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Thread: Falling through the event horizon

  1. #101  
    Forum Radioactive Isotope MagiMaster's Avatar
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    Quote Originally Posted by jartsa
    Quote Originally Posted by MagiMaster
    No. Look up the Schwartzchild radius. The radius is directly proportional to its mass.
    Every event horizon resides at the same pretty large depth, right?
    Quote Originally Posted by MagiMaster
    No. Look up the Schwartzchild radius. The radius is directly proportional to its mass.
    Anyway.

    Quote Originally Posted by kojax
    Quote Originally Posted by MagiMaster
    Dark matter and dark energy are not part of GR. They are just names for things we've calculated must exist (in some form) but we don't know what they really are. GR does not say these things exist, just our observations of the universe.
    Those calculations were made using GR. That means GR is making the prediction. Whenever you use a theory in making a calculation, whatever your calculation predicts is what the theory predicts. Without Dark Matter, the rotational speed of most Galaxies would be inexplicable. GR predicts that they will move at one speed, but we observe them to move at another, and Dark Matter is merely being introduced as an Ad hoc adjustment to make observation compatible with theory.

    I see little difference between the "evil demons make things fall" theory of gravity and the GR + Dark Matter theory. Neither of them can be compared against observation. No matter how fast or slow you see a galaxy rotating, you can always make your predictions match observation just by adding or subtracting Dark Matter.
    You misunderstand the order of events here. The galaxies were measured to be rotating too fast to be explained by what we could see. Several ideas were put forward as to what could cause that. One was that there was some kind of mass there that we couldn't see, which got labeled dark matter. One ws that gravity acted differently at those scales. Since then, other observations have ruled out everything but dark matter.

    In other words, the rotation of galaxies wasn't predicted with dark matter, but was the observation that gave rise to the idea to begin with.
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  2. #102  
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    Quote Originally Posted by MagiMaster
    No. Look up the Schwartzchild radius. The radius is directly proportional to its mass.

    My head resides at the same altitude relative to event horizon of a small
    black hole and relative to event horizon of a black hole half the
    size of the first black hole, right?
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  3. #103  
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    Quote Originally Posted by jartsa
    Quote Originally Posted by MagiMaster
    No. Look up the Schwartzchild radius. The radius is directly proportional to its mass.

    My head resides at the same altitude relative to event horizon of a small
    black hole and relative to event horizon of a black hole half the
    size of the first black hole, right?
    Ok. You must be using different definitions for some of your words, because I'm pretty sure I've answered that same question twice already. Let me try rephrasing it.

    The distance from the center of a black hole to its event horizion is proportional to its mass, and is therefore not a constant. The exact radius can be calculated with the formula given in the earlier link.
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  4. #104  
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    Quote Originally Posted by MagiMaster

    Ok. You must be using different definitions for some of your words, because I'm pretty sure I've answered that same question twice already. Let me try rephrasing it.

    The distance from the center of a black hole to its event horizion is proportional to its mass, and is therefore not a constant. The exact radius can be calculated with the formula given in the earlier link.
    It's my job to rephrase.
    A spirit level tells that two event horizons are level, right?
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  5. #105  
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    Now you're not making any sense at all. Level with what, each other? They're spheres. How can sphere's be level?
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  6. #106  
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    Quote Originally Posted by MagiMaster
    Now you're not making any sense at all. Level with what, each other? They're spheres. How can sphere's be level?
    All the seas on earth reside at sea level, all the event horizons in universe reside
    at event horizon level, right?
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  7. #107  
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    No. Good grief, man. Go away already. You're simply trolling.
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  8. #108  
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    Quote Originally Posted by jartsa
    Quote Originally Posted by MagiMaster
    Now you're not making any sense at all. Level with what, each other? They're spheres. How can sphere's be level?
    All the seas on earth reside at sea level, all the event horizons in universe reside
    at event horizon level, right?
    Yeah, now I'm sure I've answered the same question three times. About to be four, so listen carefully.

    Each black hole's mass is different, and the size of the event horizon (for any sane definition of size) depends on the mass, so the size of each event horizon is different. I don't think I can say it much more plainly than that.
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    Here is one shapely event horizon, at the bottom of the page:
    http://www.black-holes.org/explore2.html

    Is it possible to somehow understand that every point of this event
    horizon is somehow at equal depth?
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  10. #110  
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    Quote Originally Posted by MagiMaster

    Quote Originally Posted by kojax
    Quote Originally Posted by MagiMaster
    Dark matter and dark energy are not part of GR. They are just names for things we've calculated must exist (in some form) but we don't know what they really are. GR does not say these things exist, just our observations of the universe.
    Those calculations were made using GR. That means GR is making the prediction. Whenever you use a theory in making a calculation, whatever your calculation predicts is what the theory predicts. Without Dark Matter, the rotational speed of most Galaxies would be inexplicable. GR predicts that they will move at one speed, but we observe them to move at another, and Dark Matter is merely being introduced as an Ad hoc adjustment to make observation compatible with theory.

    I see little difference between the "evil demons make things fall" theory of gravity and the GR + Dark Matter theory. Neither of them can be compared against observation. No matter how fast or slow you see a galaxy rotating, you can always make your predictions match observation just by adding or subtracting Dark Matter.
    You misunderstand the order of events here. The galaxies were measured to be rotating too fast to be explained by what we could see. Several ideas were put forward as to what could cause that. One was that there was some kind of mass there that we couldn't see, which got labeled dark matter. One ws that gravity acted differently at those scales. Since then, other observations have ruled out everything but dark matter.

    In other words, the rotation of galaxies wasn't predicted with dark matter, but was the observation that gave rise to the idea to begin with.
    What I meant is that you can't look at a Galaxy, take its observable mass, and then apply Dark Matter theory to predict how fast that galaxy will be spinning.

