No, you're plotting a variation in the speed of light. The idea that you're plotting a variation in length is a revisionist cargo-cult myth. See what Einstein and Shapiro said about it:
Misleading Phrase: Collapse of wave function
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Schneibster
Registered Member
Hmmmm, that's not the modern understanding of GRT.
The essential question, and one not answered in your quotes, is from what frame does this appear to be true?
Remembering that it is not just space, but spacetime, that is warped by a gravity field, one has to ask what, in the presence of warped time, the phrase, "the speed of light," means, exactly, since speed is distance over time.
I agree that to an observer far from the gravity field, a light ray within the field might appear to travel at a different speed than c; however, to an observer local to the light ray, it will still appear to travel at c.
So the Shapiro paper is referring to the fact that the light ray appears to an observer on Earth to travel slower than the speed of light while it passes through the Sun's gravity field, but this would not be true for an observer actually measuring a small portion of the ray close to the Sun, because all her instruments would be warped to the same extent as the light. And I believe that Einstein was talking about the same effect. Today we take the frame of the observer close to the Sun; Einstein took the frame of the observer on Earth.
They come out to the same thing, in the end. It's just a matter of which frame you choose to view it from.
On edit: I kinda tend to think that if two different methods yield the same result it's a bit inconsistent to claim one of them is "wrong."
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What can I say? This modern "understanding" is wrong.
It appears to be true from the room you're in. See lower down in the second paragraph where Einstein said "The theory of special relativity, therefore, applies only to a limiting case that is nowhere precisely realized in the real world". He's referring to the infinitesimal frame in which you allegedly measure the speed of light to be constant. This is a frame of no extent. Also check out this PhysicsFAQ/Baez article where editor Don Koks says this:
Einstein talked about the speed of light changing in his new theory. In the English translation of his 1920 book "Relativity: the special and general theory" he wrote: "according to the general theory of relativity, the law of the constancy of the velocity [Einstein clearly means speed here, since velocity (a vector) is not in keeping with the rest of his sentence] of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity [speed] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers.
Space isn't warped, it's rendered inhomogeneous. Spacetime is an abstract thing. Have a look at Pete's paper at http://arxiv.org/abs/physics/0204044 :
There exists some confusion, as evidenced in the literature, regarding the nature of the gravitational field in Einstein's General Theory of Relativity. It is argued here the this confusion is a result of a change in interpretation of the gravitational field. Einstein identified the existence of gravity with the inertial motion of accelerating bodies (i.e. bodies in free-fall) whereas contemporary physicists identify the existence of gravity with space-time curvature (i.e. tidal forces). The interpretation of gravity as a curvature in space-time is an interpretation Einstein did not agree with.
It means what it says on the tin. The speed of light down by the floor is lower than it is up near the ceiling. If it didn't, optical clocks wouldn't go slower when they're lower. They don't go slower because your plot of light clock rates is curved. And they don't go slower because time is going slower. There is no time flowing through an optical clock. What there is, is light, moving.
Because of the tautology referred to by Magueijo and Moffat in http://arxiv.org/abs/0705.4507 . We define our second and our metre using the local motion of light, then use them to measure... the local motion of light!
Einstein and Shapiro said what they said.
Either the speed of light is spatially variable or it isn't. I'm going with Einstein and the evidence on that.
Uh... ok? I realize the original question kind of got buried, but I hope you answer it, because it's a pretty important point. How can you account for Bell inequality violations if you assume that the wavefunction is a physical thing that propagates at c?
Via something akin to Joy Christian's argument wherein rotations do not commute. You've seen me saying elsewhere that spin is a real rotation. See post 100 where I talked about Susskind rolling his marker around. Also see where the New Scientist article said Twenty years ago, it was heretical even to raise such an idea. Well here we are nearly ten years later, and it still is. Joy Christian got pilloried by people like Scott Aaronson who make a living out of quantum mysticism and the jam-tomorrow promise of quantum computing.
