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grav
2010-Oct-31, 07:42 PM
I have a couple of questions involving LET and SR.

In LET, Lorentz ether theory, is the ether the mechanism that physically produces length contraction and time dilation, or is the ether just considered a medium for light which has no physical consequences of its own?

In GR, there is said to exist a fabric of space-time, and gravity is the warping of the fabric of space-time. Since GR is simply an extension of SR, the fabric of space-time should exist for both, then, both relating to the same universe and all, right? So could the fabric of space-time be considered the mechanism that physically produces length contraction and time dilation in SR?

macaw
2010-Oct-31, 08:25 PM
I have a couple of questions involving LET and SR.

In LET, Lorentz ether theory, is the ether the mechanism that physically produces length contraction and time dilation, or is the ether just considered a medium for light which has no physical consequences of its own?

In LET, length contraction and time dilation are postulated, so there is no mechanism that produces them. Certainly nothing to do with the aether.




In GR, there is said to exist a fabric of space-time, and gravity is the warping of the fabric of space-time. Since GR is simply an extension of SR, the fabric of space-time should exist for both, then, both relating to the same universe and all, right? So could the fabric of space-time be considered the mechanism that physically produces length contraction and time dilation in SR?

No. You just came up with another one of your ATMs. If you took the time to learn SR , you would have learned that time dilation and length contraction are consequences of the SR postulates.

grapes
2010-Nov-01, 01:14 AM
I gotta agree with macaw, here, grav. You're holding yourself back again. :)

If you measured the shadow of a stick at 9am, and then found that the shadow had shortened by 12 Noon, you wouldn't have to insist that there be a mechanism that produces physical contraction of the shadow, and certainly not of the stick, right?

grav
2010-Nov-01, 02:44 AM
If you measured the shadow of a stick at 9am, and then found that the shadow had shortened by 12 Noon, you wouldn't have to insist that there be a mechanism that produces physical contraction of the shadow, and certainly not of the stick, right?Well, put it this way. I wouldn't just conclude that observers around the Earth that measure different sizes simultaneously for the shadow of their sticks have a different reality than my own, although they are more or less synchronized within their time zones, but I would look for a common factor between them which would produce the effect.

grav
2010-Nov-01, 02:49 AM
Let me ask this. If not through the interaction of the fabric of space-time, why do length contraction and time dilation occur, and why isn't the universe Galilean?

loglo
2010-Nov-01, 03:21 AM
They don't occur, they are inferred.

Oh and I think you need to use calculus if you want to take the limit of c to be infinity.

grav
2010-Nov-01, 03:40 AM
They don't occur, they are inferred. Could you expand on this please? Do you mean they are inferred by measurement? If so, that's fine, but they are still real effects of space-time, not just concepts, correct?

macaw
2010-Nov-01, 04:09 AM
Let me ask this. If not through the interaction of the fabric of space-time, why do length contraction and time dilation occur

Because they are a direct consequence of the SR postulates. I have shown you how they are derived from them several times already.




, and why isn't the universe Galilean?

Becuase 100 years ago, a guy named Einstein, following in the footstep of Lorentz and Poicaire , figured out why. They all started by observing that Maxwell's equations aren't Galilei invariant.

grav
2010-Nov-01, 04:27 AM
Because they are a direct consequence of the SR postulates. I have shown you how they are derived from them several times already.

Becuase 100 years ago, a guy named Einstein, following in the footstep of Lorentz and Poicaire , figured out why. They all started by observing that Maxwell's equations aren't Galilei invariant.Yes, but the universe could have just as easily have been Galilean, more easily so since it is the simplest configuration, yet it isn't, why? Is this an attribute of space-time? The Minkowski metric for flat space-time becomes the Schwarzschild metric near a body of matter, so it changes. It warps, it expands, it is something with properties that can be determined by experiment and measured by its effects upon matter and energy. So it is tangible, real, more than just a mere concept, right? This is what I am asking.

grapes
2010-Nov-01, 04:27 AM
Could you expand on this please? Do you mean they are inferred by measurement? If so, that's fine, but they are still real effects of space-time, not just concepts, correct?What do you mean by concepts?

