Notices

View Poll Results: Which do you think comes first?

Voters
3. You may not vote on this poll
  • Singularity

    0 0%
  • Event Horizon

    1 33.33%
  • Simultaneous

    1 33.33%
  • Relative to observer

    1 33.33%
Multiple Choice Poll.
Results 1 to 31 of 31
Like Tree3Likes
  • 1 Post By Markus Hanke
  • 1 Post By Markus Hanke
  • 1 Post By MagiMaster

Thread: Which came first the singularty or the event horizon?

  1. #1 Which came first the singularty or the event horizon? 
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Usually I read about the two going together.

    It seems to me , that during the initial gravitational collapse there might be a period of time where the event horizon forms before the formation of a singularity within it.

    For example:
    The density of a BH goes down as the BH grows in volume. I've been told in the past that about ~108 Solar Masses of uncompressed normal liquid water would form an event horizon even if it was evenly distributed over that entire volume.

    If that is correct, than it seems to me as the density of a given region of space goes up, that the event horizon might come first before the formation of a singularity.


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    Since the singularity is thought to be an artifact of our incomplete understanding of such events, I'd say the event horizon forms first (and last).

    It it turns out that it's not just a mathematical artifact, then they'd most likely form at about the same time, but the event horizon would have to form first as there seem to be good reasons a naked singularity wouldn't be possible. (Though that's only what I've heard. I don't remember if anyone actually explained those reasons to me.)


    Reply With Quote  
     

  4. #3  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    If that is correct, than it seems to me as the density of a given region of space goes up, that the event horizon might come first before the formation of a singularity.
    The event horizon is not a physical object, it is simply the boundary beyond which all world lines have a singularity in their future. The event horizon can thus said to be in existence as soon as that condition is fulfilled, which is likely the case at some stage during the gravitational collapse; I am not sure how meaningful it is ( since singularities can't be observed ), but saying that the event horizon forms before the singularity is probably ok. Not that we would expect physical singularities to actually exist, but that's another matter.
    Reply With Quote  
     

  5. #4  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Markus Hanke View Post
    ( since singularities can't be observed )
    Although not the original thread question. This makes me wonder about something.

    Is the asertion of there being a singularity falsifiable?
    (if the singularity can't be observed)
    Reply With Quote  
     

  6. #5  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    I don't think anyone's asserted that a singularity actually exists. Still, while the inside of an event horizon may not be (might never be) directly observable, there's always the possibility that we could work out the details through indirect observations. Even if that doesn't work out, if we have a well supported theory that covers such regions (GR doesn't quite) then we could work out what's likely to be going on by deduction. (Such a deduction wouldn't really count as a hypothesis on its own though.)
    Reply With Quote  
     

  7. #6  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by MagiMaster View Post
    I don't think anyone's asserted that a singularity actually exists.
    If you understand what is refereed to when other people ( see examples bellow ) use the term 'singularity' in reference to a BH, than you understand what is being refereed to here. That is all that is needed for the purposes of this question ( is, singularity in BH falsifiable ).

    For example:
    Quote Originally Posted by Markus Hanke
    The event horizon is not a physical object, it is simply the boundary beyond which all world lines have a singularity in their future.
    Quote Originally Posted by Markus Hanke
    You can't escape because all time-like geodesics inside the event horizon terminate at the singularity.
    - - - - -

    Quote Originally Posted by MagiMaster View Post
    Still, while the inside of an event horizon may not be (might never be) directly observable, there's always the possibility that we could work out the details through indirect observations. Even if that doesn't work out, if we have a well supported theory that covers such regions (GR doesn't quite) then we could work out what's likely to be going on by deduction. (Such a deduction wouldn't really count as a hypothesis on its own though.)
    AFAIK there is no ( even indirect ) observation possible of singularity inside a BH volume ( inside the event horizon ).

    Example;
    Quote Originally Posted by Markus Hanke
    ( since singularities can't be observed )
    @MagiMaster:
    I wasn't asking about consistency with model, or what we can deduce from our models. Many scientists already do that to deduce a singularity ( see above examples of usage ).

    I was asking.
    Is it ( singularity in BH ) falsifiable?

