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A Kunundrum!

  1. Apr 26, 2009 #1
    I read recently that magnetism plays an important role in cramming all that matter into a blackhole. But how is it possible that magnetic force could escape a black hole, having an escape velocity higher than the speed of light, therefore an impossibility of matter(or energy) escaping?
     
  2. jcsd
  3. Apr 26, 2009 #2

    Vanadium 50

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    Where exactly?
     
  4. Apr 26, 2009 #3
    http://news.nationalgeographic.com.au/news/2006/06/060621-black-holes.html [Broken]


    /\There and about a million other sites
     
    Last edited by a moderator: May 4, 2017
  5. Apr 26, 2009 #4
    Energy can escape from a black hole (it's called Hawking radiation). Levels of hawking radiation are meant to be so low that it would take longer than the predicted lifetime of the universe for a black hole to evaporate though.

    I see no reason why a black hole couldn't have a magnetic effect though (who knows, black holes may actually be magnetic monopoles :)). Particles can't escape from the black hole, but that's not to say that the black hole couldn't have a magnetic field with the electromagnetic force carried by particles that are created on the edge of the event horizon... black holes are a fairly large mystery still though (I remember one student of physics once telling me that equations regarding black holes are 'you have the equations that calculate what our theories say about black holes... then you add in a huge fudge factor that brings the calculations in line with what we've observed about black holes'... hardly good science there yet :))
     
  6. Apr 26, 2009 #5
    So its the accretion disc having the magnetic tug rather than the actual blackhole. Thanx alot makes alot more sense:D
     
  7. Apr 26, 2009 #6
    Gravity extends beyond the event horizon and so does magnetism. The event horizon is just the distance that light falls back inwards.

    To be honest, I am a bit skeptical of these researchers for saying that it must be magnetism that sucks gas from an orbiting star into the black hole. Gas particles bounce around in all different directions, meaning that a star which is barely in a stable orbit will have lots of gas particles constantly falling out of that stable orbit. Also, the magnetic force has a relatively short range compared to gravity.
     
  8. Apr 27, 2009 #7
    It makes sense to me as a way for the particles of force to exist with a magnetic field extending beyond the event horizon. I'm not saying it is correct, and I think junglebeast makes a better point in being skeptical of the idea and the accretion disk building up from random movements of an orbiting stars matter (Brownian motion, yes?).

    Still, there is no reason why a black hole can't have a magnetic field and there are numerous ways for the force particles to exist and transmit the force, so that doesn't count against the idea.
     
  9. Apr 27, 2009 #8

    Vanadium 50

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    I think that is discussing external magnetic fields. Core collapse black holes should have only a small field.
     
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