Is the 9am short shadow a concept, or an effect of space-time? Is it contracted, or is it just a matter of when we view it? Why is that any different than how fast we are going when we view it?

macaw
2010-Nov-01, 04:41 AM
Yes, but the universe could have just as easily have been Galilean,

Q1: Why would the universe be Galilean when the Maxwell equations contradict such a concept? You are 120 years late.





more easily so since it is the simplest configuration, yet it isn't, why?

Q2: Why is the Galilean "the simplest configuration"? Based on what we know now is for sure the ugliest.





Is this an attribute of space-time?

Q3: Which is an "attribute"?





The Minkowski metric for flat space-time becomes the Schwarzschild metric near a body of matter,

Q4: Is this your level of understanding of SR and GR? Because it isn't mainstream, it is ATM.







so it changes. It warps, it expands, it is something with properties that can be determined by experiment and measured by its effects upon matter and energy. So it is tangible, real, more than just a mere concept, right? This is what I am asking.

Your questions are coming through garbled. Try answering mine and maybe you'll learn something.

loglo
2010-Nov-01, 04:53 AM
Could you expand on this please? Do you mean they are inferred by measurement? If so, that's fine, but they are still real effects of space-time, not just concepts, correct?
I think it is more correct to say they are properties of a co-ordinization of space-time rather than of space-time itself. When you look at space-time locally they never appear.

grav
2010-Nov-01, 05:07 AM
What do you mean by concepts?

Is the 9am short shadow a concept, or an effect of space-time? Is it contracted, or is it just a matter of when we view it? Why is that any different than how fast we are going when we view it?I am not sure how the second part of what you are asking relates to what I am asking. I would consider any such effect as real, with a real mechanism or cause which produces it. That is what I am asking about with space-time also. The warping of space-time is said to produce gravitational fields, which involves the same processes as flat space-time but changes near a massive body. The universe is also said to be expanding space-time. That all sounds like space-time is real to me. As such, it should have real attributes which affect the behavior of matter and energy. Otherwise, it is just as useless as the old concept of an ether, just a vague concept that sounds good on paper but otherwise contributes nothing. That is what I want to know. Is space-time real and physically produces such effects or does it not really exist except as a vague concept which we manifest, with only the mathematics and consequences being real, but otherwise no actual mechanism except to say that it "just is"?

grav
2010-Nov-01, 05:16 AM
I think it is more correct to say they are properties of a co-ordinization of space-time rather than of space-time itself. When you look at space-time locally they never appear.So do you consider space-time to be a real and physical entity?

Ken G
2010-Nov-01, 05:43 AM
Actually, it was my impression that LET did indeed interpret the aether as a "ponderable medium" (in Einstein's words) that did indeed cause length contraction and time dilation, as physical effects on rulers and clocks moving through the aether. That's pretty much what Einstein did away with-- the idea that these effects required a cause. Instead, I'd say it makes much more sense to interpret length contraction and time dilation as consequences of desiring a concept of simultaneity, and the fact that length contraction and time dilation seem unphysical is actually a consequence of the unphysicality of simultaneity. The universe really doesn't support a meaningful concept of simultaneity (outside of the more general causality relationship), it's just pure coordinate choice, and shoehorning what is fundamentally coordinate independent into a fixed coordinate system is the "cause" of time dilation and length contraction.

That all contrasts sharply with LET, which asserts not only that simultaneity is a meaningful concept supported by nature (in the aether frame), it is supported in a way that is different from the Einstein simultaneity convention. No observations rule out LET, we just view it as clunky and rather missing the key points of relativity, which are philosophical in nature (i.e., not forced on us by observation, in the sense that LET is not ruled out, but chosen by us because of their aesthetic appeal).

