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Black holes and an argument I'm in

  1. May 21, 2012 #1
    Ok so I am in an argument with my mother about the nature of black holes. She is religious and has classical physics knowledge up to degree level (she has a master's in mechanical engineering) and is very, very stubborn. Ok so she has a theory that physicists have simply arrogantly overlooked the fluid mechanical aspect of galaxies and is adamant that black holes are simply a whirlpool (yes literally just like a whirlpool) and don't have any mass at at all (I know, ****ing ludicrous right?) So how can I prove her wrong? It's frustrating me so, so bad.
     
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  3. May 21, 2012 #2

    Drakkith

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    Ask her what is causing the stars at the center of the galaxy to whip around in their orbits in such a way that is only explainable by having an object of 4 million solar masses packed into a volume with a radius about the size of the orbit of Neptune. Fluid mechanics cannot explain that at all.

    http://en.wikipedia.org/wiki/Sagittarius_A*

    Besides, how likely is it that thousands of people around the world have simply "overlooked" a simple explanation? Exceedingly unlikely.

    Of course if her objections all stem from a religious aspect, then there's probably no arguing, as most people don't listen to reason if they base their opinion it.
     
  4. May 21, 2012 #3
    She thinks it's more likely because her viewpoint of physics is that it's physicists with massive ego's trying desperately to prove an initial hypothesis with layers of other hypothesises to the point where it's so complicated that a normal person (or an extremely clever person) to understand thus likes to believe a much simpler theory as these physicists are deluded by such vastly abstract mathematics to simply overlook something so simple.

    And to stars orbiting at extreme speeds seems normal to her, imagine a whirlpool the size of a galaxy, surely the centre would be rotating extremely quickly too? Well that's her viewpoint anyway. And no it's nothing religious but I thought it might be relevant to show the magnitude of the task I am up to, lol.
     
  5. May 21, 2012 #4

    Nabeshin

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    We could go over all the evidence, theoretical and observational, for black holes being precisely what they are: Objects described by einstein's GR. But honestly, from what I've read, I doubt this will get you anywhere. The kind of person who thinks that they alone, with (practically) no training in modern physics have figured something out that 100 years of physicists have 'arrogantly overlooked' cannot be swayed by such arguments. If you really want, hand her a textbook on GR and tell her to put in the effort to understand it if it makes her so uncomfortable: It's not Nature's job to be simple or understandable with analogies or small sentences.
     
  6. May 21, 2012 #5

    Drakkith

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    Then she doesn't understand a single thing about General Relativity. It has been proven to work and a black hole is simply part of the math that has been shown to work.

    What would cause the whirlpool? The interstellar medium is not dense enough to support a normal whirlpool, let alone sweep stars along with it. Only gravity can do this.
     
  7. May 21, 2012 #6
    Great sounds like a compelling argument, let's see how she replies to this haha
     
  8. May 22, 2012 #7
    If she has degree level physics, she should know that a whirlpool being rotational must have an axis and the resulting motion of the surroundings would be confined to a plane (essentially the accretion disc of a BH). The orbits of the stars discussed are not coplanar.

    The orbits are Keplerian and have high eccentricities, she should know that does not match the velocity profile of a whirlpool.

    Whirlpools are created by coriolis force where material moves into a region of low pressure. Whatever she imagines the material to be, it must be somehow being removed at the centre, for example sucked into ... a black hole.
     
  9. May 22, 2012 #8
    One more question to ask her. Why does she reject the existence of black holes?
     
  10. May 23, 2012 #9
    Another thing you might use is the luminosity of Quasars . There is no way a whirlpool could produce such luminsotiy.The effeciency of acretion given by GM/Rc^2 (about .5 for a balck hole , its .007 for nuclear fusion) is the only thing that can produce such luminosties. Whya re quasars mostly seen in z=2? Becuase balck holes have feasted on the desner matter in the earely universe, theyve now run out of fuel.
     
  11. May 23, 2012 #10

    mfb

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    Simple question: What is the difference between a black hole and her concept of a "whirlpool"?

    A black hole attracts matter, it has an axis of rotation, it actually drags the space around in its vicinity. Plus some additional features, like the possibility to have a charge, and to emit jets.
    If her "whirlpool" does something different (or in a different way), it can be disproven. If not, it is just a different name for a black hole.
     
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