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meep2000
topic
12:59:01 AM Dec 30th 2011
Black Holes do have a magnetic field. Sortof. In any case they have a magnetic charge which is the sum of all the particles that went into it. Yes I am a physics freak at times, I'm sorry, but a mistake like that should be fixed by someone with better writing skills than me.
SeptimusHeap
topic
08:56:45 AM Dec 12th 2011
Can someone establish the validity of the following example after the Justifying Edit, please?
  • And then there's the achingly stupid statement in Doctor Who, in The Impossible Planet in which it is stated that the planet in question is impossible since it's orbiting a black hole and hasn't been sucked in. This is not how gravity works! The planet could EASILY be orbiting the black hole; it would just have to be orbiting outside the event horizon.
    • Actually, this is a case where they Did The Research. Any black hole has a distance from its center, outside the event horizon, called the radius of the "Innermost Stable Circular Orbit". Outside this radius, you can orbit indefinitely. Inside this radius, but outside the event horizon, is a region where an object may only enter a decaying orbit, and will inevitably fall into the black hole in fairly short order. So, it is impossible to have a planet orbiting close to a black hole for a long time.
PaulA
topic
11:54:52 PM Sep 23rd 2010
Conversation in the Main Page. If you can come up with a new entry that is concise and avoids Wiki Schizophrenia, you can put it back.

  • The Doctor Who episode "The Impossible Planet". A planet orbiting a black hole? Why, that's impossible! It would get sucked in! What's especially painful is that the titular planet would appear to be embedded within the hole's accretion disc; it could be fixed with a change in wind direction and a couple of rewritten lines of dialogue, so that the planet manages to continue hovering over the hole, without orbiting as part of (and eventually getting ground up by) the accretion disc, and without being sandblasted out of existence by the wind. And this is a series that was originally conceived as being educational.
    • I thought this might pop up. With the exception of the planet, the black hole itself seems to function as a black hole would. The planet's the trick of the thing, being suspended in place by a species using power and technology more ancient than the man flying the blue box 'round the cosmos to incarcerate ultimate evil. So, the planet's impossible. Is there an...unrealistic planet trope?
      • The planet isn't necessarily unrealistic either. It's perfectly possible for a planet to circle around a black hole without falling in just as well as it can circle around a star and not fall.
      • To further explain, a black hole doesn't have any more or less gravity than the collapsing body that created it, so if there were planets circling a star that became a black hole, those planets would continue to circle said star unaffected until such time as the hole took in enough matter to increase its gravity. The danger of a black hole is that the entire gravitational pull of that star is now collapsed into a single point, so anything getting close gets hit with all of it at once, but you have to be within the original circumference of the collapsing body for that to make much of a difference.
    • I'd like to point out that the episode -is- called "Impossible Planet" and the fact that it was surviving near a Black Hole at all was the core plot of the episode...
      • Yes, but the point of this argument is that it is NOT impossible for a planet to orbit a black hole!
    • I think this has been said on another page: the black hole was clearly growing in size/mass/gravity or whatever, so it was 'impossible' for the planet to orbit the black hole without falling in. It was positioned right in front of it for flip sake!

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