As for why the universe is not Galilean, that appears to be because there is a "speed limit" for propagation of information. Galilean relativity requires that there be no limit in principle, which is actually kind of bizarre if you think about it. As strange as relativity seems, it actually makes more sense that there should be a speed limit. A consequence of this limit is that time is no longer the invariant separation between events-- space has a place at the table too. That space should have some input into invariant separation also makes some degree of sense-- so Galilean relativity never made as much sense as we might have first thought.

loglo
2010-Nov-01, 05:53 AM
I've been hanging out on this board too long. I am hesitant to call anything real but yes, I think space-time is a physical thing with physical properties. Some of those properties are local, some are global but some are artificially imposed by us. I would put length contraction and time dilation somewhere between the last two categories but not in the first. They are a property of an artificial construct which connects distant events which reflect a global property of space-time, namely that different paths through space-time give different constructions of space and time.

grav
2010-Nov-01, 06:30 AM
Actually, it was my impression that LET did indeed interpret the aether as a "ponderable medium" (in Einstein's words) that did indeed cause length contraction and time dilation, as physical effects on rulers and clocks moving through the aether. That's pretty much what Einstein did away with-- the idea that these effects required a cause. Instead, I'd say it makes much more sense to interpret length contraction and time dilation as consequences of desiring a concept of simultaneity, and the fact that length contraction and time dilation seem unphysical is actually a consequence of the unphysicality of simultaneity. The universe really doesn't support a meaningful concept of simultaneity (outside of the more general causality relationship), it's just pure coordinate choice, and shoehorning what is fundamentally coordinate independent into a fixed coordinate system is the "cause" of time dilation and length contraction.

That all contrasts sharply with LET, which asserts not only that simultaneity is a meaningful concept supported by nature (in the aether frame), it is supported in a way that is different from the Einstein simultaneity convention. No observations rule out LET, we just view it as clunky and rather missing the key points of relativity, which are philosophical in nature (i.e., not forced on us by observation, in the sense that LET is not ruled out, but chosen by us because of their aesthetic appeal).Thanks, Ken. That's what I thought LET was too, but I've seen replies elsewhere that indicated it either way, so I wasn't sure. You are right that the precise length contraction and time dilation we measure would be determined by the coordinatization of simultaneity we set for our clocks, although they would still exist independently.


As for why the universe is not Galilean, that appears to be because there is a "speed limit" for propagation of information. Galilean relativity requires that there be no limit in principle, which is actually kind of bizarre if you think about it. As strange as relativity seems, it actually makes more sense that there should be a speed limit. A consequence of this limit is that time is no longer the invariant separation between events-- space has a place at the table too. That space should have some input into invariant separation also makes some degree of sense-- so Galilean relativity never made as much sense as we might have first thought.That is an intesting way to think about it. There are still other simpler ways the universe could operate than relativistically, such as light being emitted at c relative to the source and otherwise travelling ballistically, pretty much still Galilean though. Although a Galilean universe would have no speed limit, information would still always travel at some finite speed. But the universe does not operate that way and I figure there has to be some reason, some real physical attributes which cause it to be the way it is.

Ken G
2010-Nov-01, 06:34 AM
I've been hanging out on this board too long. I am hesitant to call anything real but yes, I think space-time is a physical thing with physical properties. Some of those properties are local, some are global but some are artificially imposed by us. I would put length contraction and time dilation somewhere between the last two categories but not in the first. They are a property of an artificial construct which connects distant events which reflect a global property of space-time, namely that different paths through space-time give different constructions of space and time.
I agree with all that, except the idea that spacetime is a "physical thing." I suppose it depends on what one means by that, but I reserve that term for objects rather than the measurements we do using objects. So the clock is a physical thing, but the time it reads is not, that's a kind of conceptual interpretation when we call it "time." Connecting times between events that the clock reading the time was not present is even more nebulous, and is now quite far from a "physical thing." So I think of spacetime is a kind of conceptual conduit that connects events occuring to physical things, but it is not itself a physical thing. Physical things affect each other in ways that we try to understand by cooking up this idea that the events are "separated" by "spacetime intervals", and these are mathematical constructions that serve us well, like so many in physics.

