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Relativity+
- Thread starter Farsight
- Start date
Farsight---
The basic problem with your ideas is that you break explicitly Lorentz Invariance. Lorentz Invariance can be stated many ways, but one of the most familiar statements is that time isn't special. That is, one has to treat time just like a spacial dimension when doing physics. This is how physics has been done for about the last century.
This is something that has been tested quite accurately, and confirmed everytime we do a calculation wherein time is treated in a Lorentz Invariant manner. Do a google search for "tests of Lorentz Invariance".
I am quite busy now and will be for the forseeable future---I don't have time for a lot of prose. I will try to read your ideas in the future and point exactly to where the problems are.
The basic problem with your ideas is that you break explicitly Lorentz Invariance. Lorentz Invariance can be stated many ways, but one of the most familiar statements is that time isn't special. That is, one has to treat time just like a spacial dimension when doing physics. This is how physics has been done for about the last century.
This is something that has been tested quite accurately, and confirmed everytime we do a calculation wherein time is treated in a Lorentz Invariant manner. Do a google search for "tests of Lorentz Invariance".
I am quite busy now and will be for the forseeable future---I don't have time for a lot of prose. I will try to read your ideas in the future and point exactly to where the problems are.
Here---this paper was just published today.
Read the first three scentences on p. 2
http://www.arxiv.org/PS_cache/hep-ph/pdf/0703/0703291.pdf
Read the first three scentences on p. 2
http://www.arxiv.org/PS_cache/hep-ph/pdf/0703/0703291.pdf
I don't break Lorentz invariance. We always measure c at 300,000km/s because light defines time. Yes, there's a deeper truth to it, which I can paraphrase by saying c is constant in all frames but not across all frames. And if in this deeper truth I did break Lorentz Invariance, is it the end of the world? What's more important, the deeper truth or the shallower rule? Here's a quote from something I googled just now:
Relativity has been one of the most successful theories of the last century and is a cornerstone of modern physics. This review focuses on the modern experimental tests of one of the fundamental symmetries of relativity, Lorentz invariance. Over the last decade there has been tremendous interest and progress in testing Lorentz invariance. This is largely motivated by two factors. First, there have been theoretical suggestions that Lorentz invariance may not be an exact symmetry at all energies. The possibility of four-dimensional Lorentz invariance violation has been investigated in different quantum gravity models (including string theory [185, 107], warped brane worlds [70], and loop quantum gravity [120]), although no quantum gravity model predicts Lorentz violation conclusively. Other high energy models of spacetime structure, such as non-commutative field theory, do however explicitly contain Lorentz violation [98]. High energy Lorentz violation can regularize field theories, another reason it may seem plausible. Even if broken at high energies, Lorentz symmetry can still be an attractive infrared fixed point, thereby yielding an approximately Lorentz invariant low energy world [79]. Other ideas such as emergent gauge bosons [54, 189, 161, 80], varying moduli [93], axion-Wess-Zumino models [30], analogues of emergent gravity in condensed matter [40, 238], ghost condensate [34], space-time varying couplings [177, 50], or varying speed of light cosmologies [219, 209] also incorporate Lorentz violation. The ultimate fate of Lorentz invariance is therefore an important theoretical question.
I know you don't like to hear this, but here's the size of it, and it's got to be said: treating time just like a spacial dimension is wrong. You have no freedom of movement through time. Minkowski was wrong. Physics has been wrong for the last century. You'll see it eventually, one way or another. Everybody will. Einstein did. But he was too old, and too marginalised to want do anything about it. And I suspect he didn't want to end his days with people calling him names.
I got a blank page on that paper you linked to. Maybe it's my acrobat. I'll try again.
