Gravitational waves from black hole merger

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Plazma Inferno!, Feb 10, 2016.

  1. paddoboy Valued Senior Member

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  3. Edont Knoff Registered Senior Member

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    English isn't my mothers tongue, so often I'm close to the actual word, but not quite. Just assume I meant the usually used term, and that I didn't try to make up something new.

    The gravity waves which were emitted in the merger carried energy away. Energy and mass are equivalent (even if not always easy to convert), so the lost energy came from some mass-to-energy convertion and escaped the merging object in form of gravity waves.

    This is well explained in the publications though. The engery loss due to gravity waves has been observed in binary systems of pulsars, even before the gravity waves were detected themselves. The observed loss in those binary systems matched the prediction of energy loss due to gravity waves very well, and was seen as first indication that gravity waves actually exist.

    http://www.astro.cardiff.ac.uk/research/gravity/tutorial/?page=3thehulsetaylor
     
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  5. hansda Valued Senior Member

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    May be you are right. But this is also true that, no mass can escape from inside the EH of a Black Hole. https://en.wikipedia.org/wiki/Event_horizon

     
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  7. billvon Valued Senior Member

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    Unless it evaporates, in which case the event horizon effectively ceases to exist.
     
  8. paddoboy Valued Senior Member

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    Yes, when quantum effects come into play.
     
  9. Edont Knoff Registered Senior Member

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    Everything that we have is a model, frankly, we don't even know what reality really is. There are good models, in the sense that one can make predictions based on them, and that these predictions are very close to observations of reality. And there are bad models, in the sense that their predictions are either faulty or not testable.

    Einsteins space-time model is a very good one. It gave a lot of predictions, and most of those predictions were found to be correct, or at least very close to the observations.

    Still, there are hints that the model has limits. On sub-atomic scales quantum effects come into play, which are not in Einsteins model. Near singularities like inside the black holes, or the big bang (if that happened) the formulas very likely do not give sensible predictions anymore.

    But between those extremes, Einsteins idea of space-time has proven to be a very good one, a very useful one, too.

    I don't think we can ever have "physical reality". All we can have are models of it, but we have an history of improving models, and even the simpler Newtonian model that was used before Einsteins is a good one, unless speeds become very high, or objects traverse regions of changing gravity.

    Many machines are built, using the Newtonian model and work fine, because the model gives good results for mechanic problems that we face on earth surface.

    Knowing the limits of a model is also something important, e.g. to know when you can use Newtons equations, and when you need to use Einsteins, which are more copmplex and more difficult to work with.

    But asking for "physical reality" to wipe all arguments based on these models is not helpful, we don't know the physical reality, we likely cannot ever know it. But our models are very good at a large range of problems and predictions. So we better debate the limits of the models, to find out where they work and where they don't, and how to improve them, instead of just wiping them because they are not "physical reality".
     
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  10. hansda Valued Senior Member

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    I think you are talking about "Hawking Radiation".

    Hawking's Radiation is still theoretical and not yet experimentally proven. LIGO did not detect any Hawking Radiation. Mass loss due Hawking Radiation is not accounted in the LIGO analysis of mass loss.
     
    Last edited: Feb 18, 2016
  11. hansda Valued Senior Member

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    Do you think mass of an object is a model? Do you think mass of a Black Hole is model?


    Though Newton's Laws and Einstein's theories can be considered as model.
     
  12. Edont Knoff Registered Senior Member

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    I think that we don't really know yet what mass is. So yes, in my understanding it is a concept (I wouldn't want to call it a model at this point) to explain observations. So far we cannot explain the masses of the particles - we do not know why they have the masses that they show us. It seems to be arbitrary, almost random.

    I don't understand the higgs boson though, which seems to be involved in "giving" other particles their mass. But since the term "giving" is used here, it seems that mass is not an intrinsic part of a particle, but an effect that makes the particle behave (and influence others) as if it actually has some mass.