    A good theory is able to make predictions. All Dark Matter theory predicts is that GR is going to fail to predict the rate of spin. It doesn't then go on to make a prediction of its own. That makes it un-testable, just like other ideas that would usually be regarded as pseudo-science like Ghosts, or Psycho-analysis.


    Quote Originally Posted by DrRocket

    Tou don't need GR for this. Newtonian models are quite sufficient to reveal the anomaly that resulted in the dark matter hypothesis.
    This tells me that both Newtonian Gravity and General Relativity are both incomplete theories. They give accurate predictions within their range, but apparently begin to fail at long distances/scales, just like how Galilean physics is successful at non-relativistic speeds, but fails as significant fractions of C.

    I'm not saying GR will ever be thrown out entirely. It's just not adequate to take all situations into account.
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  11. #111  
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    I'm not saying GR will ever be thrown out entirely. It's just not adequate to take all situations into account.
    It probably is for everything beyond QM scales. As noted, the anomalies can be explained by extra mass. In the case of galaxies it would be in the form of an all enveloping sphere of dark matter around the galaxy.

    Dark matter does not rely solely on the revolution of galaxies. It is required to explain certain aspects of the big bang and expansion as well.
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  12. #112  
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    Quote Originally Posted by jartsa
    Here is one shapely event horizon, at the bottom of the page:
    http://www.black-holes.org/explore2.html

    Is it possible to somehow understand that every point of this event
    horizon is somehow at equal depth?
    Alright... For an individual blackhole, the event horizon is about as perfect a sphere as we will see in nature. Every "point" of the sphere will be approximately the same distance to the center of the object.
    Wise men speak because they have something to say; Fools, because they have to say something.
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  13. #113  
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    Quote Originally Posted by jartsa
    Here is one shapely event horizon, at the bottom of the page:
    http://www.black-holes.org/explore2.html

    Is it possible to somehow understand that every point of this event
    horizon is somehow at equal depth?
    I'm not sure which picture you're referring to, so I still don't know what you mean by depth here. As Arcane said, a black hole's event horizon (in the absence of other large masses, like other black holes, distorting it) will basically be a perfect sphere, at least more so that any other natural object.

    If you're talking about that first picture, then by depth I'd have to assume you're talking about those 2D rubber sheet models of gravity, and then, no, the depth depends on the mass and the mass of each black hole is different.
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  14. #114  
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    [quote="kojax"][quote=MagiMaster]

    [quote="kojax"

    What I meant is that you can't look at a Galaxy, take its observable mass, and then apply Dark Matter theory to predict how fast that galaxy will be spinning.

    A good theory is able to make predictions. All Dark Matter theory predicts is that GR is going to fail to predict the rate of spin. It doesn't then go on to make a prediction of its own. That makes it un-testable, just like other ideas that would usually be regarded as pseudo-science like Ghosts, or Psycho-analysis.
    [/quote]

    You seem to think that the whole case for Dark Matter is based only on galaxy rotation rates, This simply isn't true. A case in point is the Bullet cluster. Two galaxy clusters have collided, each with its own DM halo. During the collision the visible matter is slowed by interaction The DM however, which does not interact except by gravitation, is not. As a result the DM halos are separated from their clusters. The DM halos can be detected and mapped by their gravitational lensing.

    So the DM model predicts that if you look at such a collision you should be able to map the DM halos as being separated from the visible matter. This is exactly what we see with the Bullet cluster. This cannot be explained by any modification of gravity theory.
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    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  15. #115  
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    Since the conversation has shifted to DM and we have the attention of Janus, I have a couple of questions.

    Wouldn't the DM need to be concentrated at a galaxies center to account for stellar orbital velocities greater than that predicted by current gravitational models? Since gravitational lensing has shown the DM to be concentrated in a halo, wouldn't this cause stellar orbital velocities to be smaller than what would be predicted by accounting only for visible matter?

    Does the DM map of the bullet cluster collision indicate that the DM interacts with itself weakly, strongly, or at all? Perhaps someone could provide a link to an image?
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  16. #116  
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    Quote Originally Posted by kojax
    This tells me that both Newtonian Gravity and General Relativity are both incomplete theories. They give accurate predictions within their range, but apparently begin to fail at long distances/scales, just like how Galilean physics is successful at non-relativistic speeds, but fails as significant fractions of C.

    .
    Are you really this ignorant ?

    Certainly Newtonian gravity ad probably GR are not final theories, but hardly for the reasons that you note. They work very well at long distances/scales, but are incompatible with quantum theories.

    There is no such thing as Galilean physics --you are referring to classical Newtonian mechanics. You attempt at an analogy is WAY off base.

    You really do need to both learn a little physics and to stop spouting off when, as is common, you have no idea what you are talking about.
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  17. #117  
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    Quote Originally Posted by MagiMaster


    If you're talking about that first picture,

    Last picture, not first.
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  18. #118  
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    So now we are falling through an event horizon, in a capsule. As a scientific
    experiment we are observing what happens to small black holes, that are in
    the capsule.

    We know from simulations that when two event horizons meet they merge,
    here is an example, see the last movie in the page:
    http://www.black-holes.org/explore2.html

    So, what is the result of aforementioned experiment?
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  19. #119  
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    Quote Originally Posted by GiantEvil
    Since the conversation has shifted to DM and we have the attention of Janus, I have a couple of questions.

    Wouldn't the DM need to be concentrated at a galaxies center to account for stellar orbital velocities greater than that predicted by current gravitational models? Since gravitational lensing has shown the DM to be concentrated in a halo, wouldn't this cause stellar orbital velocities to be smaller than what would be predicted by accounting only for visible matter?
    If it was just a matter of an increase in speed, then yes. But then you wouldn't need DM; all you would have to do is increase the estimate of the mass of the central black hole. It is the rotation curve that is the issue.

