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Thread: Are we living inside a black hole?

  1. #1 Are we living inside a black hole? 
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    I was considering "boundry conditions", in particular the boundry condition referred to as the event horizon of a Black Hole. It is speculated that from within a Black hole there is literally no direction that leads out because space is bent so that all paths stay inside the black hole. This seems to be identical to our experience in attempting to find the edge of the universe. Am I missing something? is there any difference in the boundry condition that is the "edge of our universe" and the boundry conditon that is the event horizon of a black hole. Other than us being on the outside of one and the inside of the other?


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    There have been several scientific proposals for the shape of the universe. Fact is that at this time we simply do not know. Round? Donut? ... Who knows? Many shapes have been proposed.

    The age of the universe is estimated at 14 billion years. Within the maximum speed allowed in our universe.... we can see no further than this (we can see even less). It would be foolish to think that what we happen too see is the whole universe, if it is the only thing we can see and calculate knowing the maximum speed, which is the speed of light. We only have our visible universe to base estimates on.

    What is the likelyhood we happen to be in the centre? The likelyhood is that we are not in the centre of the universe.... So the Universe is therefore much larger then we will ever be able to see.

    It is like a circle with 4 quadrants. If we are in quadrant one, and the other 3 quadrants are beyond 14 billion years light speed... we will never be able to see them.

    So any guess on how big the universe is,.. I would gather... remains a guess....


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    Even if we were near an "edge" could we precieve it? Does the not the boundry condition of our univers make ubserving anything outside it an impossiblity?
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    Quote Originally Posted by Sealeaf View Post
    Even if we were near an "edge" could we precieve it? Does the not the boundry condition of our univers make ubserving anything outside it an impossiblity?
    It is a fundamental WANT-TO-KNOW. Fact is we do not know.

    Our current scientific knowledge does not go that far yet. You wanting to know does not get us any closer.

    Science does not know what the bounderies of this universe are. Observations from the back ground radiation of the universe has had some scientist thinking,... eventually them comming up with bold ideas of multi universes.

    ...

    Only time will tell. Science will provide answers in the end. Though it may not be in our lifetime.

    But that is okay. Accept that. Einstein would be jealous of us common folk,... knowing what we now know to be true.
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    I was wondering if there is a mathmatical description of the boundry condition of a black hole's event horizon and, if we have that, can we determin if it would be similar to the mathmatical discription of the 4 dimensional boundry of our universe.
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  7. #6 If we were. 
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    If i+ fact we were in the center of a black hole, wouldent new planets and matter be getting sucked in close enough for us to see? Just a thought
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    It would imply that the black holes we observe are black holes inside black holes.
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    Would that collapse the first one?
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    ~ Discussions such as this are always interesting yet un-conclusive.. As has been said.. We do not know..
    But that does not stop us wanting to know., and that's as it should be.. The quest for knowledge is the birth place of science..
    We know much of the microwave remnant of 'The Big Bang' We know of it's distance from us.. we know of it's temperature..
    and a little research will reveal all sorts of things that we can say we know.. But that word 'know' can be deceptive.
    The truth is we do not know 'so much' as we have well educated guesswork .. However I can be sure of some things..
    That we exist. That the Universe we can see is very large.. and that it is not all of it. However, It is not inside a black hole. That there might be multi universes and pink unicorns in my garden, or some one else's.. I can not and do not know...
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    Quote Originally Posted by Sealeaf View Post
    I was wondering if there is a mathmatical description of the boundry condition of a black hole's event horizon and, if we have that, can we determin if it would be similar to the mathmatical discription of the 4 dimensional boundry of our universe.
    Space-time in the region of a black hole event horizon is smooth and continuous; you wouldn't observe anything special ( locally ) if you fell through such an event horizon. Any singularities that might mathematically appear at an event horizon can be eliminated by a simple coordinate transformation.
    The same is not true for a hypothetical "boundary" to the universe; space-time there would be discontinuous and not smooth. There isn't really a physically theory in existence which can predict just what such a boundary would look like and behave like, but it would be nothing like the event horizon of a black hole, and the singularities that appear there are physical and cannot be eliminated by coordinate transformations.

    If you were to "step through" a universal boundary, you would quite simply cease to exist. This in itself causes all manner of problems, not even to mention yet the mathematical difficulties this would raise; which is why I find the existence of such a boundary highly unlikely.
    Last edited by Markus Hanke; September 10th, 2013 at 09:06 AM.
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    Also, inside a black hole you can only ever move closer to the centre of the black hole, whether there is a singularity there or not. AFAIK.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
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    Quote Originally Posted by KALSTER View Post
    Also, inside a black hole you can only ever move closer to the centre of the black hole, whether there is a singularity there or not. AFAIK.
    That's true in the sense that all world-lines within the event horizon must eventually end at the singularity; in other words - there is no escape back out from a black hole.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by KALSTER View Post
    Also, inside a black hole you can only ever move closer to the centre of the black hole, whether there is a singularity there or not. AFAIK.
    That's true in the sense that all world-lines within the event horizon must eventually end at the singularity; in other words - there is no escape back out from a black hole.
    Consequently, the universe would work differently to what we experience now if we indeed were inside an event horizon?
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

    "Gullibility kills" - Carl Sagan
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    Quote Originally Posted by KALSTER View Post
    Consequently, the universe would work differently to what we experience now if we indeed were inside an event horizon?
    Being inside an event horizon means that there is a singularity in your future that you cannot escape from ( all world lines eventually end at the singularity ); the observational evidence we have to hand is more consistent with the exact opposite, meaning that there was a singularity in our past ( the Big Bang event ), which we continue to recede from at an accelerating rate. That, and the fact that we do not appear to see any preferred direction of motion in the universe around us, would indicate to me that we are not inside a cosmological black hole.
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    Brassica oleracea Strange's Avatar
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    This question comes up with remarkable frequency. I'm not sure why. It doesn't seem an obvious idea (to me).
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by Strange View Post
    This question comes up with remarkable frequency. I'm not sure why. It doesn't seem an obvious idea (to me).
    I think to alot of us it just seems like there is this similarity to the idea of being 'contained' within the event horizon of a black hole and the way we seem to be 'contained' within the confines of our universe.

    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by KALSTER View Post
    Consequently, the universe would work differently to what we experience now if we indeed were inside an event horizon?
    Being inside an event horizon means that there is a singularity in your future that you cannot escape from ( all world lines eventually end at the singularity ); the observational evidence we have to hand is more consistent with the exact opposite, meaning that there was a singularity in our past ( the Big Bang event ), which we continue to recede from at an accelerating rate. That, and the fact that we do not appear to see any preferred direction of motion in the universe around us, would indicate to me that we are not inside a cosmological black hole.
    Sounds like this suggests something more silmilar to a theoretical 'white hole' spewing time and matter back into existence.
    Everything has its beauty, but not everyone sees it. - confucius
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    Quote Originally Posted by Ascended View Post
    I think to alot of us it just seems like there is this similarity to the idea of being 'contained' within the event horizon of a black hole and the way we seem to be 'contained' within the confines of our universe.
    ...
    Sounds like this suggests something more silmilar to a theoretical 'white hole' spewing time and matter back into existence.
    So we are back to Poplawski's "new universes created by black holes" idea that came up in another thread.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Ascended View Post
    I think to alot of us it just seems like there is this similarity to the idea of being 'contained' within the event horizon of a black hole and the way we seem to be 'contained' within the confines of our universe.
    ...
    Sounds like this suggests something more silmilar to a theoretical 'white hole' spewing time and matter back into existence.
    So we are back to Poplawski's "new universes created by black holes" idea that came up in another thread.
    Err must have missed that one, if you want to put a link to the thread or catch me up that would help as the idea "new universes created by black holes" seems to suggest multiple universes which though interesting I can't quite understand how that would work. I think what seems more apt is trying to identify similarities in our universe and it's creatation to phenomena we can observe from the outside, things like black holes. Perhaps the idea of a black hole being similar in a gravitational way might not be correct, but could we perhaps look from the perspective of seeing the universe having some other force that might take the place of gravity in a black hole. Also perhaps the concept of where energy or matter ultimately ends up after entering a black hole may eventually provide some insight into where the matter that now exists within our universe originally came from.
    Everything has its beauty, but not everyone sees it. - confucius
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    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by Strange View Post
    Are, cheers I see what you mean now
    Everything has its beauty, but not everyone sees it. - confucius
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    I hope we are existing in an Astral Singularity... (black hole). It would make a fractal cosmology very elegant.
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    Quote Originally Posted by KALSTER View Post
    Also, inside a black hole you can only ever move closer to the centre of the black hole, whether there is a singularity there or not. AFAIK.
    If it is a singularity, that means that it is a single point, and the entirety of that point is the center of mass, meaning there would be no net force toward any center, which you are already in.

    So, assuming that fractally speaking, an entire universe could exist within the singularity of another entire universe, there would be no net gravitational forces from the singularity/universe itself.

    Also, to answer the questions of others in regards to the event horizon, and things joining with the singularity... due to time dilation at the event horizon, once the singularity forms, it is cut off from the universe it was created in. Any mass/energy that is a part of the singularity is the only mass that will ever be a part of the singularity. It very neatly matches the theory of the big bang. A star collapses into a singularity, which forms the event horizon... and nothing after that initial creation will ever escape the singularity, or reach the singularity. Once the original creation event happens, no energy can enter or leave the system.

    Meanwhile, with the big bang... it starts as a singularity... space expands outward, and there is a very specific amount of energy that never leaves, and can never be added to.

