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Entropy and black holes

  1. Jun 28, 2004 #1
    A blank sheet of paper falling into a black hole would increase the area of the event horizon and the increase in area would be associated with an increase in the entropy of the black hole.If I cut away bits of a heavier sheet to write some sentences,and the cut sheet had the same mass as before, the increase in area of the event horizon would be the same as before,and would not reflect the fact that the sheet carried information.
    I would have to conclude that, in fact, the area of the horizon does
    not say anything about the information that went into a black hole and
    that as far as black holes are concerned, entropy and information are
    not linked.

    Is this sound logic?
     
  2. jcsd
  3. Jun 28, 2004 #2

    russ_watters

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    Staff: Mentor

    No. The "information" talked about with entropy isn't writing on a piece of paper, its much more fundamental: atomic/molecular structure type info.
     
  4. Jun 28, 2004 #3
    basically the imformation that can be found is the atomic bonds before it was belived that once somthing went into a black hole it became the black hole and all bonds were broken in fact there are still bonds between the atoms in a black hole and thats the type of imformation they are talking about
     
  5. Jun 28, 2004 #4
    RUSS WATERS:

    No. The "information" talked about with entropy isn't writing on a piece of paper, its much more fundamental: atomic/molecular structure type info.

    Kurious:

    How does the area of the event horizon relate to this atomic/ molecular structure info?
    I think Beckstein said that one unit of area = one bit of information.
    I could cut the heavier sheet of paper so that it had the same number of bits as
    the lighter sheet.But how would the absorption of the sheets be distinguished by the area of the event horizon of a black hole?
     
  6. Jun 28, 2004 #5
    It doesn't; apparently, it is generally accepted that no info can be obtained outside the event horizon except 3 quantities: mass, angular momentum and charge.

    Kurious; you ask the darndest questions! :rofl:
    What Bekenstein said was that the entropy S of a black hole is a universal multiple of its surface area, A.
    The formula:
    S ={kc*3/4Gh}(A)
    ...(where the first bracket {} contains the usual constants.)

    As a BH radiates into space it will gradually evaporate; Since its surface area A decreases so also will its entropy decrease.

    Creator
     
  7. Jun 29, 2004 #6
    But how would the absorption of the sheets be distinguished by the area of the event horizon of a black hole?
     
  8. Jun 29, 2004 #7
    Be distinguished? Don't know what you are referring to.
    Apparently anything thrown into the BH increases its surface area (of the event horizon) and thus its entropy.
     
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