    When you look at a galaxy, you have a central bulge and the outlying arms, The bulge is very crowded and dense so most of the visible mass of the galaxy resides there.

    As a result, you would expect the star in the outlying regions to have lower and lower orbital speeds the further from the center they were. But we don't see this, instead we see the velocities stay the same. This doesn't make sense for the distribution of mass we see. What, however, if the mass was instead distributed as a uniformly dense volume encompassing the orbits? The orbit of an object is only effected by the sphere of mass inside of its orbit. Since the speed of an orbit increases as the mass it orbits increases, and larger orbits would encompass larger masses, you get a flattening out of the orbital speeds.

    So in order to get the rotation curve we see, we would expect the DM to be distributed in a halo around the galaxy; which is what we see with gravitational lensing.
    Does the DM map of the bullet cluster collision indicate that the DM interacts with itself weakly, strongly, or at all?
    It only interacts gravitationally.

    Perhaps someone could provide a link to an image?
    Here's one that compares the visible matter to the map of the gravitational lensing caused by the DM (the green contour lines)

    Note the separation.

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  20. #120  
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    I think I understand, the DM halo is not wholly outside the galactic rim but coincident with it?
    Thanks for the answer and the image.
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  21. #121  
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    Quote Originally Posted by jartsa
    So now we are falling through an event horizon, in a capsule. As a scientific
    experiment we are observing what happens to small black holes, that are in
    the capsule.

    We know from simulations that when two event horizons meet they merge,
    here is an example, see the last movie in the page:
    http://www.black-holes.org/explore2.html

    So, what is the result of aforementioned experiment?
    The two event horizons only appear to merge from someone outside of both. If you carried a small one into a large one, you won't see anything special happen. You'd notice some distortion of the small horzion, even from outside of the big one, which would increase as you got close to the center, but that's about it.
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  22. #122  
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax
    This tells me that both Newtonian Gravity and General Relativity are both incomplete theories. They give accurate predictions within their range, but apparently begin to fail at long distances/scales, just like how Galilean physics is successful at non-relativistic speeds, but fails as significant fractions of C.

    .
    Are you really this ignorant ?

    Certainly Newtonian gravity ad probably GR are not final theories, but hardly for the reasons that you note. They work very well at long distances/scales, but are incompatible with quantum theories.
    It doesn't bother you that it fails at both the large and small scales? That would indicate a pattern that only prevails across a certain range. I mean: if it only failed at one or the other, that would be different, but if it fails at both?

    My background prior to physics was statistics. I'm very skeptical of theories that don't make predictions in a way where failure is easy to identify. The stronger the statistical improbability of the theory giving an accurate prediction if the theory itself were inaccurate, the more likely I am to take it seriously. Dark Matter seems to succeed in any situation where GR fails, and well....so would a lot of theories.

    The point Janus raised was very interesting however, and so I'm really interested in this topic. If I understand the situation right, the center of mass according to gravitational lensing in the Bullet Cluster is focused toward the area where all the stars and such are (also where the Dark Matter should be expected to reside), instead of on the X-Ray clouds which make up the majority of the mass and are moving more slowly due to electrical interactions. I guess that makes a pretty good secondary confirmation. (or I guess its tertiary, since we also have the lensing behavior of normal galaxies, in addition to their rotation speeds.) The more confirmations, the smaller the odds of them all being wrong. I looked up the wiki article on this, and it's pretty well written.

    http://en.wikipedia.org/wiki/Bullet_Cluster


    Quote Originally Posted by DrRocket

    There is no such thing as Galilean physics --you are referring to classical Newtonian mechanics. You attempt at an analogy is WAY off base.
    .
    Actually I was thinking of the Galilean transformations, but you're right I got the terminology wrong. I thought it was a pretty good analogy, but not so much an analogy as a prediction of a pattern.

    I really doubt the universe threw all the surprises at us that it was ever going to throw when it invalidated our system of reference frames. It may also plan to invalidate some of our other systems of motion as well, and probably in the same way: by making them turn out to only be valid over a certain range.

    Quote Originally Posted by KALSTER
    I'm not saying GR will ever be thrown out entirely. It's just not adequate to take all situations into account.
    It probably is for everything beyond QM scales. As noted, the anomalies can be explained by extra mass. In the case of galaxies it would be in the form of an all enveloping sphere of dark matter around the galaxy.
    How many possible gravitational theories would be capable of failing if the total mass of the system is free to be whatever we want it to be in order to fit with our theory?
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  23. #123  
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    Quote Originally Posted by kojax
    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax
    This tells me that both Newtonian Gravity and General Relativity are both incomplete theories. They give accurate predictions within their range, but apparently begin to fail at long distances/scales, just like how Galilean physics is successful at non-relativistic speeds, but fails as significant fractions of C.

    .
    Are you really this ignorant ?

    Certainly Newtonian gravity ad probably GR are not final theories, but hardly for the reasons that you note. They work very well at long distances/scales, but are incompatible with quantum theories.
    It doesn't bother you that it fails at both the large and small scales? That would indicate a pattern that only prevails across a certain range. I mean: if it only failed at one or the other, that would be different, but if it fails at both?

    My background prior to physics was statistics. I'm very skeptical of theories that don't make predictions in a way where failure is easy to identify. The stronger the statistical improbability of the theory giving an accurate prediction if the theory itself were inaccurate, the more likely I am to take it seriously. Dark Matter seems to succeed in any situation where GR fails, and well....so would a lot of theories.