    I really dig the fractal theory of the universe =3

    (When I first came across the model of the white hole, I thought it was just mathematical wanking... and now it seems to fit so nicely with the theory of the big bang. Man what a lame name... the big bang -_-; )

    ...It seems to suggest a fractal universe where gravity is reversible within singularities in their own fractal reference frame... (expansion of the universe accelerating, gravity is an acceleration...)
    Last edited by Velexia; November 18th, 2013 at 06:14 AM.
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    Quote Originally Posted by Velexia View Post
    If it is a singularity, that means that it is a single point, and the entirety of that point is the center of mass, meaning there would be no net force toward any center, which you are already in.
    I'm not sure what "it" refers to in this sentence. But a black hole is not a singularity; it (the black hole) is defined by its event horizon, which is of finite size. There is, mathematically, a singularity at the center (which becomes the future) of a black hole but this is likely to be an artefact of the fact we don't yet know how to take quantum effects into account.

    Also, in a realistic black hole, which is spinning, the singularity would be a ring rather than a point.


    Also, to answer the questions of others in regards to the event horizon, and things joining with the singularity... due to time dilation at the event horizon, once the singularity forms, it is cut off from the universe it was created in. Any mass/energy that is a part of the singularity is the only mass that will ever be a part of the singularity.
    Not quite. A black hole can increase in mass as matter falls in but it can never communicate anything about the contents through the event horizon.
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    Quote Originally Posted by Strange View Post
    I'm not sure what "it" refers to in this sentence. But a black hole is not a singularity; it (the black hole) is defined by its event horizon, which is of finite size. There is, mathematically, a singularity at the center (which becomes the future) of a black hole but this is likely to be an artefact of the fact we don't yet know how to take quantum effects into account.
    Sorry, when I think of a black hole, I think of the part that has substance... the matter and what became of it (I'm assuming it becomes a singularity). The event horizon is just a phenomena that is created by this mass, but is not really a thing in and of itself. It's a feature of the entire picture, but it is an effect rather than a cause of anything.



    Quote Originally Posted by Strange View Post
    Also, in a realistic black hole, which is spinning, the singularity would be a ring rather than a point.
    That's a fair point. A spinning singularity could very well be a ring and not a point. However, does the same idea still hold true that the empty, center of the ring is the equilibrium point (gravitationally speaking) or does the equilibrium point exist along the ring...? <- That was a really silly question involving a lack of thought. I'm going to replace it with a less silly proposition:

    A singularity, regardless of spin, cannot form a ring. The gravitational forces which create the singularity in the first place would necessarily overpower any minute forces which would cause a ring of any magntitude.


    Also, to answer the questions of others in regards to the event horizon, and things joining with the singularity... due to time dilation at the event horizon, once the singularity forms, it is cut off from the universe it was created in. Any mass/energy that is a part of the singularity is the only mass that will ever be a part of the singularity.
    Quote Originally Posted by Strange View Post
    Not quite. A black hole can increase in mass as matter falls in but it can never communicate anything about the contents through the event horizon.
    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it. (We're speaking from a reference frame of an outside observer here, which we all are and can only be in relation to a black hole). Relative to us, this matter gets so close to the horizon over a length of time that we can no longer see it... and it adds to the mass of the black hole relative to us, and even causes a larger event horizon to be seen from our frame of reference... but the matter never actually passed the original event horizon, and will never come into contact with the singularity, because that would defy relativity (we're assuming it's accurate).
    Last edited by Velexia; November 18th, 2013 at 06:58 AM.
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    Quote Originally Posted by Velexia View Post
    The event horizon is just a phenomena that is created by this mass, but is not really a thing in and of itself. It's a feature of the entire picture, but it is an effect rather than a cause of anything.
    Maybe. But it is also all we can ever know.

    That's a fair point. A spinning singularity could very well be a ring and not a point. However, does the same idea still hold true that the empty, center of the ring is the equilibrium point (gravitationally speaking) or does the equilibrium point exist along the ring...?
    I don't know. And it doesn't really matter as all we can know is the total mass, angular momentum and electric charge. From outside the event horizon, it would appear identical to any other mass of that size.

    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    It does. But I don't have time to argue about it now.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    The event horizon is just a phenomena that is created by this mass, but is not really a thing in and of itself. It's a feature of the entire picture, but it is an effect rather than a cause of anything.
    Maybe. But it is also all we can ever know.

    That's a fair point. A spinning singularity could very well be a ring and not a point. However, does the same idea still hold true that the empty, center of the ring is the equilibrium point (gravitationally speaking) or does the equilibrium point exist along the ring...?
    I don't know. And it doesn't really matter as all we can know is the total mass, angular momentum and electric charge. From outside the event horizon, it would appear identical to any other mass of that size.

    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    It does. But I don't have time to argue about it now.
    It's okay, I know exactly what your argument would be, and I would refute it, and neither of us would agree and we wouldn't get anywhere... so, maybe it's best if we leave it alone =3
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    Quote Originally Posted by Velexia View Post
    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    That is incorrect. What happens is that a far away observer never sees any matter crossing the event horizon, since it would take an infinite amount of coordinate time to reach the horizon. However, that is true only for the far away observer; an observer freely falling into the black hole will reach and cross the event horizon in a finite and well defined amount of proper time. When he reaches the horizon, space-time will look just normal to him - smooth and continuous. There is no matter accumulated and "frozen" at the horizon.

    A singularity, regardless of spin, cannot form a ring.
    That is also incorrect. The ring singularity is a feature of the Kerr metric, which describes space-time in the vicinity of a black hole with angular momentum. It is not possible for the gravitational collapse to result in a point singularity if angular momentum is present in the energy-momentum tensor.

    I know exactly what your argument would be, and I would refute it
    I very much doubt that. In fact, I am surprised at your evident lack of knowledge about these very basic things, given that you claim to have majored in astrophysics.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    That is incorrect. What happens is that a far away observer never sees any matter crossing the event horizon, since it would take an infinite amount of coordinate time to reach the horizon. However, that is true only for the far away observer; an observer freely falling into the black hole will reach and cross the event horizon in a finite and well defined amount of proper time. When he reaches the horizon, space-time will look just normal to him - smooth and continuous. There is no matter accumulated and "frozen" at the horizon.
    I disagree, but I am not going to get into for the reasons stated in my previous post. This was exactly the argument I was expecting to see, and exactly the argument I have no care to debate.

    Quote Originally Posted by Markus Hanke View Post
    A singularity, regardless of spin, cannot form a ring.
    That is also incorrect. The ring singularity is a feature of the Kerr metric, which describes space-time in the vicinity of a black hole with angular momentum. It is not possible for the gravitational collapse to result in a point singularity if angular momentum is present in the energy-momentum tensor.
    I'm a lot more interested in this, can you help me understand it? I've only gone as far as Calculus 3, so I'm a bit out of my league when trying to understand it on my own.

    Quote Originally Posted by Markus Hanke View Post
    I know exactly what your argument would be, and I would refute it
    I very much doubt that. In fact, I am surprised at your evident lack of knowledge about these very basic things, given that you claim to have majored in astrophysics.
    Don't go down this road. I don't need to deal with horseshit.

    Let's talk about ring singularities please =3
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    Quote Originally Posted by Velexia View Post
    I disagree, but I am not going to get into for the reasons stated in my previous post. This was exactly the argument I was expecting to see, and exactly the argument I have no care to debate.
    Hardly surprising, because there is nothing to debate. The proper time for an observer falling from rest at some distance into the centre of a black hole is



    which is finite and well defined ( integration constant C to be determined from boundary conditions, as usual ). Nothing "accumulates" at the event horizon.

    I'm a lot more interested in this, can you help me understand it? I've only gone as far as Calculus 3, so I'm a bit out of my league when trying to understand it on my own.
    Did you not tell us that you majored in astrophysics ? Something is seriously amiss here; if what you told us is the truth you should be intimately familiar with tensor calculus, and hence the fact that the covariant divergence of the energy-momentum tensor vanishes everywhere. This is really just a case of angular momentum conservation - total angular momentum on some hypersurface S about an event A is



    wherein



    Now, since



    we can immediately deduce that



    as well. Since the angular momentum of a point is zero, the gravitational collapse of a body with total angular momentum > 0 therefore cannot result in a point singularity since that would result in a violation of the above conservation law.

    Don't go down this road. I don't need to deal with horseshit.
    Then stop making claims which are obviously untrue.
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    Refer also here for some additional information :

    Ring singularity - Wikipedia, the free encyclopedia
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    I disagree, but I am not going to get into for the reasons stated in my previous post. This was exactly the argument I was expecting to see, and exactly the argument I have no care to debate.
    Hardly surprising, because there is nothing to debate. The proper time for an observer falling from rest at some distance into the centre of a black hole is



    which is finite and well defined ( integration constant C to be determined from boundary conditions, as usual ). Nothing "accumulates" at the event horizon.
    If you ignore the part where I specifically stated that I am only speaking about an external reference frame, since that is the only reference frame we can ever have in relation to a black hole...Sure. That equation describes part of what "happens" from the reference frame of an infalling observer (ignoring the survivability of such a descent regardless of the diameter of the event horizon). However, what I said should not be ignored, so you can take your self righteous bullshit and shove it back up your ass (and that's not in reference to the equations you posted or anything in relation to the black hole in case you are going to attempt to misinterpret that).

    In the meantime you are completely missing something that I find completely obvious, but you don't see me insulting you for missing it.

    I'm a lot more interested in this, can you help me understand it? I've only gone as far as Calculus 3, so I'm a bit out of my league when trying to understand it on my own.
    Quote Originally Posted by Markus Hanke View Post
    Did you not tell us that you majored in astrophysics ? Something is seriously amiss here; if what you told us is the truth you should be intimately familiar with tensor calculus, and hence the fact that the covariant divergence of the energy-momentum tensor vanishes everywhere.
    How are you a moderator, if you can't help but talk to people like this? Seriously? It blows my fucking mind.