I didn't quote it because it complicates the issue. I can model the internal workings of an electron to be a photon confined in periodic boundary conditions. If we view it as a soliton in a cyclic path, and this path determines charge and parity, then claiming that a system is time-symmetric could automatically make that system charge- and parity-symmetric.
See here for a good model: http://home.claranet.nl/users/benschop/electron.pdf
It isn't relevant anyway because a QM interpretation which allows for a physical collapse of the wavefunction is neither T-symmetric nor CPT-symmetric. You use the phrase "irreversible change to the state of the particle" and you are simply mistaken; you are letting your chosen interpretation of QM affect your description of the real world. Go to this link:
https://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics#Tabular_comparison
Try to find an interpretation that has a collapsing wavefunction which is deterministic and has a unique history. There is none. But you can find interpretations which give no physical relevance to the wavefunction collapse, such as pilot wave or the time-symmetric interpretation, which provide both a unique history and a unique future.
The answer is of course we can, classically. I already claimed as much regarding the coin falling to the floor.Schneibster said:
comical--there it is-- the SUPPLEMENTS(IDEAS AND METHODS)-- that i just mentioned yesterday--that farsight cannot, obviously, understand the meanings of these words..No, you're plotting a variation in the speed of light. The idea that you're plotting a variation in length is a revisionist cargo-cult myth. See what Einstein and Shapiro said about it:
Schneibster
Registered Member
Yes, that's correct. We now know that even in open space far from any galaxies there will still be curvature of spacetime due to the cosmological term in the Einstein field equations. It is, however, exactly true in the limiting case of truly flat spacetime with no curvature.
I can see you've learned quite a bit since we last spoke.
No, that I don't agree with. I would say instead that spacetime is warped, it's rendered inhomogeneous. That's what "warped" means. That's what's shown in the picture in your post #98.
And spacetime is not an abstract thing at all.
- It exerts pressure: the Casimir force. This is inescapable in our universe because vacuum fluctuations are omnipresent. In addition, see Newton's Bucket, and Mach's Principle, as used in the development of GRT.
- It causes angular momentum: rotation is apparent due to the metric tensor, which fills all of spacetime, and has existence even when its value is zero. Mach's original idea was stated as the stars and galaxies of the universe somehow pulling on one, but Einstein turned that into the metric tensor. Just as vacuum fluctuations define spacetime, so does the metric tensor.
- It causes momentum: angular momentum can always be converted into linear momentum, if the rotating object fragments. If it does, each of the pieces acquires linear momentum from the original angular momentum of the fragmented rotating object.
I would say that the terms on the left side of the Einstein field equations are all curvature terms, since they contain the Ricci curvature tensor, the scalar curvature, and the cosmological constant, all of which are mathematical curvatures. The first two have it right in their names; if you doubt the cosmological constant is a curvature, please study up on FLRW solutions to the EFE. Remember that a straight line is included in the mathematical definition of a "curve." Look it up.
I don't think Peter Brown is or can be correct considering that the Ricci curvature was already known to be a curvature formula when Einstein used it in GRT. Ricci invented tensor calculus before GRT was formulated, and defined the Ricci curvature tensor then. The book on it that he wrote on it was published in 1900. Linkie: http://www.springerlink.com/content/u21237446l22rgg7/fulltext.pdf
Light whose propagation is affected by the gravity field. And in fact, they do go slower, and it is because time is going slower, as proven by your very own Shapiro test. It's actually been done with Cassini, and the results agreed with the prediction of GRT to within 0.002% according to Wikipedia. Also, the curvature itself is insufficient to account for this. Then there's Hafele-Keating, which showed time dilation in atomic clocks flown on aircraft due to GRT. Finally, Gravity Probe A tested GRT time dilation as well. Time flows at a different rate in a gravity field, and the difference depends on the strength of the field at the location of the clock.