    The point Janus raised was very interesting however, and so I'm really interested in this topic. If I understand the situation right, the center of mass according to gravitational lensing in the Bullet Cluster is focused toward the area where all the stars and such are (also where the Dark Matter should be expected to reside), instead of on the X-Ray clouds which make up the majority of the mass and are moving more slowly due to electrical interactions. I guess that makes a pretty good secondary confirmation. (or I guess its tertiary, since we also have the lensing behavior of normal galaxies, in addition to their rotation speeds.) The more confirmations, the smaller the odds of them all being wrong. I looked up the wiki article on this, and it's pretty well written.

    http://en.wikipedia.org/wiki/Bullet_Cluster


    Quote Originally Posted by DrRocket

    There is no such thing as Galilean physics --you are referring to classical Newtonian mechanics. You attempt at an analogy is WAY off base.
    .
    Actually I was thinking of the Galilean transformations, but you're right I got the terminology wrong. I thought it was a pretty good analogy, but not so much an analogy as a prediction of a pattern.

    I really doubt the universe threw all the surprises at us that it was ever going to throw when it invalidated our system of reference frames. It may also plan to invalidate some of our other systems of motion as well, and probably in the same way: by making them turn out to only be valid over a certain range.

    Quote Originally Posted by KALSTER
    I'm not saying GR will ever be thrown out entirely. It's just not adequate to take all situations into account.
    It probably is for everything beyond QM scales. As noted, the anomalies can be explained by extra mass. In the case of galaxies it would be in the form of an all enveloping sphere of dark matter around the galaxy.
    How many possible gravitational theories would be capable of failing if the total mass of the system is free to be whatever we want it to be in order to fit with our theory?
    You're seriously misclassifying Dark Matter Theory (as you call it).

    It is in no way on par with GR. It doesn't deal with gravity. It doesn't "work where GR fails." It doesn't have this mysterious free variable you're talking about.

    From the rotation curves, the amount and distribution of extra mass was calculated. This makes the rotation curves an invalid data point for predictions, and they aren't used as such. From there, other predictions, such as gravitational lensing, were made, and these have held up.
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  24. #124  
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    Quote Originally Posted by MagiMaster
    How many possible gravitational theories would be capable of failing if the total mass of the system is free to be whatever we want it to be in order to fit with our theory?
    You're seriously misclassifying Dark Matter Theory (as you call it).

    It is in no way on par with GR. It doesn't deal with gravity. It doesn't "work where GR fails." It doesn't have this mysterious free variable you're talking about.

    From the rotation curves, the amount and distribution of extra mass was calculated. This makes the rotation curves an invalid data point for predictions, and they aren't used as such. From there, other predictions, such as gravitational lensing, were made, and these have held up.
    At this point we're just discussing semantics. Clearly the idea that Dark Matter exists is a theory. Calling it "Dark Matter Theory" is probably not orthodox of me, but hardly a serious mistake. If I cared about semantics I would study English, not Physics.

    GR gives us the formulas that were used to calculate "From the rotation curves, the amount and distribution of extra mass". If they are GR's formulas, that is exactly identical to saying that GR predicted it. There is no tremendous difference between using a theory's formulas, and using the theory itself. The amount of DM is calculated by looking at the way observation deviates from expectation, which is the same as saying that the amount of DM is predicted by asking ourselves how much we need, and where we need it, in order for the theory of GR not to fail.
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  25. #125  
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    Quote Originally Posted by kojax
    GR gives us the formulas that were used to calculate "From the rotation curves, the amount and distribution of extra mass". If they are GR's formulas, that is exactly identical to saying that GR predicted it. There is no tremendous difference between using a theory's formulas, and using the theory itself. The amount of DM is calculated by looking at the way observation deviates from expectation, which is the same as saying that the amount of DM is predicted by asking ourselves how much we need, and where we need it, in order for the theory of GR not to fail.
    Actually, as I told you earlier, the calculations are done using ordinary Newtonian models, not GR. Newtonian models are quite sufficient for this application.

    Before you make any more silly statrments, why don't you do some research and learn a little bit about the problem. Google is your friend in this case.
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  26. #126  
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    I have been following this post ( as I do many others ) and now Kojax is onboard, he/she has the ability to bring out many points that a layman ( as myself ) would not dare to. 8)
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  27. #127  
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    Quote Originally Posted by kojax
    At this point we're just discussing semantics. Clearly the idea that Dark Matter exists is a theory. Calling it "Dark Matter Theory" is probably not orthodox of me, but hardly a serious mistake. If I cared about semantics I would study English, not Physics.

    GR gives us the formulas that were used to calculate "From the rotation curves, the amount and distribution of extra mass". If they are GR's formulas, that is exactly identical to saying that GR predicted it. There is no tremendous difference between using a theory's formulas, and using the theory itself. The amount of DM is calculated by looking at the way observation deviates from expectation, which is the same as saying that the amount of DM is predicted by asking ourselves how much we need, and where we need it, in order for the theory of GR not to fail.
    This is not simply semantics. Dark matter was not conceived to address a shortcoming of GR. GR works very well in every test we've ever thrown at it. It would not suddenly fail without dark matter.

    Also, the amount and distribution of dark matter may have been calculated from the rotation curves, but since then two things have happened. First, other explainations have been ruled out. And second, other observations match predictions made based on assuming dark matter exists. You seem to be ignoring this point.
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  28. #128  
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    Quote Originally Posted by MagiMaster
    This is not simply semantics. Dark matter was not conceived to address a shortcoming of GR. GR works very well in every test we've ever thrown at it. It would not suddenly fail without dark matter.

    Also, the amount and distribution of dark matter may have been calculated from the rotation curves, but since then two things have happened. First, other explainations have been ruled out. And second, other observations match predictions made based on assuming dark matter exists. You seem to be ignoring this point.
    Correct. Dark matter has essentially nothing to do with GR. In fact, on proposed resolution (not particularly popular even with the proposer) is something known as MOND (modified Newtonian dynamics) in which the inverse square law is slightly changed http://en.wikipedia.org/wiki/Modifie...onian_dynamics.

