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I Need the explaination of The image of formation of black hole

  1. Apr 1, 2007 #1
    I Need the explaination of "The image of formation of black hole"

    Please Explain Me This

    Attached Files:

  2. jcsd
  3. Apr 1, 2007 #2


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    Staff: Mentor

    How about you explain it to us first. What can you tell us about this diagram? What do the x and y axes represent? What is the significance of the event horizon?
  4. Apr 2, 2007 #3
    Sir that is my basic problem.I ve got this image and now i am unable to understand it,Event horizin is considered as the radius of the black hole this is the point i got from the wekipedia site and in this image it is quite difficult to understand where is the collapsing star from where it is looking like the symmetric collapse?and the most confusing thing present here is the representation of the singularity as a wave form.... the co ordinates also hav nt shown here, Can u help me find out its complete discription?
  5. Apr 2, 2007 #4
    It maybe the case that the singularity is not visible to a far-away observer because light is not able to escape the collapsing star. This is essentially what we mean when we say that a black-hole has formed. The singularity is hidden from view by the event horizon, which is the boundary of that spacetime region surrounding the singularity which cannot communicate with the far-away observer.
    do any one help me to discribe it by the above attached picture?
    Last edited: Apr 2, 2007
  6. Apr 2, 2007 #5
  7. Apr 2, 2007 #6


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    Staff: Mentor

    I'll try moving this thread to the General Relativity forum. I think you'll need a specialist to help with your question.
  8. Apr 2, 2007 #7


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    Science Advisor

    The vertical dimension represents time, the horizontal dimension space. If you take a horizontal cross-section of the diagram it shows the position of the surface of the star and of the event horizon at a given time--you can see that the radius of the star steadily shrinks and the radius of the event horizon grows from the point in space and time labeled "O", until the event horizon reaches a fixed radius at the moment the collapsing star is fully inside it. The representation of the singularity as a wavy line is just a visual convention, don't take it literally.
  9. Apr 3, 2007 #8


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    Staff Emeritus
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    Yes, it's a standard space-time diagram, which puts time on the vertical axis. (I'm not quite sure where this convention came from).

    The horizontal axis represents the radial spatial coordinate using a spherical coordinate system (r, theta, phi). To fit the diagram on a 2d page, theta and phi are omitted (the problem is symmetrical in theta and phi anyway).

    The vertical lines are drawn at the instant the body collapses to form a black hole. They represent light cones at that point. They illustrate that the path of light has a constant spatial coordinate, hence the light is "trapped" by the gravity / geometry of the black hole when a certain point in the collapse process is reached.

    Until the object collapses sufficiently, the light is not trapped. The event horizon forms and the light is trapped only when the object is contained within its Schwarzschild radius.
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