Relativity has been one of the most successful theories of the last century and is a cornerstone of modern physics. This review focuses on the modern experimental tests of one of the fundamental symmetries of relativity, Lorentz invariance. Over the last decade there has been tremendous interest and progress in testing Lorentz invariance. This is largely motivated by two factors. First, there have been theoretical suggestions that Lorentz invariance may not be an exact symmetry at all energies. The possibility of four-dimensional Lorentz invariance violation has been investigated in different quantum gravity models (including string theory [185, 107], warped brane worlds [70], and loop quantum gravity [120]), although no quantum gravity model predicts Lorentz violation conclusively. Other high energy models of spacetime structure, such as non-commutative field theory, do however explicitly contain Lorentz violation [98]. High energy Lorentz violation can regularize field theories, another reason it may seem plausible. Even if broken at high energies, Lorentz symmetry can still be an attractive infrared fixed point, thereby yielding an approximately Lorentz invariant low energy world [79]. Other ideas such as emergent gauge bosons [54, 189, 161, 80], varying moduli [93], axion-Wess-Zumino models [30], analogues of emergent gravity in condensed matter [40, 238], ghost condensate [34], space-time varying couplings [177, 50], or varying speed of light cosmologies [219, 209] also incorporate Lorentz violation. The ultimate fate of Lorentz invariance is therefore an important theoretical question.
I know you don't like to hear this, but here's the size of it, and it's got to be said: treating time just like a spacial dimension is wrong. You have no freedom of movement through time. Minkowski was wrong. Physics has been wrong for the last century. You'll see it eventually, one way or another. Everybody will. Einstein did. But he was too old, and too marginalised to want do anything about it. And I suspect he didn't want to end his days with people calling him names.
I got a blank page on that paper you linked to. Maybe it's my acrobat. I'll try again.
Lorentz Invariance can be stated many ways, but one of the most familiar statements is that time isn't special. That is, one has to treat time just like a spacial dimension when doing physics. This is how physics has been done for about the last century.
I've seen you say this a number of times, and I'm curious as to why you think that. In SR, there is a difference between the way space and time are treated, in the metric. Yes, time is a dimension. But if we treated the time coordinate no differently than the spatial coordinates, then we would be using a metric of signature (++++) rather than (-+++), no?
What does this mean?Yes, there's a deeper truth to it, which I can paraphrase by saying c is constant in all frames but not across all frames.
If you lose Lorentz invariance, you lose invariance of c. No Lorentz invariance = no relativity, so your "deeper truth" would be "relativity is wrong and Einstein was wrong".And if in this deeper truth I did break Lorentz Invariance, is it the end of the world?
No-one has the religious attachment to Lorentz invariance you think they do. Lorentz invariance is open to being disproven at any time, just like any other scientific theory.I know you don't like to hear this, but here's the size of it,
Wrong in what sense and by what standards? This is not supported by your googled quote.and it's got to be said: treating time just like a spacial dimension is wrong.
Nor did anyone claim you did. "Freedom of movement" is not built into the definition of "dimension". If you think it should be, then you are free to not label time a "dimension" if you don't want to.You have no freedom of movement through time.
Why do you attach so much importance to labels, anyway?
About what, specifically?Minkowski was wrong. Physics has been wrong for the last century.
What does this mean?
In short: wherever there's time dilation it's because the local speed of light is different. But when you're local too, you still measure c at the same old 300,000km/s. It's because light defines our time.
Does General Relativity make Special Relativity wrong? Was Newton wrong? Einstein had a lot of thoughts about Relativity after GR, even though he never got them out. Look at String Theory. Theories do evolve.If you lose Lorentz invariance, you lose invariance of c. No Lorentz invariance = no relativity, so your "deeper truth" would be "relativity is wrong and Einstein was wrong".
Address that one to Ben.No-one has the religious attachment to Lorentz invariance you think they do. Lorentz invariance is open to being disproven at any time, just like any other scientific theory.
Plenty of people do insist that time is just like space, and is a genuine dimension. Maybe not here, but on other forums.Farsight: and it's got to be said: treating time just like a spacial dimension is wrong. Wrong in what sense and by what standards? This is not supported by your googled quote. Farsight: You have no freedom of movement through time. Nor did anyone claim you did. "Freedom of movement" is not built into the definition of "dimension". If you think it should be, then you are free to not label time a "dimension" if you don't want to.
It's my IT Systems Analysis background. If you call a thing something it isn't, your design falls apart. I always smile when people say "It's just semantics".Why do you attach so much importance to labels, anyway?
About spacetime as an actual entity, worldlines, and the block universe.About what, specifically?