    Singularity is being used here as it is often used in relation to a Black Hole ( BH ). Not intending to debating about the kind of singularity. The term is used here to refer to the same thing it is used by in many references to a BH.
    Last edited by IamIan; December 7th, 2013 at 05:32 AM. Reason: Who Comments are in reply to clarification
    Reply With Quote  
     

  8. #7  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    Is the asertion of there being a singularity falsifiable?
    Is it ( singularity in BH ) falsifiable?
    I think some clarification on this matter is needed.
    When we speak of singularities in relation to black holes, then we are referring to a situation where we employ the laws of GR only, and disregard all quantum effects. GR in itself is a purely classical theory and does not account for anything to do with quantum mechanics, so if we extrapolate a gravitational collapse to its end within the framework of GR, we necessarily get a curvature singularity, i.e. an object with zero volume and infinite density. However, it is crucial to understand that this is merely a simplification, a matter of convenience so to speak, because we currently do not have a consistent model of quantum gravity, and therefore cannot accurately describe what really happens beyond a certain point in time during a gravitational collapse. Thus we often speak of "singularities", but what we actually mean by that is not a point of infinite curvature ( we can be reasonably sure that such a thing doesn't exist ), but rather a region of space-time within which quantum gravitational phenomena can no longer be neglected, i.e. a region of space-time that cannot be described with currently available models of physics. So, if we say "singularity", think of an unspecified "something" with a big fat question mark on it, like a black box - we simply do not know what goes on in there. The term "singularity" is a placeholder for "unknown physics", nothing more; when I said before that world lines end in a singularity, what I actually mean by that is that world lines enter a region of space-time that cannot be described by the known laws of physics - no one knows just what happens to an object that enters such a region. It is a matter of convenience only to use the term singularity.

    As for falsifiability - there is no need for that, since we don't expect singularities ( as in : objects with infinite density ) to actually exist in the first place. It's just that we don't know what is really there; there is much speculation and many guesses, as for example the Fuzzball model. Ultimately a black hole is the highest state of degeneracy of matter, so the question simply becomes - what is that state ?

    AFAIK there is no ( even indirect ) observation possible of singularity inside a BH volume ( inside the event horizon ).
    It is in theory possible to "eliminate" a black hole event horizon by giving it enough angular momentum, i.e. by making it spin very rapidly ( Kerr black hole ). In classical GR this will create a naked singularity, which could in principle be observable. Whether or not this is physically possible or even meaningful is anyone's guess; personally I'd be sceptical.
    IamIan likes this.
    Reply With Quote  
     

  9. #8  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    This is one of those cases that I was talking about before. We're at the point where we know something's there, but we don't know enough to meaningfully ask the right questions to determine what tests would need to be done to observe it, because we don't have a good idea what it is.
    Reply With Quote  
     

  10. #9  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by MagiMaster View Post
    This is one of those cases that I was talking about before. We're at the point where we know something's there, but we don't know enough to meaningfully ask the right questions to determine what tests would need to be done to observe it, because we don't have a good idea what it is.
    Seems like a bit more than that to me.
    It seems like some unfalsifiable claims even if they are consistent with a given model or theory.

    Almost like a variation on Schrodinger's Cat. With the cat in the center of a box you are never able to look inside of. If you can't ever look inside, no claim about the cat can be falsified.

    Quote Originally Posted by Markus Hanke
    Quote Originally Posted by IamIan
    AFAIK there is no ( even indirect ) observation possible of singularity inside a BH volume ( inside the event horizon ).
    It is in theory possible to "eliminate" a black hole event horizon by giving it enough angular momentum, i.e. by making it spin very rapidly ( Kerr black hole ). In classical GR this will create a naked singularity, which could in principle be observable. Whether or not this is physically possible or even meaningful is anyone's guess; personally I'd be sceptical.
    Unless I'm missing something.
    (AFAIK) Even if we observed a naked singularity that doesn't allow a method to falsify the other. Being able to falsify the singularity inside the BH ( inside the event horizon ). Similar to seeing a cat outside the box, would not itself allow you to falsify any claims about a cat inside the box ( that you are never able to look inside of ).

    The only way out that I see, is if there is a way to make observations inside the box ( event horizon ). Otherwise, it still seems like an unfalsifiable claim ( that is consistent with the model ).

    I get what you wrote about it being effectively a big ? , not an actual object. But even claiming the ? inside the box you can't look inside of ( event horizon ) seems like an unfalsifiable claim.
    Reply With Quote  
     

  11. #10  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by IamIan View Post
    Seems like a bit more than that to me.
    It seems like some unfalsifiable claims even if they are consistent with a given model or theory.
    Falsifiability doesn't have to apply to every possible prediction of a theory. Many models make predictions that cannot be tested - because they are non-physical or the theory is being applied outside its domain. These "claims" don't need to be tested because they are not "real".

    But also, I don't think anyone claims there is actually a physical "thing" corresponding to a singularity. So there is nothing to falsify.

