Gravity: The why and the how:

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

  1. tashja Registered Senior Member

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    lol A '.edu' email address, maybe?

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    j/k

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    . You've gotten some good answers from the profs. too, Paddo.
     
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  3. tashja Registered Senior Member

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    Yes, these concepts are what make black holes unpalatable for some. Ultimately, observations will decide what those compact objects are. I keep in touch with a member of the Event Horizon Telescope team, which is currently gathering data. And even though it's too early to tell, it appears things are looking good for general relativity.
     
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  5. paddoboy Valued Senior Member

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    I don't put anyone on ignore either, but I always answer my return posts critical or otherwise. And as I explained in an earlier reply to you, it's not about having the last word...not at all, at least not with me.
    With you ignoring me, I was commenting on your usual misunderstandings with my posts, inferring that I put anything as certain and why I'm not encouching all my claims with "it's only a theory"
    I thought that deserved a reply...
     
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  7. paddoboy Valued Senior Member

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    Great stuff tashja! Especially the last sentence!
    Keep us informed, OK?
     
  8. OnlyMe Valued Senior Member

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    That sounds really good!

    I don't think general relativity is at risk, over the black hole issue, though there may be some adjustments in interpretation, as some credible quantum theory of gravity is developed. In the end QT and GR will have to get along.

    I don't believe that whatever comes of work being done on black holes, dark matter and energy, there will be anything more than adjustments. Mostly in how it is interpreted. I'd even suggest that any significant progress in any of the three, will lead to a better handle on how to approach quantum gravity.
     
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  9. paddoboy Valued Senior Member

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    Event Horizon Telescope team
    http://www.eventhorizontelescope.org/science/index.html

    Key science results so far:
    • Sgr A* is a black hole: Material is falling into the Sgr A* system. If Sgr A* had a surface no bigger than the size measured by the EHT, it would be a very bright source at infrared wavelengths. However, Sgr A* is a faint infrared source, indicating that energy is disappearing through an event horizon, the existence of which defines a black hole.

    • The accretion disc in Sgr A* is inclined to the line of sight: The material orbiting and falling into the black hole is confined to a region called the accretion disk. The size obtained from the EHT indicates that we are viewing this disk closer to edge-on than face-on. EHT data also place constraints on other parameters, such as the spin of the black hole.

    • The millimeter emission in Sgr A* is offset from the black hole: As an object gets close to a black hole, it appears bigger than it actually is. The apparent size measured by the EHT is smaller than the minimum size allowed by gravitational lensing. The emission must therefore be offset from the black hole. Models indicate that we are seeing the portion of the accretion disk that is moving toward us.

    • The variability in Sgr A* occurs near the black hole: The emission we detect from Sgr A* changes in brightness, but its apparent size does not change. While the mechanism that produces this variability is not well understood, EHT data indicate that the changes occur in the accretion flow very near the black hole.

    • The black hole in M87 is spinning: Like any other object, black holes can rotate. The small size of the emission around M87 implies that the black hole is rotating rapidly and that the accreting material is orbiting the black hole in the same direction.
     
  10. The God Valued Senior Member

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    Great Tashja...

    This thread is turning out to be very useful, Prof Link highlights the NS having quarks etc in the inner core and Prof Hamilton throwing some light on the charged BH, he has lot of papers on RN BH and Prof Link is Neutron Star expert.

    There is a small issue with the the response of Prof Hamilton. Hope you will be kind enough to get the same clarified.

    In general, a spinning and charged BH will have different kind of singularity (Ring type) not the point type. So a massive BH with some spin and some charge will have an outer EH and an inner EH....The spin energy of such BH is theorised to reside in Ergosphere (Kerr, Penrose etc). This is understandable as spin is not the intrinsic property of matter like mass and charge (not to be confused with electron spin). Now straightaway coming to the charge part, the electric field associated extends to EH (as per Prof Hamilton response), of course Prof does not mean that it extends from inner EH to outer EH, so it got to be at outer EH only. Now this explanation poses a problem at the time of accretion of a charged particle. As I said earlier charge cannot be separated out of a particle, so if an electron is crossing the outer EH of a positively charged BH, it will hold its negative charge in transit from outer EH onwards, then what happens during the transit from outer EH to singularity? For massive charged BH (large Mass), the empty space inside the outer EH is substantial, how a charged particle is expected to travel inside? May be some more words on distribution of field would clarify this.
     
  11. paddoboy Valued Senior Member

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    The outer EH you speak of is called the static limit, and any matter/energy within that static limit and the EH proper, cannot ever be at rest. It will be swirled around the ergosphere [frame dragging] in the direction of the flow of that spacetime.
    The ring Singularity is also a recognised property of the spinning BH, and if any body were to arrange his trajectory into the BH via the polar regions, and pass through the middle of this ring singularity, then the tidal gravity effects would be nullified, and one could virtually pass through unharmed theoretically speaking of course.
    The ring singularity of course is thought to exist simply because its the spin of the singularity/mass that is responsible for the ergosphere/frame dragging.
    As Professor Hamilton said a while back, it is a logically and reasonably assigned assumption to theorise properties inside the EH.
    Worth noting though, the Kerr metric and/or the Kerr-Newman are extremely complicated geometrical scenarios to work out, and evidenced by the fact that they were not developed until 1963.
     
    Last edited: Nov 3, 2015
  12. brucep Valued Senior Member

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    That's an awesome experiment. This is the paper on the top of the publications list.
    http://arxiv.org/abs/1502.07365
    Plasma blobs.
     
