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Thread: Before the universe

  1. #1 Before the universe 
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    i've been pondering on this one for a while, but i still have some problems formulating my ideas properly. here's my best shot:

    i read this article:
    http://www.fortunecity.com/emachines.../big-bang.html

    and specifically this part:
    " In this case, the uncertainty can, under special circumstances, affect the identities of space and time. For a very, very brief duration, it is possible for time and space to merge in identity, for time to become, so to speak, spacelike-just another dimension of space. "

    and it got gears turning in my head.

    Einstein Theory states that time and space forms our universe, spacetime.
    i think its most likely that outside of our universe there is space, but no time.
    time to me seems to be the inherent trait that makes something to exist.
    the big bang, would be caused by a large amount of space being converted into time, creating a spacetime bubble in space, our universe.
    time is tightly interwoven with energy. energy depends on time.
    matter would be the equivalent of space with a sprinkling of time.
    outside of our universe, because there is no time. cause and effect would break down. everything would be random,
    there wouldn't be any before to precede after.

    things are random at the quantum level too.
    so maybe at the quantum level, things are "barely existing", and time doesn't have as strong a hold on space.
    '
    well, this is pretty much the extent of my idea as it currently is. any input, corrections, and explanations of current theories would be appreciated.


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  3. #2 Re: Before the universe 
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    Quote Originally Posted by dejawolf
    i've been pondering on this one for a while, but i still have some problems formulating my ideas properly. here's my best shot:

    i read this article:
    http://www.fortunecity.com/emachines.../big-bang.html

    and specifically this part:
    " In this case, the uncertainty can, under special circumstances, affect the identities of space and time. For a very, very brief duration, it is possible for time and space to merge in identity, for time to become, so to speak, spacelike-just another dimension of space. "

    and it got gears turning in my head.

    Einstein Theory states that time and space forms our universe, spacetime.
    i think its most likely that outside of our universe there is space, but no time.
    time to me seems to be the inherent trait that makes something to exist.
    the big bang, would be caused by a large amount of space being converted into time, creating a spacetime bubble in space, our universe.
    time is tightly interwoven with energy. energy depends on time.
    matter would be the equivalent of space with a sprinkling of time.
    outside of our universe, because there is no time. cause and effect would break down. everything would be random,
    there wouldn't be any before to precede after.

    things are random at the quantum level too.
    so maybe at the quantum level, things are "barely existing", and time doesn't have as strong a hold on space.
    '
    well, this is pretty much the extent of my idea as it currently is. any input, corrections, and explanations of current theories would be appreciated.
    Davies is a physicist, but he is also an author of popularizations and he likes to sell books. The commercial motive apparently results in some sensational statements and in speculative ideas being portrayed as closer to established science than is actually the case. The article that you read is an example.

    General relativity (GR) does indeed treat space and time as a single thing -- the spacetime manifold. Space and time are local, not global concepts in GR. But what Davies talks bout is not that, but rather a speculative idea relating to some combination of quantum mechanics (QM) and GR. Unfortunately there is no current accepted theory that can handle QM and GR simultaneously. So what he is describing is an idea of Hartle and Hawking as to what might be possible if we understood things better and had such a model.

    Nobody knows what is going on when quantum effects and very large gravitational effects are both important.

    He also makes the statement that " For starters, given an infinite amount of time, anything that can happen will already have happened, for if a physical process is likely to occur with a certain nonzero probability-however small-then given an infinite amount of time the process must occur, with probability one. By now, the universe should have reached some sort of final state in which all possible physical processes have run their course. " This is flawed. It is true that " if a physical process is likely to occur with a certain nonzero probability-however small-then given an infinite amount of time the process must occur, with probability one', but this statement implies that one has the capability to apply the mathematical theory and in particular a version of the theorem known as the "Law of Large Numbers". To do that one must have a probability space that describes all physical processes and their probabilities. No such probability space is known to exist. So here we see Davies stating rank speculation as fact.

    Take that article with a grain, or a trainload, of salt.

    In the current cosmological model, based on GR, there is no "outside our universe" and no "before" the big bang. There are speculative models, very speculative, in which such ideas make sense, but neither solid theory nor solid physical evidence to support them. Maybe someday one such idea will bear fruit, but for the moment they are just speculation.

    For other very speculative ideas you might read Roger Penrose's new book Cycles of Time.. Penrose is much more careful than is Davies to note when he is speculating.


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    Interesting to ponder on, but to be sure, this would be better suited for the New Hypothesis section, no?
    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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  5. #4  
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    Quote Originally Posted by KALSTER
    Interesting to ponder on, but to be sure, this would be better suited for the New Hypothesis section, no?
    Maybe. I took it as a question regarding the article by Paul Davies more so than proposing an alternative theory. But I could have misunderstood the intent.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by KALSTER
    Interesting to ponder on, but to be sure, this would be better suited for the New Hypothesis section, no?
    Maybe. I took it as a question regarding the article by Paul Davies more so than proposing an alternative theory. But I could have misunderstood the intent.
    Actually, I posted it without having seen your reply. I think your reply would work no matter what the intent was in any case.
    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
    "All people know the same truth. Our lives consist of how we chose to distort it." - Harry Block
    "It is the mark of an educated mind to be able to entertain a thought without accepting it." - Aristotle
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    hmm, i posted a response to a post on the philosophy forum, and was told this belonged in the physics forum.

    its a proposal for a thesis, based on a few ideas i have, and that article,
    and i'd like to have it picked apart and beaten down with a little peer reviewing.

    it relies on this statement:

    "In this case, the uncertainty can, under special circumstances, affect the identities of space and time. For a very, very brief duration, it is possible for time and space to merge in identity, for time to become, so to speak, spacelike-just another dimension of space"

    is this a known physical fact, or just wild speculation, that time can be converted into a dimension of space?
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
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    I'm with Doc on this, dejawold. It's stretching relativity and quantum mechanics too far. I'll see if I can explain this in simple terms.

    A little special relativity first: if you're sitting motionless in the universe with respect to the CMBR, you measure space and time with the proverbial rods and clocks. Then when you move fast through the universe, your measurements change in line with the Lorentz transformation. Your measures of space and time "rotate", so you now measure them differently. But you don't actually change space-time in the universe, all you changed is you. You now "see it" differently. Because you're moving.

    A little quantum mechanics next: the Heisenberg Uncertainty Principle is to do with waves. Waves don't have a precise position, they're extended entities, the momentum they convey is spread out across space, they're moving, and it takes time for all the momentum to impact you. If you're moving towards a wave, your measurement of how spread out it is in space, and the time it takes for the momentum to impact you, changes. If you move very fast, the wave looks like it's a high frequency wave, and thus more like a "point particle". But again you didn't actually change the wave. All you changed is you. By moving.

    Note the importance of motion in the above. And note that the universe is what it is. Yes there's galaxies and stars and more, but in simple terms it's space full of waves and fields. Call them electromagnetic waves, gravitational fields, or quantum fields. Call some of the latter matter. These things interact, and the universe evolves. We track this back to the big bang, but that's as far as we can go. We can't assert that "time emerged out of space" and that the universe was born of a probabilistic quantum fluctuation in timeless space. The reason is this: there is no motion in timeless space, because the measure you call time is actually a cumulative measure of local motion. No motion is no motion, so there aren't any waves, and there aren't any fluctuations.

    The statement you asked about is an assertion, not a fact. However it's presented as a fact, and then it's used to present an answer that sounds plausible. But in the end it isn't one that's backed up by actual evidence. It relies instead on a shrouded inner core of mathematical abstraction that is inpenetrable to you. This is how it's usually done with this sort of thing. In the old days they used to use Latin.
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    Correct me if I'm wrong, Farsight, bu according to some solutions for black holes in GR, the predicted "singularity, being both a location and a time, can be either a timelike or spacelike slice ( or as DrR likes to say foliation ) of space/time, ie. it can be either depending on conditions, such as spin.
    Now I realise that making conclusions based upon singularities, which may not exist, is not valid, but GR's solutions do allow for time -space flip-flopping.
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    A little special relativity first: if you're sitting motionless in the universe with respect to the CMBR, you measure space and time with the proverbial rods and clocks. Then when you move fast through the universe, your measurements change in line with the Lorentz transformation. Your measures of space and time "rotate", so you now measure them differently. But you don't actually change space-time in the universe, all you changed is you. You now "see it" differently. Because you're moving.
    hmm.. so what you're saying is that when my motion is relative to the CMBR, i measure time normally.
    but when i move in relation to the CMBR, my measure of time stays the same, in my frame of reference, and the time at CMBR stays the same, but the motion causes time to be measured differently relative to eachother?
    does this have something to do with the twin comparison, where one twin is in a spaceship, the other is on earth, and when one twin moves at a speed close to the speed of light, the other twin back on earth will age more quickly than the twin in the spaceship?
    or are you saying that the twin thing is just temporary, that when you move near the speed of light, viewing from the spaceship, the twin back on earth will look to have aged more quickly than the twin in the spaceship, because of spacetime being bent, but when the other twin slows down again, they will both be the same age again?

    A little quantum mechanics next: the Heisenberg Uncertainty Principle is to do with waves. Waves don't have a precise position, they're extended entities, the momentum they convey is spread out across space, they're moving, and it takes time for all the momentum to impact you. If you're moving towards a wave, your measurement of how spread out it is in space, and the time it takes for the momentum to impact you, changes. If you move very fast, the wave looks like it's a high frequency wave, and thus more like a "point particle". But again you didn't actually change the wave. All you changed is you. By moving.
    are you talking about the "doppler effect" on light? things moving away from you at a high speed, light from the object will get shifted more towards red, because the waves between you and the object will be stretched out?

    Note the importance of motion in the above. And note that the universe is what it is. Yes there's galaxies and stars and more, but in simple terms it's space full of waves and fields. Call them electromagnetic waves, gravitational fields, or quantum fields. Call some of the latter matter. These things interact, and the universe evolves. We track this back to the big bang, but that's as far as we can go. We can't assert that "time emerged out of space" and that the universe was born of a probabilistic quantum fluctuation in timeless space. The reason is this: there is no motion in timeless space, because the measure you call time is actually a cumulative measure of local motion. No motion is no motion, so there aren't any waves, and there aren't any fluctuations.
    string theory?
    everything is waves, waves are motion, motion needs time to work.
    no time, no motion, no waves, no nothing.

    i hope i understood correctly.

    i guess what i'm saying, is that instead of an orderly line of time, you instead have all this time compressed into a point of chaos, where things move infinitely fast, or infinitely slow, or randomly.
    would something moving infinitely fast be random?
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
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  11. #10  
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    Quote Originally Posted by dejawolf

    hmm.. so what you're saying is that when my motion is relative to the CMBR, i measure time normally.
    but when i move in relation to the CMBR, my measure of time stays the same, in my frame of reference, and the time at CMBR stays the same, but the motion causes time to be measured differently relative to eachother?
    Not quite.

    In general relativity there is no universal "reference frame" and you can only compare clocks at a single point in spacetime -- at a point of intersection of the world lines of the clocks. So there is no meaning to "the motion causes time to be measured differently relative to each other".

    The length of those world lines, in the metric of spacetime is "proper time", and it is what is measured by the clocks.


    Quote Originally Posted by dejawolf
    does this have something to do with the twin comparison, where one twin is in a spaceship, the other is on earth, and when one twin moves at a speed close to the speed of light, the other twin back on earth will age more quickly than the twin in the spaceship?
    or are you saying that the twin thing is just temporary, that when you move near the speed of light, viewing from the spaceship, the twin back on earth will look to have aged more quickly than the twin in the spaceship, because of spacetime being bent, but when the other twin slows down again, they will both be the same age again?
    The twins have different world lines with different propere times. The "traveling twin has a shorter world line.

    A little quantum mechanics next: the Heisenberg Uncertainty Principle is to do with waves. Waves don't have a precise position, they're extended entities, the momentum they convey is spread out across space, they're moving, and it takes time for all the momentum to impact you. If you're moving towards a wave, your measurement of how spread out it is in space, and the time it takes for the momentum to impact you, changes. If you move very fast, the wave looks like it's a high frequency wave, and thus more like a "point particle". But again you didn't actually change the wave. All you changed is you. By moving.

    Quote Originally Posted by dejawolf
    are you talking about the "doppler effect" on light? things moving away from you at a high speed, light from the object will get shifted more towards red, because the waves between you and the object will be stretched out?
    That is the doppler effect, but you are missing the point. The point is that the effect is observer-dependent.


    Quote Originally Posted by dejawolf
    string theory?
    everything is waves, waves are motion, motion needs time to work.
    no time, no motion, no waves, no nothing.

    i hope i understood correctly.

    i guess what i'm saying, is that instead of an orderly line of time, you instead have all this time compressed into a point of chaos, where things move infinitely fast, or infinitely slow, or randomly.
    would something moving infinitely fast be random?
    No, you have misunderstood badly. This has nothing to do with string theory.

    There is no such thing as an orderly line of time, except locally.

    "all this time compressed into a point of chaos, where things move infinitely fast, or infinitely slow, or randomly" is meaningless. Nothing can move infinitely fast.
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    Quote Originally Posted by MigL
    Correct me if I'm wrong, Farsight, but according to some solutions for black holes in GR, the predicted "singularity, being both a location and a time, can be either a timelike or spacelike slice ( or as DrR likes to say foliation ) of space/time, ie. it can be either depending on conditions, such as spin. Now I realise that making conclusions based upon singularities, which may not exist, is not valid, but GR's solutions do allow for time-space flip-flopping.
    As far as I know you're right, MigL, but I'd say the important issue is whether those solutions are real solutions. When it comes to black holes and GR there's the Misner/Thorne/Wheeler "geometrical interpretation" that predicts central singularities. This is prevalent - most people are under the impression that this is what GR says. However they tend not to know about the Weinberg "field interpretation" of GR that addresses the coordinate speed of light and says clocks stop at the event horizon and that's the end of the story. When you imagine this clock to be a light clock you appreciate that light stops too, and that any local proper time is being measured on a stopped clock. This isn't some silly idea from some kid on the internet, it's from a Nobel Laureate, and IMHO it puts a very different slant on things: the solutions that go beyond the event horizon are doing a surreptitious little jump over the end of time.
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    Quote Originally Posted by dejawolf
    hmm.. so what you're saying is that when my motion is relative to the CMBR, i measure time normally. but when i move in relation to the CMBR, my measure of time stays the same, in my frame of reference, and the time at CMBR stays the same, but the motion causes time to be measured differently relative to each other?
    Kind of, but what you said sounded a bit wrong. Let me put it another way: if you have no motion relative to the CMBR, your measure of time is the same as "universe time", and you'd say the universe was 13.7 billion years old. If you're moving so fast that you see the CMBR blue-shifted in one direction and red-shifted in the opposite direction, it isn't like this. You might traverse a galaxy in what seems like 10 years to you, but all the observers on the planets you pass would say it took you 100,000 years.