Ken G
2010-Nov-01, 06:42 AM
Thanks, Ken. That's what I thought LET was too, but I've seen replies elsewhere that indicated it either way, so I wasn't sure. I think it's pretty hard to distinguish LET and SR if one does not take LET as asserting that the aether is physically causing length contraction and time dilation, so I don't see how any other conclusion could be reached, but I don't know.

There are still other simpler ways the universe could operate than relativistically, such as light being emitted at c relative to the source and otherwise travelling ballistically, pretty much still Galilean though. Although a Galilean universe would have no speed limit, information would still always travel at some finite speed.Yes, that example would say that any particular brand of information has a speed, but there would be no speed limit that was built right into reality. One could then imagine there is such a thing as "global absolute simultaneity", as for infinitely fast information usable in any frame, even if one does not have access to any such information vehicle. But if the universe itself makes that notion incoherent, because there is a limit even in principle, then you have to throw out Galilean relativity.

grav
2010-Nov-01, 07:13 AM
I've been hanging out on this board too long. I am hesitant to call anything real but yes, I think space-time is a physical thing with physical properties. Some of those properties are local, some are global but some are artificially imposed by us. I would put length contraction and time dilation somewhere between the last two categories but not in the first. They are a property of an artificial construct which connects distant events which reflect a global property of space-time, namely that different paths through space-time give different constructions of space and time.Thanks, loglo. I know it can sometimes be difficult to determine what is real and what are constructs with Relativity, so many might be hesitant to do so. I spend much of my time trying to determine just that, in order to find out whether space-time itself is real or not, with real physical properties and consequences. I guess I've always known, but it's good to see you agree so decidedly. I commend your outstandingness. :)

loglo
2010-Nov-01, 07:14 AM
I agree with all that, except the idea that spacetime is a "physical thing." I suppose it depends on what one means by that, but I reserve that term for objects rather than the measurements we do using objects. So the clock is a physical thing, but the time it reads is not, that's a kind of conceptual interpretation when we call it "time." Connecting times between events that the clock reading the time was not present is even more nebulous, and is now quite far from a "physical thing." So I think of spacetime is a kind of conceptual conduit that connects events occuring to physical things, but it is not itself a physical thing. Physical things affect each other in ways that we try to understand by cooking up this idea that the events are "separated" by "spacetime intervals", and these are mathematical constructions that serve us well, like so many in physics.

I understand, but of the alternatives (a non-physical thing, not a physical thing or not a non-physical thing) calling it a physical thing seems to be the least worst option.
I have the same issue with the concept of "event".

grav
2010-Nov-01, 07:45 AM
So I think of spacetime is a kind of conceptual conduit that connects events occuring to physical things, but it is not itself a physical thing. Physical things affect each other in ways that we try to understand by cooking up this idea that the events are "separated" by "spacetime intervals", and these are mathematical constructions that serve us well, like so many in physics.Right, like many others in physics, like the mathematics involved with particles and fields, perhaps? We have never directly seen either, so their consequences are only determined through mathematical constructs, but does that make them any less real? We predicted the existence of the neutrino with such a mathematical construct, for instance, but we have never actually seen a neutrino directly either. The only difference I can see offhand with that is that particles and fields are localized while space-time is everywhere, so there is no pointing here or there and saying, "that is space-time".

The universe is expanding and seemingly equivalently we say that space-time is expanding, so why would we say that the universe is real while space-time is not, or how should we make the distinction? What about a gravitational field, which we consider to be the warping of space-time? If the field is real, then why would we not consider space-time to be real as well? If we are to use those contexts to describe what is happening to space-time, then shouldn't it have physical attributes?