    Quote Originally Posted by Markus Hanke View Post
    This is really just a case of angular momentum conservation - total angular momentum on some hypersurface S about an event A is



    wherein



    Now, since



    we can immediately deduce that



    as well. Since the angular momentum of a point is zero, the gravitational collapse of a body with total angular momentum > 0 therefore cannot result in a point singularity since that would result in a violation of the above conservation law.
    I'm going to read this a few times, and probably ask some questions about it, if you can manage to refrain from acting the way you have been. I'm shaking my head in utter disbelief at your choices of words, and attitude.

    Quote Originally Posted by Markus Hanke View Post
    Don't go down this road. I don't need to deal with horseshit.
    Then stop making claims which are obviously untrue.
    That's an opinion.
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    "With a fluid rotating body, its distribution of mass is not spherical (it shows an equatorial bulge), and it has angular momentum. Since a point cannot support rotation or angular momentum in classical physics (general relativity being a classical theory), the minimal shape of the singularity that can support these properties is instead a ring with zero thickness but non-zero radius, and this is referred to as a ring singularity or Kerr singularity."

    This seems to ignore some of the properties of the black hole singularity from the start... Which is the reason I proposed such an outlandish idea in the first place.

    Edit: Such as the forces of gravity which caused the collapse in the first place, overpowering nuclear forces, eletromagnetic forces, etc... everything keeping the matter from collapsing in on itself in the first place.

    I'm not sure I want to touch on infinite curvature and such here... But this could also be a factor?
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    Quote Originally Posted by Velexia View Post
    If you ignore the part where I specifically stated that I am only speaking about an external reference frame, since that is the only reference frame we can ever have in relation to a black hole...Sure.
    What you said is this :

    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    As it stands this is wrong even for an external observer, because he does not see anything accumulating at the event horizon; any in falling matter will appear increasingly redshifted, and will eventually just "fade away". No accumulation is observed.

    That's an opinion.
    Yes it is.
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    Quote Originally Posted by Velexia View Post
    [I disagree, but I am not going to get into for the reasons stated in my previous post. This was exactly the argument I was expecting to see, and exactly the argument I have no care to debate.
    There are plenty of other arguments against this common misconception. But as you know what they are, I know how you will object to them and you know how I will respond, etc. why don't we just skip to the bit where you admit you were wrong?
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    [I disagree, but I am not going to get into for the reasons stated in my previous post. This was exactly the argument I was expecting to see, and exactly the argument I have no care to debate.
    There are plenty of other arguments against this common misconception. But as you know what they are, I know how you will object to them and you know how I will respond, etc. why don't we just skip to the bit where you admit you were wrong?
    I can no more admit I am wrong, than you can admit that you are wrong. I can point out though, that my position, and your position are both valid points in opposing theories. I simply believe that one of those theories is correct, and the rest are not. Maybe there are only two competing theories at this point, but I'm sure there are at least three.
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    Quote Originally Posted by Velexia View Post
    so you can take your self righteous bullshit and shove it back up your ass
    It blows my fucking mind.
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    Quote Originally Posted by Velexia View Post
    ignoring the survivability of such a descent regardless of the diameter of the event horizon
    Completely survivable, for a realistically large black hole.
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    Quote Originally Posted by Velexia View Post
    I can point out though, that my position, and your position are both valid points in opposing theories.
    A position isn't valid if it is physically incorrect. As I explained to you, no observer will ever observe an accumulation of matter at the event horizon.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    If you ignore the part where I specifically stated that I am only speaking about an external reference frame, since that is the only reference frame we can ever have in relation to a black hole...Sure.
    What you said is this :

    That's a somewhat faulty interpretation. The matter acretes (sp <_< ?) around the event horizon, but never actually passes though it.
    As it stands this is wrong even for an external observer, because he does not see anything accumulating at the event horizon; any in falling matter will appear increasingly redshifted, and will eventually just "fade away". No accumulation is observed.
    I did talk about this, actually. As for the accumulation, it is inferred, as it cannot be seen. You're ignoring the obvious to attempt to tear apart my position, and yet... by ignoring the obvious, you are only trying to tear down my position by stating exactly what I was referring to.

    Good job.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    ignoring the survivability of such a descent regardless of the diameter of the event horizon
    Completely survivable, for a realistically large black hole.
    Find me a black hole, a suitably "large" one, that has nothing else around it which would be hazardous to your existence. I mean, not that you really can, since it's a black hole, and we can really only find them by their effects on surrounding matter, but I mean, seriously... You wouldn't find one fitting that description anyway.

    That was my entire reason for ruling suitably large black holes out.

    There is one other point which is, you won't be able to relay anything you discover to anyone observing from a distance, so again, it's moot.

    Edit: We are totally crabwalking straight into the discussion I was trying to avoid... but I kinda like talking to you, so maybe it's not so bad =3
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    Quote Originally Posted by Velexia View Post
    As for the accumulation, it is inferred, as it cannot be seen.
    How is it inferred? It can't be seen and it is not predicted by any theory I know of. What is this "opposing theory" of which you speak?
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    Quote Originally Posted by Velexia View Post
    As for the accumulation, it is inferred, as it cannot be seen.
    It is not inferred either. If no matter ever crosses the event horizon, the black hole would not form in the first place. By the very existence of such a horizon do we infer that a complete gravitational collapse actually took place.
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    Quote Originally Posted by Velexia View Post
    Find me a black hole, a suitably "large" one, that has nothing else around it which would be hazardous to your existence.
    OK. It wouldn't be survivable because of the accretion disk. Fair enough. (I assumed you were speaking of tidal forces, or something, given the context.)
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    Quote Originally Posted by Velexia View Post
    You wouldn't find one fitting that description anyway.
    The lenticular galaxy NGC 1277 has a supermassive black hole with mass of the order of 17 billion solar masses at its centre; it would take you 72.2 hours to fall from rest at the event horizon into the centre of this black hole. Is that large enough ?
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    so you can take your self righteous bullshit and shove it back up your ass
    It blows my fucking mind.
    MODERATOR WARNING : One more such profanity and you will find yourself on an extended vacation. I told you exactly what I thought of your claims, but I didn't find it necessary to use profanity when doing so. This is an issue where you will only receive one warning, so please refrain from that kind of language or face the consequences.
    I knew that was going to result in red text. But how would you react without your red text? I would hope that maybe you'd think about how you've treated me, and maybe act more polite in the future, considering I am pretty much a complete stranger to you. But hey, it's the internet, and people let their egos run wild around here don't they.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    As for the accumulation, it is inferred, as it cannot be seen.
    It is not inferred either. If no matter ever crosses the event horizon, the black hole would not form in the first place. By the very existence of such a horizon do we infer that a complete gravitational collapse actually took place.
    The collapse into a singularity causes the event horizon, which does not exist prior to the event. If you assert that it does exist in some abstract way prior to the event, it certainly does not exist in such a way as to have any of the properties which it has after the event.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    Find me a black hole, a suitably "large" one, that has nothing else around it which would be hazardous to your existence.
    OK. It wouldn't be survivable because of the accretion disk. Fair enough. (I assumed you were speaking of tidal forces, or something, given the context.)
    Well the tidal forces surely come into play for the smaller ones, but since I well know that a large enough black hole has tidal forces at the event horizon which are of little consequence.... Anyway, yeah, moving on =3
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    You wouldn't find one fitting that description anyway.
    The lenticular galaxy NGC 1277 has a supermassive black hole with mass of the order of 17 billion solar masses at its centre; it would take you 72.2 hours to fall from rest at the event horizon into the centre of this black hole. Is that large enough ?
    Doesn't matter, regardless, but yeah that should be large enough to make the tidal forces negligible.
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    Quote Originally Posted by Velexia View Post
    I knew that was going to result in red text. But how would you react without your red text? I would hope that maybe you'd think about how you've treated me, and maybe act more polite in the future, considering I am pretty much a complete stranger to you. But hey, it's the internet, and people let their egos run wild around here don't they.
    How did I treat you, exactly ? You made claims which aren't in accord with basic astrophysics, while at the same time saying that this is the area you majored in - an obvious contradiction. I pointed that out to you. What would you have done in my stead ? I did not call you names, or used profanity, or insulted you. If you feel I was impolite, then I apologise, though I don't know where the impoliteness is in stating the obvious. If you have genuine questions, then post them and we will do our best to provide an answer...if you just make claims which aren't in accord with currently understood physics, then I will call you on those.
    John Galt likes this.
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    Quote Originally Posted by Velexia View Post
    The collapse into a singularity causes the event horizon, which does not exist prior to the event. If you assert that it does exist in some abstract way prior to the event, it certainly does not exist in such a way as to have any of the properties which it has after the event.
    The existence of the event horizon is independent of the existence of the singularity (other than the fact they are both the result of the same theory).

    If the total mass of the black hole were evenly spread out within the volume, concentrated in something the size of a grapefruit, or compressed to an actual singularity (if such a thing is possible) it would make no difference to the event horizon or the universe outside. This must be the case because of the "no hair" theorem.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    The collapse into a singularity causes the event horizon, which does not exist prior to the event. If you assert that it does exist in some abstract way prior to the event, it certainly does not exist in such a way as to have any of the properties which it has after the event.
    The existence of the event horizon is independent of the existence of the singularity (other than the fact they are both the result of the same theory).