    Quote Originally Posted by dejawolf
    does this have something to do with the twin comparison, where one twin is in a spaceship, the other is on earth, and when one twin moves at a speed close to the speed of light, the other twin back on earth will age more quickly than the twin in the spaceship?
    Yes. Clocks don't clock up "the flow of time", what they really clock up is local motion. The rate of this local motion is reduced when you move fast through the universe. Note though that if there were no outside references such as the CMBR or stars and planets, you wouldn't know you were moving. If I zipped past you at close to the speed of light you see my clocks running slow, and I see your clocks running slow. This is often offered as a paradox, but it's just a "perspective" thing. If we're a long way apart I look smaller to you and you look smaller to me, but we don't say "Wooo! Paradox!"

    Quote Originally Posted by dejawolf
    or are you saying that the twin thing is just temporary, that when you move near the speed of light, viewing from the spaceship, the twin back on earth will look to have aged more quickly than the twin in the spaceship, because of spacetime being bent, but when the other twin slows down again, they will both be the same age again?
    No.

    Quote Originally Posted by dejawolf
    are you talking about the "doppler effect" on light? things moving away from you at a high speed, light from the object will get shifted more towards red, because the waves between you and the object will be stretched out?
    Yes, the doppler effect does come into it.

    Quote Originally Posted by dejawolf
    string theory? everything is waves, waves are motion, motion needs time to work. no time, no motion, no waves, no nothing.
    Not string theory, quantum theory, but otherwise yes.

    Quote Originally Posted by dejawolf
    i guess what i'm saying, is that instead of an orderly line of time, you instead have all this time compressed into a point of chaos, where things move infinitely fast, or infinitely slow, or randomly.would something moving infinitely fast be random?
    No, things move infinitely slow. So they don't move at all. And since clocks clock up local motion and "the time" is a cumulative measure of local motion, that means that when nothing moves, there is no time.
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    Quote Originally Posted by Farsight
    As far as I know you're right, MigL, but I'd say the important issue is whether those solutions are real solutions. When it comes to black holes and GR there's the Misner/Thorne/Wheeler "geometrical interpretation" that predicts central singularities. This is prevalent - most people are under the impression that this is what GR says. However they tend not to know about the Weinberg "field interpretation" of GR that addresses the coordinate speed of light and says clocks stop at the event horizon and that's the end of the story. When you imagine this clock to be a light clock you appreciate that light stops too, and that any local proper time is being measured on a stopped clock. This isn't some silly idea from some kid on the internet, it's from a Nobel Laureate, and IMHO it puts a very different slant on things: the solutions that go beyond the event horizon are doing a surreptitious little jump over the end of time.
    The theory of singularities for black holes and the big bang (the singularities are a bit different) is due to Hawking and Penrose, not MTW.

    It is not contested, an you will find a very brief discussion in Weinberg's Gravitation and Cosmology, Principles and Applications of the General Theory of Relativity (see in particular pps. 348,349) . Apparently someone neglected to tell Weinberg of his alternate theory.

    The only references that I can find to this alternative interpretation seem to be you. http://www.thenakedscientists.com/fo...?topic=28291.0 and this article http://www.mathpages.com/rr/s7-02/7-02.htm which appears to be in error in both substance and in referring to Weinberg's book.

    Proper time is not an abstraction. It is in fact what clocks measure. It is the length of a world line and the time measured by a clock having that world line.

    What is misleading is the singular nature of the event horizon in Schwarzchild coordinates. It is now well-known that this is not a real singularity but is an artifact of the coordinate system itself -- a limitation of the local chart in geometric language.
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    Quote Originally Posted by Farsight
    You might traverse a galaxy in what seems like 10 years to you, but all the observers on the planets you pass would say it took you 100,000 years.
    ok. this is the way i've always understood it, in that traveling very fast is essentially a time machine. what i said was not what i meant.
    i said "but the motion causes time to be measured differently relative to each other?"
    but it should have been
    "but the motion causes time to BE different relative to each other?"

    Quote Originally Posted by Farsight
    This is often offered as a paradox, but it's just a "perspective" thing. If we're a long way apart I look smaller to you and you look smaller to me, but we don't say "Wooo! Paradox!"
    ok. just had to make sure that the way i understood things were correct.

    Quote Originally Posted by Farsight
    No, things move infinitely slow. So they don't move at all. And since clocks clock up local motion and "the time" is a cumulative measure of local motion, that means that when nothing moves, there is no time.
    hmmm. can things be completely stationary?
    afaik, you can only get very close to absolute zero, but you can never make something cool to the exact point of absolute zero, which would be complete motionlessness. and what would happend if something completely stopped moving?
    would it stop existing?

    also, another question. can a wave be of infinite length, or does it always propagate between 2 points in space?
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    Quote Originally Posted by DrRocket
    The theory of singularities for black holes and the big bang (the singularities are a bit different) is due to Hawking and Penrose, not MTW. It is not contested, an you will find a very brief discussion in Weinberg's Gravitation and Cosmology, Principles and Applications of the General Theory of Relativity (see in particular pps. 348,349) . Apparently someone neglected to tell Weinberg of his alternate theory...
    SW says "I don't agree with Brown. The difference between me and Misner, Thorne, and Wheeler is not in the consequences of general relativity, but in its motivation". I'll check this further.

    Quote Originally Posted by DrRocket
    Proper time is not an abstraction. It is in fact what clocks measure. It is the length of a world line and the time measured by a clock having that world line.
    It is an abstraction. Clocks clock up local motion. A world line is an abstract thing, not something real. And when a clock stops, it doesn't measure anything.

    Quote Originally Posted by DrRocket
    What is misleading is the singular nature of the event horizon in Schwarzchild coordinates. It is now well-known that this is not a real singularity but is an artifact of the coordinate system itself -- a limitation of the local chart in geometric language.
    Sorry Doc, but the coordinate system is abstract too. And there's no getting past the end of time. Perhaps we hould have a new thread on what's well-known covering http://casa.colorado.edu/~ajsh/schwp.html .
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    Quote Originally Posted by dejawolf
    ok. this is the way i've always understood it, in that traveling very fast is essentially a time machine. what i said was not what i meant.
    i said "but the motion causes time to be measured differently relative to each other?" but it should have been "but the motion causes time to BE different relative to each other?"
    There are no time machines, dejawolf. You were right with "but the motion causes time to be measured differently" because time is a cumulative measure of local motion. If you sped off into space at .999c then turned round and came back to meet me, we meet up at the same time. You don't miss me by a year. You experienced less local motion so you experienced less of the thing we call time, that's all. You didn't travel through time, you travelled through space.

    Quote Originally Posted by dejawolf
    hmmm. can things be completely stationary? afaik, you can only get very close to absolute zero, but you can never make something cool to the exact point of absolute zero, which would be complete motionlessness. and what would happend if something completely stopped moving? would it stop existing?
    Temperature is something of a side issue. It's a measure of the average rate of local motion. But see http://imagine.gsfc.nasa.gov/docs/as...s/971111e.html re black holes. The bigger the black hole, the colder it is. It doesn't stop existing.

    Quote Originally Posted by dejawolf
    also, another question. can a wave be of infinite length
    No. There are no infinities in nature.

    Quote Originally Posted by dejawolf
    or does it always propagate between 2 points in space?
    No. A standing wave doesn't propagate. Of course, one might then say that it isn't really a wave. The evanescent wave aka near field is an example of this.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    What is misleading is the singular nature of the event horizon in Schwarzchild coordinates. It is now well-known that this is not a real singularity but is an artifact of the coordinate system itself -- a limitation of the local chart in geometric language.
    Sorry Doc, but the coordinate system is abstract too. And there's no getting past the end of time. Perhaps we hould have a new thread on what's well-known covering http://casa.colorado.edu/~ajsh/schwp.html.
    It is well known, as DrRocket said, that the Schwarzschild radius (the event horizon) is a coordinate singularity, an artifact of the Schwarzschild coordinates, which is shown not be singular when using Kruskal-Szekeres coordinates, as shown at the bottom of the page you linked. If you are falling into a black hole, time does not end at the event horizon.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    The theory of singularities for black holes and the big bang (the singularities are a bit different) is due to Hawking and Penrose, not MTW. It is not contested, an you will find a very brief discussion in Weinberg's Gravitation and Cosmology, Principles and Applications of the General Theory of Relativity (see in particular pps. 348,349) . Apparently someone neglected to tell Weinberg of his alternate theory...
    SW says "I don't agree with Brown. The difference between me and Misner, Thorne, and Wheeler is not in the consequences of general relativity, but in its motivation". I'll check this further.
    ????

    Motivation is philosophy. What we are talking about are consequences.

    Who is Brown ?

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    Proper time is not an abstraction. It is in fact what clocks measure. It is the length of a world line and the time measured by a clock having that world line.
    It is an abstraction. Clocks clock up local motion. A world line is an abstract thing, not something real. And when a clock stops, it doesn't measure anything.
    A clock only stops when it malfunctions. Time does not in any way shape or form stop at the event horizon of a black hole.

    Proper time is precisely what is measured by your wristwatch. In fact propertime is sometines called "wristwatch time" -- it is time along the world line of the wearer.

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    What is misleading is the singular nature of the event horizon in Schwarzchild coordinates. It is now well-known that this is not a real singularity but is an artifact of the coordinate system itself -- a limitation of the local chart[ in geometric language.
    Sorry Doc, but the coordinate system is abstract too. And there's no getting past the end of time. Perhaps we hould have a new thread on what's well-known covering http://casa.colorado.edu/~ajsh/schwp.html.
    Your link does not work.

    The is no "end of time" associated with the event horizon of a black hole. Neither is the horizon singular.

    ANY coordinate system, indeed any mathematical model is an abstraction. What is your point ?
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    The link as posted has an erroneous full stop at the end, here is the fixed link:

    http://casa.colorado.edu/~ajsh/schwp.html
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    Quote Originally Posted by SpeedFreek
    The link as posted has an erroneous full stop at the end, here is the fixed link:

    http://casa.colorado.edu/~ajsh/schwp.html
    OK

    This simply shows the "singularity" of the Schwarzchild coordinate system, which is NOT a true singularity.

    The basic problem is that GR treats spacetime as a Lorentzian manifold and manifolds are described locally by charts, which physicists call coordinate systems. Charts are not global, and one can find singularities, as with the Schwarzchild system, that are due solely to the limitations of the chart, but are not physically meaningful.

    There is nothing to discuss here. The problems with the event horizon "singularity" are, as you noted, well known. There is no singularity.
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    Quote Originally Posted by SpeedFreek
    It is well known, as DrRocket said, that the Schwarzschild radius (the event horizon) is a coordinate singularity, an artifact of the Schwarzschild coordinates, which is shown not be singular when using Kruskal-Szekeres coordinates, as shown at the bottom of the page you linked. If you are falling into a black hole, time does not end at the event horizon.
    There's no other way to say this, SpeedFreek, so I'll spit it out: it's well known, but it's wrong. Take a look at the Schwarzschild spacetime diagram on http://casa.colorado.edu/~ajsh/schwp.html . Note that the vertical axis represents time. The curves on the right of sweep up to future infinity. Kruskal-Szekeres and Eddington–Finkelstein coordinates employ a mathematical sleight of hand to get past this. Imagine you're falling into a black hole whilst I observe from a safe distance, and we plot your proper time against mine, which we describe as coordinate timei:

    You Me
    1ns 1ns
    2ns 11ns
    3ns 111s
    4ns 1111ns
    5ns 11111ns
    6ns 111111ns
    etc etc

    This is in line with . You are increasingly time dilated such that each "tick" of your proper time takes a longer and longer coordinate time. It ends up with your finite proper time taking infinite coordinate time, so in the real world it never actually happens. If you started falling into that black hole a million Earth years ago, you haven't crossed the event horizon yet, and you never ever will. You end up measuring your proper time on a stopped clock.

    You can see this future infinity in other diagrams such as this one:

    http://www.jessemazer.com/images/Sch...ilddiagram.jpg

    Getting past this future infinity is akin to "Zeno's paradox" in reverse.
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    Quote Originally Posted by DrRocket
    Who is Brown?
    Kevin Brown, the author of Mathspages.

    Quote Originally Posted by DrRocket
    A clock only stops when it malfunctions. Time does not in any way shape or form stop at the event horizon of a black hole. Proper time is precisely what is measured by your wristwatch. In fact proper time is sometines called "wristwatch time" -- it is time along the world line of the wearer.
    Take the back off your wristwatch. Can you see a worldline in there being measured? Or in fact, any proper time? No. What you can see is little cogs and wheels, and what they're doing is moving. Your watch counts these motions and displays you an accumulation that you call "the time". When you are gravitationally time dilated, that motion is occurring at a reduced rate. When you are infinitely time dilated, that motion isn't occurring at all.

    Quote Originally Posted by DrRocket
    Your link does not work.
    Apologies, I've now inserted a space between it and the full-stop.

    Quote Originally Posted by DrRocket
    The is no "end of time" associated with the event horizon of a black hole. Neither is the horizon singular.
    But there is a future infinity. There's no getting past that.