    We don't currently have a theory that realistically predicts what occurs inside the event horizon (near the singularity). When we have a theory of quantum gravity, that may change. That may also enable us to test the "whatever it is" that replaces the singularity in the theory.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  12. #11  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    The only way out that I see, is if there is a way to make observations inside the box ( event horizon ). Otherwise, it still seems like an unfalsifiable claim ( that is consistent with the model ).
    Like I said, we don't expect singularities to be physically real anyway, so why bother trying to "falsify" them ? The end stages of a gravitational collapse are outside the domain of applicability of GR.
    However, if you really want to see what's there and what is not, you can always allow yourself to fall into the black hole, and take a look yourself...so in principle at least it is all testable and falsifiable, it's just that you won't get a chance to share your finding with anyone else.
    IamIan likes this.
    Reply With Quote  
     

  13. #12  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by IamIan View Post
    The only way out that I see, is if there is a way to make observations inside the box ( event horizon ). Otherwise, it still seems like an unfalsifiable claim ( that is consistent with the model ).
    Like I said, we don't expect singularities to be physically real anyway, so why bother trying to "falsify" them ? The end stages of a gravitational collapse are outside the domain of applicability of GR.
    However, if you really want to see what's there and what is not, you can always allow yourself to fall into the black hole, and take a look yourself...so in principle at least it is all testable and falsifiable, it's just that you won't get a chance to share your finding with anyone else.
    I like that solution.

    Side Note:
    It was not about falsifying the singularity by itself as a physically real thing. I was specifically referencing and using it as it was used ( even if that usage wasn't for a real physical thing ). It was about the context of how it was and is used in discussions of BH. People have and do still make claims of properties, effects, etc. AFAIK falsifiable and falsifying claims is the bedrock on which all of science is built (that's why to bother).

    Quote Originally Posted by Strange
    Falsifiability doesn't have to apply to every possible prediction of a theory. Many models make predictions that cannot be tested - because they are non-physical or the theory is being applied outside its domain. These "claims" don't need to be tested because they are not "real".

    But also, I don't think anyone claims there is actually a physical "thing" corresponding to a singularity. So there is nothing to falsify.
    If there is nothing to falsify about a prediction, than AFAIK that forces any such prediction to be an unfalsifiable prediction. Which to me would also seem to bring into serious doubt if it is even a scientific prediction in the first place.

    Actually a physical thing or not , has not prevented its usage , or claims being made about it. Such claims should be falsifiable ( if they are scientific claims ). Like the falsifiable solution Markus gave above. I am not using the term any differently than it has already been used ( I'm referencing that previous usage ).
    Reply With Quote  
     

  14. #13  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    I really don't understand what you are trying to say. Once again you seem to have a poor grasp of how science works (or a poor way of expressing yourself).

    Theories are falsified, not specific values produced by those theories.

    To test Newtonian gravity, you don't need to test every possible value of mass and distance; you just test the general relationship - after all, that is what the theory is about: the relationship.

    Newtonian gravity is well-tested - including being shown to be inaccurate ("false") under some conditions. However, there is an exactly equivalent singularity when r=0 (force becomes infinite). No one needs to test that "claim"; it is just an inevitable consequence of the mathematics.

    The existence of singularities in GR is also a mathematical fact. That is not a "claim" that needs to be falsified: it can be proved mathematically.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  15. #14  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    People have and do still make claims of properties, effects, etc.
    I think it is important to understand that these properties pertain to the BH as a whole, and not to the singularity. Trying to endow a singularity with properties is pretty meaningless, since all you can get is infinities.
    Reply With Quote  
     

  16. #15  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Strange View Post
    I really don't understand what you are trying to say. Once again you seem to have a poor grasp of how science works (or a poor way of expressing yourself).
    About Bold
    Tip = Unnecessary and counterproductive to successful communication.

    Quote Originally Posted by Strange View Post
    Theories are falsified, not specific values produced by those theories.

    To test Newtonian gravity, you don't need to test every possible value of mass and distance; you just test the general relationship - after all, that is what the theory is about: the relationship.

    Newtonian gravity is well-tested - including being shown to be inaccurate ("false") under some conditions. However, there is an exactly equivalent singularity when r=0 (force becomes infinite). No one needs to test that "claim"; it is just an inevitable consequence of the mathematics.

    The existence of singularities in GR is also a mathematical fact. That is not a "claim" that needs to be falsified: it can be proved mathematically.
    #1> As for "need to"
    People don't "need to" do allot of things. But 'need' is it's own entirely conversation.