Ken G
2010-Nov-01, 02:12 PM
I understand, but of the alternatives (a non-physical thing, not a physical thing or not a non-physical thing) calling it a physical thing seems to be the least worst option.From the point of view of pure philosophy, one is certainly welcome to decide for one's self the meaning of "physical reality." But from a physics standpoint, there is actually an important difference between a "physically real" spacetime, and one that is just a mathematical concept for connecting causes and effects, which has to do with "Mach's principle." Newton and Liebnitz (who agreed on almost nothing except the final answer, an important lesson about how science works) had a famous debate on the subject of the physical reality of space and time (they of course both thought those two things were globally separable, instead of just locally as we now have it, so here we are just talking about space itself). Newton concluded space was physically real, because a bucket of water needed to know it was rotating with respect to that space in order to get a curved surface. Liebnitz argued on philosophical grounds that all motion had to be relative to some other body, but he could not answer why the water in the spinning bucket climbed up the edges. It took 2 centuries, and Mach, to come up with a possible answer-- the meaning of the inertial path is set by the rest of the mass in the universe.

Now, no one knows if Mach's principle is true (it inspired GR but even GR may not actually adhere to it very closely), but it is certainly philosophically attractive. But note that if the rest of the mass of the universe determines the inertial paths, it is a small step from there to just saying that all motion is a relationship between objects, and what we think of as spacetime is nothing but the connectedness that establishes that relationship. That the matter is connected would be viewed as real, but these invisible connections, manifested in our physical interpretation of spacetime, could certainly just be a mathematical contrivance for helping us to picture how that connection works. The fact that you still cannot actually measure a chunk of spacetime is potentially telling in this distinction (did you ever perceive space or time yourself, or did you perceive objects or events that you interpreted as separated from you by distance or time?). But yes, it's certainly philosophy, and open to interpretation!

Ken G
2010-Nov-01, 02:20 PM
Right, like many others in physics, like the mathematics involved with particles and fields, perhaps? Yes, the status of fields is quite unclear. Some view them as ephemeral conceptual connections between matter, others view them as the real things while matter is the concept, matter is just phenomena in how fields behave. Our problem is that we never perceive anything directly, but always through a layer of our own interpretation.


The only difference I can see offhand with that is that particles and fields are localized while space-time is everywhere, so there is no pointing here or there and saying, "that is space-time".Yes, one might indeed settle on that as one's distinction between what is real and what is a construct, if such a distinction can even be made.

What about a gravitational field, which we consider to be the warping of space-time? If the field is real, then why would we not consider space-time to be real as well? If we are to use those contexts to describe what is happening to space-time, then shouldn't it have physical attributes?Not necessarily. It is the difference between a map and a territory. We can say that gravitational interactions are real by virtue of their phenomena, and then how we choose to model them is the construct. The fact that everything is a kind of model, since model-making is what intelligence does, makes that tidy distinction somewhat in doubt.

grav
2010-Nov-01, 04:04 PM
Thank you, Ken. That is very enlightening, and I suppose that is now what this thread boils down to, what constitutes physical reality and what does not. I define real as that which has a physical effect upon other things, by producing some change or constraining things in some way, as do particles, fields, and space-time. Others might be relunctant to do so because models and mathematical constructs often change, so all we are left with are the direct observations in the end and the rest is left as a mental construct about what has taken place, and even our own perceptions sometimes come into question these days. What is certain, however, is that something has happened in order for any event to take place, something is there which causes some change to occur. I perceive that as a physically real mechanism acting upon another physically real entity. The precise details about the interaction don't matter. It may turn out that what we now perceive as space-time is actually related to Mach's principle and simply a gravitational field in itself, acting upon other gravitational fields of matter and energy, while the term space-time might then be reserved for something else. But it still doesn't matter, as long as the mechanism is still there, something which affects the behavior of something else, which is what I consider to be physically real, so only the terminology and precise modelling might change. But until then, vacuum energy, universal pressure, ether, space-time, until the details are ironed out and yet regardless of them, as long as it has some definite outcome on the behavior of matter and energy and obeys the mathematics for what we observe, then it is real, it exists, something is physically there, and by whatever name one chooses to call it, it is all the same to me.

Ken G
2010-Nov-02, 12:36 AM
Yes, I think that's all perfectly fair. And in regard to the LET, one must allow that all scientific knowledge is provisional-- there is no observation that is inconsistent with LET, and who knows, at the very next turn in this journey of discovery, LET could return with a vengeance. That kind of thing is not unusual in science, so it's best to never cover our tracks too completely.

macaw
2010-Nov-02, 01:40 AM
who knows, at the very next turn in this journey of discovery, LET could return with a vengeance. .