    Quote Originally Posted by DrRocket
    ANY coordinate system, indeed any mathematical model is an abstraction. What is your point?
    Don't mistake abstraction for reality. Clocks clock up local motion, and that's it. Infinitely time dilation means local motion is zero. So clocks stop, and proper time isn't proper at all.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    A clock only stops when it malfunctions. Time does not in any way shape or form stop at the event horizon of a black hole. Proper time is precisely what is measured by your wristwatch. In fact proper time is sometines called "wristwatch time" -- it is time along the world line of the wearer.
    Take the back off your wristwatch. Can you see a worldline in there being measured? Or in fact, any proper time? No. What you can see is little cogs and wheels, and what they're doing is moving. Your watch counts these motions and displays you an accumulation that you call "the time". When you are gravitationally time dilated, that motion is occurring at a reduced rate. When you are infinitely time dilated, that motion isn't occurring at all.
    There are lots of different kinds of clocks. They all measure proper time. That is what they measure and it is the only thing that they measure.


    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    The is no "end of time" associated with the event horizon of a black hole. Neither is the horizon singular.
    But there is a future infinity. There's no getting past that.
    Not only can one not get past a future infinity, one cannot get to it.

    Time need not even be unbounded, though it probably is. Were the "big crunch" viable, a finite end of time would be viable also. The point is that it is not ruled a priori by general relativity.

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    ANY coordinate system, indeed any mathematical model is an abstraction. What is your point?
    Don't mistake abstraction for reality. Clocks clock up local motion, and that's it. Infinitely time dilation means local motion is zero. So clocks stop, and proper time isn't proper at all.
    Abstraction is how we come to grips with the reality of physics. You cannot cleanly separate the two. Clocks do not clock up local motion -- take the standard cesium clock for instance. You seem to have your own personal theory of time.

    Your theory is not accepted physics, and in fact you have not made your theory precise.

    If you are going to make statements like "clocks clock up local motion, and that's it" then you need to make that statement precise and show how it fits into predictive physical models -- show the math.
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    Quote Originally Posted by Farsight
    If you started falling into that black hole a million Earth years ago, you haven't crossed the event horizon yet, and you never ever will. You end up measuring your proper time on a stopped clock.
    Yours is a common misconception, based on a misunderstanding of the interchangeability of coordinate systems in GR and a mixing up of reference frames.

    What you describe is correct from the frame of view of a distant observer, but not in the frame of the infaller.

    Try this introductory article to black holes, it describes the difference I am talking about:

    http://arxiv.org/abs/astro-ph/9801252

    Take note of the text describing figure 6, where the "two times of the black hole" are explained - the apparent time tends towards infinity as it approaches the event horizon, whereas the proper time (the time held by an infaller) reaches the singularity at the origin, in a finite time.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    It is well known, as DrRocket said, that the Schwarzschild radius (the event horizon) is a coordinate singularity, an artifact of the Schwarzschild coordinates, which is shown not be singular when using Kruskal-Szekeres coordinates, as shown at the bottom of the page you linked. If you are falling into a black hole, time does not end at the event horizon.
    There's no other way to say this, SpeedFreek, so I'll spit it out: it's well known, but it's wrong. Take a look at the Schwarzschild spacetime diagram on http://casa.colorado.edu/~ajsh/schwp.html
    Speedfreak is correct. Period.

    See pages 78-97 in General Relativity and the Einstein Equations by Yvonne Choquet-Bruhat for adiscussion of black holes abd the Schwarzchild and Kruskal spacetimes.
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    Quote Originally Posted by DrRocket
    There are lots of different kinds of clocks. They all measure proper time. That is what they measure and it is the only thing that they measure.
    Wrong. They all clock up motion. A pendulum clock does it, a mechanical wristwatch does it, a quartz clock does it, a sundial does it. So does a light clock, and so does an atomic clock, which relies on electromagnetic phenomena and thus is a form of light clock. A nuclear clock is arguably different, though low energy proton-antiproton annihilation to gamma photons suggests it might not be. But regardless, it always comes back to motion. A day relies on the motion of the earth around its axis, a year relies on the motion of the earth around the sun. And so on.

    Quote Originally Posted by DrRocket
    Not only can one not get past a future infinity, one cannot get to it.
    Agreed.

    Quote Originally Posted by DrRocket
    Time need not even be unbounded, though it probably is. Were the "big crunch" viable, a finite end of time would be viable also. The point is that it is not ruled a priori by general relativity.
    IMHO the big crunch is junk. Re GR, I'd draw your attention to Einstein's operational definition of time, and his equations of motion. Shift the emphasis to motion, and the end of time is the end of motion.

    Quote Originally Posted by DrRocket
    Abstraction is how we come to grips with the reality of physics. You cannot cleanly separate the two. Clocks do not clock up local motion -- take the standard cesium clock for instance. You seem to have your own personal theory of time.
    I can tell you all about the NIST caesium fountain atomic clock. And it's not my personal theory of time. It's Einstein's. Or should I say Godel and Einstein's, from 1949. But even that's a rehash of Presentism from 1908, and in the end we can trace it as far back as Aristotle.

    Quote Originally Posted by DrRocket
    Your theory is not accepted physics, and in fact you have not made your theory precise. If you are going to make statements like "clocks clock up local motion, and that's it" then you need to make that statement precise and show how it fits into predictive physical models -- show the math.
    Don't trot out the "accepted physics" excuse and retreat to math. Not when you're cornered on a discussion forum and it's the same math, and moreover when that the math does not explain what t is. All the math in the world is useless compared to the ontological empirical evidence in front of your eyes when it comes to what does a clock clocks up?
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    Quote Originally Posted by SpeedFreek
    Yours is a common misconception, based on a misunderstanding of the interchangeability of coordinate systems in GR and a mixing up of reference frames. What you describe is correct from the frame of view of a distant observer, but not in the frame of the infaller.
    Mine is no misconception. Think it through for yourself instead of repeating what you've been taught. What happens "in the infaller's frame" takes an infinite coordinate time to occur, in the real universe. That means it hasn't happened yet, and it never ever will.

    Quote Originally Posted by SpeedFreek
    Try this introductory article to black holes, it describes the difference I am talking about: http://arxiv.org/abs/astro-ph/9801252
    It's old hat. It's steeped in the proper-time misconception that everybody is taught.

    Quote Originally Posted by SpeedFreek
    Take note of the text describing figure 6, where the "two times of the black hole" are explained - the apparent time tends towards infinity as it approaches the event horizon, whereas the proper time (the time held by an infaller) reaches the singularity at the origin, in a finite time.
    I noted this sort of thing years ago, and would draw your attention to the way the apparent time goes to infinity. That isn't "apparent" time, that's the time measured by all observers out in the universe. They all agree that te infaller take forever to cross the event horizon. Like I said, Eddington-Finkelstein coordinates employs a mathematical sleight-of-hand to get past this future infinity. That proper time is being measured on a clock that goes slower and slower until it stops. But the "measurements" carry on regardless.
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    Surely you understand that, if you want to know what is happening in the frame of the infaller, you have to take into account what effect the curvature of spacetime has on observations made of that infaller, if those observations are made at a distance?
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    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    There are lots of different kinds of clocks. They all measure proper time. That is what they measure and it is the only thing that they measure.
    Wrong. They all clock up motion. A pendulum clock does it, a mechanical wristwatch does it, a quartz clock does it, a sundial does it. So does a light clock, and so does an atomic clock, which relies on electromagnetic phenomena and thus is a form of light clock. A nuclear clock is arguably different, though low energy proton-antiproton annihilation to gamma photons suggests it might not be. But regardless, it always comes back to motion. A day relies on the motion of the earth around its axis, a year relies on the motion of the earth around the sun. And so on.
    wrong

    Clocks are intended to and do measure time, proper time.

    They may do that through s system that involves motion governed by physical principles that include a notion of time, but what they measure is proper time. Period.



    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    Time need not even be unbounded, though it probably is. Were the "big crunch" viable, a finite end of time would be viable also. The point is that it is not ruled a priori by general relativity.
    IMHO the big crunch is junk. Re GR, I'd draw your attention to Einstein's operational definition of time, and his equations of motion. Shift the emphasis to motion, and the end of time is the end of motion.
    The big crunch is not junk, but as I said it is pretty well ruled out by the observation that the expansion of space is accelerating. what it is is a scenario that is consistent with GR (without a cosmological constant) in which time does end.

    The only operational definition of time is that "it is what clocks measure". That might not be philosophically satisfying, but it is all that we have.

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    Abstraction is how we come to grips with the reality of physics. You cannot cleanly separate the two. Clocks do not clock up local motion -- take the standard cesium clock for instance. You seem to have your own personal theory of time.
    I can tell you all about the NIST caesium fountain atomic clock. And it's not my personal theory of time. It's Einstein's. Or should I say Godel and Einstein's, from 1949. But even that's a rehash of Presentism from 1908, and in the end we can trace it as far back as Aristotle.
    The closest that I am aware is a statement by Einstein that time was probably statistical in nature. But he could not make that precise or produce a theory incorporating such a notion.

    In any case you are confusing philosophical musings with scientific theories.

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    Your theory is not accepted physics, and in fact you have not made your theory precise. If you are going to make statements like "clocks clock up local motion, and that's it" then you need to make that statement precise and show how it fits into predictive physical models -- show the math.
    Don't trot out the "accepted physics" excuse and retreat to math. Not when you're cornered on a discussion forum and it's the same math, and moreover when that the math does not explain what t is. All the math in the world is useless compared to the ontological empirical evidence in front of your eyes when it comes to what does a clock clocks up?
    Bullshit

    This is the Physics forum, not the Philosophy forum.

    There is NO theory for what time is, only a theory regarding how motion depends on it and how it is measured by different observers.

    We don't have a theory for what length is either. Length is what rulers measure.

    In general relativity length and time are mixed together by curvature and lose individual meaning. They are only local approximations which live on the tangent bundle to spacetime and not on the spacetime manifold itself. Minkowski was right -- "Henceforth space by itself, and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality." Einstein understood this and it became a centerpiece of general relativity.

    Time in GR is proper time. It is dependent on the world line of the observer -- in fact it is the length of the world line in the Lorentzian metric. And just like Einstein, if you want to propose an alternate view of time , you are obligated to put in the context of a quantitative theory -- SHOW THE MATH.

    So stuff that into your ontological pipe and smoke it.
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    Length is what rulers measure.
    ena
    Philosophical plain mistaken ; Rubbish.
    Philosophy has well investigated the possibility for meaningfull phrases and came to the conclusion there is no possibillity. It,s the way words are used that has to show meaning. What this type of phrase shows is a rather primitive technological type of animism ; as if rulers and clocks meassure and these measurements then hold truths. People meassure length not rulers and they use rulers and clocks as tools to have some standard to relate to in communication.

    And because the measurement is a comparing, relating activity the relation can never be described as a property (of what is meassure) to one side of the ecquation.

    The tiny change of mass for the kilogramm in France is a good example for what happens if a measurement is made a property of something or suggested to be. The kg has become lighter, it has lost mass. But same time this is impossible...because it is the kg. Panic
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    Quote Originally Posted by SpeedFreek
    Surely you understand that, if you want to know what is happening in the frame of the infaller, you have to take into account what effect the curvature of spacetime has on observations made of that infaller, if those observations are made at a distance?
    I understand that. It's taking a longer and longer coordinate time for the observer to make those observations, tending towards an infinite coordinate time. Let me try to get it across another way. He's falling into a black hole, and on our "gedanken subspace radio" we can hear him saying Are we there yet? Only his words are being stretched out by the increasing time dilation, such that it takes him a minute, then an hour, then a year, then a million years to ask the question. And our answer, if he could hear it, is "No son, you're not there yet, and you never will be". His observations end up taking forever. Thus they never actually happen. The notion that they do happen, in his proper time, is a myth.


    Quote Originally Posted by DrRocket
    wrong. Clocks are intended to and do measure time, proper time. They may do that through a system that involves motion governed by physical principles that include a notion of time, but what they measure is proper time. Period...

    Bullshit. This is the Physics forum, not the Philosophy forum. There is NO theory for what time is, only a theory regarding how motion depends on it and how it is measured by different observers... So stuff that into your ontological pipe and smoke it.
    You're in denial, Doc. Time depends on motion, not the other way around. The evidence for that is patent, and it's there in what does a clock clock up? But you cling to abstraction with such conviction that there's no getting through to you. You'd rather believe that a wristwatch is somehow measuring the length of a worldline streaming through, it instead of counting and accumulating the motions of its parts and displaying the result as "the time now". The empirical scientific evidence in front of your eyes counts for naught compared to what your textbook says. We call this "lost in maths".
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    If time depends on motion, than motion depends on time.
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    Quote Originally Posted by Shortsight
    Time depends on motion, not the other way around. The evidence for that is patent, and it's there in what does a clock clock up? ... You'd rather believe that a wristwatch is somehow measuring the length of a worldline streaming through, it instead of counting and accumulating the motions of its parts and displaying the result as "the time now". The empirical scientific evidence in front of your eyes counts for naught compared to what your textbook says. We call this "lost in maths".
    This is just silly. This is equivalent to you saying that the marks on a ruler are length (or height, or breadth) when they are merely a mechanical contrivance for measuring length (etc). Equally the motion of the clock is simply a mechanical means of measuring the passage of time. The motion does not create time just as the marks on the ruler and the ruler itself do not create length.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    Surely you understand that, if you want to know what is happening in the frame of the infaller, you have to take into account what effect the curvature of spacetime has on observations made of that infaller, if those observations are made at a distance?
    I understand that. It's taking a longer and longer coordinate time for the observer to make those observations, tending towards an infinite coordinate time.
    Nonsense. How can it take a longer and longer coordinate time for the observer to make those observations? The observer holds proper time, but calculates the coordinate time for another frame of reference. This is basic stuff, really.

    Quote Originally Posted by Farsight
    Let me try to get it across another way. He's falling into a black hole, and on our "gedanken subspace radio" we can hear him saying Are we there yet? Only his words are being stretched out by the increasing time dilation, such that it takes him a minute, then an hour, then a year, then a million years to ask the question. And our answer, if he could hear it, is "No son, you're not there yet, and you never will be". His observations end up taking forever. Thus they never actually happen. The notion that they do happen, in his proper time, is a myth.
    You are mixing reference frames, and I am beginning to think you are using terms without knowing their meaning. The distant observers observations of the coordinate time of the infaller end up taking forever, sure, but the proper time of the infaller ticks on inexorably as he reaches the singularity at r=0 in a finite time.