    #2> Let's take a closer look at your own example there.

    Newtonian Gravity produces an inevitable consequence of the mathematics it is based on. That consequence was (as you wrote):
    Quote Originally Posted by Strange
    shown to be inaccurate ("false") under some conditions
    But, being falsifiable it was able to be shown as that. Despite the Newtonian Gravity based mathematics. Even if those things can be 'proven mathematically' , in the Newtonian model.

    We benefited from that falsifiability. No matter what the Newtonian model 'proved mathematically' ( based on it's model ).

    #3> I do not think being a mathematical consequence of some model should exempt a claim from the importance of falsifiability. It didn't for the Newtonian Model, and I don't think GR based claims should be exempt either. Even (especially) if they are a mathematical consequence of that model.

    #4> I see a difference between.
    4A> Singularities existing are consistent with GR. Or even, nothing in GR prevents singularities from existing.
    and your claim of:
    4B> "The existence of singularities in GR is also a mathematical fact."

    - - - - - - - - - - - -

    Quote Originally Posted by Markus Hanke View Post
    I think it is important to understand that these properties pertain to the BH as a whole, and not to the singularity. Trying to endow a singularity with properties is pretty meaningless, since all you can get is infinities.
    Yet people seem to do it anyway.

    As it pertains to the BH as a whole would be exactly the context of usage referenced here for people's use of 'singularity'.

    Note about it's usage as a whole in this thread:
    As was discussed earlier in this thread. It is possible that a BH's event horizon forms prior to the matter within it collapsing into a singularity ( as to describe that which others have already used the term for ). So that which we describe as 'singularity' might not necessarily be present in a BH at every instant in time that there is that BH. Which means there can be conditions of one without the other. Which was also pointed out in your example of 'naked singularities'.
    Reply With Quote  
     

  17. #16  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    So that which we describe as 'singularity' might not necessarily be present in a BH at every instant in time that there is that BH.
    Refer back to post 7 - we don't expect singularities to be physically real at all.
    Reply With Quote  
     

  18. #17  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by IamIan View Post
    So that which we describe as 'singularity' might not necessarily be present in a BH at every instant in time that there is that BH.
    Refer back to post 7 - we don't expect singularities to be physically real at all.
    Sense this keeps coming up (I have no idea why), perhaps it might help if I once again try to address this misconception. Even if I have no idea where people got this idea, or why they keep coming back to it over and over again.

    It might help to only keep the part I emphasized in bold as bold , instead of modifying my quote to add bold to the whole sentence. I corrected your version of my quote so that it correctly matches the way I wrote it , in the above.

    I've tried to explain this misconception 5 times in previous posts, and this time will make 6 times , on this same misconception. Maybe 6th time will be the charm.

    That which you yourself described as a singularity. For the purposes here. When I reference your description of what you were referring to. I am making a pointer to your own reference.

    A = B = C
    A = C

    Think of what you were referring to when you used the term. It isn't anymore complicated than that.

    In a similar way , "The event horizon is not a physical object". Yet we can discuss what is referred to by the reference "event horizon". That is similar here as "singularity" is a reference to describe something. It doesn't have to be a physical something. It is a reference. We could go out in the world and replace this usage of the term singularity with "potato" and the reference would still mean the same thing no matter what label term is used for the reference.

    Normally the benefit of a reference term like 'singularity' as a reference , is that it greatly condenses and simplifies dialogue about that concept that it refers to. One doesn't have to re-describe the concept every single time. One just uses the reference term "singularity" to make the reference. For some reason that normal mechanism has broken down here.

    For example:

    I think it is massively easier for communication and dialogue to just use the term singularity each time as a reference. Not repeating a description like the bellow every single time. Bold part being my point (I've tried to make 6 times now), in your own words.

    Quote Originally Posted by Markus Hanke
    Thus we often speak of "singularities", but what we actually mean by that is not a point of infinite curvature ( we can be reasonably sure that such a thing doesn't exist ), but rather a region of space-time within which quantum gravitational phenomena can no longer be neglected, i.e. a region of space-time that cannot be described with currently available models of physics. So, if we say "singularity", think of an unspecified "something" with a big fat question mark on it, like a black box - we simply do not know what goes on in there. The term "singularity" is a placeholder for "unknown physics", nothing more; when I said before that world lines end in a singularity, what I actually mean by that is that world lines enter a region of space-time that cannot be described by the known laws of physics - no one knows just what happens to an object that enters such a region. It is a matter of convenience only to use the term singularity.
    Reply With Quote  
     

  19. #18  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    What you don't seem to get is that "singularity" is a mathematical term to describe what happens to the equations at that point. It implies that the theory is no longer applicable.

