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A Q: Black hole event horizon vs distortion effects

  1. Jan 23, 2017 #1


    I'm having a hard time finding realistic black hole simulations, but I saw one recently (black hole size comparison on youtube) that showed the following 3 black holes (attached).

    I noticed that the larger the black hole, the smaller the "distortion zone" was relative to the radius of the event horizon.

    Was this simulation accurate? I had imagined that the distortion zone relative to the event horizon radius always remained the same before I saw this.

    Thank you!
  2. jcsd
  3. Jan 23, 2017 #2


    Staff: Mentor

    Can you give a link? I can't tell from the image what the simulation is doing.
  4. Jan 23, 2017 #3
    Here is the link to this video:
  5. Jan 23, 2017 #4


    Staff: Mentor

    Is this the video that the images are from? If so, a YouTube post is not a useful source; I need something that describes how the size of the "distortion zone" is being determined.
  6. Jan 24, 2017 #5

    That is why I'm asking this question - there seems to be a lot of spacetime graphs out there or other representations (like this video) that show the idea of a gravity well funneling downwards, but that don't have realistic spacetime curves. This is the classic example:

    So I'm asking specifically about how to determine the spacetime curve, or if somebody can link me to a realistic example of small vs large black hole spacetime curvature.

    To ask my question a different way, please see my diagram below. Which is more realistic, example A, or example B?
  7. Jan 24, 2017 #6


    User Avatar
    Science Advisor
    Gold Member

    I spent a bit of time trying to find any sourcing for the images in that YouTube video, but could not find anything. I checked several reputable sources of imaging for black holes, and could find nothing similar to these images. Without some better reference, I don't see a way to discuss this. Note that actually generating such images accurately is a significant project, so no one here is going to be in a position to answer this question from first principles.
  8. Jan 24, 2017 #7
  9. Jan 24, 2017 #8


    Staff: Mentor

    If you're interested in what the spacetime geometry looks like, none of the diagrams or videos you have linked to will help. They all show space, not spacetime.

    The geometry of spacetime is four-dimensional, so we can't visualize it directly. But spacetime curvature is the same thing as tidal gravity, so if you imagine how tidal gravity acts on freely falling objects, you are imagining spacetime curvature. For example, objects separated radially will diverge due to tidal gravity, so spacetime curvature along the radial dimension (more precisely, along the "time-radial" dimension, since "diverge" means "separation increases with time") is negative; whereas objects separated tangentially will converge due to tidal gravity, so spacetime curvature along the tangential dimensions is positive. (This is for a spherically symmetric massive object.)

    This still shows space, not spacetime.
  10. Jan 24, 2017 #9


    Staff: Mentor

    Still shows space, not spacetime.

    This one is of something completely different from the topic of this thread. (Did you notice the phrase "five-dimensional coalescing black hole solutions"?)

    I'm not so sure, since none of these show spacetime, and none of them explain how the "distortion distance" is calculated.
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