    Nobody's proper time ever stops - what a ridiculous notion!
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    Wow, I missed a good discussion over the last few days.
    If I may be allowed to weigh with my opinion, sorry Farsight, but speedfreak is right. Consider again the two participants in your experiment. The lucky one observing from far away, and the unlucky one falling into the black hole. According to GR the lucky one (his frame of reference) sees the unlucky one approach the event horizon slower and slower, until he is finally frozen at the event horizon. This ISN'T what actually happens. From the frame of reference of the unlucky one there is no slowing of time rather if he's looking back , he sees time accelerate in the outside universe. He crosses the event horizon at which point the only thing in his future is the (possible) singularity. If we assume that he can survive the tidal forces until he impacts the (possible) singularity so that he may observe the outside universe, he would see outside time infinitely speeded up so that when he reaches the end of his timeline at the (possible) singularity hi will have witnessed the end of time in the outside universe. Before you attack this I admit that tidal forces would keep you from doing this even well outside the event horizon unless we are considering 10^9 solar mass sized black holes where you would have low tidal forces well inside the event horizon.

    As far as your argument with DrR,sorry again but both time and space are abstractions, and we measure them by comparing them to something which we define or general knowledge. So one kilometre is 1000 of what we define as a metre and one hour is 3600 of what we define as a second. But regardless of our measuring systems, there is no denying the fact that the quantity we measure as time is linked with space by GR (or by Minkowsky). We can measure its passage and its direction (towards entropy increase), I don't know what else you need to make it areal quantity.
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    Quote Originally Posted by Farsight
    You're in denial, Doc. Time depends on motion, not the other way around. The evidence for that is patent, and it's there in what does a clock clock up? But you cling to abstraction with such conviction that there's no getting through to you. You'd rather believe that a wristwatch is somehow measuring the length of a worldline streaming through, it instead of counting and accumulating the motions of its parts and displaying the result as "the time now". The empirical scientific evidence in front of your eyes counts for naught compared to what your textbook says. We call this "lost in maths".
    wrong

    For all the reasons given earlier.

    You are the one in denial. Open your own eyes -- to the mountain of evidence that supports GR and to what GR actually says. We call that "understanding reality" and not being blinded by our limited experience.
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    Quote Originally Posted by Ellatha
    If time depends on motion, than motion depends on time.
    I'm afraid that's not true, Ellatha. Think about something else: the gravitational field around a body depends on the concentration of mass-energy in that body. So we say gravity depends on mass. We don't say mass depends on gravity. Yes people tend to say "you need time to have motion", but there's no actual evidence of what this thing called time actually is. The evidence of what clocks clock up, is however patent. Things move inside that clock. If they don't, the clock is stopped. Apply this to the whole universe and there is no time any more.

    Quote Originally Posted by Ophiolite
    This is just silly. This is equivalent to you saying that the marks on a ruler are length (or height, or breadth) when they are merely a mechanical contrivance for measuring length (etc). Equally the motion of the clock is simply a mechanical means of measuring the passage of time. The motion does not create time just as the marks on the ruler and the ruler itself do not create length.
    It isn't silly, Ophiolite. Hold your hands up a yard apart. That gap between them is a space. Whilst you can't see anything there, you can see that the space is there. There is definitely a gap between your hands. So we can say space is real. Now waggle your hands. You can see them moving. Hence we can say motion is real. Now try doing something similar for time. You can't. You can't see "time passing" because that's just a figure of speech. Here's the deal: things move, sh*t happens, that's it.

    Quote Originally Posted by SpeedFreek
    Nonsense. How can it take a longer and longer coordinate time for the observer to make those observations? The observer holds proper time, but calculates the coordinate time for another frame of reference. This is basic stuff, really.
    Yes, it's basic stuff. And gravitational time dilation is absolutely real. If you descend to a place where gravitational potential is lower, your clocks run slower, along with all other processes. We allow for this in the GPS clock settings. You don't notice it of course, because all processes "run slower". If you descend to a place where gravitational potential is very low, like near a black hole, your clocks and processes run very slow indeed. You could for example take a video camera with you, continuously recording. When you come back to the ship, the camera has recorded an hour's worth of tape, but you've been gone for a week. That means the tape reel was going slower than another tape reel in the ship. It's that simple.

    Quote Originally Posted by SpeedFreek
    You are mixing reference frames, and I am beginning to think you are using terms without knowing their meaning.
    Don't clutch at straws. I know what all the terms mean.

    Quote Originally Posted by SpeedFreek
    The distant observers observations of the coordinate time of the infaller end up taking forever, sure, but the proper time of the infaller ticks on inexorably as he reaches the singularity at r=0 in a finite time. Nobody's proper time ever stops - what a ridiculous notion!
    That's what happens at the event horizon. The gravitational time dilation is infinite. Your tape reel stops, along with everything else. Including your clocks, your tape reels, and you. Everything is stopped, forever. What's ridiculous is believing that somehow things just carry on tickety-boo in some never-never land beyond the end of time. Your proper time is now being measured on a stopped clock. So there isn't any.
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    Quote Originally Posted by Farsight
    I'm afraid that's not true, Ellatha.
    No need to fear anything; it is true.


    Quote Originally Posted by Farsight
    Think about something else: the gravitational field around a body depends on the concentration of mass-energy in that body. So we say gravity depends on mass. We don't say mass depends on gravity.
    It does not matter what we do say, the fact is that if you were to change the gravity than the mass would also change, and vice versa.

    E.g., if we have z = xy, than we say that x is inversely proportional to y, and that z is directly proportional to both x and y.

    Quote Originally Posted by Farsight
    Yes people tend to say "you need time to have motion", but there's no actual evidence of what this thing called time actually is. The evidence of what clocks clock up, is however patent. Things move inside that clock. If they don't, the clock is stopped. Apply this to the whole universe and there is no time any more.
    For an object to move without time it would have to be able to move at an infinite number of distance units per time units, (i..e, infinite m/s = infinite k/h = infinite m/h, etc...). Einstein has shown through his theories of relativity that it is impossible to move at the speed of light, and the speed of light is less than infinity.
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    Quote Originally Posted by MigL
    Wow, I missed a good discussion over the last few days.
    If I may be allowed to weigh with my opinion, sorry Farsight, but speedfreak is right.
    Yes, it is interesting, isn't it? Speedfreak isn't right, but let's see why you think he is.

    Quote Originally Posted by MigL
    Consider again the two participants in your experiment. The lucky one observing from far away, and the unlucky one falling into the black hole. According to GR the lucky one (his frame of reference) sees the unlucky one approach the event horizon slower and slower, until he is finally frozen at the event horizon.
    Fair enough. No problem with that.

    Quote Originally Posted by MigL
    This ISN'T what actually happens. From the frame of reference of the unlucky one there is no slowing of time rather if he's looking back, he sees time accelerate in the outside universe.
    Yep. He will see everything going faster and faster and faster. The outside universe hasn't changed of course. He sees it going faster and faster and faster because he's going slower and slower and slower.

    Quote Originally Posted by MigL
    He crosses the event horizon at which point the only thing in his future is the (possible) singularity. If we assume that he can survive the tidal forces until he impacts the (possible) singularity so that he may observe the outside universe, he would see outside time infinitely speeded up so that when he reaches the end of his timeline at the (possible) singularity he will have witnessed the end of time in the outside universe. Before you attack this I admit that tidal forces would keep you from doing this even well outside the event horizon unless we are considering 10^9 solar mass sized black holes where you would have low tidal forces well inside the event horizon.
    No problem with the tidal forces, let's set them aside. The problem is with the event horizon. He only crosses it "at the end of time in the outside universe". So he never ever does. Look at this picture and ask yourself why the peak is cut off and how that light cone manages to get past the end of time!

    http://www.jessemazer.com/images/Sch...ilddiagram.jpg

    Quote Originally Posted by MigL
    As far as your argument with DrR,sorry again but both time and space are abstractions, and we measure them by comparing them to something which we define or general knowledge. So one kilometre is 1000 of what we define as a metre and one hour is 3600 of what we define as a second. But regardless of our measuring systems, there is no denying the fact that the quantity we measure as time is linked with space by GR (or by Minkowsky). We can measure its passage and its direction (towards entropy increase), I don't know what else you need to make it a real quantity.
    Space isn't an abstraction. I'll repeat what I said to Ophiolite: Hold your hands up a yard apart. That gap between them is a space. Whilst you can't see anything there, you can see that the space is there. There is definitely a gap between your hands. So we can say space is real. Now waggle your hands. You can see them moving. Hence we can say motion is real. Now try doing something similar for time. You can't. You can't see "time passing" because that's just a figure of speech. Again, the important thing to appreciate is what does a clock clock up? Space and time are linked because we use the motion of light to calibrate our rods and clocks, and our motion affects our measurements.
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    Quote Originally Posted by Ellatha
    It does not matter what we do say, the fact is that if you were to change the gravity than the mass would also change, and vice versa. E.g., if we have z = xy, than we say that x is inversely proportional to y, and that z is directly proportional to both x and y.
    A mass causes gravity, Ellatha. You can change the mass to change the gravity, no problem. Strictly speaking energy causes gravity, so changing the system energy content changes the gravity. However you can't change the gravity to change the mass-energy. Conservation of energy applies. The symmetry and equality just isn't there, and it isn't there between motion and time either.

    Quote Originally Posted by Ellatha
    For an object to move without time it would have to be able to move at an infinite number of distance units per time units, (i..e, infinite m/s = infinite k/h = infinite m/h, etc...).
    You're not seeing the simplicity of it. Things move, through space. We can see them moving, motion is real. We measure the rate of motion using rods and clocks, and we calibrate those rods and clocks using the motion of light. We have this thing called time because things move.

    Quote Originally Posted by Ellatha
    Einstein has shown through his theories of relativity that it is impossible to move at the speed of light, and the speed of light is less than infinity.
    Agreed.
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    Quote Originally Posted by Farsight
    We have this thing called time because things move.

    [
    This is your opinion but it is backed by not one ounce of accepted theory or any experiment. Yet you state it as fact.

    Prove it.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    The distant observers observations of the coordinate time of the infaller end up taking forever, sure, but the proper time of the infaller ticks on inexorably as he reaches the singularity at r=0 in a finite time. Nobody's proper time ever stops - what a ridiculous notion!
    That's what happens at the event horizon. The gravitational time dilation is infinite. Your tape reel stops, along with everything else. Including your clocks, your tape reels, and you. Everything is stopped, forever. What's ridiculous is believing that somehow things just carry on tickety-boo in some never-never land beyond the end of time. Your proper time is now being measured on a stopped clock. So there isn't any.
    Obvious Question #1:

    How does a black hole gain mass, if nothing falling towards a black hole ever crosses the event horizon?
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  44. #43 Re: Before the universe 
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    Quote Originally Posted by DrRocket
    He also makes the statement that " For starters, given an infinite amount of time, anything that can happen will already have happened, for if a physical process is likely to occur with a certain nonzero probability-however small-then given an infinite amount of time the process must occur, with probability one. By now, the universe should have reached some sort of final state in which all possible physical processes have run their course. " This is flawed. It is true that " if a physical process is likely to occur with a certain nonzero probability-however small-then given an infinite amount of time the process must occur, with probability one', but this statement implies that one has the capability to apply the mathematical theory and in particular a version of the theorem known as the "Law of Large Numbers". To do that one must have a probability space that describes all physical processes and their probabilities. No such probability space is known to exist. So here we see Davies stating rank speculation as fact.
    Does this theory mean that we are not alone in the universe?
    That the probability of that an other intellegent race is, will or have exicisted are bigger then that it has not,will not or have not exicisted?

    another race is/will/have exicisted odds>another race is/will/have not exicisted odds
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    Quote Originally Posted by Farsight
    Quote Originally Posted by Ophiolite
    This is just silly. This is equivalent to you saying that the marks on a ruler are length (or height, or breadth) when they are merely a mechanical contrivance for measuring length (etc). Equally the motion of the clock is simply a mechanical means of measuring the passage of time. The motion does not create time just as the marks on the ruler and the ruler itself do not create length.
    It isn't silly, Ophiolite. Hold your hands up a yard apart. That gap between them is a space. Whilst you can't see anything there, you can see that the space is there. There is definitely a gap between your hands. So we can say space is real. Now waggle your hands. You can see them moving. Hence we can say motion is real. Now try doing something similar for time. You can't. You can't see "time passing" because that's just a figure of speech. Here's the deal: things move, sh*t happens, that's it.
    Would you measure temperature with a set of scales? Would you measure mass with a spectrometer? Would you expect the measurement (and appreciation) of length to be the same as that of time? Apparently you would and therein lies one of your many errors.

    When I 'waggle my hands' I can very clearly can see time passing. I can see a sequence of events which are serially consequential. These events occur within time, just as marks on a ruler occur 'within length'.

    Your concepts are silly and really merit no attention whatsoever. I reply not in the hope of persauding you - you seem beyond hope - but of clarifying the position for the inexperienced reader who may be seduced by your lunacy.
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    Quote Originally Posted by Farsight
    A mass causes gravity, Ellatha. You can change the mass to change the gravity, no problem. Strictly speaking energy causes gravity, so changing the system energy content changes the gravity. However you can't change the gravity to change the mass-energy. Conservation of energy applies. The symmetry and equality just isn't there, and it isn't there between motion and time either.
    You cannot change an object's mass anymore than you can change its gravity. Mass is merely energy that is always separated by a constant, in the same way that mass and weight are always separated by a constant (of course, weight varies depending on location; energy doesn't). Energy is always conserved.

    Quote Originally Posted by Farsight
    You're not seeing the simplicity of it. Things move, through space. We can see them moving, motion is real. We measure the rate of motion using rods and clocks, and we calibrate those rods and clocks using the motion of light. We have this thing called time because things move.
    You are trying to make things simpler than they really are; time exists with or without motion.
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    Quote Originally Posted by Ellatha
    You cannot change an object's mass anymore than you can change its gravity.
    Agreed. I meant change the mass by adding more material.

    Quote Originally Posted by Ellatha
    Mass is merely energy that is always separated by a constant, in the same way that mass and weight are always separated by a constant (of course, weight varies depending on location; energy doesn't). Energy is always conserved.
    Yes, energy is always conserved. Adding more material is adding more energy. You can also add energy in the guise of heat. A hot body comprises more energy than a cold body, and hence more mass, as per Does the inertia of a body depend upon its' energy content?

