Translational Motion of Black Hole

Discussion in 'Astronomy, Exobiology, & Cosmology' started by RajeshTrivedi, Jun 6, 2015.

  1. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    ...........The gravity doesn't have to get out of the black hole. General relativity is a local theory, which means that the field at a certain point in spacetime is determined entirely by things going on at places that can communicate with it at speeds less than or equal to c. If a star collapses into a black hole, the gravitational field outside the black hole may be calculated entirely from the properties of the star and its external gravitational field before it becomes a black hole.........


    The above quote (not mine) does express the factual theoretical point. As per my understanding what it implies is that the Gravity of the collapsing star before it becomes a BH (collapses to singularity) manifests itself around the spacetime (outside EH), because once it becomes a BH the communication with outside world (>EH) is not known to us.

    This explanation would have been fantastic if we treat a BH as static object, no translation motion with respect to....?, I really do not know with respect to what, say infinity. But a BH has a translation motion, in the case when BH itself moves, it cannot synchronize with the spacetime outside where the field resides. Synchronization is required for the simple reason that multiple properties are assigned to the field around. Is it not a paradox, one way we are saying that there is a theoretical disjoint on either side of EH, and on the other way we are accepting the synchronized translation movement of the field outside and whatever inside..

    PS :
    1. Fossil Field, Gravity Gravitates, Non Linearity of EFEs, Frozen Star...none appears to me to resolve this.
     
    danshawen likes this.
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Schmelzer Valued Senior Member

    Messages:
    3,604
    You should not forget that you are not obliged to consider the part behind the horizon at all. According to mainstream standard GR, you can choose a time-like coordinate that even for T->oo the horizon is not reached. Everything which happens now according to the notion of contemporaneity defined by this time happens before the horizon is created. Clocks inside the "BH" are, in this coordinate, extremely time-dilated, but this is not a reason to care - once clock time dilation is possible, extrem clock time dilation is possible too.

    If you think that such a time coordinate would have to be an extremely strange and artificial on: First, from GR point of view this would not matter at all, all systems of coordinates are on equal rights. Second, this time coordinate is even the most natural candidate for a preferred time coordinate, namely, harmonic time, with natural Minkowski time as the initial value before the collapse.

    In these coordinates, a moving "BH" behaves like a moving frozen star. It differs from the frozen star of my ether theory because it is not exactly "frozen", with a fixed radius and a fixed surface time dilation, but the radius continues to shrink toward the Schwarzschild radius, and the time dilation continues to increase without limit.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. paddoboy Valued Senior Member

    Messages:
    21,225
    We have a star. It has a gravitational field [warped spacetime]
    It starts collapsing into a BH. It is the mass collapsing, not the gravitational field [warped spacetime]
    eg:
    Our Sun has a Schwarzchild radius of around 2.5kms? If we squeeze the Sun's mass within that radius it becomes a BH, but all the planets orbit as before...no change.
    BHs are no different gravitationally than an ordinary object of equal mass. It's only when an object gets very close that BHs behave differently.
    BHs EH do increase as it swallows more matter. The gravitational field as a result does increase.
    Fossil fields and nonlinearity are legitimate properties of BHs and the spacetime that go to make them up and explain any changes when the BH swallows more mass.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    Schmelzer,

    The OnlyMe reference to Prof quote is taken from an earlier closed thread....This does not fit well with moving BH..

    Moreover extreme clock time dilation can be defined, it can be definitive...but not for when clock is inside EH...There is a mathematical disjoint between the time on either side.

    Some typo here, you are referring to an object as BH even when its radius > Schwarzschild radius.
     
  8. Schmelzer Valued Senior Member

    Messages:
    3,604
    Not mathematical (they can be described using the same global coordinates) but causal.

    To use "clock time dilation" in a meaningful way, you have to define a reasonable system of coordinates, which would define the meaning of a sentence like "there is no clock time dilation" as "g_00(x,t) does not depend on x".

    No typo here, because I have put BH in quotation marks to indicate that this is not really a BH.
     
  9. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    Thats the crux, now re read my OP again and please think how it fits well with present definition of BH, the singularity, the property of EH, the space time around, the spin vis a vis the moving BH.
     
  10. paddoboy Valued Senior Member

    Messages:
    21,225

    A relevant point I should add. From any remote outside FoR, no mass will ever be seen to cross the EH, just infinitely redshifted beyond viewing capabilities, and gradually fading from view.
    This of course once again raises the importance of the legitimacy of all frames of references.
     
  11. paddoboy Valued Senior Member

    Messages:
    21,225

    Please Register or Log in to view the hidden image!

    I read your OP.
    Fossil fields, nonlinearity and the legitimacy of all frames of references, overcomes any and all problems you seem to visualise.
     
  12. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    Please do not look at the OP from the perspective of a "final object" just > EH. I am talking about Physics around prevalent BH.
     
  13. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    So, please do enlighten......making a mere statement is not sufficient.
     
  14. paddoboy Valued Senior Member

    Messages:
    21,225
  15. paddoboy Valued Senior Member

    Messages:
    21,225
    Time literally stops at the EH, but we never get to see it stopped, the same reason we never get to see anything cross the EH.
    Consequently it is a null and void concept to compare any time interval outside the EH with any time interval inside the EH.
     