    Thr point is not that MOND is the solution, but rather that the problem is not a GR problem.

    "Dark matter" as it stands is not a solution, but just a name for the mystery. To be a solution one would need to know what dark matter really is. There are some guesses, and much ongoing research, but no one knows what it is or if it really exists. The best available guess is that it is some sort of weakly interacting matter, but that is still just a guess.
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  29. #129 Guesses 
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    Is that all we can come up with here? Dark matter and dark energy are but
    attempts to explain our ignorance of the physics we do not yet understand.
    Yet they are proposed as an explanation and solution to problems of which
    we have no knowledge of. Tut, tut. I always thought science was about
    reason, knowledge, and evaluation of known facts.
    Not regressing into a faith based mentality based upon a belief not
    substantionated by fact or reason.
    Nokton.
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  30. #130  
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    *facepalm*

    So when the situation arises where we know something exists, and we can measure some of its properties, but we don't know what it really is, what are we supposed to do? Throw our hands up and say it's too hard?

    No. We name it, measure it, hypothesize, experiment. It's called the scientific method. At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
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  31. #131  
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    I second MagiMaster's "*facepalm*".
    Sometime's science is about making wild guesses, then designing an experiment to test the idea.
    I mentioned DM once in "Scientific study of Religion" and got accused of pseudoscience.
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  32. #132  
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    Quote Originally Posted by MagiMaster
    *facepalm*

    So when the situation arises where we know something exists, and we can measure some of its properties, but we don't know what it really is, what are we supposed to do? Throw our hands up and say it's too hard?

    No. We name it, measure it, hypothesize, experiment. It's called the scientific method. At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
    Basically dark matter is a recognition that our current knowledge is inadequate to explain what we see and therefore that research is needed. As you note, this is in the highest tradition of objective science.

    Confusion arises only when people fail to recognize that dsrk matter is a working hypothesis and noy established physics.

    We don't know that dark matter exists, but evidence is mounting.
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  33. #133  
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    Quote Originally Posted by MagiMaster
    At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
    More accurately, no one even knows if dark matter and dark energy exist, and there is a pretty good chance that they don't. I for one, refute its existence.
    "Doubt is the origin of Wisdom" - Rene Descartes
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  34. #134  
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    Quote Originally Posted by Waveman28
    Quote Originally Posted by MagiMaster
    At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
    More accurately, no one even knows if dark matter and dark energy exist, and there is a pretty good chance that they don't. I for one, refute its existence.
    As DrRocket mentioned, the evidence currently favors the hypothesis that dark matter exists.
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  35. #135  
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    Quote Originally Posted by MagiMaster
    As DrRocket mentioned, the evidence currently favors the hypothesis that dark matter exists.
    Does it?
    "Doubt is the origin of Wisdom" - Rene Descartes
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  36. #136  
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    Quote Originally Posted by Waveman28
    Quote Originally Posted by MagiMaster
    As DrRocket mentioned, the evidence currently favors the hypothesis that dark matter exists.
    Does it?
    So Waveman28, why shouldn't current evidence support the possibility of DM?
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  37. #137 Facepalm 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by MagiMaster
    *facepalm*

    So when the situation arises where we know something exists, and we can measure some of its properties, but we don't know what it really is, what are we supposed to do? Throw our hands up and say it's too hard?

    No. We name it, measure it, hypothesize, experiment. It's called the scientific method. At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
    Basically dark matter is a recognition that our current knowledge is inadequate to explain what we see and therefore that research is needed. As you note, this is in the highest tradition of objective science.

    Confusion arises only when people fail to recognize that dsrk matter is a working hypothesis and noy established physics.

    We don't know that dark matter exists, but evidence is mounting.
    I am intrigued by the the notion of throwing our hands up it's too hard.
    Would not a scientist better say, there is insufficient data to support a
    meaningful conclusion at this time. That both recognises the hypothesis.
    and our limited understanding of it.
    nokton.
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  38. #138  
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    ...

    So just because we give it a name, we're suddenly making too many assumptions? If you ask any real scientist, they'll tell you that dark matter is just a name and that we know a few of its properties, but not what it really is. They'll probably also go on about what they think is the most likely explanation, but none of them will say anything's for certain.
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  39. #139  
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    Quote Originally Posted by MagiMaster
    Quote Originally Posted by Waveman28
    Quote Originally Posted by MagiMaster
    At the moment, no one knows what dark matter or dark energy really are. We know there's something there though, so we give it a name and work to figure it out.
    More accurately, no one even knows if dark matter and dark energy exist, and there is a pretty good chance that they don't. I for one, refute its existence.
    As DrRocket mentioned, the evidence currently favors the hypothesis that dark matter exists.
    That means that the probability is perceived to be slightly greater for than against. I don't disagree with that. MOND and other solutions are lagging somewhat behind it in terms of confirmation, though that could be the simple result of fewer eyes looking. I just wanted to be clear that if a person disagrees with Dark Matter as a solution, that doesn't make them a pseudo scientist. It's only if you disagree with established physics that you're a pseudo scientist (unless you have some really compelling evidence..... in which case science will soon agree with you.)

    Quote Originally Posted by DrRocket

    Basically dark matter is a recognition that our current knowledge is inadequate to explain what we see and therefore that research is needed. As you note, this is in the highest tradition of objective science.

    Confusion arises only when people fail to recognize that dsrk matter is a working hypothesis and noy established physics.

    We don't know that dark matter exists, but evidence is mounting.
    So it is not established physics, and it is ok to be critical of it.