  13. paddoboy Valued Senior Member

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    Thanks bruce, awesome it is!
     
  14. brucep Valued Senior Member

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    They can measure the tidal effects on the components of the falling plasma blob. Instead of the dying pulse train we have the increasing tidal effects on the plasma components as they follow the natural motion to the evh. One interesting thing to note is the energy per unit mass is a constant of the motion as shown over the three trajectory for a=0, .5, 1. a being the rotation parameter of a spinning black hole. a=.5 = .5c, and a=1 = c. This shows that all three paths are inertial. No other forces acting upon the motion. Since the spacetime is a vacuum solution the only effect changing the trajectory is the 'frame dragging' for the .5 and 1. The modification of the two paths due to frame dragging effect is very small. A very small angular velocity with 0 angular momentum for an object being frame dragged.
     
    Last edited: Nov 3, 2015
  15. The God Valued Senior Member

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    The point is regarding travel of charged particle inside outer EH, frame dragging apart. If it is charged and electric field is envisaged only at outer EH as Per Prof Hamilton response, then travel till singularity is mostly academic, it appears to be highly mathematical but least realistic that the matter leaves rotational energy, charge and even gravitational energy at EH only...the inside of EH has become some kind of 'sanctum sanctorum', leave everything at EH and then enter. Fine, spacetime inside EH is falling at c (or higher), it is extremelty curved, but it is nobody's case that the motion of a charged particle cannot be defined under such circumstances. Moreover inside inner EH (Cauchy Horizon) the time gets back to time like from spacelike aspect between outer EH and inner EH.
     
  16. The God Valued Senior Member

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    What is this?

    Anything proposed after 1963 on GR should be more complicated then Kerr Metric ? Yeah ??

    Leave it, for you finding the volume of a sphere with radius given is complicated so obviously Kerr Metric maths is completely ruled out for you in this life...
     
  17. paddoboy Valued Senior Member

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    Not much more needs to be said here now as I'm sure most here agree that the contentious issues [if they genuinely existed at all] are done and dusted at least in the eyes of most.

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  18. paddoboy Valued Senior Member

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    Yeah certainly just as I said and once again re-enforced by Professor Hamilton......
    http://jila.colorado.edu/~ajsh/insidebh/rn.html
    the Reissner-Norström geometry — was discovered within a few years of Einstein's development of general relativity, it took until 1963 before Roy Kerr3 discovered the geometry of a rotating black hole. After that, Newman et al. (1965)4 quickly generalized Kerr's solution to a black hole that has both charge and spin. The no-hair theorem implies that the Kerr-Newman geometry constitutes the most general description of an isolated black hole outside its horizon.

    As might be imagined from the long time it took to discover black hole solutions with spin, the Kerr-Newman geometry is technically much more complicated than the comparatively simple Reissner-Nordström geometry. It is for this reason that (as of 2009) I have yet to implement rotating black holes in the Black Hole Flight Simulator, and instead I have used the Reissner-Nordström geometry as a surrogate for the Kerr geometry in the visualizations on this website. You can be sure that one day I hope to have the opportunity to implement the Kerr-Newman geometry in the BHFS, but it will not be easy, and it will take time.
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    But I suppose that the good Professor is unaware of any all knowing omnipotent god like creatures such as your self.

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    [tic mode on obviously]
     
    Last edited: Nov 7, 2015
  19. James R Just this guy, you know? Staff Member

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    The God:

    My opinion is that you should stop your petty stalking of paddoboy across the forum. It makes you look a bit needy and pathetic.
     
  20. The God Valued Senior Member

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    I am not stalking Paddoboy, and neither I am interested in him..

    Probably you are so on and off...that you miss the discussion...Most of the time Paddoboy makes incorrect assertions, all copied from popular science and spreads false information.

    Yes, It makes me look helpless and pathetic, because Paddoboy is an extremal liar, he changes his stand and he never admits his errors. What do you do if you are encountered with a person like him ? Keep silence, thats what you are doing, your silence and letting inaccuracies perpetuate in science forum is causing this..

    Why Schmelzer has to call him 'uneducable' ? Why Q-reeus called him 'shit picker' " ? and why many others call him crankpot ? Why I had to give evidence of his lies ? Don't you realise that? Simply because the man is pathetic liar and dishonest troll.

    I am challenging you, find out a single inaccuracy in my argument with Paddoboy, I will apologise...

    I am sorry James R, your conclusion is misplaced and you are conveying wrong message, you can only push likes of farsight, well wisher...and you will never openly tell anything to Paddoboy. Why ?
     
    Last edited: Nov 16, 2015
  21. paddoboy Valued Senior Member

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    Except the links and references I have given, and the professional replies from tashja, all support what I have said.
    And all you have mentioned are shall we say independent, alternative hypothesis pushers, that I have crossed swords.
    I could if you like sink to your cesspool depths and list all the reputable posters who have similar opinions of you.

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    No you wont...When the links from Professor Hamilton and others are raised, you will use the old chestnut that most alternative pushers use, about pop science or the other one you are fond of in wanting me to explain in my own words....Both cop outs.
     
  22. paddoboy Valued Senior Member

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    The two points that the god has continually denied and which I have supplied reputable links supporting are
    [1] A charged BH [although a rarity] will be negated as per the following links.

     
    Last edited: Nov 16, 2015
  23. paddoboy Valued Senior Member

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    deleted.
     

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