    If the total mass of the black hole were evenly spread out within the volume, concentrated in something the size of a grapefruit, or compressed to an actual singularity (if such a thing is possible) it would make no difference to the event horizon or the universe outside. This must be the case because of the "no hair" theorem.
    The event horizon only exists when a suitable amount of mass exists within a specific diameter... thus before the star collapses into that diameter, the event horizon does not exist, and if I am interpreting the equation which predicted the existence of black holes correctly, once it has gotten to this point it will necessarily collapse all the way into a singularity. Nothing has passed through any event horizon.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    I knew that was going to result in red text. But how would you react without your red text? I would hope that maybe you'd think about how you've treated me, and maybe act more polite in the future, considering I am pretty much a complete stranger to you. But hey, it's the internet, and people let their egos run wild around here don't they.
    How did I treat you, exactly ? You made claims which aren't in accord with basic astrophysics, while at the same time saying that this is the area you majored in - an obvious contradiction. I pointed that out to you. What would you have done in my stead ? I did not call you names, or used profanity, or insulted you. If you feel I was impolite, then I apologise, though I don't know where the impoliteness is in stating the obvious. If you have genuine questions, then post them and we will do our best to provide an answer...if you just make claims which aren't in accord with currently understood physics, then I will call you on those.
    You attacked me, not my arguments. It's really that simple. I will not abide such rude behavior from anyone.
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    Quote Originally Posted by Velexia View Post
    The event horizon only exists when a suitable amount of mass exists within a specific diameter... thus before the star collapses into that diameter, the event horizon does not exist, and if I am interpreting the equation which predicted the existence of black holes correctly, once it has gotten to this point it will necessarily collapse all the way into a singularity.
    The event horizon exists as soon as sufficient mass is within the Schwarzschild radius. So it seems you are now saying that the singularity forms after the event horizon? Seems reasonable to me. (If there is a singularity.)

    Nothing has passed through any event horizon.
    My understanding is that in a supernova collapse, the event horizon forms at the center (where the density is highest) and then accelerates outward to encompass more material (perhaps faster than the material could fall in - but I don't understand much about this process).

    But there is, of course, nothing to stop more material falling through the event horizon and making it grow.
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    Quote Originally Posted by Velexia View Post
    You attacked me, not my arguments. It's really that simple. I will not abide such rude behavior from anyone.
    As far as I can tell, you resorted to obscenities in response to: "Hardly surprising, because there is nothing to debate" and "Did you not tell us that you majored in astrophysics?" Neither seems to be an attack.

    The reaction seemed a little over the top for a couple of harmless comments. <shrug> I guess some people are more sensitive than others.
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    Quote Originally Posted by Velexia View Post
    You attacked me, not my arguments. It's really that simple. I will not abide such rude behavior from anyone.
    There was not attack. But regardless, there is a "Report" function underneath all posts - use it if you feel hard done by. Profanities aren't the way to go.
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    I've read that some scientists believe that this could be a potentially viable explanation for how the universe began. I understand it from a theoretical view, but I thought that a black hole could never support life. (?) So, as interesting as the idea sounds, I don't completely follow. :/
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    The event horizon only exists when a suitable amount of mass exists within a specific diameter... thus before the star collapses into that diameter, the event horizon does not exist, and if I am interpreting the equation which predicted the existence of black holes correctly, once it has gotten to this point it will necessarily collapse all the way into a singularity.
    The event horizon exists as soon as sufficient mass is within the Schwarzschild radius. So it seems you are now saying that the singularity forms after the event horizon? Seems reasonable to me. (If there is a singularity.)
    Makes sense to me. But we have to keep in mind that the event horizon only exists because of the critical density of the mass.

    Nothing has passed through any event horizon.
    Quote Originally Posted by Strange View Post
    My understanding is that in a supernova collapse, the event horizon forms at the center (where the density is highest) and then accelerates outward to encompass more material (perhaps faster than the material could fall in - but I don't understand much about this process).

    But there is, of course, nothing to stop more material falling through the event horizon and making it grow.
    If this is the case with a supernova, which certiantly seems plausible given a star of enough mass, I would assert that the event horizon growing is a relative effect seen by an outside observer, where the matter is creating shells of successively larger event horizons. The matter acreting on the original horizon creates a shell relative to the matter that is father away, and that farther matter creates still another shell and so on, but from the perspective of the original acreted matter, there is only one event horizon, and the mass above it is still falling in toward that singular event horizon.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    You attacked me, not my arguments. It's really that simple. I will not abide such rude behavior from anyone.
    As far as I can tell, you resorted to obscenities in response to: "Hardly surprising, because there is nothing to debate" and "Did you not tell us that you majored in astrophysics?" Neither seems to be an attack.

    The reaction seemed a little over the top for a couple of harmless comments. <shrug> I guess some people are more sensitive than others.
    It was a culmination of continuous attacks upon my character that threw me over the edge. I suppose it can be seen as an overreaction, but to get philosophical for a moment, by my life experiences and genetics it was my only possible reaction, as a way of trying to get the undesired assault on my ego to stop (especially since it really does nothing to further the discussion).

    I did my best to curtail it, but I felt it had to be done, and I'm partially sorry, but really, I just want to discuss without having to defend myself from opinions about my character. Please tear apart my arguments to your hearts desire, and I'll do my best to find the most logical explanation from everything said, and I hope everyone else does the same.
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    Quote Originally Posted by Velexia View Post
    Please tear apart my arguments to your hearts desire, and I'll do my best to find the most logical explanation from everything said, and I hope everyone else does the same.
    I have found myself treading on eggshells when answering your posts because you have reacted so aggressively to people commenting on your ideas. You appear to take that personally and respond with insults.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    Please tear apart my arguments to your hearts desire, and I'll do my best to find the most logical explanation from everything said, and I hope everyone else does the same.
    I have found myself treading on eggshells when answering your posts because you have reacted so aggressively to people commenting on your ideas. You appear to take that personally and respond with insults.
    I challenge you to provide me with a valid example of that. I mean, I don't really want you to, but I think maybe the order of events simply caused a misinterpretation on your part.

    I'd rather keep crabwalking toward time dilation and relative observers. Or go to bed, I could do that too, heh. It's now 9am for me.
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    Quote Originally Posted by Velexia View Post
    I'd rather keep crabwalking toward time dilation and relative observers.
    Isn't that the thing you didn't want to discuss? (Because you are wrong. )
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    I'd rather keep crabwalking toward time dilation and relative observers.
    Isn't that the thing you didn't want to discuss? (Because you are wrong. )
    It is, but we were slowly headed there anyway...

    I got into this on another forum once, and it pretty much involved hundreds of insults thrown at me, and 50 pages... and myself exasperated, trying to describe it in every way I can possibly conceive of from every angle and pretty much no one even bothering to consider any of it (save a few people).
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    Can we all accept that time dilation is a real thing, which is caused by both gravity and velocity? (since these are both empirical facts I hope we can...)
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    Quote Originally Posted by Velexia View Post
    Can we all accept that time dilation is a real thing, which is caused by both gravity and velocity? (since these are both empirical facts I hope we can...)
    Of course.
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    Quote Originally Posted by Velexia View Post
    It is, but we were slowly headed there anyway...
    Maybe you need to make it clear what you are claiming.

    Matter does fall through the event horizon and this happens in a finite time, even for an external observer.

    It is often claimed that an observer would see infalling matter "stuck" at the event horizon forever. This is, fairly obviously, not true even if you ignore red-shift.
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    And we are all hopefully well acquainted with relativity... so

    If I am traveling at a relativistic speed into space... and you are on earth, chilling (at rest)... I will look at my clock, and it will appear normal, and through means that need not be explained because they are irrelevant to the example I can also look at your clock and it appears to move faster than my own.

    Meanwhile, you look at your clock, it it appears normal, and by similar means look at my clock and see that it appears to be slow.

    And we can ignore the fake paradox of both of us moving relative to a third perspective and having a wholly different view of each other's clocks because that example does not have any bearing on black holes.

    Yus?
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    Quote Originally Posted by Velexia View Post
    If I am traveling at a relativistic speed into space... and you are on earth, chilling (at rest)... I will look at my clock, and it will appear normal, and through means that need not be explained because they are irrelevant to the example I can also look at your clock and it appears to move faster than my own.
    Why would it appear to be faster?
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    Alriiiight...

    I think they are called world lines, correct me if I am wrong... and if I draw them in such a way that you are at rest and I progress through space at near the speed of light... I could experience 5 years in the time it takes for you to experience 6. This is time dilation at work. Thus, your clock moves faster, from my perspective. This is an actual effect, not just a peculiarity of visual phenomena. You literally change faster than I do, by being at rest. When we fly an atomic clock around at some velocity, and then compare it to an atomic clock that was at rest, the clock at rest will have recorded more time than the moving clock.
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    To be perfectly clear, actual velocity, relative to the speed of light is what is important, not simply apparent velocity. The reference frame of importance is light's reference frame. So basically, if I am moving closer to the speed of light than you are, I will experience less time than you will.
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    Furthermore, gravity also distorts time. Time moves slower where gravity is stronger. Where gravity is weaker, time moves faster.

    Both time dilation due to gravity and time dilation due to velocity relative to the velocity of light are tested, empirical facts, and if necessary I can use my google fu to link you to the experiments which proved them.
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    Quote Originally Posted by Velexia View Post
    To be perfectly clear, actual velocity, relative to the speed of light is what is important, not simply apparent velocity. The reference frame of importance is light's reference frame. So basically, if I am moving closer to the speed of light than you are, I will experience less time than you will.
    This makes no sense. Light is not a reference frame. How can it be? Moving closer to the speed of light compared to what?

    I thought you said you had studied science? I'm sorry if you think that is some sort of personal attack but I am just confused as to why anyone would say such a thing, unless they have never studied any science at all.
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    This leads to two different ways in which to experience time dilation near a black hole's event horizon, and both of them lead to the same end. The reason that gravity has the same effect as velocity at the even horizon is the very same cause of the event horizon in the first place, at the swartzchild radius. If you, by some miracle, touch the event horizon, in order to stop your descent you must travel at exactly the speed of light. Having mass, this is impossible. So if we ignore gravitational time dilation, and the very reason that the event horizon exists... you would pass through it and head for the singularity.