    At the same time, the fate of GR is still somewhat tied to its success or failure. If it succeeds, GR will have withstood yet another severe test, and Einstein's work will be that much more celebrated. If it fails, then at the least GR will require modification.
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  40. #140  
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    No. If it fails, it means that we still don't know, but after everything else, it's unlikely that modifying GR will be the solution (at least, not to this particular problem.)

    Also, it's been pointed out that modifying gravity cannot account for some of the observations that have been made, ruling those out.
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  41. #141 Albert and the forum 
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    Quote Originally Posted by MagiMaster
    No. If it fails, it means that we still don't know, but after everything else, it's unlikely that modifying GR will be the solution (at least, not to this particular problem.)

    Also, it's been pointed out that modifying gravity cannot account for some of the observations that have been made, ruling those out.
    May we look at this another way, we are not modifying GR, but evaluating it
    in a different way. Check out John Webb, the University of New South Wales,
    and his theory of light absorbance over time in the early stages of the universe.
    If I make a point MagiMaster, how many really understand Alberts equations,
    precious few, though those that do claim to be many.
    You will understand of what I speak.
    nokton.
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  42. #142  
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    Quote Originally Posted by GiantEvil
    Quote Originally Posted by Waveman28
    Quote Originally Posted by MagiMaster
    As DrRocket mentioned, the evidence currently favors the hypothesis that dark matter exists.
    Does it?
    So Waveman28, why shouldn't current evidence support the possibility of DM?
    Possibility isn't a very powerful term. Even though dark matter may be theoretically possible, the likelihood of it being true is a different matter altogether (no pun).
    "Doubt is the origin of Wisdom" - Rene Descartes
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  43. #143 Re: Albert and the forum 
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    Quote Originally Posted by nokton
    Quote Originally Posted by MagiMaster
    No. If it fails, it means that we still don't know, but after everything else, it's unlikely that modifying GR will be the solution (at least, not to this particular problem.)

    Also, it's been pointed out that modifying gravity cannot account for some of the observations that have been made, ruling those out.
    May we look at this another way, we are not modifying GR, but evaluating it
    in a different way. Check out John Webb, the University of New South Wales,
    and his theory of light absorbance over time in the early stages of the universe.
    If I make a point MagiMaster, how many really understand Alberts equations,
    precious few, though those that do claim to be many.
    You will understand of what I speak.
    nokton.
    No, sorry, but I can't understand you. And I've claimed to not understand GR, beyond the basics at least, but I know enough to understand that GR does not hinge on the success or failure of dark matter.
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  44. #144 Re: Albert and the forum 
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    Quote Originally Posted by MagiMaster
    No, sorry, but I can't understand you. And I've claimed to not understand GR, beyond the basics at least, but I know enough to understand that GR does not hinge on the success or failure of dark matter.
    The foundational points of GR will remain regardless of what happens. Gravitational time dilation, and the equivalence principle are pretty much unquestionable. The rest, however, like the Einstein Field Equations, are so complicated that in most cases they can't even be solved entirely, and we have to settle for approximations. In those rare few cases where a perfect solution is possible, the theory agrees with observation very well, but that doesn't mean another theory couldn't arrive at the same predictions.

    http://en.wikipedia.org/wiki/Exact_solutions


    It just seems to me like there has to be a simpler way to describe this effect than one that requires "a system of 10 coupled, nonlinear, hyperbolic-elliptic partial differential equations" I might expect that level of complexity to arise if we were looking at a very large number of different forces and bodies acting on one another, but not all that for just one force. That's just not plausible to me. I suspect that sooner or later, somebody is going to come up with a much simpler set of equations using the same assumptions, which will not require DM in order to work.

    http://en.wikipedia.org/wiki/Einstei...hematical_form
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  45. #145 Re: Albert and the forum 
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    Quote Originally Posted by MagiMaster
    Quote Originally Posted by nokton
    Quote Originally Posted by MagiMaster
    No. If it fails, it means that we still don't know, but after everything else, it's unlikely that modifying GR will be the solution (at least, not to this particular problem.)

    Also, it's been pointed out that modifying gravity cannot account for some of the observations that have been made, ruling those out.
    May we look at this another way, we are not modifying GR, but evaluating it
    in a different way. Check out John Webb, the University of New South Wales,
    and his theory of light absorbance over time in the early stages of the universe.
    If I make a point MagiMaster, how many really understand Alberts equations,
    precious few, though those that do claim to be many.
    You will understand of what I speak.
    nokton.
    No, sorry, but I can't understand you. And I've claimed to not understand GR, beyond the basics at least, but I know enough to understand that GR does not hinge on the success or failure of dark matter.
    Thanx your post MagiMaster. May I venture an opinion to you.
    Albert was about explaining concepts (his experience in the lift demonstrates
    this). Now, the fact is carts and horses, one cannot understand what one
    cannot comprehend. Albert was always about using mathematics to explain
    and describe his concepts. One doesn't have to get deeply involved in the
    math in order to grasp the concept Albert was trying to describe.
    The math was Alberts way of a proof of his contention, and it works very well.
    The rub is, how we interpret Alberts math in GR to the enth degree.
    Any small variation in the equations can lead to conclusions Albert could
    not predict, but have serious impact on how we understand space, time and
    the universe.
    nokton
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  46. #146  
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    Possibility isn't a very powerful term. Even though dark matter may be theoretically possible, the likelihood of it being true is a different matter altogether (no pun).
    Mr. Waveman28, you are wasting your time arguing semantics. I am giving you an opportunity to state your reasoning as to why DM is not existential.
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  47. #147 Re: Albert and the forum 
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    Quote Originally Posted by kojax
    It just seems to me like there has to be a simpler way to describe this effect than one that requires "a system of 10 coupled, nonlinear, hyperbolic-elliptic partial differential equations" I might expect that level of complexity to arise if we were looking at a very large number of different forces and bodies acting on one another, but not all that for just one force. That's just not plausible to me. I suspect that sooner or later, somebody is going to come up with a much simpler set of equations using the same assumptions, which will not require DM in order to work.
    Sure. It'd be nice, but there's every possibility that the final theory will be even more complicated, not less.