    As said above, I don't think we can ever know "physical reality". We observe and we try to find explanations for our observations. Mass is an observation, we don't know if it is something on it's own, or just an effect of something more basic - lately things seem to look like that to me. Also the equivalence of mass and energy, that energy can bend space-time as mass does, seems to say to me, that energy is the "true" thing, and mass is something derived.

    So yes, mass is a model. A model that we use to describe effects, a handy word to label the thing. We don't know if it's real. I suspect there are more basic things, and mass is a derived property.
     
  13. Schmelzer Valued Senior Member

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    Mass is simply a parameter of a model.
     
  14. Edont Knoff Registered Senior Member

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    Thanks. I missed that point. This is a much better way to put it.
     
  15. hansda Valued Senior Member

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    If mass is a model, what is the reality of it? If we do not believe in our observation of the reality, then what should we believe to know the reality?
     
  16. Edont Knoff Registered Senior Member

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    I believe in our observations. But I distinguish between observation and reality. At times we only observe parts of reality. Sometimes we observe the "shadow" of something, and do not know that there is another entity that casts the shadow, so we might mistake the picture of the shadow with the real thing. In case of mass, I think we have the shadow, not the real thing yet, which casts the shadow.

    And there still is the chance that I'm a disembodied brain in tube, floating in a nourishment solution and wired to a simualtion that is my "reality". I guess I'll never have a chance to find that out. I might be a dream of some other entity, which has the ability to create sentient beings in their dream - so there is no reality at all, it's all just imagination.

    Thus I work with models. I don't believe, but I observe. The models allow me to make predictions, good models allow me to make good predictions. This is what I need to plan and "live". It's irrelevant if I live in a simulation or as an illusion, unless the rules change suddenly and the models fail - but then I'll know that reality isn't stable for me, but changin, fleeting, and I must deal with the fact. So far I'm getting along well with the models and the not-knowing if anything is real - I just use the chances that it provides, and make use of the rules, as far as I can understand them. Reality seemed to be stable, or, my memories were adjusted each time the rules were adjusted, and I just can't compare to any "old" state, due to wrong memories.
     
    Last edited: Feb 18, 2016
  17. hansda Valued Senior Member

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    Science is based on observation. Any experimental confirmation is based on observation. Scientific evidence is based on our observation. If we do not believe in our observations, what should we consider as scientific evidence? How should we experimentally verify some theoretical predictions?
     
  18. hansda Valued Senior Member

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    Are you referring to Hawking Radiation? You also can see my post #87.
     
  19. billvon Valued Senior Member

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    Hawking radiation results in the loss of mass that leads to black hole evaporation, yes. (Per current theory.)
    That makes sense. Hawking radiation dominates only in the case of very small black holes, since the power emitted by a black hole via Hawking radiation is proportional to 1/M^2. These were two very large black holes (about 30 solar masses.) A black hole with a single solar mass would emit about 1x10^-28 watts of radiation, an undetectable amount over any significant distance. These black holes would have been emitting 900 times less than that.
     
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  20. hansda Valued Senior Member

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    OK.

    Suppose a black hole with 30 solar mass collides with another black hole of 60 solar mass; how much mass will be lost due gravitational radiation?
     
  21. billvon Valued Senior Member

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    I don't know. Estimates for the recent collision were around 10^60 joules.
     
  22. paddoboy Valued Senior Member

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    Yes.
    And correct that Hawking Radiation has never been detected, particularly with this LIGO experiment.
    It is though a fundamental part of quantum theory and what Hawking proposed is quite reasonable and logical and the reason why most cosmologists accept it and the inevitable evaporation of all BH's, albeit over very large expanses of time.
     
  23. hansda Valued Senior Member

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    At least, can you give some formulations for this mass loss in the collision? Consider m1 and m2 as the masses of two black holes.( The way the mass loss for hawking radiation is around 1/m^2 ). It is said that the mass loss is happening as per GR. Which formulation they used in this calculation? Is there any standard formula for this? I believe some energy loss also would have been due energy transformation into sound and heat energy. Some visible smaller massive bodies like asteroids and comets also could have been formed due to collision of these two giant massive invisible black holes.
     

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