It's my IT Systems Analysis background. If you call a thing something it isn't, your design falls apart. I always smile when people say "It's just semantics".
Fortunately, human beings aren't stupid like IT systems are. Computers only know what they are told. Human beings can determine meaning from context. The fact of the matter is that labels are entirely arbitrary, and ultimately meaningless in and of themselves. So I would agree with przyk when he says that if you want to use the word "dimension" to indicate "something you can move through", then you are certainly free to do so. But that doesn't make it wrong when someone else refers to time as a "dimension" in the mathematical sense. Indeed, it is not wrong to refer to time as a dimension in that sense.
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Think you could give a worked example? I'm not following here.In short: wherever there's time dilation it's because the local speed of light is different. But when you're local too, you still measure c at the same old 300,000km/s. It's because light defines our time.
Theories evolve, but that wasn't my point. If a theory breaks Lorentz invariance, it breaks relativity. It doesn´t make sense to talk about relativity evolving beyond Lorentz invariance. You either stick with or drop both.Does General Relativity make Special Relativity wrong? Was Newton wrong? Einstein had a lot of thoughts about Relativity after GR, even though he never got them out. Look at String Theory. Theories do evolve.
Do they claim they can move around freely through time?Plenty of people do insist that time is just like space, and is a genuine dimension. Maybe not here, but on other forums.
But labels need to be programmed into a computer at some point, and the initial assignments are arbitrary. The world won't end if you create a pseudo-C compiler that expects "zargloff" instead of "int". It doesn't mean anything to call "int" right and "zargloff" wrong, and demand that all compilers only use "int". What you care about is properties, ie. what difference the choice of using integer or floating point variables (whatever you or your compiler calls them) will make on the speed and precision of calculations, and the end result this will have on your program. So with that in mind...It's my IT Systems Analysis background. If you call a thing something it isn't, your design falls apart. I always smile when people say "It's just semantics".
"Actual" as opposed to what? And most importantly, what observable difference would it make? Otherwise, you're looking for absolute truth where it doesn't exist.About spacetime as an actual entity
Think you could give a worked example? I'm not following here.
Imagine you've got twins A and B standing at your desk laden with their rulers and clocks and video recorders and other equipment. They each go off to their assigned black-box space capsules, and return much later.
Twin A is noticeably older now, with grey hairs and creases round his eyes. He demonstrates to your satisfaction that according to his measurements seven years have elapsed, during which time he has continuously measured c to be 300,000km/s. He therefore calculates that since you were all last together light has travelled seven lightyears.
Twin B however is not noticeably older. But he can demonstrate to your satisfaction that according to his measurements, only one year has elapsed, during which time he has continuously measured c to be 300,000km/s. He therefore calculates that since you were all last together light has travelled one lightyear.
At this point an argument breaks out between the twins. One insists that light has travelled seven lightyears, the other insists that light has travelled one lightyear. They say they can't both be right, because the speed of light is constant. They ask you to reveal which one is right, and wonder if you'll say that Twin B was sent on a fast round trip at .99c and didn't notice the acceleration because of the drugs. You say no, and explain that even if this were so, the explanation would employ the current mutually-shared reference frame as a preferred or absolute reference frame, and would say that both lightpaths were actually seven light years long.
Instead you reveal that twenty years have elapsed, and you're on a space station in a parking orbit around Cygnus X1. Each twin has been on a ride round the hole. And on Earth, a hundred years have elapsed.
There can be no preferred frame, not this one, not Earth's. There is no definitive lightpath length. And that means c varied across those frames, even though inside them it never did.
I guess we'll have to agree to differ on that. The Lorentz invariance is still there. It's not a fundamental law, it's just the postulate that got SR going, and describes how you see the world through your reference frame. When you step back from the reference frames and see them all together, you get the big picture and you see why you always measure c to be 300,000km/s. Because light defines your time. Because spacetime is a space. Then you get to the real heart of relativity. It's like the Principle of Equivalence that gave Einstein the idea for GR. It doesn't hold, but it doesn't break GR. IMHO Einstein knew all this stuff but was somewhat marginalised later in life. Maybe if he'd been younger he might have made more of it. I can't be sure.Theories evolve, but that wasn't my point. If a theory breaks Lorentz invariance, it breaks relativity. It doesn´t make sense to talk about relativity evolving beyond Lorentz invariance. You either stick with or drop both.