    The event horizon is a "thing" (even if it is not a physical object). A singularity isn't a "thing".
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  20. #19  
    Moderator Moderator Markus Hanke's Avatar
    Join Date
    Nov 2011
    Location
    Ireland
    Posts
    7,302
    Quote Originally Posted by IamIan View Post
    I think it is massively easier for communication and dialogue to just use the term singularity each time as a reference.
    I agree, but one needs to be very clear on what it is that is referenced; that is my whole point. We do not expect to find a physical point-like object with infinite density in the "centre" of a black hole, once quantum effects are accounted for ( which, to be clear again, we cannot yet do ).
    Reply With Quote  
     

  21. #20  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by IamIan View Post
    I think it is massively easier for communication and dialogue to just use the term singularity each time as a reference.
    I agree, but one needs to be very clear on what it is that is referenced; that is my whole point. We do not expect to find a physical point-like object with infinite density in the "centre" of a black hole, once quantum effects are accounted for ( which, to be clear again, we cannot yet do ).
    I agree. That is why I kept trying to make it clear and clarify. I do not recall ever claiming to expect to find such a 'physical point-like object with infinite density'. Yet, for some unknown reason, people kept extrapolating such a thing , despite multiple efforts to clarify/correct the misconception, it persists. I don't understand the mental leap people are making. I'm out of ideas on how else to clarify/correct the misconception.

    - - - - - - - - - - -

    Quote Originally Posted by Strange View Post
    What you don't seem to get is that "singularity" is a mathematical term to describe what happens to the equations at that point. It implies that the theory is no longer applicable.

    The event horizon is a "thing" (even if it is not a physical object). A singularity isn't a "thing".
    You continue to misunderstand.
    After 6 failed attempts to correct this misunderstanding you insist on keeping. I'm out of ideas on how to get through to you. It boils down to, the perception you continue to express about me is incorrect (weather you see it or not).

    I wouldn't (myself) call it a "Mathematical Term". If you prefer to call it a"Mathematical Term" , do what you like. I prefer 'reference'. As it refers to the more detailed conceptual description being described.

    I would not myself call it a "mathematical term", because that term 'singularity' already has it's own usage in mathematics. That mathematical use of the term 'singularity' does not give the specific conceptual description used here for gravity, space-time, curvature, density, etc. The mathematical use of the term 'singularity' is far more generic. 1/x where x=0 is a mathematical singularity. But, that 1/x where x=0 is not the same 'singularity' being described here in terms of physics ( gravity , density, curvature , etc. ).

    But as I wrote, feel free to do so if you like. I prefer to use it in the physics version and more context specific concept as it is being used here instead of that far more generic usage as a 'mathematical term'.
    Reply With Quote  
     

  22. #21  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    Actually, the singularity at the center of a black hole is exactly that kind of singularity: a place where the math gives us a divide by 0 error. Once we have better math (something that doesn't give such an error), we'll probably end up calling it something else. In the mean time, no one is extrapolating anything about the singularity itself (a.k.a. the whatever at the center of a black hole). There's plenty we can work out about what goes on around it though as the math still works there.

    BTW, we keep pointing this kind of thing out because it seems like you still have some misconceptions that are going to prevent you from learning more about this subject. So we'll keep pointing it out until that's cleared up.

    Edit: An example, sort of. The event horizon is not extrapolated from the singularity. It would exist for any object squeezed into a small enough space. For all we know, there might be some exotic form of matter due to some quantum strangeness that can resist those pressures and there might be a solid surface a little ways inside the event horizon. No singularity needed. From outside, we wouldn't be able to tell the difference (as far as I know at least). All that matters from outside the event horizon is that there's a large mass inside (which we can actually measure in a variety of ways).
    Strange likes this.
    Reply With Quote  
     

  23. #22  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Well said.

    And there are various theories (hypotheses, strictly, I suppose) that avoid a singularity at the centre.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  24. #23  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by MagiMaster View Post
    Quote Originally Posted by IamIan
    I prefer to use it in the physics version and more context specific concept as it is being used here instead of that far more generic usage as a 'mathematical term'.
    Actually, the singularity at the center of a black hole is exactly that kind of singularity: a place where the math gives us a divide by 0 error.
    You've misunderstood.

    That kind of 'singularity' as a 'mathematical term' Makes ZERO claim of gravity anything, ZERO physics, ZERO claim of curvature. The 'mathematical singularity' is as I wrote above a far more 'generic' use of the term singularity.