    However, the closer you get to the event horizon, the slower time moves for you, despite your experience of time appearing normal. Time moves slower near an event horizon, than it would in empty space, or any space further from the event horizon than where you are.

    If you, by some miracle, touch the event horizon, due to gravitational time dilation... Time stops for you, relative to an observer farther from the event horizon (any distance farther). Time also stops when you reach the velocity of light in a similar manner... despite you, still experiencing time as appearing normal.

    However it is only your local time that appears normal. Just as, to a reference frame not infinitesimally close to the event horizon, farther than you are from it by any distance, local time appears normal. When you, ever so close to the event horizon, look at my clock, on earth, say... (ignoring how such a thing is possible since it is irrelevant, you can just observe the changes in the universe "above" you) my clock hands are spinning impossibly fast, and faster with each passing moment, however many you have left (let's pretend this is the biggest black hole ever, and it takes 5 days to go the last leg of the journey). If I watch your clock, it is going slower and slower with each passing moment, so slow I can hardly tell it is moving at all, if I can even tell, at all past a certain point. (Note we are also ignoring the blueshift and redshift of light which would further make these observations difficult).

    So, what this says is, it takes anything outside an event horizon an infinite amount of time to reach the event horizon from an observer chilling farther away.... and an infinite amount of time passes in the outside universe as you fall toward the event horizon.

    And yes, this is backed up by the math. Hell the only reason I am even aware of it is because of the math. Before my experience with the subject matter in depth, I only knew that black holes were cool.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    To be perfectly clear, actual velocity, relative to the speed of light is what is important, not simply apparent velocity. The reference frame of importance is light's reference frame. So basically, if I am moving closer to the speed of light than you are, I will experience less time than you will.
    This makes no sense. Light is not a reference frame. How can it be? Moving closer to the speed of light compared to what?

    I thought you said you had studied science? I'm sorry if you think that is some sort of personal attack but I am just confused as to why anyone would say such a thing, unless they have never studied any science at all.

    Moving closer to the speed of light, relative to actual light speed. Since nothing with mass can go the speed of light, this should make perfect sense to you. There are objects which can have an apparent speed faster than light, but no objects with mass that can actually achieve it. This only makes even more sense when you consider that the speed of light is constant regardless of the speed of any observing frame of reference.

    I take that as a bit of a personal attack, yes, by virtue of ignorance on the subject matter. But ignorance is not a fault, so, no harm done.
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    I've said enough on the matter to thoroughly explain it, and I really needn't say any more, so I won't. You are free to do with the information what you will.

    I'm off to bed. It was a pleasure =3
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    Quote Originally Posted by Velexia View Post
    Moving closer to the speed of light, relative to actual light speed.
    How can you measure speed relative to the speed of light: everybody observes the same speed of light. You can only measure speed relative to another object.

    This only makes even more sense when you consider that the speed of light is constant regardless of the speed of any observing frame of reference.
    If everyone measures the speed of light as c, then how can you measure your speed relative to it?
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    Quote Originally Posted by Velexia View Post
    I've said enough on the matter to thoroughly explain it, and I really needn't say any more, so I won't. You are free to do with the information what you will.
    I will use it to conclude that your claims to have studied astrophysics was a lie.
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    I can't resist. Educate yourself. I really need to sleep.

    Time dilation - Wikipedia, the free encyclopedia
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    Quote Originally Posted by Velexia View Post
    I can't resist. Educate yourself.
    That's great coming from someone as ignorant as you.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by Velexia View Post
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    I'd rather keep crabwalking toward time dilation and relative observers.
    Isn't that the thing you didn't want to discuss? (Because you are wrong. )
    It is, but we were slowly headed there anyway...

    I got into this on another forum once, and it pretty much involved hundreds of insults thrown at me, and 50 pages... and myself exasperated, trying to describe it in every way I can possibly conceive of from every angle and pretty much no one even bothering to consider any of it (save a few people).
    And it hasn't occured to you that problem might be you, rather than the rest of us?

    Oh dear, did I just insult you. Please use the convenient report function. Or preferably, grow a pair.
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    Quote Originally Posted by Velexia View Post
    Can we all accept that time dilation is a real thing, which is caused by both gravity and velocity? (since these are both empirical facts I hope we can...)
    There are two distinct kinds of time dilation - relative time dilation due to relative motion, and gravitational time dilation due to space-time curvature. These are not the same - relative time dilation concerns coordinate time, whereas gravitational time dilation acts on proper time.

    I can also look at your clock and it appears to move faster than my own.
    Incorrect. Ignoring the effects of gravity, you will see the clock on earth also dilated, not speeding up. That is the meaning of symmetry between inertial frames.

    When we fly an atomic clock around at some velocity, and then compare it to an atomic clock that was at rest, the clock at rest will have recorded more time than the moving clock.
    Yes, and that is because these frames were not symmetric - the one that was flying around and then stopped (!) experienced acceleration, whereas the earth bound one did not. Hence the difference in proper times. If you compare spatially separated clocks ( such as a satellite ), you are actually comparing proper time with coordinate time, so relative time dilation needs to be added into this as well.

    Moving closer to the speed of light, relative to actual light speed. Since nothing with mass can go the speed of light, this should make perfect sense to you.
    Light is not a valid frame of reference, as Strange has correctly pointed out. You cannot determine your velocity "relative to light", because the speed of light is the same for all observers.

    If you, by some miracle, touch the event horizon, due to gravitational time dilation... Time stops for you, relative to an observer farther from the event horizon (any distance farther).
    No it doesn't; time progresses as normal for you. Schwarzschild coordinate time is not defined at the event horizon, and your own proper time progresses as normal - you cross the event horizon in a finite proper time, as calculated for you earlier. Remember that it is proper time that your watch in your own frame records, not coordinate time.

    So, what this says is, it takes anything outside an event horizon an infinite amount of time to reach the event horizon from an observer chilling farther away.... and an infinite amount of time passes in the outside universe as you fall toward the event horizon.
    There is no such thing as "time" ( as in : an absolute time ) - there is only coordinate time and proper time. Only coordinate time is infinite here, not proper time. Since it is proper time which measures the length of an observer's world line, all observers agree that an object falls through the event horizon into the centre, even if they cannot visually see this.

    I take that as a bit of a personal attack, yes, by virtue of ignorance on the subject matter. But ignorance is not a fault, so, no harm done.
    Tell me - do you know why ( as in : physical reason ) coordinate time and proper time do not coincide for spatially separated observers in the vicinity of a black hole ?
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    Quote Originally Posted by Strange View Post
    I will use it to conclude that your claims to have studied astrophysics was a lie.
    Yes. It was obvious to me right away. He doesn't even understand the basics of relativity, let alone the finer points.
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    Quote Originally Posted by PhDemon View Post
    As proven in this thread:

    Photons? I am doubtful.

    they are just another halfwit with delusions of competence after reading a few popsci books.

    (And yes that is an insult, a thoroughly deserved one -- feel free to report it).
    That's a halfwit opinion, made up from pure ignorance and desire to be a troll on the internet. I am happy to report you.

    If you even bothered for one half of a (P*#%^&QR(PQ second to look into the books that I mentioned in that post you'd see that they are ORIGINAL #%^*##@% PAPERS ON THE _$P%&)($)$%(%#@ SUBJECT! *#^%###@%#@#@^(_%^_% YOU )#%^&$%^&_&$%& )%&*)%)%)(%&!!!!!!!!!!

    Or in the case of A Stubbornly Persistent Illusion, something Einstein himself wrote in reference to Special and General Relativity. Pardon me while I go drown some puppies and pretend they are you.
    Last edited by Velexia; November 18th, 2013 at 06:45 PM.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by Velexia View Post
    Can we all accept that time dilation is a real thing, which is caused by both gravity and velocity? (since these are both empirical facts I hope we can...)
    There are two distinct kinds of time dilation - relative time dilation due to relative motion, and gravitational time dilation due to space-time curvature. These are not the same - relative time dilation concerns coordinate time, whereas gravitational time dilation acts on proper time.

    I can also look at your clock and it appears to move faster than my own.
    Incorrect. Ignoring the effects of gravity, you will see the clock on earth also dilated, not speeding up. That is the meaning of symmetry between inertial frames.

    When we fly an atomic clock around at some velocity, and then compare it to an atomic clock that was at rest, the clock at rest will have recorded more time than the moving clock.
    Yes, and that is because these frames were not symmetric - the one that was flying around and then stopped (!) experienced acceleration, whereas the earth bound one did not. Hence the difference in proper times. If you compare spatially separated clocks ( such as a satellite ), you are actually comparing proper time with coordinate time, so relative time dilation needs to be added into this as well.

    Moving closer to the speed of light, relative to actual light speed. Since nothing with mass can go the speed of light, this should make perfect sense to you.
    Light is not a valid frame of reference, as Strange has correctly pointed out. You cannot determine your velocity "relative to light", because the speed of light is the same for all observers.

    If you, by some miracle, touch the event horizon, due to gravitational time dilation... Time stops for you, relative to an observer farther from the event horizon (any distance farther).
    No it doesn't; time progresses as normal for you. Schwarzschild coordinate time is not defined at the event horizon, and your own proper time progresses as normal - you cross the event horizon in a finite proper time, as calculated for you earlier. Remember that it is proper time that your watch in your own frame records, not coordinate time.

    So, what this says is, it takes anything outside an event horizon an infinite amount of time to reach the event horizon from an observer chilling farther away.... and an infinite amount of time passes in the outside universe as you fall toward the event horizon.
    There is no such thing as "time" ( as in : an absolute time ) - there is only coordinate time and proper time. Only coordinate time is infinite here, not proper time. Since it is proper time which measures the length of an observer's world line, all observers agree that an object falls through the event horizon into the centre, even if they cannot visually see this.