    Quote Originally Posted by Ellatha
    You are trying to make things simpler than they really are; time exists with or without motion.
    Then show me some. All your attempts to demonstrate time will rely on motion.

    Quote Originally Posted by SpeedFreek
    How does a black hole gain mass, if nothing falling towards a black hole ever crosses the event horizon?
    Like an iceball gains mass when you flick a drop of water at it. It's the original "frozen star" concept of a black hole, see http://en.wikipedia.org/wiki/Black_h...ral_relativity
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    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    How does a black hole gain mass, if nothing falling towards a black hole ever crosses the event horizon?
    Like an iceball gains mass when you flick a drop of water at it. It's the original "frozen star" concept of a black hole, see http://en.wikipedia.org/wiki/Black_h...ral_relativity
    You seem to be flipping and flopping backwards and forwards rather like a fish out of water.

    First you accuse me of parroting the old "proper time" pedagogy, believing what I was taught, and imply that a paper I linked that was state of the art a little over 10 years ago is out of date with your more modern concepts. Now you seem to be reverting to an even older interpretation that was discounted by the mainstream decades ago.

    I looked at the wiki article. Which parts do you want me to read, and which do you want me to ignore? From the very article you linked:

    To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.
    On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.
    Once a black hole has formed, it can continue to grow by absorbing additional matter. Any black hole will continually absorb gas and interstellar dust from its direct surroundings and omnipresent cosmic background radiation. This is the primary process through which supermassive black holes seem to have grown. A similar process has been suggested for the formation of intermediate-mass black holes in globular clusters.
    Another possibility is for a black hole to merge with other objects such as stars or even other black holes. This is thought to have been important especially for the early development of supermassive black holes, which are thought to have formed from the coagulation of many smaller objects.The process has also been proposed as the origin of some intermediate-mass black holes.
    So, I repeat the question - how does a black hole gain mass if nothing ever crosses the event horizon? Iceballs and water droplets don't cut it.
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    Further to speedfreak's question another one from me that I'd like an answer to. Time only moves in one direction, towards greater entropy, yet you can wiggle your fingers back and forth. Movement is not constrained, time is. I don't see how one can be a subjective interpretation of the other.

    Getting rid of time as an actual quantity would not only harm GR but QM as well, since decay is not governed by any motion but by a probability. I hope you have other theories to replace these as they are the cornerstones of modern science.
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  50. #49  
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    Quote Originally Posted by Farsight
    I meant change the mass by adding more material.
    So? That demonstrates nothing. All you are doing is adding another object and taking the sum of their mass: the mass of the individual objects remains the same.

    Quote Originally Posted by Farsight
    Yes, energy is always conserved. Adding more material is adding more energy. You can also add energy in the guise of heat. A hot body comprises more energy than a cold body, and hence more mass, as per Does the inertia of a body depend upon its' energy content?
    I've already replied to this.

    Quote Originally Posted by Farsight
    Then show me some. All your attempts to demonstrate time will rely on motion.
    Sure:













    QED

    We know what you are suggesting work on the basis of current, established physics; your statements regarding physics are not rational, in fact not even arational, they are irrational.
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    Quote Originally Posted by MigL
    Further to speedfreak's question another one from me that I'd like an answer to. Time only moves in one direction, towards greater entropy, yet you can wiggle your fingers back and forth. Movement is not constrained, time is. I don't see how one can be a subjective interpretation of the other.

    Getting rid of time as an actual quantity would not only harm GR but QM as well, since decay is not governed by any motion but by a probability. I hope you have other theories to replace these as they are the cornerstones of modern science.
    Lots of people have speculated about some more fundamental notion of the origin of time and its nature. See some of the writings of Roger Penrose. But no one has been able to formulate any useable theory beyond general relativity. Such musings are nothing more than interesting speculation.

    You can find all sorts of speculative notions stated as facts from the world of crankdom, but in fact nobody has any definition ofv time beyond "time is what clocks measure".

    The same holds true for distance. Distance is what rulers measure. It just seems that distance is less mysterious to the human psyche than is time.

    General relativity deepens the mystery a bit by showing us that both time and space are really only local notions and are mixed together by curvature to comprise spacetime.
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    Quote Originally Posted by SpeedFreek
    You seem to be flipping and flopping backwards and forwards rather like a fish out of water.
    No I'm not. Face up to the fact that in this real universe it takes forever to cross that event horizon.

    Quote Originally Posted by SpeedFreek
    First you accuse me of parroting the old "proper time" pedagogy, believing what I was taught, and imply that a paper I linked that was state of the art a little over 10 years ago is out of date with your more modern concepts. Now you seem to be reverting to an even older interpretation that was discounted by the mainstream decades ago.
    It's the right interpretation. Getting past future infinity and measuring time with a stopped clock is a nonsense. You know why I say this? Do you know where I got it from? Einstein. He started with the constant speed of light as a postulate in 1905 when he was doing special relativity, but by 1911 he was getting into general relativity. That's when he wrote On the Influence of Gravitation on the Propagation of Light, where he said: "If we call the velocity of light at the origin of co-ordinates cº, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = cº(1 + Φ/c²)". This is the speed of light varying with gravitational potential. It wasn't a one-off, because in 1912 he said it again when he wrote "On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential". He repeated this in 1913 when he said: "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis". Here it is again in 1915 saying "the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned." Don't be misled by the word velocity, Einstein was talking about c, and that's a speed, a scalar rather than a vector quantity. So what's happening with the infinite gravitational time dilation at the event horizon? The speed of light is zero there. So the answer is nothing's happening.

    Quote Originally Posted by SpeedFreek
    I looked at the wiki article. Which parts do you want me to read...
    To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time, all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational redshift. Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.
    Yep, this bit.

    Quote Originally Posted by SpeedFreek
    ...and which do you want me to ignore?
    On the other hand, an observer falling into a black hole does not notice any of these effects as he crosses the event horizon. According to his own clock, he crosses the event horizon after a finite time, although he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.
    This bit. His clock isn't ticking. He only crosses the event horizon at the end of time. So he never ever crosses it.

    Quote Originally Posted by SpeedFreek
    So, I repeat the question - how does a black hole gain mass if nothing ever crosses the event horizon? Iceballs and water droplets don't cut it.
    Simple. It accretes matter-energy. It's a region of space where the speed of light is zero, so it's frozen. Light will not propagate through this region so time and distance do not apply. See http://en.wikipedia.org/wiki/Gravastar and note the void in the fabric of space and time. Also note that this is even more of a hole than the normal description of a black hole featuring a central singularity.
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    Quote Originally Posted by MigL
    Further to speedfreak's question another one from me that I'd like an answer to. Time only moves in one direction, towards greater entropy, yet you can wiggle your fingers back and forth. Movement is not constrained, time is. I don't see how one can be a subjective interpretation of the other.
    Real things move in real spatial directions, but time doesn't move in any direction at all. That's an abstraction, and a figure of speech. People say things like "we're travelling into the future at one second per second", but the only travelling that's actually going on is the motion of things through space.

    Quote Originally Posted by MigL
    Getting rid of time as an actual quantity would not only harm GR but QM as well, since decay is not governed by any motion but by a probability. I hope you have other theories to replace these as they are the cornerstones of modern science.
    What I'm telling you about comes from Einstein. I've mentioned this before. I'm not just making it up. It doesn't harm GR or QM, it helps them by shooting down some of the baggage they've acquired over the years.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    You seem to be flipping and flopping backwards and forwards rather like a fish out of water.
    No I'm not. Face up to the fact that in this real universe it takes forever to cross that event horizon.
    That is just flat wrong. Read any GR test that addresses black holes -- several have been noted earlier.

    Quote Originally Posted by Farsight
    Quote Originally Posted by SpeedFreek
    First you accuse me of parroting the old "proper time" pedagogy, believing what I was taught, and imply that a paper I linked that was state of the art a little over 10 years ago is out of date with your more modern concepts. Now you seem to be reverting to an even older interpretation that was discounted by the mainstream decades ago.
    It's the right interpretation. Getting past future infinity and measuring time with a stopped clock is a nonsense. You know why I say this? Do you know where I got it from? Einstein. He started with the constant speed of light as a postulate in 1905 when he was doing special relativity, but by 1911 he was getting into general relativity. That's when he wrote On the Influence of Gravitation on the Propagation of Light, where he said: "If we call the velocity of light at the origin of co-ordinates cº, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = cº(1 + Φ/c²)". This is the speed of light varying with gravitational potential. It wasn't a one-off, because in 1912 he said it again when he wrote "On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential". He repeated this in 1913 when he said: "I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis". Here it is again in 1915 saying "the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned." Don't be misled by the word velocity, Einstein was talking about c, and that's a speed, a scalar rather than a vector quantity. So what's happening with the infinite gravitational time dilation at the event horizon? The speed of light is zero there. So the answer is nothing's happening.
    Wrong again. Why are you quoting Einstein from the period before which general relativity was properly formulated, and manyn years before the theory was applied to gravitational collapse and black holes were understood ? This is just plain silly.

    The theory of black holes originates with Chandrasakhar not Einstein. Einstein was of the opinion that, while the equations of GR would allow black holes, that nature would not. He was apparently wrong.

    Einstein was a smart guy. He was not an oracle.
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    Quote Originally Posted by Ellatha
    Quote Originally Posted by Farsight
    Then show me some. All your attempts to demonstrate time will rely on motion.
    Sure:






    Geddoutofit. That isn't showing me time. Hiding behind mathematics is no substitute for empirical observational scientific evidence. I can show you space and motion by holding up my hands and waggling them. But you can't show me time.

    Quote Originally Posted by Ellatha
    We know what you are suggesting work on the basis of current, established physics; your statements regarding physics are not rational, in fact not even arational, they are irrational.
    My statements are perfectly rational. And they originate from Einstein.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Farsight
    No I'm not. Face up to the fact that in this real universe it takes forever to cross that event horizon.
    That is just flat wrong. Read any GR test that addresses black holes -- several have been noted earlier.
    LOL, outright denial instead of logical argument. No, it isn't flat wrong. The outside observer sees the infaller taking forever. The infaller's finite proper time is flat wrong. His clocks are stopped.

    Quote Originally Posted by DrRocket
    Wrong again. Why are you quoting Einstein from the period before which general relativity was properly formulated, and manyn years before the theory was applied to gravitational collapse and black holes were understood? This is just plain silly.
    What's silly is the never-never land beyond future infinity. And if you want more Einstein quotes about c, he says it again in late 1915, on page 150 of Doc 30, within The Foundation of the General Theory of Relativity. Note where he says "the principle of the constancy of the velocity of light in vacuo must be modified." Or see section 22 of the 1916 book Relativity: The Special and General Theory:

    "In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)".

    Like I was saying Einstein is talking about c, a speed. It's obvious he's talking about speed because he’s repeatedly referring to “the principle” or "one of the two fundamental assumptions". He was talking about the special relativity postulate, which is the constant speed of light. And it's even more obvious if you go back to the original German. What he actually said was "die Ausbreitungs-geschwindigkeit des Lichtes mit dem Orte variiert." I’ve got the original German version, and it translates into the speed of light varies with the locality.

    Quote Originally Posted by DrRocket
    The theory of black holes originates with Chandrasakhar not Einstein. Einstein was of the opinion that, while the equations of GR would allow black holes, that nature would not. He was apparently wrong. Einstein was a smart guy. He was not an oracle.
    I don't dismiss the scientific evidence, and I don't dismiss Einstein either.
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    Quote Originally Posted by Farsight
    Or see section 22 of the 1916 book Relativity: The Special and General Theory:

    "In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)".

    Like I was saying Einstein is talking about c, a speed. It's obvious he's talking about speed because he’s repeatedly referring to “the principle” or "one of the two fundamental assumptions". He was talking about the special relativity postulate, which is the constant speed of light. And it's even more obvious if you go back to the original German. What he actually said was "die Ausbreitungs-geschwindigkeit des Lichtes mit dem Orte variiert." I’ve got the original German version, and it translates into the speed of light varies with the locality.
    You need to quit citing passages from a book that Einstein wrote for a lay audience and actually understand the theory.

    Light rays do not follow curved paths. They follow spacetime geodesics, and a geodesic is as straight as it gets. The speed if light along a geodesic is c.
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    I understand the theory, Doc. You don't. Just listen to yourself. Light rays do not follow curved paths. You obviously haven't been paying attention to to what Einstein actually said:

    "A curvature of rays of light can only take place when the speed of light varies with the locality".

    So let's try you with some scientific evidence and simple logic:

    Take two identical light clocks, keep them flat to avoid any issues with radial length contraction. Take one down to the surface of a planet, leave the other one up in space. You find that the clocks lose synchronisation. The one at the surface goes slower. What does a clock clock up? The flow of time? Like that worldline whizzing through your wristwatch? No. Those clocks are clocking up the motion of light. So when one clock goes slower, it's because the light goes slower. Maybe you'd prefer the Shapiro delay. It's a delay. The light goes slower when it passes by the sun. That's it Doc, just like Einstein said. It's that simple.
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    Quote Originally Posted by Farsight
    I understand the theory, Doc. You don't. Just listen to yourself. Light rays do not follow curved paths. You obviously haven't been paying attention to to what Einstein actually said:

    "A curvature of rays of light can only take place when the speed of light varies with the locality".

    So let's try you with some scientific evidence and simple logic:

    Take two identical light clocks, keep them flat to avoid any issues with radial length contraction. Take one down to the surface of a planet, leave the other one up in space. You find that the clocks lose synchronisation. The one at the surface goes slower. What does a clock clock up? The flow of time? Like that worldline whizzing through your wristwatch? No. Those clocks are clocking up the motion of light. So when one clock goes slower, it's because the light goes slower. Maybe you'd prefer the Shapiro delay. It's a delay. The light goes slower when it passes by the sun. That's it Doc, just like Einstein said. It's that simple.
    Wrong

    Clocks do not "clock up" the motion of light. This is ridiculous. Clocks measure time. Proper time. And in general relativity proper time is the only physical time.

    Each clock will measure proper time along its individual world line. The clocks lose synchronizatio in the sense that they will not show the same time if brought back together for comparison. But in general relativity there is no such thing as synchronization of clocks in the sense that one sees in special relativity. There is no universal time in a curved spacetime. Time is a quantity associated with a world line. There is no "time here" vs "time there".

