Interesting Article : "Are We All Wrong About Black Holes?"

Discussion in 'Astronomy, Exobiology, & Cosmology' started by dumbest man on earth, Sep 9, 2019.

  1. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    Came across this recently, thought some Members might find it interesting...
    https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/
    " Q&A
    Are We All Wrong About Black Holes?
    Craig Callender worries that the analogy between black holes and thermodynamics has been stretched too far.

    In the early 1970s, people studying general relativity, our modern theory of gravity, noticed rough similarities between the properties of black holes and the laws of thermodynamics. Stephen Hawking proved that the area of a black hole’s event horizon — the surface that marks its boundary — cannot decrease. That sounded suspiciously like the second law of thermodynamics, which says entropy — a measure of disorder — cannot decrease.

    Yet at the time, Hawking and others emphasized that the laws of black holes only looked like thermodynamics on paper; they did not actually relate to thermodynamic concepts like temperature or entropy.
    ...

    What problems do you see with treating a black hole as a thermodynamic system?
    I see basically three. The first problem is: What is a black hole? People often think of black holes as just kind of a dark sphere, like in a Hollywood movie or something; they’re thinking of it like a star that collapsed. But a mathematical black hole, the basis of black hole thermodynamics, is not the material from the star that’s collapsed. That’s all gone into the singularity. The black hole is what’s left.

    The black hole isn’t a solid thing at the center. The system is really the entire space-time.
    Yes, it’s this global notion for which black hole thermodynamics was developed, in which case the system really is the whole space-time.

    Here is another way to think about the worry. Suppose a star collapses and forms an event horizon. But now another star falls past this event horizon and it collapses, so it’s inside the first. You can’t think that each one has its own little horizon that is behaving thermodynamically. It’s only the one horizon.

    Here’s another. The event horizon changes shape depending on what’s about to be thrown into it. It’s clairvoyant. Weird, but there is nothing spooky here so long as we remember that the event horizon is only defined globally. It’s not a locally observable quantity. "
    https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/

    I heartily recommend reading the whole article...
     
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  3. DaveC426913 Valued Senior Member

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    Sorry, so we might be "wrong about black holes" because "people think" they're like Hollywood depicts them?

    Does this article have any content?
     
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  5. paddoboy Valued Senior Member

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    Done! Yes dmoe, quite an interesting article if somewhat not fully supported and slightly sensationalist as well.
    plus I find the following rather a weird conclusion....
    " But a mathematical black hole, the basis of black hole thermodynamics, is not the material from the star that’s collapsed. That’s all gone into the singularity. The black hole is what’s left."

    He seems to be saying and inferring to a singularity of infinite qualities.
    Physicists now days do not accept any singularity defined by any infinite qualities, rather simply a singularity as defined by the failure of GR.


    Here are some more far more factual and interesting information re BHs
    https://www.ligo.caltech.edu/page/gravitational-waves

    https://www.ligo.caltech.edu/news

    https://en.wikipedia.org/wiki/Black_hole_thermodynamics
     
    Last edited: Sep 9, 2019
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  7. paddoboy Valued Senior Member

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    His conclusion... "The black hole isn’t a solid thing at the center. The system is really the entire space-time."
    of course is correct, in that GR tells us that once the Schwarzchild radius is reached and breached, further collapse is compulsory, up to at least the quantum/Planck region where GR breaks down. The BH itself is defined at where the escape velocity equals "c" or what we know as the EH.
     
  8. mathman Valued Senior Member

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    Black holes (if left alone) get smaller in time (Hawking radiation).
     
    paddoboy likes this.
  9. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    I found the article interesting because it is about how : " Craig Callender worries that the analogy between black holes and thermodynamics has been stretched too far.

    But a mathematical black hole, the basis of black hole thermodynamics, is not the material from the star that’s collapsed. That’s all gone into the singularity. The black hole is what’s left.

    The black hole isn’t a solid thing at the center. The system is really the entire space-time.

    Yes, it’s this global notion for which black hole thermodynamics was developed, in which case the system really is the whole space-time." - https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/

    Also, I heartily recommended reading the whole article because : " Craig Callender, a philosopher of science at the University of California, San Diego, argues that the connection between black holes and thermodynamics is less ironclad than assumed. "
     
  10. paddoboy Valued Senior Member

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    Craig is entitled to his opinion as a philosopher. But the facts remain, that while we have no empirical knowledge of what is inside a BH's EH, we can reasonably speculate with GR, which tells us that once the Schwarzchild radius is reached, further collapse is compulsory. At least up to the quantum/Planck realm where GR fails us. On that score physicists today reject any singularity as defined by infinite qualities of spacetime curvature or density. The only singularity accepted is that as defined by the failure of our current models. So that tells us that at or below that quantum level, the mass from whence the BH was formed, will remain, in some as yet unknown state. It does not simply disappear according to latest estimates.
     
  11. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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    I started this Thread for those that might be interested in the article : https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/
    The article is about : " Craig Callender worries that the analogy between black holes and thermodynamics has been stretched too far. / Craig Callender, a philosopher of science at the University of California, San Diego, argues that the connection between black holes and thermodynamics is less ironclad than assumed. " - https://www.quantamagazine.org/craig-callender-are-we-all-wrong-about-black-holes-20190905/

    I heartily recommend reading the whole article.
     
  12. paddoboy Valued Senior Member

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    The whole article read my friend. And yes interesting for its actual lack of content.
     
  13. dumbest man on earth Real Eyes Realize Real Lies Valued Senior Member

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  14. DaveC426913 Valued Senior Member

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  15. paddoboy Valued Senior Member

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    This is also the dmoe!

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