativity.......

    Pl read about what is a "metric" and what is a "model"....after that if you still feel that river model is actually a river metric, we can discuss.
     
  23. James R Just this guy, you know? Staff Member

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    In the first few lines of the paper linked above, the authors display the "river" metric (which, as they note, has a long history). That metric is a valid metric describing the Schwarzschild geometry, if I understand it correctly.

    So, I'm still not seeing what your complaint is.
     

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