    That 'mathematical singularity' could be about strawberries, Silvester Stallone, LiFePO4 , weather, etc.

    What is being discussed here, is a far more specific use of the term 'singularity'. Using the mathematical far more generic use of the term will NOT specify the actual more specific correct reference being made here in in relation of physics , BHs, etc.

    It's like using the word 'guy' in the very generic sense of men, compared to the far more specific case of 'guy' used in a conversation that makes a far more specific reference to a single specific person. The far more generic use in both cases is sooo generic it does not correctly narrow the reference to the specific reference being made in that context.

    In Physics (how it is being used here) the term singularity is short hand for "Gravitational Singularity" and is a far more specific narrowly defined usage of the term, than the far more generic 'mathematical term' usage. That more narrow/specific physics version is how it is being used in here in the types of discussions in this thread.

    Quote Originally Posted by MagiMaster View Post
    In the mean time, no one is extrapolating anything about the singularity itself (a.k.a. the whatever at the center of a black hole).
    Although it is not the point I was trying to make previously , this claim you make here is incorrect.
    There are many people extrapolating and claiming things about the singularity itself.
    I can give examples if you like.

    Quote Originally Posted by MagiMaster View Post
    BTW, we keep pointing this kind of thing out because it seems like you still have some misconceptions that are going to prevent you from learning more about this subject. So we'll keep pointing it out until that's cleared up.
    Except that isn't what is happening.
    Please point out to me ANYWHERE in this thread I EVER claimed the singularity was an actual physical object, as others keep criticizing me for that which , I HAVE NEVER DONE.

    I 8 times now have made efforts to corrected this false assumption. Yet almost religiously people continue to criticize and point out the same thing. THAT I HAVE NEVER CLAIMED!!!

    Quote Originally Posted by MagiMaster View Post
    Edit: An example, sort of. The event horizon is not extrapolated from the singularity.
    Who ever said it was?

    Quote Originally Posted by MagiMaster View Post
    It would exist for any object squeezed into a small enough space. For all we know, there might be some exotic form of matter due to some quantum strangeness that can resist those pressures and there might be a solid surface a little ways inside the event horizon. No singularity needed.
    Welcome back to what I wrote about in post #1 back on 12-4-13.
    Thanks for repeating the same concept , and coming full circle in 11 days back to where I started with.

    Should I now criticize you 8+ times repeatedly (as others keep doing to me) in post after post (no matter what you write, just keep correcting you for the same thing you never claimed)? With the same broken record of 'singularity is not expected to be a real physical object'. Even though you (like me) never claimed that is was.
    Reply With Quote  
     

  25. #24  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by IamIan View Post
    That kind of 'singularity' as a 'mathematical term' Makes ZERO claim of gravity anything, ZERO physics, ZERO claim of curvature. The 'mathematical singularity' is as I wrote above a far more 'generic' use of the term singularity.
    I'm sorry, but you are wrong. A singularity in the context of "strawberries" (really?) would, presumably, involve dividing by zero. There is a technical definition of singularity in this context (something to do with determinants of tensors, or somesuch) and all it means is that if you try to apply the theory at that point (not always a "point") then you get infinities; e.g. infinite curvature.

    All it means is that we don't know how to model things under those conditions.

    You complain that people misinterpret you. But as everybody seems to misunderstand you in roughly the same way, maybe you need to think about where the problem lies.... Or, as you keep requesting, just drop the subject.
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  26. #25  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    @IamIan, I didn't point out any specific misunderstandings or claim that my example was what your were misunderstanding. It's just an example of one possibility of a black hole without a singularity.

    As for the singularity, what have people extrapolated from it? I don't know of any scientific claims about the singularity itself. (Popular science is something else, but not particularly relevant.) The only thing I can think of off the top of my head is Marcus (IIRC) saying that the singularity would be in the future of any trajectory inside the black hole (paraphrased as I don't remember the exact wording). That is not a property of the singularity though. That's a property of the black hole and would remain true if we replaced the singularity with a tiny, dense ball (or any other shape) instead.
    Reply With Quote  
     

  27. #26  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by MagiMaster View Post
    I don't know of any scientific claims about the singularity itself.
    Just a quick ~2 minute search yielded:
    1. Not observable. (cosmic censorship hypothesis)
    2. A singularity can be observable to the outside universe. If 'naked'. Link
    3. Naked singularities can be used as particle accelerators Link
    4. Physical aspects of a naked singularity explosion Link
    5. Different properties of a Naked Singularity (vs one in a BH ) cause differences in the accretion disk Link
    6. The entropy properties of a singularity Link
    7. causal characterization of singularities Link
    8. the singularity is isotropic for all relevant initial condition Link
    9. etc.