Not quite. Opinions tend to vary, but a common theme is that we move forwards through time at one second per second and can increase this via relativistic effects, but we can't or don't as yet know how to move backwards through time.Do they claim they can move around freely through time?
Trust me on this. If you want an IT disaster on your hands just give your variables, subroutines, functions, programs, files and tables meaningless names.But labels need to be programmed into a computer at some point, and the initial assignments are arbitrary. The world won't end if you create a pseudo-C compiler that expects "zargloff" instead of "int"...
Actual as opposed to mathematical, I guess. In physics we're trying to understand how the world works, what's there. Look at the opening paragraphs of TIME EXPLAINED where I talk about our senses and how I'm trying to "look beyond" what we see or hear or smell. I'm trying to see what's there, and I can't see any time there. The block universe isn't there. Reference frames are abstract things, we might look through them, but they aren't actually there either. Nor I suspect are gravitons, or Higgs bosons. Current physics just doesn't explain what's there. Not enough. Otherwise we wouldn't be here talking about it."Actual" as opposed to what? And most importantly, what observable difference would it make? Otherwise, you're looking for absolute truth where it doesn't exist.
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I've seen you say this a number of times, and I'm curious as to why you think that. In SR, there is a difference between the way space and time are treated, in the metric. Yes, time is a dimension. But if we treated the time coordinate no differently than the spatial coordinates, then we would be using a metric of signature (++++) rather than (-+++), no?
You are exactly correct. This is, in essence, Farsight's confusion. His main thesis is that time isn't a dimension, as near as I can tell.
The idea of Lorentz invariance is a broad one, with many implications. You seem to know a bit about this stuff, so I will give a bit more technical answer.
GR is formulated on a Lorentzian manifold, with signature (-+++). This signature encodes the causal structure of space-time---that is, one can define an inner product on the space-time which tells you how to make a light-cone. Once you know this, then you are led to conclude that the quantities in your theory should be invariant under the isometries of Minkowski space---the Poincare group. This is because there is a perfectly good Minkowski space living at every point in your Lorentzian metric.
Now, the Lorentz group, telling you about rotations and boosts in your Minkowski space, is a subgroup of the Poincare group. The idea of Lorentz invariance is that a quantity must transform trivially under this subgroup.
One last thing. If we were to talk about a Euclidean manifold, we would have the metric signature (++++). Every point in the Euclidean manifold has a perfectly sensibly Euclidean space living there. In this case, there would be no boosts, just rotations. That is, in some sense, "boost" is a dynamical quantity, involving a velocity. If there is no time dimension, then there is no velocity.
Ok. Now the punchline. In Lorentzian space, if one were to preform a boost along one axis, and a boost along another axis, they would find that they end up with a rotation. This means that we have mixed a dynamical quantity (the boost) with a static quantity (a rotation).
So, for example, we sometimes speak of Lorentz four-vectors. We cannot have a "Lorentz three-vector" because the Lorentz transformations wouldn't know how to act on it. The Lorentz transformations are 4x4 matrices, and must act on 4 component vectors. In general, the Lorentz transformations will mix up the components of the four vectors---this means that the time component of a four vector gets mixed in with all the other components as well.
So really, the idea of Lorentz invariance is essential to physics as we know it. If we don't treat time like a dimension, then the Lorentz transformations don't work. If they don't work, then we lose the interpretation of space as a four dimensional Lorentzian manifold, and we destroy GR.
przyk said:No-one has the religious attachment to Lorentz invariance you think they do. Lorentz invariance is open to being disproven at any time, just like any other scientific theory.
You are certainly right about this---people are trying to disprove Lorentz Invariance inasmuch as they are trying to disprove ALL of science. This is a good thing, and is how science is done.
The people who are trying to disprove Lorentz Invariance also limit their violations to very high energies, and don't start threads called "Time Explained".
I'm not trying to disprove Lorentz Invariance, Ben. Regardless of how fast I travel, I'll still measure c to be 300,000km/s along with everything else that goes with it: I won't see a change in the laws of physics.