    I take that as a bit of a personal attack, yes, by virtue of ignorance on the subject matter. But ignorance is not a fault, so, no harm done.
    Tell me - do you know why ( as in : physical reason ) coordinate time and proper time do not coincide for spatially separated observers in the vicinity of a black hole ?
    You've got a lot of disagreements in here based purely on your desire to disagree with me, which is absolutely hilarious, considering that in pretty much every case, they seem to reflect a desire to misread literally everything said here, or simply not read everything that was said. It is most stunningly apparent here: "No it doesn't; time progresses as normal for you."

    Try reading the entire sentence, and get some reading comprehension.

    I bet it feels nice to be on a bandwagon, but it does you no service. I mean, hell the very next words say that the reference frame for your time having stopped is NOT YOUR REFERENCE FRAME.

    You people make me want to devour babies. The level of moronic behavior on a Science thread by Moderators and regulars alike is completely appalling.

    I'm going to try to continue reading this post to see if it has anything of merit to say, at all.
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    Quote Originally Posted by John Galt View Post
    Quote Originally Posted by Velexia View Post
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Velexia View Post
    I'd rather keep crabwalking toward time dilation and relative observers.
    Isn't that the thing you didn't want to discuss? (Because you are wrong. )
    It is, but we were slowly headed there anyway...

    I got into this on another forum once, and it pretty much involved hundreds of insults thrown at me, and 50 pages... and myself exasperated, trying to describe it in every way I can possibly conceive of from every angle and pretty much no one even bothering to consider any of it (save a few people).
    And it hasn't occured to you that problem might be you, rather than the rest of us?

    Oh dear, did I just insult you. Please use the convenient report function. Or preferably, grow a pair.
    Alright, I'll grow a pair.

    GROW THE #@)(%^ UP YOU IGNORANT MORON.

    Is that good enough for you?

    Go commit seppuku for being an idiot on the internet.

    I never really expected much from someone naming themselves "John Galt". Glad to know my intuition was spot on there.
    Last edited by Velexia; November 18th, 2013 at 06:59 PM.
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    Alright Markus Hawke, for your reading pleasure: Twin paradox - Wikipedia, the free encyclopedia

    "This result appears puzzling because each twin sees the other twin as traveling, and so, according to an incorrect naive application of time dilation, each should paradoxically find the other to have aged more slowly."
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    Quote Originally Posted by PhDemon View Post
    ...and that's a full retard meltdown and one more for the ignore list.
    Good, I have no desire to read your stupid bullshit anyway. Willfull ignorance is stupidity, and bullshit is bullshit.
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    See this is why I don't like getting into this subject on the internet. By virtue of the anonymity of the internet, people let the worst sides of themselves out... and the internet is chock full of people like the lot of you, even on a science forum of all places.

    I know time dilation is hard, but FFS, only for someone who is incapable of complex thought.

    This website should be renamed "TheKindergartenScienceForum" where mostly we are just mean to each other, since we don't know how to behave like rational thinking people.
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    I think I'll do something for my sanity, and only respond to intelligent rational people who wish to have a discussion from now on.

    So go throw yourselves a nice self congratulatory troll party, celebrating your willful ignorance and immaturity.
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    Velexia, I really do think you would do well to examine your own role here.

    Markus has built up an excellent reputation on this site by demonstrating, over the course of years, a commendable grasp of general and special relativity and related aspects of cosmology. Other knowledgeable individuals have confirmed this view. Moreover, on the rare occasions he has been in error has been quick to acknowledge that error and even quicker to express thanks to the individual who has corrected him and thereby deepened his knowledge.

    I am an incompetent in matters of GR and SR, but I am an expert in identifying a line of reason, an application of logic and a well structured argument. Markus has delivered these routinely and consistently through several thousand posts. HE has also displayed remarkable patience and objectivity in dismantling faulty arguments.

    On the other hand you have joined the forum and almost from your first post have adopted an arrogant attitude. I am a member of several forums and in each instance I have lurked for a while, figured out the tenor of the place, then eased into participation. I am a stranger in a strange land and tact and caution are not only polite, they are also productive. Now perhaps you did not intend that arrogance, however, several members besides myself clearly saw it. On top of that, you were making assertions that did not match reality. Not a good start.



    Quote Originally Posted by Velexia View Post
    You've got a lot of disagreements in here based purely on your desire to disagree with me, which is absolutely hilarious, considering that in pretty much every case, they seem to reflect a desire to misread literally everything said here, or simply not read everything that was said. It is most stunningly apparent here: "No it doesn't; time progresses as normal for you."

    Try reading the entire sentence, and get some reading comprehension.
    In all of the many posts Markus has made I do not recall a single instance where he has disagreed for the sake of disagreeing. Do you feel you are a better judge of motivations after knowing the man for a few days than I?

    As far as reading comprehension goes the primary responsibility for communicating an idea lies with the writer, not the reader. Do you disagree?

    Alright, I'll grow a pair.

    GROW THE #@)(%^ UP YOU IGNORANT MORON.
    I was aiming more for the notion that you should be less sensitive to negative remarks, real or imagined. I'm sorry I did not make that clear. The error was mine. (You see how this work?)


    I never really expected much from someone naming themselves "John Galt". Glad to know my intuition was spot on there.
    Atlas Shrugged is one of my top five works of fiction. However, I am opposed to almost every aspect of Ayn Rand's philosophy, so your intuition has done you no good there. The selection of the name was for subtle reasons, connected with the forum, that are now history.

    See this is why I don't like getting into this subject on the internet. By virtue of the anonymity of the internet, people let the worst sides of themselves out... and the internet is chock full of people like the lot of you, even on a science forum of all places.

    I know time dilation is hard, but FFS, only for someone who is incapable of complex thought.

    This website should be renamed "TheKindergartenScienceForum" where mostly we are just mean to each other, since we don't know how to behave like rational thinking people.
    You will find many threads and posts where ideas are exchanged in a civil manner, where people are educated and educate, where new ideas are explored and old ones confirmed. You will also find threads where members become irate and frustrated. This is typically because one member will adopt a hostile attitude, or refuse to acknowledge facts, or present weak arguments.

    Which brings us full circle. Have another look at your own behaviour and posting style from the outset. Will you claim you are blameless in this unseemly exchange? I'd be interested to know.
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    Pretty sure I know the source of confusion for people assuming that you can actually pass through an event horizon without an infinite amount of time passing in the universe around you. Having associated gravitational time dilation with acceleration, you've thus forgotten gravity, and focus purely on acceleration, and assume that despite local time and non local time differing, because you are accelerating toward the singularity, given a finite amount of time, you must necessarily pass through the horizon with no complications.

    In part you are correct. In your local reference frame, ignoring all non local reference frames, you simply fall straight in. But you can't simply ignore the non local reference frames, because what is happening out there, outside of your reference frame is real.

    So, give complex thinking a try, and start thinking about both reference frames together, and how they relate to one another.

    Also, remember F=ma. Think about what velocity will have been imparted to you, by the acceleration due to gravity, at the event horizon. You see, whether through velocity, or acceleration, there is no escaping time dilation.

    So, rather than assuming that I am just some ignorant fool, and a liar... why not try to think. What you find may surprise you.
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    Quote Originally Posted by John Galt View Post
    Velexia, I really do think you would do well to examine your own role here.

    Markus has built up an excellent reputation on this site by demonstrating, over the course of years, a commendable grasp of general and special relativity and related aspects of cosmology. Other knowledgeable individuals have confirmed this view. Moreover, on the rare occasions he has been in error has been quick to acknowledge that error and even quicker to express thanks to the individual who has corrected him and thereby deepened his knowledge.

    I am an incompetent in matters of GR and SR, but I am an expert in identifying a line of reason, an application of logic and a well structured argument. Markus has delivered these routinely and consistently through several thousand posts. HE has also displayed remarkable patience and objectivity in dismantling faulty arguments.

    On the other hand you have joined the forum and almost from your first post have adopted an arrogant attitude. I am a member of several forums and in each instance I have lurked for a while, figured out the tenor of the place, then eased into participation. I am a stranger in a strange land and tact and caution are not only polite, they are also productive. Now perhaps you did not intend that arrogance, however, several members besides myself clearly saw it. On top of that, you were making assertions that did not match reality. Not a good start.



    Quote Originally Posted by Velexia View Post
    You've got a lot of disagreements in here based purely on your desire to disagree with me, which is absolutely hilarious, considering that in pretty much every case, they seem to reflect a desire to misread literally everything said here, or simply not read everything that was said. It is most stunningly apparent here: "No it doesn't; time progresses as normal for you."

    Try reading the entire sentence, and get some reading comprehension.
    In all of the many posts Markus has made I do not recall a single instance where he has disagreed for the sake of disagreeing. Do you feel you are a better judge of motivations after knowing the man for a few days than I?

    As far as reading comprehension goes the primary responsibility for communicating an idea lies with the writer, not the reader. Do you disagree?

    Alright, I'll grow a pair.

    GROW THE #@)(%^ UP YOU IGNORANT MORON.
    I was aiming more for the notion that you should be less sensitive to negative remarks, real or imagined. I'm sorry I did not make that clear. The error was mine. (You see how this work?)


    I never really expected much from someone naming themselves "John Galt". Glad to know my intuition was spot on there.
    Atlas Shrugged is one of my top five works of fiction. However, I am opposed to almost every aspect of Ayn Rand's philosophy, so your intuition has done you no good there. The selection of the name was for subtle reasons, connected with the forum, that are now history.

    See this is why I don't like getting into this subject on the internet. By virtue of the anonymity of the internet, people let the worst sides of themselves out... and the internet is chock full of people like the lot of you, even on a science forum of all places.