    Far from "no one is extrapolating anything about the singularity itself" there seem to be lots of people extrapolating a variety of things.

    Weather any of them pan out , is yet to be seen. It is also (I think) a bit beyond the scope of this thread.

    - - - - - - -

    Quote Originally Posted by Strange View Post
    I'm sorry, but you are wrong. A singularity in the context of "strawberries" (really?) would, presumably, involve dividing by zero.
    yes , and it is easy.
    1 / x
    where x = kg of strawberries in a given container.
    when x = 0 you are dividing by zero.
    That satisfies the 'mathematical term' generic usage of the term 'singularity'.

    Why pick on strawberries? The point being made is the same.

    The far more generic as a 'mathematical term' usage of 'singularity' can and does apply to other things. Things that are NOT the far more specific 'singularity' reference as it is being used in the context of this thread.

    We are not talking about the technological singularity , we are not talking about 1/x singularity , we are not talking about sin (1/x) singularity, or singularities that come up in the mathematics of economics, etc.

    Here in this thread we are referencing a far more specific 'singularity'.

    Quote Originally Posted by Strange View Post
    You complain that people misinterpret you. But as everybody seems to misunderstand you in roughly the same way, maybe you need to think about where the problem lies.... Or, as you keep requesting, just drop the subject.
    Your extreme over generalization claim of 'everyone' is incorrect. I have no were near this degree of problems of misunderstanding talking to the vast majority of other people. Not in real life, not in other forums, not in the physics classes I've had, etc. So far it has been a very localized phenomenon to a few people on this forum. That is with the recognition that it is not one of my strengths.

    - - - - - - - - - - - - - - -

    I had joined this forum initially , in hopes of exploring and learning more in an interactive format on a more frequent basis than I had previously. I have had some of that. Communication here (with a few) , has been far harder than expected far more often than expected. Despite the frequency of isolated local difficulties and frustrations , the initial goal continues to be fruitful and successful. I have explored. I have learned. A net plus.
    Reply With Quote  
     

  28. #27  
    Forum Radioactive Isotope MagiMaster's Avatar
    Join Date
    Jul 2006
    Posts
    3,440
    I'm pretty sure at least several of the items on your list would apply to non-singular black hole interiors and the people making those claims are not extrapolating anything from the mathematical singularity predicted by GR. (That is, they're predicting things based on a small, dense something, but not literally from a point of infinite density.) I don't have time right now to read over all the links, so I can't say for sure which ones that'd include, but from memory, #1 should not depend on the inside of a black hole containing a mathematical singularity.

    Edit: I'm pretty sure Strange meant everyone on this forum, or at least everyone on this thread.
    Reply With Quote  
     

  29. #28  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Quote Originally Posted by IamIan View Post
    Quote Originally Posted by Strange View Post
    I'm sorry, but you are wrong. A singularity in the context of "strawberries" (really?) would, presumably, involve dividing by zero.
    yes , and it is easy.
    1 / x
    where x = kg of strawberries in a given container.
    when x = 0 you are dividing by zero.
    That satisfies the 'mathematical term' generic usage of the term 'singularity'.
    Exactly. And that mathematical singularity tells you nothing about strawberries - in the same way that the mathematical singularity associated with a black hole tells you nothing about black holes. In both cases, it just reveals an undefined situation.

    Why pick on strawberries?
    Dunno. It was your idea.

    Here in this thread we are referencing a far more specific 'singularity'.
    If this is not a singularity in the strict mathematical sense, then I am confused. You appear (to me) to be flipping between "I just mean the same thing by singularity as everyone else" (i.e. it is an artefact of the mathematics at that point) and saying "but not that".

    And then you get frustrated when we (OK, I) don't understand you.

    Despite the frequency of isolated local difficulties and frustrations , the initial goal continues to be fruitful and successful. I have explored. I have learned. A net plus.
    Good. I'm glad it is worthwhile. From my point of view, it is still interesting to try and work out what you are talking about!
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  30. #29  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by MagiMaster View Post
    I'm pretty sure at least several of the items on your list would apply to non-singular black hole interiors and the people making those claims are not extrapolating anything from the mathematical singularity predicted by GR. (That is, they're predicting things based on a small, dense something, but not literally from a point of infinite density.) I don't have time right now to read over all the links, so I can't say for sure which ones that'd include, but from memory, #1 should not depend on the inside of a black hole containing a mathematical singularity.