    Also consider that those equations don't simply describe "one force," they describe gravity and how everything interacts with everything else through it.

    Quote Originally Posted by nokton
    Thanx your post MagiMaster. May I venture an opinion to you.
    Albert was about explaining concepts (his experience in the lift demonstrates
    this). Now, the fact is carts and horses, one cannot understand what one
    cannot comprehend. Albert was always about using mathematics to explain
    and describe his concepts. One doesn't have to get deeply involved in the
    math in order to grasp the concept Albert was trying to describe.
    The math was Alberts way of a proof of his contention, and it works very well.
    The rub is, how we interpret Alberts math in GR to the enth degree.
    Any small variation in the equations can lead to conclusions Albert could
    not predict, but have serious impact on how we understand space, time and
    the universe.
    nokton
    Nope. Still can't really understand what you're getting at, but it's sounding like you have some misconceptions about how math and physics are related.
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  48. #148 Re: Albert and the forum 
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    Quote Originally Posted by MagiMaster
    Quote Originally Posted by kojax
    It just seems to me like there has to be a simpler way to describe this effect than one that requires "a system of 10 coupled, nonlinear, hyperbolic-elliptic partial differential equations" I might expect that level of complexity to arise if we were looking at a very large number of different forces and bodies acting on one another, but not all that for just one force. That's just not plausible to me. I suspect that sooner or later, somebody is going to come up with a much simpler set of equations using the same assumptions, which will not require DM in order to work.
    Sure. It'd be nice, but there's every possibility that the final theory will be even more complicated, not less.

    Also consider that those equations don't simply describe "one force," they describe gravity and how everything interacts with everything else through it.

    Quote Originally Posted by nokton
    Thanx your post MagiMaster. May I venture an opinion to you.
    Albert was about explaining concepts (his experience in the lift demonstrates
    this). Now, the fact is carts and horses, one cannot understand what one
    cannot comprehend. Albert was always about using mathematics to explain
    and describe his concepts. One doesn't have to get deeply involved in the
    math in order to grasp the concept Albert was trying to describe.
    The math was Alberts way of a proof of his contention, and it works very well.
    The rub is, how we interpret Alberts math in GR to the enth degree.
    Any small variation in the equations can lead to conclusions Albert could
    not predict, but have serious impact on how we understand space, time and
    the universe.
    nokton
    Nope. Still can't really understand what you're getting at, but it's sounding like you have some misconceptions about how math and physics are related.
    Thanx your post MagiMaster, I have no misconceptions about math and physics,
    rather I have some concern about how they are interpreted.
    Math and physics can be written down, and work, but if we cannot grasp
    the concept of why 2 and 2 make 4, or the meaning of PI, then how can we
    understand our labours to find the truth.
    nokton.
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  49. #149 Re: Albert and the forum 
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    Quote Originally Posted by nokton
    Thanx your post MagiMaster, I have no misconceptions about math and physics,
    rather I have some concern about how they are interpreted.
    Math and physics can be written down, and work, but if we cannot grasp
    the concept of why 2 and 2 make 4, or the meaning of PI, then how can we
    understand our labours to find the truth.
    nokton.
    Just because you can't understand them doesn't mean they aren't understandable.

    Really, science doesn't care about understanding, it cares about explaining. If the math explains everything, that's all there is to it. The philosophers can try to understand things. (At least, in the sense you're using the word.) There is no "meaning" behind GR, or QM, or Newtonian mechanics, or any other theory. They're just ways of explaining how things work, not why.
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  50. #150 Albert and the forum 
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    Take issue with you about understanding and explaining.
    Point one, how can you explain something you not understand.
    Point two, a beam of light passes through a pane of glass, and
    slows down, then resumes its speed, what causes this? And why
    did it slow down? I respect your posts Magi, but do not suffer fools.
    nokton.
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  51. #151 Re: Albert and the forum 
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    Quote Originally Posted by nokton
    Take issue with you about understanding and explaining.
    Point one, how can you explain something you not understand.
    Take your own advice, in which case you should remain completely silent.

    Quote Originally Posted by nokton
    Point two, a beam of light passes through a pane of glass, and
    slows down, then resumes its speed, what causes this? And why
    did it slow down? I respect your posts Magi, but do not suffer fools.
    nokton.
    That is exactly what happens, though it may be counterintuitive to a fool.

    It is what is responsible for refraction, the principle on which lenses operate. It is not unlike the situation with sound, which is dependent on material properties, at least insofar as macroscopic effects are concerned.

    With light there are some things that need to be understood, even if the understanding is beyond your capability. First, photons always, on average, travel at c -- that is basic quantum electrodynamics. Second, the propagation of light through a medium is a process of interaction between photons and the electrons in the atoms of the medium, which results in a net propagation speed that is less than c. There is no mystery in the propagation speed returning to c when the photons reach a vacuum or in having a different propagation speed in a different medium.

    So what is revealed is that nokton does not suffer himself, who is after all just another fool.
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  52. #152  
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    DrRocket beat me to an explanation for light and glass, but I'll add that in science we often come up with ways of explaining things that we don't completely understand. We know for a fact that we don't understand all the intricacies of the universe, but between GR and QED, we can explain it pretty well. It's just how science works.

