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Why are black holes shaped like hurricanes?

  1. Jun 28, 2012 #1
    If a black hole is a center of unbelievable gravitational force why is it always illustrated as a hurricane? These depictions remind me of a drain in one's bath where the water swirls in from the sides and drops in through the top of the drain. Wouldn't objects be drawn in centrally from all directions? You see I'm assumming that a black hole is actually a core or spherically shaped with equal gravitational forces being emitted throughout -its difficult for me to see it otherwise. If a black hole is actually a hole then the drain image makes sense-but a hole demands an actual rip or break in space---right???
     
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  3. Jun 28, 2012 #2

    HallsofIvy

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    Objects would go directly toward the black hole only if they had NO initial component of velocity that was not directly toward the black hole. And that is true, of course, for almost everything!
     
  4. Jun 28, 2012 #3

    D H

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    Our sun is a spherically shaped object with equal gravitational forces being emitted throughout, and yet the planets and asteroids (1) don't plunge radially into the sun, and (2) are all in more or less the same plane.

    The problem isn't so much why do accretion disks form. That's a consequence of conservation of angular momentum. The problem is why stuff falls into black holes. It's orbiting. Why should it fall in?

    The infall is explainable in that the orbiting stuff is emitting electromagnetic radiation. That loss of energy means it has to fall to a lower orbit, but there's a problem: where does the lost angular momentum go? To solve this you need to look to relativistic magnetohydrodynamics. This loss of angular momentum has been explained to some extent, but there are still big open issues here that are nice material for a PhD thesis or two or more.
     
  5. Jun 29, 2012 #4
    Because it looks cool, and it turns out that it's easy to set up.

    Search for whirlpool in http://www.imdb.com/title/tt0078869/trivia

    Pictures of real black holes have a disc of material falling in and a jet coming out.
     
  6. Jun 29, 2012 #5
    It should be noted what is pictured is infalling radiation and matter being sucked into the black hole. Black Holes are 'black',,,they emit nothing from the interior and reflect no radiation[light] ....and are therefore invisible.....

    Just like you can't see the energy in a hurricane: what you see is clouds, particles, maybe lightning, dirt and particles swirling around......
     
  7. Jun 29, 2012 #6

    phinds

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    It is illustrated that way by people who don't know physics and are looking for a pretty image. It IS the way "feeding" black holes look, but once a black hole has eaten everything in the neighborhood, it just looks like a hole. (it ISN'T a hole, but it looks, and to some extent, acts like one).
     
  8. Jun 30, 2012 #7
    This sounds pretty definite. But aren't black holes more mysterious than this?

    For instance, don't they hide behind event horizons, so that you can't actually see how they look, just as Naty1 says. And what pictures were you referring to, twofish-quant, when you said: "Pictures of real black holes have a disc of material falling in and a jet coming out." Images obtained with telescopes? Or artists impressions of what are assumed to be invisible black holes?

    But the assumed whirlpool-like character referred to in the O.P. may only be a rather unjustified reflection of the observed fact that nearly all astronomical objects rotate and store angular momentum. The reason for this, I think, is simple, and I bang on about it. It is generally assumed that IN THE BEGINNING there was (somewhat mysteriously) a Gravitating Fluid (see the Standard Model of Cosmology --- or Genesis, if you prefer).

    Gravity is a central force that shears fluids. (To see this, think of a fluid disc of test-mass particles following circular orbits around a central mass. Orbital speed is inversely proportional to the square root of individual orbit radii; wheras in a rigid rotating disc, speed is proportional to radius. Such a non-rigid fluid disc, or any cloud of particles gravitating in a non-uniform field, is inevitably sheared by gravity.)

    Sheared fluids are known to form a great variety of rotating structures and substructures. Vortices, hurricanes, whirlpools and whorls are examples.

    One therefore expects asteroids, planets, stars, galaxies and black holes to rotate, since they are all structures ultimately arising from the gravitational condensation of the primeval Gravitating Fluid.

    Depicting invisible black holes as whirlpools may be making an unjustified assumption, but artistic licence is no crime.
     
  9. Jun 30, 2012 #8

    mfb

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    I think you mean "do" here.

    While I think it is possible to see jets, I doubt that there are real images of accretion disks. However, it is possible to measure the velocity & gravitational potential distribution of material in them and infer their profile based on this data.

    Right. It is not just the inflowing material - the black holes usually rotate, too.
     
  10. Jul 1, 2012 #9
     
  11. Jul 1, 2012 #10
    I should have had a question mark behind my "don't they hide behind event horizons".

    In return, may I ask how measurements can be made of accretion discs that cannot be resolved into images? Line broadening, perhaps? What exactly is "this data" you refer to?
     
  12. Jul 1, 2012 #11
    if in fact the hurricane, or bath tub scenario is a good analogy, could the loss of angular momentum be reconciled by the infalling material orbiting faster as it drops down into the black hole...so as while the object is emitting emr and therefore expending energy, its descent is more gradual because of its increasing acceleration or ''throw'' as it falls further ?
     
    Last edited: Jul 1, 2012
  13. Jul 1, 2012 #12

    phinds

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  14. Jul 1, 2012 #13

    mfb

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    Line broadening (velocity) and shift (gravitational potential), right. Usually with iron at ~5 keV. See http://relativity.livingreviews.org/Articles/lrr-2008-9/articlesu6.html [Broken], for example. It has a description and a lot of links to reference articles. And http://www.tiara.sinica.edu.tw/activities/workshop/2006-4/presentation/Reynolds_workshop2006.pdf [Broken] is a presentation about that.


    Lower orbits have a lower angular momentum, even if the objects are moving faster. At least in the non-relativistic region, but I would expect to have this relation everywhere.
     
    Last edited by a moderator: May 6, 2017
  15. Jul 2, 2012 #14
    That is why I used a galaxy to compare to the hurricane the OP mentioned. On the other hand I predict we find that all matter including black holes never stops feeding (as long as there is space), even when it looks like they’re not feeding.
     
  16. Jul 2, 2012 #15

    Drakkith

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    I'm sorry I don't understand what you are saying here. What do you mean by "we find that all matter including black holes never stops feeding"? How is matter in general feeding on anything?
     
  17. Jul 2, 2012 #16

    D H

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    There appears to be a general confusion in this thread. A black hole itself is not depicted as a hurricane. A black hole is just black. It's the stuff circling around the black hole, the accretion disc, that is depicted in this manner. With some degree of artistic license.
     
  18. Jul 2, 2012 #17
    Hopefully I'm not making any mistatements here, but "Feeding" would seem to be another way of expressing what DH just expressed above. The black hole is "gobbling up" matter that falls within it's gravitational range. But it doesn't necessarily happen all at once to the "prey" like "tractor beams" in science fiction movies. Falling into orbit around the black hole matter is pulled inexorably closer and closer. Thus, the spiral. If there is no matter anywhere near the black hole, then it would be invisible, which, I presume, is a "non-feeding" black hole.
     
  19. Jul 2, 2012 #18

    phinds

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    Very good point.
     
  20. Jul 2, 2012 #19

    Drakkith

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    My confusion lies with the posters claim of "all matter" feeds. All matter interacts via gravitation, so if that is what the poster meant then it makes sense.
     
  21. Jul 2, 2012 #20
    A black hole is the ultimate 'roach motel' [a trap for capturing roaches] :

    " You can get in but you can't get out".
     
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