  16. Q-reeus Valued Senior Member

    Messages:
    2,497
    Self-consistency or not of BH collapse etc. is totally independent of whether viewed from a FOR where said BH is stationary or undergoing e.g. constant rectilinear motion. All that changes, all that could change in latter case, is the usual results of a Lorentz boost - e.g. pancaking of field lines, existence of a gravitomagnetic field, etc. All effects of Lorentz transformations owing to relative motion. Otherwise, you are in effect claiming there is something unique about a BH that demands an absolute FOR. Are you?
     
  17. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    No, I am not. Let us keep this FOR business momentarily out, let us take for example BH at the center of our Galaxy, now our Galaxy is moving, so obviously the BH at center is also moving. The theory is that we really cannot assign any meaningful physical values to BH singularity, we cannot have a temporal link with what is inside EH...so we must assign the values like angular momentum, mass, gravity etc to the field/spacetime outside EH, what it means is that field around which is present in the spacetime outside EH in true sense is responsible for the effect of BH on the objects away from EH, like onlyme referred to Prof that collapsing mass/gravity is assigned to filed outside EH......So far so good, if the BH inside were to be static. But as made clear the BH also moves, so spacetime around also changes spatially, so there is no escape in the conclusion that inside of EH is responsible for the motion of field outside....which violates the present theory, something amiss somewhere, may be in my understanding ?
     
  18. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    Schmelzer,

    Are you saying that time on either side can be related ? Like dt on this side with dT on that side of EH.

    In fact pragmatically there could be a mathematical disjoint depending on the type of coordinates one uses, but there cannot be a causal disjoint...thats my logical opinion. If we conclude that there is no causal disjoint, then BH can keep moving.
     
  19. Q-reeus Valued Senior Member

    Messages:
    2,497
    The matter of causally disconnected interior and exterior 'fossil field' is quite separate to motion of 'BH' as a whole. Such motion is meaningless unless referenced to something else. Once it's accepted a BH or whatever moving past you is no different to saying you are moving past the BH or whatever, it should immediately be obvious we are just talking about Lorentz transformations - which are always relative. If you have some faulty picture of 'a moving BH' 'perturbing the fluid of space', that's a conceptual issue that needs discarding.
     
  20. danshawen Valued Senior Member

    Messages:
    3,942
    That would indeed explain a few things about BH's. What sort of experiments could be done (observational experiments) to confirm the idea that it is the space outside of its EH that continues to exert gravitational attraction? Would it appear to lose any mass at all after its initial collapse? It might explain dark matter if there is an awful lot more effective mass spread out over a larger volume, wouldn't it? Galactic mass distribution would not be as it appears observationally.
     
    Last edited: Jun 6, 2015
    RajeshTrivedi likes this.
  21. RajeshTrivedi Valued Senior Member

    Messages:
    1,366
    Actually I have no picture of a BH.....

    On the serious front, let me re attempt, say the BH is moving with respect to CMBR, its spatial coordinates are changing with respect to CMBR, the spacetime around BH (>EH) spatial coordinates are also changing with respect to CMBR....so at t = o, the spatial coordinates of an element point outside but close to EH is (x1,y1,z1) having all the assigned properties of BH....now at t = t1 this spatial element point is moved to (x2,y2,z2), as per present theory now the entire assigned properties of BH related with field must move to (x2,y2,z2)....How ? What is the mechanism, the field cannot move on its own to a different point, this is only possible if inside of EH is manifesting itself.
     
  22. Schmelzer Valued Senior Member

    Messages:
    3,604
    We can relate them - by choosing a time coordinate and, then, using (explicitly or implicitly) phrases of type "at the same time".

    We can postulate that one particular of these choices defines some true, real absolute time - but this would require to reject GR spacetime ideology and to use another one. If we associate this "true time" with some possible physical content - like, say, the time which defines which of the measurements in Bell-type experiments, that of Alice or that of Bob, happens first, and in some hidden way sends the information about the measurement FTL to the other end - then, in this modified theory, they would be related.

    If one remains in the context of GR, the relation we introduce with phrases like "at the same time" is purely subjective, and cannot have any objective background. What is causally related is defined in GR by the light cones and nothing else. In this understanding, there can be no causal influence from the inside to the outside. In the other direction, it is not much better - most signals from outside are also unable to reach the collapsing body before the singularity is created.

    If, in a quantum theory of gravity, the gravitational field becomes uncertain, the light cone becomes uncertain too, and, therefore, the notion of causality too. This is one part of the problems of quantization of gravity.
     
  23. Q-reeus Valued Senior Member

    Messages:
    2,497
    A third reference such as CMBR changes nothing - it has no effect on the relative motions involving you and BH. You are still thinking it's something like a hole moving through a semiconductor or such. No. There is just an instantaneous Lorentz transformation of whatever local influence the BH has in your patch. One can infer how the overall exterior BH spacetime then transforms, but it's always experienced as a local field transformation that is entirely relative. Whatever one imagines is going on deep in the bowels of a 'BH' is irrelevant to that only the BH exterior spacetime is accessible and Lorentz transforms no different to that of say owing to a planet. Again - 'BH moving' is no more fundamental than 'you moving'. It's all relative, as in Special Relativity.
     

Share This Page