I repeat, what does "the speed of light" mean in the presence of time dilation? Obviously if the rate of time changes in a particular reference frame, then light moving within that frame will move at c according to the rate of time within that frame. An observer within the frame won't notice it, but one looking from outside will. This is why I asked you what frame you were talking about, and referred to it again at the end of my post #102.
But here's the kicker: take your measuring stick or clock outside the gravity field and they still measure a meter and a second! And since this is so, it's far easier to say that they're a meter and a second wherever they are. If you can only measure a meter properly in flat space, which you yourself above said doesn't exist, then what is the use of a meter?
Yes, and I explained why it amounts to the same thing but viewed from a different perspective; specifically, from a different frame of reference.
I disagree. Either the speed of light is spatially variable or the rate of time changes in different gravity fields. And I'm going with the modern interpretation, which yields a system of units that can actually be used as opposed to a system that can never be measured because the conditions to do so don't exist in our universe.
BTW, picking and choosing what you will pay attention to in peoples' posts can lead to a lot of problems, as you just found out by not paying attention to my question, "From what frame?"
Ah. I might have guessed you'd invoke Joy Christian. That's too big a can of worms for this thread, so I'll just ask one more question:
If the quantum state of two photons is $$|\psi\rangle=(|+\rangle\otimes|+\rangle+|-\rangle\otimes|-\rangle)/\sqrt{2}$$, where the tensor product is between two photons in spacelike-separated coherent states and +/- denote opposite circular polarizations, what does the physical field look like?
I just have to say: seeing you and Farsight argue non-mainstream positions in side-by-side posts, your rigor and willingness to engage skeptics' arguments on their own terms makes a world of difference. Keep it up.
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Schneibster
Registered Member
Errr, of course it complicates the issue, it proves you're incorrect. Which you failed to acknowledge.
QM is not time-symmetric because you must also reverse the charges and the handedness if you reverse time or physical law will be violated. This is called "CPT symmetry," and I suggest you look it up.
Worse yet, your version of "time symmetry" doesn't exist in either classical or quantum mechanics. An interaction is an interaction and it is irreversible, and this is the root of the irreversibility of thermodynamics. The fluctuation theorem proves that, and it's been experimentally tested.
Since photons have no charge, and electrons have no "inner workings," that would be quite a trick. Please do. But I kinda doubt it.
How could a photon on a "cyclic path," whatever that is, "determine" charge and parity? I was right to doubt it
The reason for the confinement is not discussed, nor is any way of getting a photon into this soliton state proposed. It is brought in as a postulate, in other words they assume that this can happen and don't ever discuss how or why. That is the first problem with the paper.
The second problem is that the behavior of electrons is experimentally confirmed far upward of 100 GeV, and exactly conforms to the Dirac/Standard Model expectations. No photon, no matter what its supposed topology, is going to show no difference from Dirac/Feynman QED to that high an energy level; and particularly with no confinement mechanism discussed, this is a fatal flaw.
The third problem is that the Dirac equation is not derived at any point, and that is another fatal flaw. Electrons follow the Dirac equation, and I repeat, this has been confirmed over 100 GeV; without deriving the Dirac equation there is no demonstration that this object is actually an electron; never mind whether it exists or not, which is questionable at best without a confinement mechanism discussed.
The fourth problem is that electrons show no internal structure at over 100 GeV. This thing is asymmetric, by definition, and there is no evidence at all of asymmetry in electrons that would at least give this hypothesis some grounding in real experimental data; and that also is a fatal flaw, because to have a high enough energy to maintain this state and appear fully symmetric to this high an energy, the photon would have to be of far more energy than is present in an electron. Like many orders of magnitude more.
For bogus points (bogus is the opposite of bonus, I don't mean to impugn the authors' integrity, they were just having fun), the semi-classical treatment makes the hypothesis presented intractable to analysis with QM. So we can't even connect it up with the Standard Model. This is probably why the authors didn't attempt to derive the Dirac equation.