You raised it as an objection, pryzk described it as a law, and I said he should be asking why it's a law. A law is a blank wall, not an explanation.
OK, Ophiolite, let's hear your considered feedback on RELATIVITY+. This is the linking essay that gives a brief overview, so if you have some feedback on the detail of say TIME EXPLAINED please use that thread. And please can we try to stick to alpha rules here please.
You raised it as an objection, pryzk described it as a law, and I said he should be asking why it's a law. A law is a blank wall, not an explanation.
OK, Ophiolite, let's hear your considered feedback on RELATIVITY+. This is the linking essay that gives a brief overview, so if you have some feedback on the detail of say TIME EXPLAINED please use that thread. And please can we try to stick to alpha rules here please.
You raised it as an objection, pryzk described it as a law, and I said he should be asking why it's a law. A law is a blank wall, not an explanation.
Of course it's an explanation. An explanation in general is nothing other than a set of hypotheses (the explanans), and a deductively valid argument proceding from those hypotheses whose conclusion is that which is to be explained (the explanandum). In a scientific explanation, the explanans are informed by observing the way matter behaves. Lorentz invariance is just such an explanans.
What you seem to be saying is that rather than use Lorentz invariance as an explanans to explain why the speed of light is invariant, physicists should be looking for another set of explanans to which Lorentz invariance is the explanandum. Perhaps one day such a set of hypotheses will be discernable from the results of future experiments.
But it still wouldn't mean that Lorentz invariance is not a perfectly valid set of hypotheses for a scientific explanation.
You are exactly correct.
I'm glad to hear that you agree, because your remarks taken at face value looked false to me. It appeared as though your position was that time is not treated differently from space in any respect in modern physics. But of course, it is treated differently in certain respects in SR, and even moreso in QM.
This is, in essence, Farsight's confusion. His main thesis is that time isn't a dimension, as near as I can tell.
I think that your remarks may have confused him as well, because they confused me! For instance take his comment that space and time must be different in some way because you can jump back 1 meter, but not 1 second. Well, of course he's right about that! But when you give him the blanket comment that he "breaks Lorentz invariance", I'm sure he's thinking in his head, "If Lorentz invariance means that I can jump back in time 1 second, then Lorentz invariance is complete bunkum."
I think that your remarks may have confused him as well, because they confused me! For instance take his comment that space and time must be different in some way because you can jump back 1 meter, but not 1 second. Well, of course he's right about that! But when you give him the blanket comment that he "breaks Lorentz invariance", I'm sure he's thinking in his head, "If Lorentz invariance means that I can jump back in time 1 second, then Lorentz invariance is complete bunkum."
Apologies if I have not been altogether clear, but treating time differnetly, in the manner that Farsight advocates, explicitly and undeniably breaks Lorentz Invariance. Farsight doesn't understand Lorentz Invariance, and (s)he hasn't bothered trying. If one wants to try to understand something, with the expectation of changing/improving it, then they should make sure that they completely understand the thing first.
Farsight has said, more or less that (s)he doesn't believe that it is a dimension, as have others here. To them I say "Well, then, you break Lorentz Invariance." Instead of showing my that Lorentz violating effects fit the current experimental bounds, or explaining how the Lorentz violations occur naturally in a physical theory, or how one can find some way to maintain the appearance of Lorentz Invariance in some effective theory, they make evasive answers and dodge the questions.
The reason that you cannot "jump backwards in time" is because the Lorentzian manifold has a causal structure---at any point in space-time the vectors of zero norm (i.e. the world-lines of two orthogonal beams of light in the x-t plane) trace out a light cone. Jumping backwards would imply that you are jumping outside of your light cone, which is strictly forbidden.
But if you jump forward in one direction and then another, you will find that you have rotated very slightly in the process---you have mixed up spatial rotations with temporal transitions. (The rotations in Euclidean time correspond to Lorentzian boosts.) This means that you have mixed up your time and space directions, which lead to the conclusion that quantities labeled "Lorentz Invariant" must place time and space on equal footing. The Lorentz Transformations are 4x4 matrices and act of 4x4 vectors. This is the great insight of Einstein, and at the heart of Lorentz Invariance.