    And light paths are still geodesics in spacetime. And geodesics are still as "straight" as it gets on a manifold.

    I have no idea what you mean by a flat clock. If your spacetime is flat there is NO gravitational time dilation. Gravitational time dilation results from spacetime curvature. Your experiment is self-contradictory.

    You don't know what in the hell you are talking about.

    Better go read some more. A somewhat more modern treatment might help you understand what Einstein's theory really says. He was brilliant, but not always clear, and he needed a lot of help from Marcel Grossman to formulate the theory precisely in mathematical language. The modern texts have benefited from a lot of subsequent work and are more clear than Einstein's attempts at an explanation for laymen.
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    Your two clock experiment has some misconceptoions. The results are as you state, the ground clock runs slower than the orbiting clock; but the conclusions you draw are confused.It's not because it clocks-up a slower passage of time, it's because it followes a longer geodesic and takes more time to make the trip. Where space/time is more highly curved the apparent time for passage is longer to an observer outside that frame of reference.
    Consider the embedding diagram of a black hole, the one everyone is familiar with that looks like a piece of graph paper which is funneled in the middle ( I know Einstein-Rosen embedding diagrams are technically wrong and we should be using Penrose diagrams, but it will do for our purposes ), note that as you approach the central part of the black hole the curvature goes from horizontal ( far away ) to near vertical ( cose to event horizon and inside ). This means that the radial length to get to the centre of the black hole becomes longer and longer or alternately takes alonger and longer period of time. Once the curvature is vertical you would need an infinite length of time to get any closer to the centre as the distance has now become infinite. Note that vertical curvature happens well past the event horizon because at the event horizon the curvature is such that a speed of c will acheive a stable orbit. Vertical curvature, ie infinite time, ie infinite distance to the centre is only acheived when the curvature of our embedding diagram is vertical, ie ifinite speed to maintain orbit ( impossible ), ie right at the singularity.

    So again, if you could still see the outside universe as you fall into a black hole, you would see the end of time of the outside universe as you become singular, NOT at the event horizon. And you will still have fallen into the black hole , not frozen at the event horizon, since even to an observer outside your frame of reference, he may see you slowing down as you approach the event horizon, but the light reflected from you that he sees will be shifting towards longer and longer wavelength so that at the event horizon it will be shifted so far to the red ( loss of energy ) that there is effectively no light reflected from you, ie you have disappeared. You CANNOT see objects or material' frozen' at the event horizon.
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    Quote Originally Posted by MigL
    Your two clock experiment has some misconceptoions. The results are as you state, the ground clock runs slower than the orbiting clock; but the conclusions you draw are confused.It's not because it clocks-up a slower passage of time, it's because it followes a longer geodesic and takes more time to make the trip. Where space/time is more highly curved the apparent time for passage is longer to an observer outside that frame of reference.
    Farsight has things all screwed up, but this is not the reason.

    Unless your clock is in freefall {orbiting is free fall) it does not follow a geodesic path in spacetime. The orbiting clock does follow a geodesic path, and between two fixed spacetime points the geodesic is the longest path.

    A spacetime geodesic is determined by the Lorentzian metric which has signature +,-,-,- {or -,+,+,+) and unlike a positive-definite Riemannian metric results in length maximization by geodesics.
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    I'm just going by the fact that a geodesic in 'flat' (little or no gravity) space/time is shorter than a geoesic in strongly curved ( strong gravitational field ) space/time.
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    Quote Originally Posted by MigL
    I'm just going by the fact that a geodesic in 'flat' (little or no gravity) space/time is shorter than a geoesic in strongly curved ( strong gravitational field ) space/time.
    That doesn't make any sense. You cannot compare two geodesics on different manifolds.

    All that one can sensibly compare are the lengths of various paths with common end points. In GR a geodesic is the longest of such paths.

    Note that is important that the geodesic is in spacetime, elliptical not space. A satellite orbiting the Earth follows a spacetime geodesic, but that orbit is obviously not a geodesic in space.
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    Very well. Take two points in cartesian space, say x,y,z,t and x1,y1,z1,t1, and calculate the distance between them. Now curve that space, doesn't matter if positively or negatively, and recalculate the distance. My point is that it will always be longer.
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    Quote Originally Posted by MigL
    Very well. Take two points in cartesian space, say x,y,z,t and x1,y1,z1,t1, and calculate the distance between them. Now curve that space, doesn't matter if positively or negatively, and recalculate the distance. My point is that it will always be longer.
    Take a piece of paper. Roll it into a cylinder. The distance between points is exactly the same. That is why a cylinder is flat. "Curved" doesn't mean what you might think.

    You cannot do what you propose unless the resulting surface is flat.
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    Take a piece of paper, try to roll it into a sphere or a saddle shape, you cannot. You either need to add material (paper) or subtract it to obtain a smooth shape.
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    Quote Originally Posted by MigL
    Take a piece of paper, try to roll it into a sphere or a saddle shape, you cannot. You either need to add material (paper) or subtract it to obtain a smooth shape.
    Yes. That is one manifestation of curvature.

    But you see that you must add or subtract material or stretch or shrink (or both) the membrane of the manifold. That is why the before/after distance comparison that you suggested is not meaningful. There is no natural map between "before" and "after. There may be lots of different ways to do it, or none, but no natural way. And among the many ways you may stretch or compress locally in arbitrary ways.

    That is just how topology and geometry work.
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    Oh, I see what you mean. You cannot do a transformation to get from one to the other. Just like distorted,flat world maps as opposed to globe maps.
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    Quote Originally Posted by Farsight
    Geddoutofit. That isn't showing me time. Hiding behind mathematics is no substitute for empirical observational scientific evidence. I can show you space and motion by holding up my hands and waggling them. But you can't show me time.
    Nor do I have to; you are dusting mathematics under the rug whenever it disagrees with your theory, and the only reason you do so is for that very reason.

    Quote Originally Posted by Farsight
    My statements are perfectly rational. And they originate from Einstein.
    No they aren't; you have not given any counter arguments for the mathematical arguments I presented, rather suggested that I'm being irrational for using mathematics, when in fact mathematics is a critical part of physics and historically resulted in the derivation of new theorems (for example, Newton's second law of motion to derive impulse).
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    Farsight,

    Wouldn,t it be clearer to imply rhytm also ?
    Like the way you move you,re hands if you would do that in front of some musicians you would be the direktor to the music. Music is all about time and timing and can do perfectly fine without clocks (or even direktors).

    For fysics the word time is more specific t is not for time but for time-coordinate.
    The moment a clock is put on for timing that moment is mostly considered to be coordinate zero. But to another clock that moment could be coordinate 1, 2, 1,4566, n or maybe (?) not even a real amount or part of a second ; rth[2], pi ?.

    Considered coordinate 0 because there is nothing against considering it to be coordinate 3 or -4 s. time is not a coordinate t in fysics dt is time. But a moment can,t exist without a moment after ór before.

    Because there can,t be a detection without time. a moment doesn,t allow to detect that moment because a moment for a detection would imply a frecquency that is endlessly high for the detection (light with an endlessly high frecquency).

    For instance the unverse started at coordinate zero. After 0,000.0001 sec frecquency can,t be using a second as a second doesn,t exist yet, the universe is too short lived to contain a second. frecquency would have to be expressed /0,000.0001 sec. The closer to coordinate zero the higher the frecquency.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Farsight
    I understand the theory, Doc. You don't. Just listen to yourself. Light rays do not follow curved paths. You obviously haven't been paying attention to to what Einstein actually said:

    "A curvature of rays of light can only take place when the speed of light varies with the locality".

    So let's try you with some scientific evidence and simple logic:

    Take two identical light clocks, keep them flat to avoid any issues with radial length contraction. Take one down to the surface of a planet, leave the other one up in space. You find that the clocks lose synchronisation. The one at the surface goes slower. What does a clock clock up? The flow of time? Like that worldline whizzing through your wristwatch? No. Those clocks are clocking up the motion of light. So when one clock goes slower, it's because the light goes slower. Maybe you'd prefer the Shapiro delay. It's a delay. The light goes slower when it passes by the sun. That's it Doc, just like Einstein said. It's that simple.
    Wrong. Clocks do not "clock up" the motion of light. This is ridiculous...
    No it isn't. Your dismissal of Einstein and scientific evidence is ridiculous. As is your continued abuse of other posters.
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    Quote Originally Posted by MigL
    Your two clock experiment has some misconceptoions. The results are as you state, the ground clock runs slower than the orbiting clock; but the conclusions you draw are confused. It's not because it clocks-up a slower passage of time, it's because it followes a longer geodesic and takes more time to make the trip. Where space/time is more highly curved the apparent time for passage is longer to an observer outside that frame of reference.
    I'm not confused MigL, and nor was Einstein. Rerun the gedanken experiment with the astronauts carrying video cameras. When they come back one has recorded over .9 of a reel of tape, whilst the other has recorded over .8 of a reel. The simple fact of the matter is that the second astronaut's tape moved slower.

    Quote Originally Posted by MigL
    Consider the embedding diagram of a black hole, the one everyone is familiar with that looks like a piece of graph paper which is funneled in the middle ( I know Einstein-Rosen embedding diagrams are technically wrong and we should be using Penrose diagrams, but it will do for our purposes ), note that as you approach the central part of the black hole the curvature goes from horizontal ( far away ) to near vertical ( cose to event horizon and inside ).
    Here's one:

    http://demonstrations.wolfram.com/Sc...eddingDiagram/

    Click on "watch web preview" and you get a demo which varies the mass and radius.

    Quote Originally Posted by MigL
    This means that the radial length to get to the centre of the black hole becomes longer and longer or alternately takes alonger and longer period of time. Once the curvature is vertical you would need an infinite length of time to get any closer to the centre as the distance has now become infinite.
    Fair enough. You never get to the centre.

    Quote Originally Posted by MigL
    Note that vertical curvature happens well past the event horizon because at the event horizon the curvature is such that a speed of c will acheive a stable orbit. Vertical curvature, ie infinite time, ie infinite distance to the centre is only acheived when the curvature of our embedding diagram is vertical, ie ifinite speed to maintain orbit ( impossible ), ie right at the singularity.
    Which embedding diagram are you looking at? There's one here that partly matches your description, but it's vertical at the event horizon.

    Quote Originally Posted by MigL
    So again, if you could still see the outside universe as you fall into a black hole, you would see the end of time of the outside universe as you become singular, NOT at the event horizon.
    Please check this MigL.

    Quote Originally Posted by MigL
    And you will still have fallen into the black hole, not frozen at the event horizon, since even to an observer outside your frame of reference, he may see you slowing down as you approach the event horizon, but the light reflected from you that he sees will be shifting towards longer and longer wavelength so that at the event horizon it will be shifted so far to the red ( loss of energy ) that there is effectively no light reflected from you, ie you have disappeared. You CANNOT see objects or material' frozen' at the event horizon.
    No you can't see object/material frozen at the event horizon. But that's where the gravitational time dilation goes infinite, so that's where the coordinate speed of light goes to zero. And you can't exceed the speed of light.
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    Quote Originally Posted by Farsight
    ]No it isn't. Your dismissal of Einstein and scientific evidence is ridiculous. As is your continued abuse of other posters.
    You apparently regard being told that you are wrong as abuse.

    Too bad.

    You in particular need to be strongly corrected.

    That is because you often come across as quite credible, and sometimes are. But more often, particularly recently, you present nonsense as fact.

    A few weeks ago I received a PM from another forum participant -- another PhD with a deep knowledge of physics. He wanted to know what I thought of you. We were both initially impressed with some of your posts. But some were a bit ditzy, and he wanted to know if I concurred with his growing feeling that you are just a crank.

    I told him that I was not sure. Some of your posts were mostly clear and correct, but others were off target. You are clearly not the run-of-the-mill crank.

    However, you have continued to drift, going from posting rather odd and at best speculative notions as fact to more recently advocating utter nonsense as fact. One symptom is your insinuations of conspiracy to suppress new science by the mainstream journals. Another is your refusal to make your statements precise and your criticism of the use of mathematics.

    The other guy was quicker and more perceptive than me. You have indeed revealed yourself as an ambassador of crankdom. Because of your ability to present nonsense in an apparently credible manner, you are a pareticularly insidious threat to the neophyte participants in this forum.

    You make false charges. I dismiss neither Einstein nor scientific evidence.

    ALL of the evidence supports what I have said. So does the accepted theory, which is built upon Einstein's work. But it is built upon the final product of Einstein's discovery, refined, honed and polished by Einstein and others since the original announcement of general relativity. It is more than just the rough structure of 1915, but includes insights of Einstein and others in the nearly a century since then. Einstein, just like others, made mistakes -- there is even a book dedicated to them. Einstein's genius was in part his ability to press on to great insight despite those mistakes. Understanding general relativity requires more than parrroting words that you don't understand from a book written by Einstein in the very early years for a lay audience.

    No, I don't dismiss Einstein or scientific evidence. I dismiss you. I dismiss the bullshit that you attempt to substitute for established scientific theory.

    You are a danger to the young people who wish to understand real science.
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    Stick with the physics Doc. Ad-hominem abuse is no substitute for scientific evidence, logic, and bona-fide references. All it does is make you look like a arrogant quack who is outraged because somebody knows more physics than you.

    Quote Originally Posted by MigL
    I'm just going by the fact that a geodesic in 'flat' (little or no gravity) space/time is shorter than a geoesic in strongly curved ( strong gravitational field ) space/time.
    Take a bit of care with curvature. This depiction of gravitational potential is akin to the embedding diagrams you mentioned:


    CCSA image by AllenMcC, see http://en.wikipedia.org/wiki/Gravitational_potential

    The slope you can see is plotting the gravitational force. The curvature you can see is plotting the tidal force. A light beam going across from left to right would be bent a little, and its path would be geodesic depicting the curved spacetime. Gravitational time dilation increases with depth of field. At the bottom of the depiction there's a small region where gravitational potential is at a minimum. This corresponds to a void at say the centre of the earth. There's no curvature at this location, and no gravitational force, but this is the place where the gravitational time dilation is at a maximum and thus the coordinate speed of light is at a minimum.
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    Quote Originally Posted by Farsight
    Stick with the physics Doc. Ad-hominem abuse is no substitute for scientific evidence, logic, and bona-fide references. All it does is make you look like a arrogant quack who is outraged because somebody knows more physics than you.
    LOTS of people know more physics than I do. I had breakfast with one last week.