It's an amusing curiosity of a paper, but it's not anything serious, and in the Acknowledgements the authors pretty much say so.
Ummmm, QM interpretations don't have T- or CPT-symmetry. And QM doesn't have T-symmetry.
Are you seriously claiming that interactions are not irreversible changes to the states of particles? And by "irreversible" I mean that after the interaction, the interacting particles fly off in various separate directions and cannot be brought back, not that you cannot reverse the Feynman diagram (and the handedness and charges).
I need only demonstrate a single such interaction, and I have one in mind. A neutron enters from the left and undergoes decay at the vertex. A proton, an electron, and an electron antineutrino emerge from the vertex, and fly away in different directions.
OK, show how you're going to bring the proton, electron, and electron antineutrino back together again to make a neutron. And I don't mean "some" proton, "some" electron, and "some" neutrino; I mean that proton, that electron, and that electron antineutrino. Nor may you reverse time; that is unphysical. Time reversal is a symmetry, not an operation. In this case all it means is some proton, electron, and electron antineutrino could come together at a vertex and there is a probability that is non-zero that a neutron would emerge from the vertex. It doesn't mean you can put the neutron back together from the same particles it decayed into.
So you're now claiming that these interpretations don't include interactions? Because you still haven't shown that a particular interaction is actually reversible. And this is the fourth time I'm asking.
No, you can't and let me demonstrate it:
You see a die lying on the floor. It's a six. There's a person standing over it and they say they just threw it.
Now tell me which hand they threw it from.
Good luck with that.
Being fair. In the UK (maybe everywhere else too) we flip a coin by balancing it on a finger and flipping it with the thumb. I do it like that anyway - doesn't matter. Point is we can build a mechanical flipper. We can make the mechanics as good as we like (or can afford). We can (at a guess) build a thing to flip the coin over about 20 times and throw a heads every time. Is there a theoretical number of flips beyond which the result can't be preordained?
Edit ... showing how any system can slide from 'classical' to random would be just as good.
Edit ... showing how any system can slide from 'classical' to random would be just as good.
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I'm afraid you don't. Why don't you start a thread on that? All this GR is rather hijacking the wavefunction thread.
I think you're confusing me with somebody else, Schneibster.
You've missed the important point, which is that inhomogeneous space is the reality that underlies curved spacetime. That picture is misleading in that it suggests space is warped or curved. Instead space is inhomogeneous, and this inhomogeneity is not uniform. It reduces with distance, if you could plot it you would see a curve on your plot.
I'm afraid it is. There's no motion in spacetime. And we live in a world of space and motion.
Vacuum fluctuations cause the Casimir effect, and there's no motion in spacetime.
The metric tensor is little more than a measurement matrix.
Rotation causes angular momentum.
Space is very real and omnipresent, as is motion. I can hold my hands up a foot apart and show you the gap, the space bwetween then. And I can wave my hands to show you motion. In this respect space and time are empirical. But can you say the same of time? Or of spacetime? No, you can't.
The FLRW metric "starts with the assumption of homogeneity and isotropy of space". And Einstein described a gravitational field, which is typically labelled as curved spacetime, as a place where space is neither homogeneous nor isotropic.
I'll look into that. But meanwhile IMHO important point in Peter's paper is the differences between the Einstein interpretation and the modern interpretation. Most people aren't aware of any differences or different interpretations.
No. There is no actual thing called time going slower. We define our second using the motion of light. When the light goes slower we say time goes slower.
Open up a clock. You won't find time flowing in there. A clock is not some cosmic gas meter. A clock features some kind of regular cyclical motion, be it the motion of a pendulum or a crystal or light. When that motion goes slower the clock goes slower.
You are confusing cause and effect. Read what Einstiee said. The speed of light is spatially variable, it's that simple.
We define a second by watching nine billion microwaves go by, then jumping up and crying that's a second. Then we use this second to measure the speed of those microwaves. Duh!
It's just another abstract thing.