This is not going to happen. LET has been developed as a "theory of electron" by Lorentz. We know (courtesy of Dirac) that Lorentz' theory was not correct and it has been long superseeded by Dirac's. You can't turn the clock back, LET is dead and burried.

Ken G
2010-Nov-02, 02:59 AM
This is not going to happen. LET has been developed as a "theory of electron" by Lorentz. We know (courtesy of Dirac) that Lorentz' theory was not correct and it has been long superseeded by Dirac's. You can't turn the clock back, LET is dead and burried.Ah, you are referring to Dirac's relativistic version of quantum mechanics. I see that as a completely orthogonal issue-- Dirac just made QM relativistic, but since SR and LET make all the same relativistic predictions, I cannot at first glance see how Dirac could not have used LET as his springboard just as easily. What's more, I completely agree with this snippet from the Wiki on Lorentz aether theory:
" Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment. However, in LET the existence of an undetectable ether is assumed and the validity of the relativity principle seems to be only coincidental, which is one reason why SR is commonly preferred over LET."
That is more or less what I said above, so either both I and the Wiki have it wrong, or you are using a different interpretation of the meaning of the LET. To me, that moniker means little more than the idea that there is an aether that is a ponderable medium that alters the rate that clocks tick and the length of rulers moving through it. Please remember that Lorentz used this model to derive the transformations that bear his name, so I hardly think that any physics that is consistent with the Lorentz transformations is inconsistent with LET. Instead, the reason we have dropped LET is purely philosophical/pedagogical-- Einstein's interpretation makes more sense, and is a better launching pad for the philosophy that underpins GR. Since many don't think GR is the final theory of gravity, that's why I say we don't know that LET might return in some form or other. These are all just the reasons we should know our history and have a firm grasp of the philosophical issues, lest reports of the demise of LET be exaggerated! :)

(As one who rather likes Mach's thinking, I personally would not look to the return of the aether, but I don't control the future observations that might unify gravity and QM.)

macaw
2010-Nov-02, 03:34 AM
Ah, you are referring to Dirac's relativistic version of quantum mechanics. I see that as a completely orthogonal issue-- Dirac just made QM relativistic, but since SR and LET make all the same relativistic predictions,

I am referring more to the ad-hoc theory of electron that is LET, the theory that WAS discredited by Dirac's relativistic formulation. So, no LET will not come back . EVer.

Ken G
2010-Nov-02, 07:05 AM
Again, you are simply applying an unnecessary and restricted meaning to the LET. The one I gave is much more responsive to the actual issues here, given that LET was devised before quantum mechanics and might just as easily have been used to motivate Dirac's approach. Instead of just repeating your rather nonconstructive stance, you might want to actually comment on what I said above. For example, you may wish to comment on the Wiki quote I gave, and why you think the entire Wiki article on LET is completely wrong. And while you are at it, please comment on how any theory that respects Lorentz covariance can be inconsistent with LET, as Lorentz covariance (which most will think of as using the Lorentz transformations to translate between observers) is the primary output of LET. Einstein's formulation simply finds a philosophically/pedagogically preferred route to all the same invariant quantities.

macaw
2010-Nov-02, 03:51 PM
Again, you are simply applying an unnecessary and restricted meaning to the LET. The one I gave is much more responsive to the actual issues here, given that LET was devised before quantum mechanics and might just as easily have been used to motivate Dirac's approach. Instead of just repeating your rather nonconstructive stance, you might want to actually comment on what I said above. For example, you may wish to comment on the Wiki quote I gave, and why you think the entire Wiki article on LET is completely wrong. And while you are at it, please comment on how any theory that respects Lorentz covariance can be inconsistent with LET, as Lorentz covariance (which most will think of as using the Lorentz transformations to translate between observers) is the primary output of LET. Einstein's formulation simply finds a philosophically/pedagogically preferred route to all the same invariant quantities.