    I know time dilation is hard, but FFS, only for someone who is incapable of complex thought.

    This website should be renamed "TheKindergartenScienceForum" where mostly we are just mean to each other, since we don't know how to behave like rational thinking people.
    You will find many threads and posts where ideas are exchanged in a civil manner, where people are educated and educate, where new ideas are explored and old ones confirmed. You will also find threads where members become irate and frustrated. This is typically because one member will adopt a hostile attitude, or refuse to acknowledge facts, or present weak arguments.

    Which brings us full circle. Have another look at your own behaviour and posting style from the outset. Will you claim you are blameless in this unseemly exchange? I'd be interested to know.

    You're going to have to highlight for me, what you saw from me as arrogant, because I can't, for the life of me, see it. I'm being sincere. Maybe it was a misinterpretation on your part, through no fault of your own, but faulty nonetheless? (You'll have to forgive me for assuming the fault is not my own, egos like to do that. If you can show me convincingly where my fault lies, I'll do my best to take it to heart).

    I was making assertions in the form of a hypothesis, and asking for convincing evidence to disprove it, because I was having trouble finding it on my own. There's literally nothing wrong with that. It's the scientific process.

    The forum administrator was able to participate in the discussion AND provide me with the proof I needed, without being immature about it. That's a real saving grace for the entire forum, honestly. At least the Forum Administrator demonstrates appropriate behavior (and thank you for that KALSTER!)

    If Markus is not disagreeing to disagree then he lacks reading comprehension, or perhaps the ability to read an entire sentence before formulating a retort as highlighted by this quote

    "No it doesn't; time progresses as normal for you."

    from him, in reference to this sentence:

    "If you, by some miracle, touch the event horizon, due to gravitational time dilation... Time stops for you, relative to an observer farther from the event horizon (any distance farther). Time also stops when you reach the velocity of light in a similar manner... despite you, still experiencing time as appearing normal."

    I should not have to deal with negative remarks directed at me, as a person. It's inflammatory, rude, against the forum rules if I am not mistaken, and not conducive to rational discussion.

    Well, the name nonetheless gave an impression, and you acted in a manner ill befitting a moderator, so forgive me for drawing the conclusions I did. I am not in a position to know the subtleties regarding your choice of the name and can only form an opinion based on my own experiences.

    I may have communicated poorly, in an environment such as an internet forum, where people are quick to jump to their first conclusions, possibly without any attempt to comprehend the intended message, or even perhaps, read the entire post. I am not the most eloquent person, and careful speech so as not to allow for any misinterpretation is seriously tiring and makes gentle reading tedious.

    I was at fault for assuming people would behave in a polite, mature manner, and that they had a solid grasp of concepts I was addressing (such as in the case of time dilation). In the case of my first post/thread, I had a lack of facts, and was literally, seeking out those facts. In every post I did my best to clearly state that I was not convinced by what I had seen thus far, and was seeking something convincing. When I found it, I happily took it to heart, since it was my desire not come up with some crackpot theory, but to broaden my understanding through factual evidence.

    For the most part I received hostility, insults, and rude behavior.

    So yes, I slowly became more and more agitated, until at last I flipped the %^&* out, because there is only so much unwarranted abuse one can take, and the only reason I had to endure it in the first place is because the anonymity of the internet makes people feel safe to be the asshole they are inside. If people acted like this in person, they'd get punched in the goddamned face (not that I am the type to punch people in the face... I'd simply not associate with them, but somebody would, and they would have deserved it).
    Last edited by Velexia; November 18th, 2013 at 08:46 PM.
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  93. #92  
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    I have to go to work in five or ten minutes. This is a brief explanation.

    You criticsed the Argument from Authority, I think. But the vast majority of us, until and unless we have studied a specific topic in scrupulous and excrutiating detail have to, as a practical matter, acept the consensus view provided by experts in that field. When we encounter something we feel is questionable there are two possible positions to take:

    1. I am not convinced by this and believe it may be wrong. Show me, beyond any reasonable dount that it is correct, or at least the best available explanation.
    2. I do not understand why this is thought to be correct. Experts say it is and they have studied it much more detail than I, therefore I am likely wrong and would llike to understand why.

    The first approach, which is the one I saw you take, is arrogant. The second is not.

    I illustrate further with two personal anecdotes.

    I do not believe in the Big Bang theory. I object to it on philosophical and personal grounds. However, I accept it is currently the best available explanation for the evidence and have defended it on this and other forums.

    Several years ago I found what appeared to be an error in the calculation process for killing a kicking oil well. It was very clear cut. I did not take the position, this is wrong, please go ahead and show me why it isn't. I said, this appears to be wring, but I doubt it can be. Where am I making the mistake.

    I am not a humble person, but I am also not - I think - arrogant. You appeared to be.

    And as a side note, although I have certainly insulted people and used offensive language on forums I have never, despite provocation far more extreme than anything you have experioenced here, I have never advocated physical violence. There are plenty of forums where you would have been permanently booted off for that.
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  94. #93  
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    Quote Originally Posted by John Galt View Post
    I have to go to work in five or ten minutes. This is a brief explanation.

    You criticsed the Argument from Authority, I think. But the vast majority of us, until and unless we have studied a specific topic in scrupulous and excrutiating detail have to, as a practical matter, acept the consensus view provided by experts in that field. When we encounter something we feel is questionable there are two possible positions to take:

    1. I am not convinced by this and believe it may be wrong. Show me, beyond any reasonable dount that it is correct, or at least the best available explanation.
    2. I do not understand why this is thought to be correct. Experts say it is and they have studied it much more detail than I, therefore I am likely wrong and would llike to understand why.

    The first approach, which is the one I saw you take, is arrogant. The second is not.

    I illustrate further with two personal anecdotes.

    I do not believe in the Big Bang theory. I object to it on philosophical and personal grounds. However, I accept it is currently the best available explanation for the evidence and have defended it on this and other forums.

    Several years ago I found what appeared to be an error in the calculation process for killing a kicking oil well. It was very clear cut. I did not take the position, this is wrong, please go ahead and show me why it isn't. I said, this appears to be wring, but I doubt it can be. Where am I making the mistake.

    I am not a humble person, but I am also not - I think - arrogant. You appeared to be.

    And as a side note, although I have certainly insulted people and used offensive language on forums I have never, despite provocation far more extreme than anything you have experioenced here, I have never advocated physical violence. There are plenty of forums where you would have been permanently booted off for that.
    I suppose I can can see why you see it as arrogant. I still don't see it as arrogant myself. I simply see it as a different position... one where I am not assuming that I don't understand what I am currently aware of, but rather that I understand that there must be something I am not currently aware of, which would give a solid ground for the existence of the thing I am doubting. See, if I thought, for example, that I misunderstood the facts already laid out before me, I would have approached it in the second manner. But that wasn't the case. Had I gone with the second approach, the focus would be on trying to force me to accept the common interpretation of experiments I was already aware of, and having read thoroughly into those experiments, and the thoughts and interpretations at the source (rather than a game of telephone), and not being convinced by them, there was literally no way that a second hand reiteration was going to help. So I necessarily HAD to ask to see other evidence. I'm sorry if that seemed arrogant to you, but there was really no other course of action available to me.

    I honestly doubt the big bang theory as well, but I don't have enough ground to take my own doubt seriously, because I do not fully understand the reasoning behind why they interpret the microwave background radiation in the way they do (in this case, I can easily take the second stance).

    I didn't advocate physical violence, you misread. I simply stated that, in an open environment such as, in person, were a person to be rude to his or her fellows in the manner they have been here, eventually, someone would inevitably punch them in the face, and I would not care (because the ego is like that).

    I don't think violence is ever right, and I never resort to physical force beyond that necessary to protect myself from physical harm. As an anecdote, I was in the Army, and I held a loaded weapon, safety off, at what was potentially a hostile person in a foreign land, and with every fiber of my being I had NO desire to squeeze the trigger on which my finger rested, and yet, I was obligated to do just that if necessary. It would have devastated me for life, and it brings a tear to my eye merely to think about it, and I am glad beyond words that the situation didn't escalate, because I see myself in every person, and every person is deserving of life and freedom from oppression and violence despite nature's tendency to put us at odds...

    So please, don't for a moment think that I advocate violence.
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  95. #94  
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    Quote Originally Posted by Velexia View Post
    So please, don't for a moment think that I advocate violence.
    In an earlier post you recommended the following course of action for myself.

    Go commit seppuku for being an idiot on the internet.
    I am afraid I find that a violent suggestion.
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  96. #95  
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    Quote Originally Posted by Velexia View Post
    You've got a lot of disagreements in here based purely on your desire to disagree with me.
    No, the disagreements are based on the theory of relativity. I told you before that I will call on claims that aren't physically accurate, and I will continue to do so.

    The level of moronic behavior on a Science thread by Moderators and regulars alike is completely appalling.
    GROW THE #@)(%^ UP YOU IGNORANT MORON.
    Very mature indeed.

    I know time dilation is hard, but FFS, only for someone who is incapable of complex thought.
    Yes, almost seems like it, doesn't it.

    So go throw yourselves a nice self congratulatory troll party, celebrating your willful ignorance and immaturity.
    Uh-huh.

    Pretty sure I know the source of confusion for people assuming that you can actually pass through an event horizon without an infinite amount of time passing in the universe around you.
    Do you mean coordinate time or proper time ? Because everyone agrees on proper time...and that is quite finite.

    Having associated gravitational time dilation with acceleration
    Who does that ? The calculation I gave you is simply a line integral along the world line of the in-falling observer; that world line does not terminate at the event horizon. Or are you claiming differently ? If so, I'd be interested to be shown your maths in support of your claims.

