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B Stupid Beginner Questions about Event Horizons

  1. Dec 26, 2016 #1
    I have searched the threads. Got some great insight but didn't find the answers to some of my questions

    Questions about Event Horizons

    Most of the textbooks and papers I have read no longer picture or talk about Einstein's original concept of a black hole; the Einstein - Rosen bridge. First question: is this universal?

    Many texts say the event horizon is a sphere. Is this universally accepted? Or does it only apply to non rotating black holes?

    Does an EH sphere eliminate the need for an accretion disk since matter can flow into a sphere from every angle?

    Are black holes still considered "infinite singularities"? I ask because a sphere is finite with a measurable volume.

    Does a 3 billion solar mass black hole like M87 have a greater volume than a 10 solar mass black hole?

    Which sides of the sphere do the relativistic jets shoot out of?

    If it isn't a sphere then where are the jets in relation to the accretion discs? Do the jets disrupt the disc?

    All conceptual drawings I have seen leave out one or more components. Is it possible to fit all the components of a black hole theory into a single detailed drawing?

    Thanks ahead of time for your patience.
  2. jcsd
  3. Dec 26, 2016 #2
    There is no "need" for an accretion disc.
    However, event horizon is small. If the infalling matter were in small amounts, most infalling particles would not fall in the black hole because they would pass the vicinity of black hole on hyperbolic or relativistic open orbits - only matter very directly falling towards the hole would enter the event horizon.
    If larger amounts of matter fall in, particles near the black hole on a flyby may collide with other particles flying by black hole in different directions, be slowed down by such collision and caught into orbit around the hole.
    Now, if there is some direction/half-plane in which slightly more matter happens to fall in than from other direction, the matter falling in from that direction would concentrate in an accretion disc. The matter falling in from other directions would be slowed down by colliding with accretion disc and would fall in the hole - only (some of the) matter in the disc would be left over orbiting.
  4. Dec 26, 2016 #3


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    The particles that comprise black hole jets are believed to originate from their accretion disc. The jets themselves emanate from the magnetic poles of a black hole where the magnetic field is weak enough to allow sufficiently energetic particles to escape - much like earth's auroras originate from the magnetic poles of earth. The magnetic poles of earth and black holes are aligned with their spin axis. See http://www.sciencemag.org/news/2014/11/what-powers-black-holes-mighty-jets for discussion
    Last edited: Dec 26, 2016
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