I was commenting on your lack of understanding why LET has been dead and buried for nearly a century. This is sufficient.

Ken G
2010-Nov-02, 04:32 PM
Your last three posts have said nothing but unsubstantiated assertions that do not agree with most people's idea of what an aether theory is. The Wiki article discusses what the LET is. You apparently have a different idea, but you won't share. So we can ignore you, and adopt the mainstream stance that a modern understanding of the LET, putting aside any historical elements that preceded quantum mechanics, is simply the pedagogical/philosophical stance that there is a real aether and it has real effects on rulers and clocks. It suffices to derive the Lorentz transformations (indeed, Poincare agreed with Lorentz' interpretation, which is why he named them after Lorentz-- thanks Tensor), so of course it is consistent with any physical theory that is also consistent with Lorentz transformations (in particular, special relativity). Presently, it is pedagogically clunky, and does not generalize well to general relativity because it does not respect the same core philosophy as GR. Since GR is viewed by many as not a final destination in the theories of gravity, this may actually some day be viewed as a feature of LET rather than a bug. You don't need to understand this, but I thought you might want to. Others do, so I needed to correct your first post.

macaw
2010-Nov-02, 05:21 PM
Your last three posts have said nothing but unsubstantiated assertions that do not agree with most people's idea of what an aether theory is. .

Why don't you read "Electromagnetic phaenomena in a system moving with any velocity less than that of light" by Lorentz and you'll find out. Pay special attention to the stuff dealing with the theory of the electron.

grav
2010-Nov-02, 06:29 PM
... I completely agree with this snippet from the Wiki on Lorentz aether theory:
" Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment. However, in LET the existence of an undetectable ether is assumed and the validity of the relativity principle seems to be only coincidental, which is one reason why SR is commonly preferred over LET."Yes, that second statement does seem to be the one main drawback when considering the mechanism of an aether. While Lorentz only assumed that the aether contracted bodies by a factor on the magnitude of 1 - n (v/c)^2 to the second order, where n is an unknown variable, whereby the aether could still potentially be detected, Einstein assumed that a precisely null result will always be found by experiment so derived sqrt[1 - (v/c)^2]. In terms of what that would mean for the aether, I posted this elsewhere...


After Einstein's SR is accepted, even if only in terms of the mathematics involved, we can then turn back and have a look at what that would mean when applied in terms of an aether. First of all, it would mean that there is no absolute frame for an aether. All observers' points of view in the aether would be exactly the same as any other. Every frame would measure the same motions of each other, the same time dilation, length contraction, simultaneity differences when applying the Einstein simultaneity convention, and the same isotropic speed of light. There would no longer be an absolute frame for the aether, but any preferred frame would be the same as any other preferred frame. That means that the aether would appear isotropically to every inertial frame. That is, if it were detectable. The null result of any experiment that can be performed also means that any absolute motion relative to the aether cannot be determined, since any preferred inertial frame will be at rest to the aether and observe the same time dilation and length contraction of other frames as other frames observe of the preferred frame. Another problem is that this precise time dilation and length contraction imposed by an aether would seem to be only coincidental. There is no specific mechanical reason that the aether should constrain itself to these exact values of sqrt[1 - (v/c)^2] in order to render it undetectable. If it does so, then it would seem that the aether is bound to impose similar conditions upon itself as it does objects that move through it, such that it also abides by the mathematics of SR, whereby the mathematics of SR then supercede LET. So although the idea of an aether does have the advantage of allowing a mechanical reason for time dilation and length contraction to take place rather than just strange distortions of reality according to each frame, the mathematics of SR still becomes predominant and so is more important, at least unless or until someone can show why the aether should maintain such precise conditions as would be necessary.
Of course, I will get to work on that right away. :)

macaw
2010-Nov-02, 06:36 PM
While Lorentz only assumed that the aether contracted bodies by a factor on the magnitude of 1 - n (v/c)^2 to the second order,

Q5: Where did Lorentz write such a thing? Can you give a citation or you made this up?





where n is an unknown variable, whereby the aether could still potentially be detected, Einstein assumed that a precisely null result will always be found by experiment so derived sqrt[1 - (v/c)^2]. In terms of what that would mean for the aether, I posted this elsewhere...