I'm going for the correct interpretation.
I pay attention. Let's have a new thread. Rpenner can you do a split?
Sorry Fednis. But I do not believe in magic and mysticism.
Again, I have to go. Sorry. Can we start with a single linearly-polarized photon, then a single circularly polarized photon, then two.
I do not believe in magic and mysticism, and I'm with Einstein. I'll get back to you.
Kept out of this thread till now, but that statement just got me bursting my sides with laughter. Good one Farsight - and to think there was no pun intended!
While I appreciate that you pointed out the distinction between CPT symmetry versus plain time symmetry, I think this comment about thermodynamics is missing the point a little. While the second law of thermodynamics is one of the best-established principles in all of physics, it can't be derived from first principles. In classical mechanics, relativity, or quantum mechanics without measurement, all the same rules hold when time runs in reverse, up to a couple of variable flips (ie. charge and parity). Even if it's not physically possible to exactly reverse the trajectories of every particle, the theory tells us that doing so would reverse the dynamics and fully recover the initial state. RJBeery's problem with measurement collapse is that it does not have this symmetry; the Copenhagen interpretation gives us no way to "un-measure" a variable, even in principle. I'm not sure whether I agree that this presents a problem, but the irreversibility of measurement collapse is fundamentally different from the irreversibility of thermodynamics.
Fine by me. If it makes the description simpler, feel free to go with two linearly polarized photons (ie. +/- are horizontal/vertical polarizations in the formula above). I just want to see you describe two photons, with maximally entangled polarization and widely-separated wavepackets.
Your problem isn't with anything I've said, your problem is in considering alternative interpretations. I'm telling you they exist, I'm providing links to them, and I've shown a table which lists those which are time-symmetric.
That's easy. The heat signatures in the walls and carpet provide evidence of the earlier trajectory of the die. It's possible in theory to reverse any classical physical state even if it is practically impossible. Classical physics is 100% time reversible; this is Physics 101. Are you a Physicist, may I ask?Schneibster said:
well, we for sure know that you are not, correct?
Schneibster
Registered Member
Now that's just plain flat wrong. My two favorites are TI and CH; I often joke that I believe them on alternate days. Everett/MW has too many invisible moving parts for me. Copenhagen sweeps too much under the carpet. Bohm's not bad, but TI's better and tells more about what's supposed to be going on; CH proponents say that CH is "Copenhagen done right," and I think TI is "Bohm done right." I have an opinion that the various interpretations are all correct, but that some are more useful than others.
I'd argue first that detecting those heat signatures depends on you having arrived immediately afterward before they had time to irreversibly dissipate (thermodynamics) which is not part of the conditions I specified, and second that what you're talking about is not time reversal symmetry (as I have been saying now for several posts).
Nope, nor did I ever claim to be, and this looks like an argument from authority, a well-known logical fallacy. You might want to have a look at my "Hi there" post.
Schneibster
Registered Member
Have you ever investigated the fluctuation theorem? I recommend it to your attention. It links QM with thermodynamics by deriving the laws of thermodynamics from, among other assumptions, the laws of QM. It has been proven in the laboratory by predicting and being confirmed.
I would argue that being able to recover the initial state is not time reversal symmetry; time reversal symmetry is solely and only the statement that if time were reversed and the interaction run backwards it would not violate any physical laws, which is quite distinct from being able to recover the original state.
I didn't say they were the same thing; I said the irreversibility of thermodynamics is a consequence of the irreversibility of interaction (of which measurement is one, but not the only, type). And note that I did not say that interactions do not have time reversal symmetry; I merely said they are irreversible in that the original state cannot be recovered from the final state except as a probability. Multiple initial states can account for the final state and if you reverse the interaction, it may or may not proceed in the opposite way. Time reversal symmetry only means that if-- I repeat if-- it does proceed in the opposite way, it will not violate any physical laws.
Schneibster
Registered Member
Krash, you were right. Thanks for your patience.