    But you can't simply ignore the non local reference frames, because what is happening out there, outside of your reference frame is real.
    When I look out my window ( disregarding any topological features ) I see the horizon as flat and straight; can I thus assume that the Earth must be flat, because that's what it looks like to me ?
    I ask you again - do you understand the difference between coordinate time and proper time, and why they are distinct notions in Schwarzschild space-time ?

    I was making assertions in the form of a hypothesis
    No, you are making claims. That is not the same thing.

    I should not have to deal with negative remarks directed at me, as a person. It's inflammatory, rude, against the forum rules if I am not mistaken, and not conducive to rational discussion.
    How is "time progresses as normal for you" ( which is physical fact ) to be construed as any of the above ? Also, do you deny that all free-falling frames of reference are locally Minkowskian ?

    For the most part I received hostility, insults, and rude behavior.
    You have received specific answers to specific points; and you have received corrections to misunderstandings.
    You have received physics.
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  97. #96  
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    Quote Originally Posted by Velexia View Post
    "This result appears puzzling because each twin sees the other twin as traveling, and so, according to an incorrect naive application of time dilation, each should paradoxically find the other to have aged more slowly."
    No surprise, since in the twin paradox the two frames are not symmetric, due to the presence of acceleration in one of them, so "naively" applying the relative time dilation formula without accounting for acceleration will lead to an apparent paradox. If treated properly with acceleration, the net difference in proper times when they come back together at rest then becomes obvious and expected. They still see each other to be ageing more slowly while in transit, but not at the same rate.
    I find it kind of telling that you choose to quote from an article on the twin paradox, when the point originally made ( relative time dilation ) deals with purely inertial frames...

    Consider this : The mathematical description of going from one inertial frame into another is realised by introducing a linear transformation between two vectors x' and x of the form



    wherein L is a general transformation matrix which represents an as-per-yet unspecified boost and rotation in arbitrary directions, and the 4-vector a represents a shift of origin. We now demand the following restriction to hold :



    which corresponds to the simple observation that, when performing a rotation and its inverse, you always arrive at the original vector, i.e. a rotation and its inverse chained together will yield the unity matrix. In tensor language this corresponds to



    In order to prove that each inertial observer sees the other one as dilated, one now only needs to show that such a transformation L leaves the space-time line element ds invariant, meaning that the distance between two events in space-time is the same for all inertial observers :



    Quod erad demonstrandum. Note that the above invariance of the line element also means that all observers agree on the amount of proper time between two given events in space-time, but not on the coordinate time.
    Last edited by Markus Hanke; November 19th, 2013 at 06:48 AM.
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  98. #97  
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    Moderator here.

    Velexia.

    I have nothing to offer in this kind of discussion, but I can read.

    The first thing that leaps out at me is seppuku. Had I been reading this thread at the time that was posted, you would have got a formal warning at least, maybe a couple of days suspension - right then and there. But I'll do it now.

    Formal Warning
    Never, ever say anything like that again - or you will be banned, maybe permanently.

    Arrogance and related issues. I don't need to know anything about SR or GR to perceive that your words and your general style are combative and unresponsive to sensible comments. You need to re-calibrate your approach. This is not a debating society and the topic is not one amenable to a win or lose debate anyway.

    If you have a question, ask a question. Don't set up pointless contests. Read the answers you get - carefully. If it's still not clear, describe the problem as you see it, then ask another question.

    Now, of course, I'll have to keep an eye on your contributions. Try to do better. Please.
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  99. #98  
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    Velexia is holding a number of misconceptions which are, in fact, rather common; in think it might thus be instructive, also for the casual reader, to address these in a general manner :


    Inertial frames & symmetry

    Consider a rocket cruising through space at uniform velocity ( no acceleration ! ), making this an inertial frame; inside is an astronaut. He looks out the window, and sees an asteroid passing by at very high but constant ( relativistic ) speed. Assume further that both rocket and asteroid carry gigantic watches which can be seen and read from everywhere.
    The first thing we need to realise in scenarios involving two perfectly inertial frames is there is no such thing as absolute velocity - the astronaut cannot tell whether it is him moving past a stationary asteroid, or whether he is stationary and the asteroid passes by him, or some combination of movements. The same goes from the perspective of the asteroid. All they can tell is that there is relative motion between them; the two frames themselves are identical in every way, they both experience the exact same laws of physics.
    From the frame of the rocket, it is the asteroid moving - when the astronaut looks at the asteroid's clock he sees it moving very fast, and hence time dilated. This means that the astronaut sees the asteroid's clock ticking slower from his own frame. Now turn it upside down - the asteroid looks at the rocket. It will think that it is in fact the rocket passing by it very fast, whereas itself is stationary. Hence it sees the rocket's clock moving very fast and therefore also time dilated, i.e. ticking slower.

    What this means is that both frames see the other one time dilated; both frames see exactly the same thing, experience exactly the same laws of physics. This is what it means for inertial frames to be symmetric.


    Proper time and coordinate time

    Consider two fixed events in space-time (1) and (2); now consider two observers A and B which travel with the same uniform velocity ( no acceleration ! ) between these same two events along the same trajectory, but in opposite directions. They both carry watches which are clearly visible and readable from everywhere. The first thing to note now is that of course both stopwatches must record the same elapsed time between (1) and (2), since they are moving on the same trajectory in opposite directions. When the clocks are stopped at their destinations, and then brought together and compared, they will show the exact same total proper time. This is proper time - the time a clock travelling between two events physically records. All observers agree on this proper time.

    Now let's look at the frames while they are in transit - observer A looks at observer B and sees him travelling at very high speed towards or away from him. Hence, because there is relative motion, he sees clock B time dilated. The same holds for clock B - it sees clock A travelling very fast, and hence time dilated. This notion of time, the time an observer sees when looking upon another frame of reference with his own method of performing measurements, possibly some distance away, is called coordinate time. It is called that because it depends on the observers, and their states of relative motion. Different observers do not agree on proper time readings. Dilation between coordinate times is called relative time dilation, whereas dilation between proper times is called gravitational time dilation. The former is purely a result of relative motion, the latter is a result of acceleration and/or the presence of gravity, and they are additive if both motion and acceleration/gravity are present. Now, it is important to clearly distinguish between these two notions, because of the following - what clocks travelling between two events record is always proper time; relative time dilation does not affect proper time, whereas gravitational time dilation does effect proper time. Another important thing is this ( without derivation ) : proper time is exactly the length of an observer's world line; this is an invariant, i.e. all observers agree on this world line no matter what. The same is not true for coordinate time.

    Now consider the case of matter falling into a black hole. The world line of such an in falling observer extends from outside the black hole, through the event horizon, and into the singularity. Everywhere along that world line ( except at the singularity itself ) space-time is smooth and continuous, and the world line has a finite, well defined length. All observers agree on this, since it is proper time. Such an in falling observer sees this from his own frame :

    Step by Step into a Black Hole

    Not so for some distant observer outside the black hole - he sees the object first speeding up towards the black hole, then gradually slowing down and getting dimmer and redder as it approaches the event horizon ( which looks like a perfectly black disk to him ), and eventually fading away into invisibility. He does not see the object "frozen" in place at the event horizon; what happens is rather that the light emanating from the in falling object has longer and longer distances along increasingly complicated null geodesics to travel before it reaches him, hence it appears to him that the object is falling more and more slowly. Ultimately this is because light propagates at finite speed, and it does so along null geodesics in space-time. In the immediate vicinity of a black hole, space-time is highly curved, and light follows that curvature on curved trajectories, like so :



    From the point if view of such a distant observer, the object is never seen entering the event horizon; on that observer's clock it takes an infinite amount of time for the object to reach the black hole. However, because that infinity is in coordinate time, this is true only for the distant observer in his own frame of reference. Concluding that, because a distant observer never sees the object reach the event horizon, the object itself never crosses it in its own local frame of reference is a logical fallacy, because the clock readings and measurements taken by the distant observer are valid only in his own local frame, nowhere else.

    As for the specific claim on this thread, that matter accumulates just above the event horizon - that is of course something that no observer sees at all, it is a a false conclusion reached via the erroneous assumption that the distant observer's local clock and ruler readings are equally valid for the in falling matter itself. That is not the case though, since the space-time around the black hole is not globally flat.

    I hope that this clarifies the matter somewhat. If anyone requires textbook references for this, please do let me know; otherwise any textbook on relativity will confirm the above.
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    Quote Originally Posted by John Galt View Post
    Quote Originally Posted by Velexia View Post
    So please, don't for a moment think that I advocate violence.
    In an earlier post you recommended the following course of action for myself.

    Go commit seppuku for being an idiot on the internet.
    I am afraid I find that a violent suggestion.
    Because obviously, I totally meant that. I was being literal, and most seriously wanted you to do it. -eyeroll-

    I am so violent. Arrr -gnaws on kittens-
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    Me again.

    Velexia, take some notes. Write them down. Perhaps stick them on a post-it note and attach to your screen.

    I take it from your #101 ...

    Because obviously, I totally meant that. I was being literal, and most seriously wanted you to do it. -eyeroll-


    I am so violent. Arrr -gnaws on kittens-


    ... that you're claiming that what you said was perfectly OK because it was "just a joke". And that killjoys like me should get a grip, take a deep breath, and get a sense of humour. Or some other such witless rubbish commonly thrown at teachers by the year 9 class.

    My sense of humour is in perfect working order. It's a sense of humour. Some things are funny. Many things are not. Some people claim to have been "just joking" when what they're really doing is trying to hide the offensiveness of their remarks from behind a humour shield. That's what you're doing now. This shield is made of tissue paper. It's worthless.

    I'm revising the warning I gave earlier because it seems to have made no impression on you.

    Formal Warning

    Last Warning

    Never, ever say anything like that again.

    Never, ever pretend that offensive remarks are OK because you think you're being funny.

    ...... or you will be banned, maybe permanently.
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