Yes, you are spamming Physforums with the same ATM ideas. They keep moving your threads away from the main board. What does this tell you?

grav
2010-Nov-02, 07:07 PM
Where did Lorentz write such a thing? Can you give a citation or you made this up?I have seen it stated of his earlier works, possibly "Theory of electrons", although I haven't read it myself. In his 1904 paper (http://en.wikisource.org/wiki/Electromagnetic_phenomena), he does apply k = 1 / sqrt(1 - (w/c)^2) in section 4, although rather matter of factly, it seems to me, with no reasons given and not so much derived from any postulates but as though he just happened upon it as a possible solution and decided to try it out, just the opposite of what Einstein does.

macaw
2010-Nov-02, 07:12 PM
I have seen it stated of his earlier works,

Q6: Where?



possibly "Theory of electrons", although I haven't read it myself.

Q7: So, you decided to make it up?




In his 1904 paper (http://en.wikisource.org/wiki/Electromagnetic_phenomena), he does apply k = 1 / sqrt(1 - (w/c)^2) in section 4, although rather matter of factly, it seems to me, not so much derived but as though he just happened upon the solution and decided to try it out, just the opposite of what Einstein does.

This is what makes Lorentz' theory ad-hoc.

grav
2010-Nov-02, 07:39 PM
This is what makes Lorentz' theory ad-hoc.It would appear so, his paper at any rate.

Ken G
2010-Nov-02, 08:13 PM
Why don't you read "Electromagnetic phaenomena in a system moving with any velocity less than that of light" by Lorentz and you'll find out. Pay special attention to the stuff dealing with the theory of the electron.
I'm afraid that is equally non-useful. As I said above, neither I, nor the OP question, nor the Wiki entry on LET, are the least bit interested in historical anecdotes about efforts to presage quantum mechanics that could have used LET or SR and just not been on the right track. All three in that list are interested in the potential role of an aether in having physical effects on measuring apparatuses that provide a different path to the same Lorentz transformations. And as I said, any theory that is Lorentz invariant, including Dirac's quantum mechanics, are consistent with LET framed in those terms, which suggests that Dirac could have come up with his theory by starting from Lorentz's just as easily as starting from Einstein's. But I believe I said all that, at least that's what my words were supposed to mean. None of your remarks speak to any of those issues, nor do they provide any indication that they even understand them.

macaw
2010-Nov-02, 11:03 PM
I'm afraid that is equally non-useful.

Of course it is, it points out your fringe beliefs in a comeback of LET are pre-empted by the fact that LET, as constructed by Lorentz has been pushed aside by what we consider today mainstream theories of the elementary particles. If you think that LET might make a comeback, then you are part of a fringe minority. There is nothing I can do about that, mainstream physics has moved on since circa 1930.

Ken G
2010-Nov-03, 01:09 AM
Of course it is, it points out your fringe beliefs in a comeback of LET are pre-empted by the fact that LET, as constructed by Lorentz has been pushed aside by what we consider today mainstream theories of the elementary particles.Hmm, let's see, my "fringe beliefs" are supported by two Wiki quotes (that you have not commented on, of course), while all you keep doing is repeating your same narrow interpretation of the meaning of aether theory. I already said what I'm calling that, what Wiki is calling it, and what the OP was asking about. You've said nothing, other than that Lorentz, and a thousand other physicists of his day, failed to originate quantum mechanics. No kidding.
If you think that LET might make a comeback, then you are part of a fringe minority.My views on the likelihood of such a comback were made quite clear in every post I made, which I assume you can read. Perhaps you should review them. The fact is, no one in physics should give a whit for what anyone thinks is the "likelihood" of any future theory. What was the likelihood of quantum mechanics? What was the likelihood that Galilean relativity would be wrong? This is physics, not horse racing.