    One we have an explanation, the philosophers can work out an understanding of what its explaining.
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  53. #153  
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    Quote Originally Posted by MagiMaster
    One we have an explanation, the philosophers can work out an understanding of what its explaining.
    If you put all of the philosophers in the world end-to-end, they would not reach a ..........conclusion.
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  54. #154 Re: Albert and the forum 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by nokton
    Take issue with you about understanding and explaining.
    Point one, how can you explain something you not understand.
    Take your own advice, in which case you should remain completely silent.

    Quote Originally Posted by nokton
    Point two, a beam of light passes through a pane of glass, and
    slows down, then resumes its speed, what causes this? And why
    did it slow down? I respect your posts Magi, but do not suffer fools.
    nokton.
    That is exactly what happens, though it may be counterintuitive to a fool.

    It is what is responsible for refraction, the principle on which lenses operate. It is not unlike the situation with sound, which is dependent on material properties, at least insofar as macroscopic effects are concerned.

    With light there are some things that need to be understood, even if the understanding is beyond your capability. First, photons always, on average, travel at c -- that is basic quantum electrodynamics. Second, the propagation of light through a medium is a process of interaction between photons and the electrons in the atoms of the medium, which results in a net propagation speed that is less than c. There is no mystery in the propagation speed returning to c when the photons reach a vacuum or in having a different propagation speed in a different medium.

    So what is revealed is that nokton does not suffer himself, who is after all just another fool.
    I find the above interesting, but not entirely accurate or convincing. Light has
    wavelengths, and the medium that light passes though can absorb some
    wavelengths. Quantum electrodynamics can predict the wavelengths of light
    absorbed by magnesium and iron atoms. Point is, 12 billion years ago, iron
    and magnesium absorbed photon wavelengths differently. This brings SR into
    question, any comments valued and respected.
    nokton.
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  55. #155  
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    Wait, are you saying that elements have undergone evolution in the past 12 billion years? In what way were photons absorbed differently 12 billion years ago?
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  56. #156 Re: Albert and the forum 
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    Quote Originally Posted by nokton
    I find the above interesting, but not entirely accurate or convincing. Light has
    wavelengths, and the medium that light passes though can absorb some
    wavelengths. Quantum electrodynamics can predict the wavelengths of light
    absorbed by magnesium and iron atoms. Point is, 12 billion years ago, iron
    and magnesium absorbed photon wavelengths differently. This brings SR into
    question, any comments valued and respected.
    nokton.
    The quote is accurate whether you find it that way or not.

    "Convincing" is dependent on the background and intelligence of the reader. I have little hope of convincing you, and care less.

    Your assertion regarding differences in physical law over a time span of 12 billion years are without any foundation -- pure rubbish just like the rest of your concept of physics. You are a menace to innocent young lurkers. You would be a threat to yourself if there were anything of value to threaten.

    Please limit posts of this garbage to the Pseodoscience forum where it belongs.
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  57. #157  
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    Thank you for the clarification DrRocket. I hadn't heard anything of the sort, but I had not heard anything to the contrary. All that remained was the intuition that it was bad physics. :?
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  58. #158 Re: Albert and the forum 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by nokton
    I find the above interesting, but not entirely accurate or convincing. Light has
    wavelengths, and the medium that light passes though can absorb some
    wavelengths. Quantum electrodynamics can predict the wavelengths of light
    absorbed by magnesium and iron atoms. Point is, 12 billion years ago, iron
    and magnesium absorbed photon wavelengths differently. This brings SR into
    question, any comments valued and respected.
    nokton.
    The quote is accurate whether you find it that way or not.

    "Convincing" is dependent on the background and intelligence of the reader. I have little hope of convincing you, and care less.

    Your assertion regarding differences in physical law over a time span of 12 billion years are without any foundation -- pure rubbish just like the rest of your concept of physics. You are a menace to innocent young lurkers. You would be a threat to yourself if there were anything of value to threaten.

    Then check out New Scientist 23 October, headline, Dawn of a new Physics
    Check out John Webbs findings, and the fact that no one can fault an
    error in his analysis.
    You are a product of rote learning and have a closed mind.
    Open it.
    nokton.


    Please limit posts of this garbage to the Pseodoscience forum where it belongs.
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  59. #159 Re: Falling through the event horizon 
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    Quote Originally Posted by geo_man
    If a hapless traveller falls into a black hole, is there any way for him to tell whether he has crossed the event horizon?
    He never crosses the event horizon. To an outside observer his time slows down as he approaches it. To him, however, the event horizon recedes in front of him so he never reaches it; his local spacetime remains normal to him. Behind him he sees the outer universe blueshift as its time appears to speed up relative to him.
    You learn something new each day if you're not careful!
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  60. #160 Falling through the event horizon 
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    You getting close muppet, thats why the spaghetti effect can never happen.
    One caveat, light is destroyed when it passes the event horizon, and the
    information within it, you cannot visualise the universe outside once you
    are inside the event horizon......
    Nokton.
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  61. #161 Re: Falling through the event horizon 
    . DrRocket's Avatar
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    Aug 2008
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    5,486
    Quote Originally Posted by nokton
    You getting close muppet, thats why the spaghetti effect can never happen.
    One caveat, light is destroyed when it passes the event horizon, and the
    information within it, you cannot visualise the universe outside once you
    are inside the event horizon......
    Nokton.
    Are you inside a black hole ? There is certainly no information being transmitted.
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  62. #162 event horizon 
    Forum Junior
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    Dr, enjoy your esoteric cogitations, and respect your right to hold your
    opinions, without prejudice. My last was based on hypotheses, not
    real time observation, hoped you would have realised that.
    A few days ago, posed an hypothetical puzzle, no mirrors or tricks, three
    students each facing each other with white caps on, knowing only that there
    were 5 caps,two black and 3 white, but not knowing what colour cap they had
    on. How did student 1 know what colour cap he had on? Look forward to your
    response.
    nokton.
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