    You are not one of them.

    My post was not an ad hominem argument. I did not attack an argument on the basis that you made it. I simply pointed ou your lack of credibility nased upon the fallacious nature of some of your statements -- quite a different thing.

    So YOU stick with the physics. Real physics and not your personal distortions of it.



    FYI

    Ad hominem argument : You are an idiot, therefore your argument is illogical nd invalid.

    Deduction: Your argument is illogical and invalid, therefore you are an idiot.
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    Quote Originally Posted by Farsight
    There's no curvature at this location, and no gravitational force, but this is the place where the gravitational time dilation is at a maximum and thus the coordinate speed of light is at a minimum.
    Coordinate speed is not physical speed. It is an artifact of an arbitrary coordinate choice and results from taking derivatives with respect to those coordinates rather than using the covariant derivative. Only the covariant derivative is physically meaningful.
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    The major motivation for Einstein in formulating general relativity was what Einstein called "general covariance". General covariance is Einstein's interpretation of the rather loose notion known as Mach's Principle, which was an influence on Einstein. The underlying notion is that physical laws should be formulated in a way that is independent of any choice of coordinate system.

    The way to implement general covariance is, as Einstein did with the help of Marcel Grossman, use the methods of Riemannian geometry and tensor analysis. Modern treatments also use differential forms, an equivalent but sometimes more clear approach that was not available to Einstein. These more modern tools, including connections and the covariant derivative were not known when general relativity was invented.

    But nevertheless, Einstein did formulate general relativity as a "generally covariant" theory. In particular that means that notions tied to any particular coordinate choice should be held suspect until thoroughly understood. They can be misleading or downright wrong -- as with the "singularity" at the Schwarzchild radius or with "coordinate speed", or "coordinate time". In the presence of curvature proper time is the only time that is meaningful, and local speed involving proper time and the covariant derivative is the only speed that is meaningful . In flat spacetime, proper time is coordinate time and the covariant derivative is the ordinary coordinate derivative.


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

    One must read early Einstein very carefully as he did not have the advantage of modern tools to make himself clear. One is generally better off reading more modern treatments, such as Misner, Thorne and Wheeler. But make no mistake, the general relativity of MTW is the same general relativity of Einstein of 1915, just cast in the more clear coordinate-free mathematics of modern differential geometry that is now available.
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    Quote Originally Posted by DrRocket
    But nevertheless, Einstein did formulate general relativity as a "generally covariant" theory. In particular that means that notions tied to any particular coordinate choice should be held suspect until thoroughly understood.
    Yes, but the history of this is interesting. I am working entirely from A. Pais's excellent biog. of Einstein, and have had to try and fill in a lot of gaps; I may have a few things wrong

    It seems that for a couple of years prior to publishing his field equations E. was convinced that there could be no generally covariant field theory for gravitation.

    For, suppose, says E. a region of spacetime endowed with a gravitational source, given by the energy-momentum tensor . Assume that there is a metric tensor field which is everywhere completely and uniquely determined by this source.

    Suppose that in there is a coordinate system . Insist that can be partitioned such that in we may not have that whereas in we may have that . This is equivalent to being a region of "sufficiently far" from the source

    Now apply a generally covariant transformation such that whereas (This is allowed by "general covariance" as DrRocket alluded to).

    Then in we have that and therefore, by hypothesis there.

    Consider the field elements as being the 10 functions in the 4 variables Then, in one has that

    Now turn to and, using the usual benign abuse of notation write and then define and have that as a new metric field in .

    But, says E. (I am putting words in his mouth here!) we have that , and two distinct metric fields over the same coordinates which are seemingly determined by the same source. In other words, if there is no source the metric tensor is undetermined.

    This cannot be so for a theory to be generally covariant. Apparently he called it a "failure of causality". Early in 1915 E. saw that coordinates could be chosen arbitrarily at each and every point in spacetime and "therefore" that the metric is not completely and uniquely determined by the source (Mmm, what is the logic here? It escapes me!) and therefore concluded that a field theory of gravitation could indeed be generally covariant.
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    Quote Originally Posted by MigL
    Take a piece of paper, try to roll it into a sphere or a saddle shape, you cannot. You either need to add material (paper) or subtract it to obtain a smooth shape.
    This might be of topic or it is of topic:P

    But a sphare as we know it does not exist, is there any shape in universe where the radius is the same no matter where you messure from?

    And if you artificaly build a perfect sphare it could only be sphareic in 273 celcius.

    And something that orbits around something just follow the shape of that body, it aint a circular movement.

    weird quote, but it is something I been thinking about.
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    Quote Originally Posted by Guitarist
    Quote Originally Posted by DrRocket
    But nevertheless, Einstein did formulate general relativity as a "generally covariant" theory. In particular that means that notions tied to any particular coordinate choice should be held suspect until thoroughly understood.
    Yes, but the history of this is interesting. I am working entirely from A. Pais's excellent biog. of Einstein, and have had to try and fill in a lot of gaps; I may have a few things wrong

    It seems that for a couple of years prior to publishing his field equations E. was convinced that there could be no generally covariant field theory for gravitation.

    For, suppose, says E. a region of spacetime endowed with a gravitational source, given by the energy-momentum tensor . Assume that there is a metric tensor field which is everywhere completely and uniquely determined by this source.

    Suppose that in there is a coordinate system . Insist that can be partitioned such that in we may not have that whereas in we may have that . This is equivalent to being a region of "sufficiently far" from the source

    Now apply a generally covariant transformation such that whereas (This is allowed by "general covariance" as DrRocket alluded to).

    Then in we have that and therefore, by hypothesis there.

    Consider the field elements as being the 10 functions in the 4 variables Then, in one has that

    Now turn to and, using the usual benign abuse of notation write and then define and have that as a new metric field in .

    But, says E. (I am putting words in his mouth here!) we have that , and two distinct metric fields over the same coordinates which are seemingly determined by the same source. In other words, if there is no source the metric tensor is undetermined.

    This cannot be so for a theory to be generally covariant. Apparently he called it a "failure of causality". Early in 1915 E. saw that coordinates could be chosen arbitrarily at each and every point in spacetime and "therefore" that the metric is not completely and uniquely determined by the source (Mmm, what is the logic here? It escapes me!) and therefore concluded that a field theory of gravitation could indeed be generally covariant.
    The key is that spacetme is a manifold and may not admit global coordinates, but the machinery of manifold theory was not available to Einstein in 1915. That makes his accomplishment just that much more impressive. But it also makes the early treatments of GR more difficult to understand, particularly to those schooled in modern mathematics.

    I have not read this particular biography of Einstein. On your recommendation I just located and ordered a copy. Thanks
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    If every choice of coordinates is allowed then why not for time ?

    For instance the dali landscape where you see all these deformed clocks. Dali refers to this. I can imagine being somewhere seeing different clocks at all possible altitudes. One clock could be on the same gravittional geodesic plane as my eyes, another one on an altitude corresponding with my feet. These clocks have different rhytm for me when I look at them. Which clock meassures "my yime" now ? One meassures the time for my feet the other for my head. Consecquence would be that my feet and my head are not the same age. Absurd yes but not different then the twinparadox.

    Other clocks I can see at much higher altitude or lower. All these clocks having a frecquency 1/s to there own time but different to other clocks.
    But as none of them can really show me my time (what altitude would that have to be, my toes or my head) why would I take one clock as a preferred one.

    The laws of fysics being the same for everyone does not imply that every clock has to be the same for anyone as meassuring the same second. The deformed dali clocks all show a different rhytm to an observer who sees them all at same time even if they are in rest to each other. Simply because they are at different altitudes. not every clock has to show the same second.

    Dali deformes the second in a traditional lanscape and space of painting (space is not deformed) Fysics keeps the second unified thus not deformed resulting in a deformed spacetime. Obviously these are two paradoxal notions in our culture (which is more then just fysics or just art offcourse) that come out in this discussion.

    All we do know is that for each clock it,s own frecquency is 1/1. That says something about the clock and Cesium. The cesium can be at different heigths, adapts it rhytm natural and stays in tune. But it only stays in tune thanks to adaptation which we can see as different rhytm for different clocks. The second comes after seeing the clock, it,s how we interprete the clock.
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    Ghrasp: I mentioned the NIST caesium fountain clock a few pages back. It's to do with the definition of the second:

    "Since 1967, the second has been defined to be the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom. This definition refers to a caesium atom at rest at a temperature of 0 K (absolute zero), and with appropriate corrections for gravitational time dilation."

    In the NIST caesium fountain clock, lasers and a microwave cavity are employed to cause hyperfine transitions, which are electron “spin flips” within caesium atoms. Electrons can be literally made out of light via pair production, and the hyperfine transition is an electromagnetic event which emits microwaves - light in the wider sense. A peak frequency in this emitted light is found and measured by a detector. But note that frequency is measured in Hertz, which is defined as cycles per second, and this clock is being used to define the second. Thus what the detectors are really doing is counting incoming microwave peaks. When they get to 9,192,631,770, that's a second. Hence the frequency is 9,192,631,770 Hertz by definition.

    There's mention of gravitational time dilation in the wiki article. If you were to take this clock and place it in a region of low gravitational potential, it would be like pressing a slow-motion button. All electromagnetic and other processes occur at a slower rate, including the hyperfine transition and the motion of the resultant light towards the detector. However regardless of this, when the detectors get to 9,192,631,770, that's a second.

    It's important to realise here that electromagnetic processes including light are moving slower, and this is why the second is bigger. We then use this second, defined using the motion of light, to measure the speed of light. That's why we always measure the local speed of light in vacuo to be 299,792,458 m/s. The speed of light varies, just like Einstein said. But nowadays some people absolutely insist it doesn't, despite Einstein, and despite the scientific evidence and simple logic which they can not refute.
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    Quote Originally Posted by Ellatha
    No they aren't; you have not given any counter arguments for the mathematical arguments I presented, rather suggested that I'm being irrational for using mathematics, when in fact mathematics is a critical part of physics and historically resulted in the derivation of new theorems (for example, Newton's second law of motion to derive impulse).
    I'm not dusting mathematics under the rug. I'm just giving priority to empirical scientific evidence. Just look at a clock and ask yourself what does a clock clock up? You can't see a world line streaming through, or any time flowing or passing. All you can see is things moving.
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    Quote Originally Posted by Farsight
    I'm not dusting mathematics under the rug. I'm just giving priority to empirical scientific evidence. Just look at a clock and ask yourself what does a clock clock up? You can't see a world line streaming through, or any time flowing or passing. All you can see is things moving.
    Mathematical evidence is every bit, and perhaps even more precise, than empirical scientific results. This is why mathematics only requires pencil and paper.
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    Quote Originally Posted by Farsight
    ...I'm just giving priority to empirical scientific evidence. Just look at a clock and ask yourself what does a clock clock up? You can't see a world line streaming through, or any time flowing or passing. All you can see is things moving.
    At the risk of stirring up a hornets nest, I suggest that if you were to take a pilgrimage to Nepal for a year and return to this forum, everyone here - including yourself - would agree that time has passed since your last post.

    After reading this rather lengthy thread, I can't figure out what point you're trying to make.

    As I understand it, in General Relativity two test particles can each be assigned a set of co-ordinates. Those co-ordinates define the test particle's position in both space and time - and are said to describe an event rather than a place.

    The two test particles can exist at the same spatial co-ordinates, and they can exist at the same temporal co-ordinates. As far as I know, however, they can't both exist at the same spatial and temporal co-ordinates.

    Are you asserting that this is not actually true in the real world?

    Chris
    It is difficult to say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow.
    Robert H. Goddard - 1904
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    Quote Originally Posted by Ellatha
    Mathematical evidence is every bit, and perhaps even more precise, than empirical scientific results. This is why mathematics only requires pencil and paper.
    We use mathematics to codify rules and build theories which we then test against scientific evidence. Your expressions from a couple of pages ago don't tell you what time is, or that we define the second using the motion of light as per the NIST clock above. Mathematics doesn't tell you that we also use the motion of light to define the metre. And it doesn’t give you a picture of what’s actually happening in pair production or beta-minus decay or low energy proton/antiproton annihilation:


    Image credit: CSIRO, see http://outreach.atnf.csiro.au/educat...e/bigbang.html

    Yes, mathematics will tell you that c=√(1/ε0μ0) and that Z0=√(μ00), but it doesn't deliver an understanding of the other meaning of special relativity. Or gravitational time dilation. There's no magic to it. Einstein told us about the non-constant speed of light along with his equations of motion, but his legacy is forgotten: when the light goes slower, you don't see it going slower, not locally. Because everything goes slower. Including your clocks. Including you.
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    Quote Originally Posted by Farsight
    The speed of light varies, just like Einstein said.
    No, he NEVER said that, he said that the velocity of light is invariant as an assumption under the SR formulation (look it up). Don't you realize that SR is a kinematic theory (i.e. no forces acting) so that by Newtons first law it is permissible (but perhaps not very hygienic) to equate speed with velocity? (At least for light, which propagates isotropically)

    Contrast this to GR, which a dynamical theory, where he explicitly states that the assumption that the velocity (=speed) of light in SR is constant may not be valid in GR, by which we may assume the simple fact that in a dynamical theory speed and velocity are not the same thing. This much is obvious

    Quote Originally Posted by Farsight
    It's important to realise here that electromagnetic processes including light are moving slower {in a lower gravitational well}
    Which is equivalent to the assertion that Newtons Laws and Maxwell's equations are coordinate-dependent; t'would be a funny old world if that were the case!

    Even Galileo realized this, you have a better theory?
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    Hence the frequency is 9,192,631,770 Hertz by definition.
    I know that,s how a clock works (because that,s what you actually are explaining). But it is not how the second works. The second (reading a clock) is interpreting that particular clock, going by the manual and counting seconds (as the clock counts this natural cesium rhytm as it,s designed to do so).