    Edit: I'm pretty sure Strange meant everyone on this forum, or at least everyone on this thread.
    There only has to be one for:
    "no one is extrapolating anything about the singularity itself" , to be falsified.

    Anything includes, well, anything.
    No one requires , well , no one.

    One person anywhere/when (extrapolating anything about it) would falsify 'no one'.

    If a far more narrow field was intended, than I misunderstood the scope of the claim of that phrase:
    "no one is extrapolating anything about the singularity itself"

    - - - - - - - - - - - - - - - - - - -

    Quote Originally Posted by Strange View Post
    Despite the frequency of isolated local difficulties and frustrations , the initial goal continues to be fruitful and successful. I have explored. I have learned. A net plus.
    Good. I'm glad it is worthwhile. From my point of view, it is still interesting to try and work out what you are talking about!
    Everybody wins

    Quote Originally Posted by Strange View Post
    Here in this thread we are referencing a far more specific 'singularity'.
    If this is not a singularity in the strict mathematical sense, then I am confused. You appear (to me) to be flipping between "I just mean the same thing by singularity as everyone else" (i.e. it is an artefact of the mathematics at that point) and saying "but not that".

    And then you get frustrated when we (OK, I) don't understand you.
    Not that it isn't a singularity in the strict mathematical sense.
    More precisely it is not 'just' a singularity in the strict mathematical sense.
    It is more specific than the mathematical term (generic) usage.

    The Mathematical Term Usage is generic.
    That Strawberry example is a 'singularity' by the generic 'mathematical term' usage. So would many other singularities be.

    Here we are not referring to any of those other types of 'singularities' (that the generic mathematical usage would include in it's usage of the term).

    Here we are far more specific.
    Here we are for more narrow in what we are referring to by the term 'singularity'.
    Not just any type of singularity , this is far more specific.

    Quote Originally Posted by Markus Hanke
    Thus we often speak of "singularities", but what we actually mean by that is not a point of infinite curvature ( we can be reasonably sure that such a thing doesn't exist ), but rather a region of space-time within which quantum gravitational phenomena can no longer be neglected, i.e. a region of space-time that cannot be described with currently available models of physics. So, if we say "singularity", think of an unspecified "something" with a big fat question mark on it, like a black box - we simply do not know what goes on in there. The term "singularity" is a placeholder for "unknown physics", nothing more; when I said before that world lines end in a singularity, what I actually mean by that is that world lines enter a region of space-time that cannot be described by the known laws of physics - no one knows just what happens to an object that enters such a region. It is a matter of convenience only to use the term singularity.
    This usage here of singularity is not about just any generic mathematical singularity. Not about mathematical singularities that appear in economics, or Chemistry, or Strawberries, or Computer Science, etc.

    This is a far more specific / narrow usage of the term 'singularity' as a reference here.

    And yes, here this more narrow , more specific usage , is how we are using the term 'singularity'. How I have been using it the whole time.
    Reply With Quote  
     

  31. #30  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    Location
    喫茶店
    Posts
    17,036
    Hmmm... OK, we'll leave it there. (Although I would say that usage is more general / broader than the narrow, specific mathematical definition...)
    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  
     

  32. #31  
    Forum Freshman IamIan's Avatar
    Join Date
    Oct 2013
    Posts
    81
    Quote Originally Posted by Strange View Post
    Hmmm... OK, we'll leave it there. (Although I would say that usage is more general / broader than the narrow, specific mathematical definition...)
    I have no issue with agreeing to disagree , if you wish to just leave it at that.

    (Although, I disagree. I think Markus' usage is far more specific , than the wide open , low resolution, generic, mathematical usage --- which could include Markus' usage or millions of other variations not about the concept as Markus describes it at all. )
    Reply With Quote  
     

Similar Threads

  1. Event Horizon
    By supernova13 in forum Science-Fiction and Non-Fiction
    Replies: 0
    Last Post: December 11th, 2012, 02:31 PM
  2. the event horizon
    By Bipasha Ghosh in forum Astronomy & Cosmology
    Replies: 2
    Last Post: October 12th, 2011, 02:03 AM
  3. What would you see looking out from an event horizon?
    By mulliganstew in forum Astronomy & Cosmology
    Replies: 0
    Last Post: April 14th, 2011, 08:18 PM
  4. Event horizon
    By jan-pieterv in forum Physics
    Replies: 11
    Last Post: July 4th, 2010, 12:08 PM
  5. Beyond the event horizon
    By Quantime in forum Physics
    Replies: 5
    Last Post: August 24th, 2008, 06:19 AM
Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •