Second law of thermodynamics and black holes ?

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Discussion Overview

The discussion centers on the relationship between the second law of thermodynamics and black holes, particularly regarding entropy and the implications of black hole evaporation. Participants explore theoretical frameworks, including Hawking radiation, and question the validity of thermodynamic laws in the context of black holes.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how the second law of thermodynamics applies to black holes, particularly when mass with entropy is absorbed, suggesting it may seem to violate the law.
  • Another participant asserts that the entropy of an isolated system can only increase, implying that any model suggesting otherwise is likely incorrect.
  • There is a discussion about Hawking radiation and its implications for the validity of thermodynamic laws, with one participant questioning whether Hawking radiation has been validated and how it can be observed.
  • Another participant confirms that Hawking radiation has not been observationally verified but suggests it could be validated through observation of emitted radiation from black holes.
  • Concerns are raised about alternative models that might contradict the second law, with a participant suggesting that any such model would likely be flawed in its formulation.

Areas of Agreement / Disagreement

Participants generally disagree on the implications of black holes for the second law of thermodynamics, with some asserting that thermodynamic laws remain valid while others question how they apply in the context of black holes and Hawking radiation.

Contextual Notes

The discussion highlights unresolved questions about the observational validation of Hawking radiation and the theoretical implications of black hole evaporation on entropy and thermodynamic laws.

HossamCFD
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second law of thermodynamics and black holes ?!

I am having a hard time thinking about the perservation of the second law of thermodynamics in black holes. If we throw a mass that have some level of disorder (entropy) into a black hole, it will disappear and that will appear to us as violating the second law of thermodynamics (entropy can only increase or at least remains constant in an adiabatic reversible process). yet some said (I think Hawking was one of them) that when B.H absorbs mass its area will increase and that is an indication that entropy is preserved inside a B.H. I have no problem accepting that, however, what if a B.H evaporates ? does that imply that entropy dicreased in our universe? can the second law of thermodynamics cease to be valid in B.Hs ?
 
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Can the second law of thermodynamics cease to be valid in B.Hs?

Negative.

The entropy of an isolated system can only increase.

If such a mathematical model predicts an affirmative result, then the mathematical model probably has been formulated incorrectly with respect to Thermodynamics and General Relativity.

Theoretically with respect to Hawking radiation all the laws of thermodynamics are valid with all masses down to quantum particles and quantum Planck scales, where these scales themselves become quantum limits due to singularities.
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I see, so you're saying that given that Hawking's radiation are true, the second law of thermodynamics is valid, right ?

I understand that Hawking radiation is one of the few theories that combine quantum mechanics with general relativity, but has it been validated yet ? or even can it be validated ?

one more thing, I am curious to know what are the alternatives to the Hawking hypothesis that contradicts with the second law ?
 
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HossamCFD said:
given that Hawking's radiation are true, the second law of thermodynamics is valid, right?

All the laws of thermodynamics are valid and therefore Hawking radiation is a valid theory based upon that consequence.

HossamCFD said:
has it been validated yet?
Hawking radiation has not been observationally verified.

HossamCFD said:
can it be validated?
Affirmative, by observing the radiation emitted by a Black_Hole or quantum Black_Hole particle.
HossamCFD said:
what are the alternatives to the Hawking hypothesis that contradicts with the second law?
If such a mathematical model predicts an affirmative result, then the mathematical model probably has been formulated incorrectly with respect to Thermodynamics and General Relativity.
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