    But what natural law could convince Mr Dali which clock he should prefer to read "his own time" ? Is there a preferred clock in this landscape ? Hence Dali came to this landscape of deformed clocks being a methaphore for deformed seconds.

    If you are at a mountaintop or a satellite while I am in a valley if we both watch the clock at our wrist, for a second we use one word (identic) corresponding to clocks of same make. But different clocks because the environment/circumstances are different and the clock/cesium can,t be seperated from it. Hence the word second has different meaning as we look at different things (only same make, same type of substances)
    One definition, ignoring all locality, can,t take these differences away. Such attempts of defining things should be rejected (ignored).
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    Quote Originally Posted by Farsight
    I'm not dusting mathematics under the rug. I'm just giving priority to empirical scientific evidence. Just look at a clock and ask yourself what does a clock clock up? You can't see a world line streaming through, or any time flowing or passing. All you can see is things moving.
    Yes, you are. The theory does not fit your personal idiosyncratic ideas, so you simply ignore the real science under the guise of "empirical scientific evidence". Your "evidence" is neither scientific nor actual evidence, but only the usual rationalization of internet cranks for delusional "theories". Your false appeal to "empirical evidence" is a mirror copy of a strategy employed by "electric universe" proponents -- quintessential internet cranks.

    What you have done, in fact, is to cast aside special and general relativity and have misinterpreted and corrupted bits and pieces of Einstein's early writings in a sophist attempt to justify nonsense. Electric universe nuts base their sophistry on selective quotes and misinterpretations of Hans Alfven. Birds of a feather.

    The very word "moving" requires changes in position over time. You reject the very notion of time because you cannot see it. But even your example in which you perceive the distance between your outstretched hands requires that the position of you hands be perceived simultaneously and therefore cannot be isolated from the notion of time.

    There exists no fundamental definition of time. Nor does there exist a fundamental definition of space. General relativity tells us that in fact time and space are just two aspects of a single thing -- spacetime. Moreover what one observer perceives as time or space may differ from the perception of another observer. That realization is what is supported by real empirical scientific evidence. This fundamental principle of science requires mathematics and abstract thought for understanding.

    You are dusting both mathematics and physics under the rug. The reason is clear. They belie your assertions.
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    Quote Originally Posted by CSMYTH3025
    At the risk of stirring up a hornets nest, I suggest that if you were to take a pilgrimage to Nepal for a year and return to this forum, everyone here - including yourself - would agree that time has passed since your last post. After reading this rather lengthy thread, I can't figure out what point you're trying to make.
    The point I'm trying to make is that clocks clock up motion, atomic clocks are light clocks, and when such a clock goes slow it's because the light goes slow. This isn't my idea, Einstein spoke repeatedly of the variable speed of light, but you tend not to hear about it. Then in 1949 Godel and he really sussed what time was all about, but you tend not to hear about that either.

    Quote Originally Posted by CSMYTH3025
    As I understand it, in General Relativity two test particles can each be assigned a set of co-ordinates. Those co-ordinates define the test particle's position in both space and time - and are said to describe an event rather than a place. The two test particles can exist at the same spatial co-ordinates, and they can exist at the same temporal co-ordinates. As far as I know, however, they can't both exist at the same spatial and temporal co-ordinates.
    That's maybe more special relativity rather than general relativity, but fair enough re events. The issue though is that spatial coordinates are very different to the time coordinate. You have freedom of motion in space, you can go to a point in space. You don't have the same freedom of motion in time, because time is an emergent property of motion through space.

    Quote Originally Posted by CSMYTH3025
    Are you asserting that this is not actually true in the real world?
    See above. Events happen, things move. And you definitely need to specify those four coordinates to arrange a meeting. But the block universe of Minkowski spacetime doesn't truly exist. It's a "mathematical space". What's out there is space, real space, and motion through it.
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    Quote Originally Posted by Farsight
    ..... time is an emergent property of motion through space.
    A simple declarative sentence with no basis whatever in science.

    Prove it with real science and mathematics, like a scientist. Or continue to rely on unsubstantiated rhetoric like a crank.
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    Quote Originally Posted by Farsight
    Then in 1949 Godel and he really sussed what time was all about, but you tend not to hear about that either.

    Godel died due to starvation because his wife was hospitalized and could not cook for him. He feared any other source of food might be poisoned. You don't hear much about that either. So what ?

    Nobody knows what time is all about. That most certainly includes you.
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    Quote Originally Posted by Guitarist
    Quote Originally Posted by Farsight
    The speed of light varies, just like Einstein said.
    No, he NEVER said that, he said that the velocity of light is invariant as an assumption under the SR formulation (look it up).
    I've looked it up. Yes he did say that. You should read the thread. And translate "die Ausbreitungs-geschwindigkeit des Lichtes mit dem Orte variiert".

    Quote Originally Posted by Guitarist
    Don't you realize that SR is a kinematic theory (i.e. no forces acting) so that by Newtons first law it is permissible (but perhaps not very hygienic) to equate speed with velocity? (At least for light, which propagates isotropically)
    You're clutching at straws, c is a speed, not a vector quantity.

    Quote Originally Posted by Guitarist
    Contrast this to GR, which a dynamical theory, where he explicitly states that the assumption that the velocity (=speed) of light in SR is constant may not be valid in GR, by which we may assume the simple fact that in a dynamical theory speed and velocity are not the same thing. This much is obvious.
    Don't assume. Just read what he said. He said it time and time again.

    Quote Originally Posted by Guitarist
    Quote Originally Posted by Farsight
    It's important to realise here that electromagnetic processes including light are moving slower {in a lower gravitational well}
    Which is equivalent to the assertion that Newtons Laws and Maxwell's equations are coordinate-dependent; t'would be a funny old world if that were the case!
    It isn't equivalent to that at all. It's just simple patent evidence. Take two identical light clocks, lay them flat to avoid issues with radial length contraction, put them at different altitudes, and watch them lose synchronisation. Those light clocks are clocking up the motion of light. That's all they're doing.

    Quote Originally Posted by Guitarist
    Even Galileo realized this, you have a better theory?
    Not me. Einstein.
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    Quote Originally Posted by Farsight
    Quote Originally Posted by Guitarist
    Quote Originally Posted by Farsight
    The speed of light varies, just like Einstein said.
    No, he NEVER said that, he said that the velocity of light is invariant as an assumption under the SR formulation (look it up).
    I've looked it up. Yes he did say that. You should read the thread. And translate "die Ausbreitungs-geschwindigkeit des Lichtes mit dem Orte variiert".
    You parrot without understanding.

    As has been explained to you several times:

    1. The speed of light is constant in all inertial frames in both special and general relativity.

    2. In accelerating (non-inertial) frames you can get anything that you want, but it is rather meaningless.

    3. Coordinate times and coordinate speeds are not bphysically meaningful except in flat space. It is invariants that are meaningful. That is critical to both special and general relativity. The meaningful time is proper time, not coordinate time. the speed of light is invariant.

    4. Einstein's words that you quote but do not understand refer to non-inertial frames and coordinate-dependent quantities.

    Since you do not seem amenable to reason, but like web citations read the proper understanding of your Einstein quote here:

    http://www.webcitation.org/5lLQD61qh

    So. in reality, and with understanding, Guitarist is correct. He did not say what you seem to think he said.
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    We experience space, or distances, and time passage because we live a slow speed existence. You, farsight, claim we can only deduce the pasage of time by observing motion or change in things, but can you deduce distance travelled without a reference frame ? For example, if you only have one object in the universe and it moves fro one 'point' to another ( ? ), has it really moved, and can you ever prove that it has if it did ??

    It is a similar case as your argument, you cannot tell the passing of time without movement. But in the above mentioned case of a singular object, you cannot tell movement without measuring elapsed time.

    Fixed, absolute, events, ie both a time and a place, only exist in 4 dimensional Minkowsky space/time and are only possible if both time and space have real quantities. Just because our low speed senses cannot see the big picture of space/time does not mean they should be dismissed as subjective.
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    Oh, and don't get me wrong, I may not agree with your point of view, but this is one of the more exciting threads, and hopefully we all learn something from it.
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    DrR, further to our conversation regarding the length of geodesics in a strong gravitational field as opposed to "flat' space, let me try another approach and tell me if it makes more sense.
    Take a two dimensional analogy of flat space, absent of gravitational fields, alarge sheet of rubber stretched between four poins, or alternately an air matress. Any line drawn on this 2D surface will have an easily calculated length.
    Onto this 2D space we introduce a strong gravitator, a bowling ball, which warps this 2D surface by indenting it. If we again draw a line on this modified 2D surface, the length is no as easy to calculate, but is easily proven to be longer than the previous case. I say modified because it is warped outside of its original 2D plane into a 3rd dimension.
    We now extend this analogy to a 3D volume. The strong gravitator will again warp this volume into a 4th dimension, outside of its original volume, but the end result is the same, lines in this modified space, or geodesics will also be longer. They will be longest in areas of strong gravity.

    Now I realise that we cannot compare the two states directly because as you stated, there is no transformation to go from one to the other, but you should be able to draw some general conclusions as to the warping os space/time close to a gravitator.

    Or am I still wrong ? I realise I'm not being too precise by stating things as I have, but it still makes sense to me. Please point out wrong assumptions or conclusions in my analogy.
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    Quote Originally Posted by MigL
    We experience space, or distances, and time passage because we live a slow speed existence. You, farsight, claim we can only deduce the passage of time by observing motion or change in things, but can you deduce distance travelled without a reference frame?
    I'd say no, but would qualify that by saying you have to take care with reference frames. You can't look up to the sky and point one out. You can point out objects in the sky, and you can see them moving, but a reference frame is only an artefact of measurement that relies on the existence of objects and motion.

    Quote Originally Posted by MigL
    For example, if you only have one object in the universe and it moves from one 'point' to another ( ? ), has it really moved, and can you ever prove that it has if it did??
    I'd say no, because motion is relative.

    Quote Originally Posted by MigL
    It is a similar case as your argument, you cannot tell the passing of time without movement. But in the above mentioned case of a singular object, you cannot tell movement without measuring elapsed time.
    It's not like that, MigL. If you're in a simple universe you can tell if an object moves. You can see it happening because light moves from the object to your eye, and nerve impulses move to your visual cortex and around your brain. But when you measure how long it moved for, you use a clock, and that's moving too.

    Quote Originally Posted by MigL
    Fixed, absolute, events, ie both a time and a place, only exist in 4 dimensional Minkowsky space/time and are only possible if both time and space have real quantities. Just because our low speed senses cannot see the big picture of space/time does not mean they should be dismissed as subjective.
    I'm not dismissing them as subjective. I say that time exists like heat exists. Heat isn't subjective, heat burns. But at the fundamental level, heat is an emergent proprty of motion. Ditto for time. It's just a matter of shifting your stance a little to hold your hands up and waggle them, then saying I can see space and motion, but I can't see time flowing by. Then you appreciate that some of the things people say about time are just a figure of speech.

    Quote Originally Posted by MigL
    Oh, and don't get me wrong, I may not agree with your point of view, but this is one of the more exciting threads, and hopefully we all learn something from it.
    A pleasure MigL. If we all agreed with one another about everything, a discussion forum wouldn't be much fun. I think the important thing is to talk about things in an open friendly fashion and accepting the evidence and logic offered by others. Edit: LOL, see below. Sometimes even my patience is tested.
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    Quote Originally Posted by DrRocket
    You parrot without understanding. As has been explained to you several times:

    1. The speed of light is constant in all inertial frames in both special and general relativity.

    2. In accelerating (non-inertial) frames you can get anything that you want, but it is rather meaningless.

    3. Coordinate times and coordinate speeds are not physically meaningful except in flat space. It is invariants that are meaningful. That is critical to both special and general relativity. The meaningful time is proper time, not coordinate time. the speed of light is invariant.

    4. Einstein's words that you quote but do not understand refer to non-inertial frames and coordinate-dependent quantities...
    Oh shut up you pompous mathematical quack. Face up to what Einstein said about the variable speed of light, and and face up to the scientific evidence. Then take two identical light clocks, lay them flat to avoid issues with radial length contraction, put them at different altitudes, and watch them lose synchronisation. Those light clocks are clocking up the motion of light. That's all they're doing. When one clock goes slower than the other we call it gravitational time dilation. When one clock is subject to infinite gravitational time dilation, then in this real universe that clock isn't ticking. So the "meaningful" proper time measured on it is being measured in cloud cuckoo land.
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    Quote Originally Posted by MigL
    Take a two dimensional analogy of flat space, absent of gravitational fields, alarge sheet of rubber stretched between four poins, or alternately an air matress. Any line drawn on this 2D surface will have an easily calculated length. Onto this 2D space we introduce a strong gravitator, a bowling ball, which warps this 2D surface by indenting it. If we again draw a line on this modified 2D surface, the length is no as easy to calculate, but is easily proven to be longer than the previous case. I say modified because it is warped outside of its original 2D plane into a 3rd dimension. We now extend this analogy to a 3D volume. The strong gravitator will again warp this volume into a 4th dimension, outside of its original volume, but the end result is the same, lines in this modified space, or geodesics will also be longer. They will be longest in areas of strong gravity...
    Excuse me for butting in, but a better analogy is to start with a block of rubber. A strong gravitator then alters the rubber around it, such that ripples in the rubber go slower near the object. An example of this kind of thing is Inhomogeneous Vacuum: An Alternative Interpretation of Curved Spacetime by Ye Xing-Hao and Lin Qiang, Chinese Physics Letters, Issue 25, No. 5. This is in line with Einstein's 1920 Leyden address where he said "According to this theory the metrical qualities of the continuum of space-time differ in the environment of different points of space-time, and are partly conditioned by the matter existing outside of the territory under consideration. This space-time variability of the reciprocal relations of the standards of space and time, or, perhaps, the recognition of the fact that “empty space” in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitation potentials gμν)..."
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    Have you considered the idea that Einstein may have not been the messiah, and that some of his writings may be wrong? I am not necessarily suggesting that Einstein is wrong in this case, although I'm rather sure that there is error in his writings.

    I have found that those who commit their beliefs in the works of a single author become enslaved to the extent that they are no longer able to think for themselves and make their own opinions. Rarely is one such person capable of notable discovery. This is, in much the same way what the Scholastics and Cartesians did with Aristotle and Descartes, respectively.
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