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Author Topic: How does a 'field' become observer dependent?  (Read 201069 times)

Offline yor_on

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How does a 'field' become observer dependent?
« on: 02/08/2013 13:39:08 »
a field, described as we usually do is the same, no matter observers, as long as they are at rest with it. But, assuming that observer dependencies as Lorentz contractions (as well as time dilations) are real measurable properties (which they are as far as I know). How does a 'global field', as a 'universally common  field' as the Higgs field is supposed to be, if I got it right? Allow for observer dependencies? If we only can agree on it, being at rest with each other relative it.

Two observers can't even define it to a same time and place otherwise?
So, anyone has an idea how it may do it?

Einstein's Pathway to Special Relativity.

Observer dependent entanglement.  (Interesting but 'heavy construction' mathematically)

And I don't think Lorentz transformations explains it :)
« Last Edit: 02/08/2013 13:49:07 by yor_on »


 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #1 on: 02/08/2013 14:04:32 »
I'll start it. If you want to consider it a 'universally covering field, with ripples' you then seem to have to assume that observers will define it, distorting this common field somehow through their observations, through motions, accelerations, energy, mass energy etc. But it can't be a illusion. What one observer measure as real must be real, no matter if another observer define it differently. Either that, or you disallow local experiments for a theoretical solution, which then becomes a 'space' we can't measure on.

but we can measure Lorentz contractions, and time dilations, and they will give different observers different answers. And 'time' is not a spatial dimension, you can't treat it as the other three we define.
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #2 on: 04/08/2013 15:26:20 »
Ok, let's take a EM field. Is it finite, or infinite? If it is of a infinite reach, does it propagate at 'c'? I'm assuming that this goes for the electric as well as for the magnetic component. And, although it is frame dependent we can assume it a entity for this. So now we have  EM fields, constantly produced in our universe, and canceled, as by flipping a switch. If they propagate at 'c', then it demands there being something for them to propagate in, right? That would then be? A vacuum?

If I now assume a 'flat space', is that a space without gravity, or a space, always defined by gravity? I think it is a space defined by gravity. But we meet the same confusing definition for gravity. It 'propagates' at 'c'.

So what is a vacuum? And how does it get its existence, if not by gravity? If we use an idea of a Big Bangs origin being of no certain point (unable to back track to some specific position in our 'commonly same' universe), but of all points, then what about its metric? Which should be gravity? Also of all points? And EM? Also of all points?

(Isn't that a very local definition?)

What if I said that what gives this vacuum a reality, and a measurable existence, should be gravity? What would then a EM field do? It too has to follow geodesics, doesn't it? Meaning it shouldn't be able to exist outside gravity's definition of a space? If I assume this to be wrong then? Still defining gravity as what defines a measurable vacuum. Then a EM field is able to propagate between 'universes'? Assuming there is something allowing for such a thing to exist.

Anyway, when we speak of 'fields' it's the EM field I first think of. So, what is a field?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #3 on: 04/08/2013 17:07:33 »
Let's make it even simpler. If I turn on the light, is that a EM field? Does it propagate at 'c'? When I switch it of, is the EM field still propagating from its origin, towards infinity? And if I let it be on then? Is a EM field constantly leaving that lightbulb, or is it a 'static' field, staying put? If it is, what part of it is propagating?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #4 on: 07/08/2013 16:20:47 »
It isn't that a field (doesn't) makes a lot of sense. It solve problems with both QM and Relativity, as I hope then :) The question to me is how to understand it? It has to be observer dependent, at least from a macroscopic definition. That actually means that you need both a locally true, as well as a globally true description of this 'field', and it's not enough to define common properties, at least not as I would like it. I prefer direct experiments, but the field description is rather far from experiments, as it seems to me?

No matter if one would prefer to define a field from locality, then introducing 'global parameters' joining the local parameters into a seamless universe. Or, if you like it as it acts locally, one 'seamless universe', then defining observer dependencies as something 'extra', or?
=
My writing nowadays jumps over, sometimes rather important, words it seems :)

 The static electromagnetic field.
« Last Edit: 07/08/2013 20:10:53 by yor_on »
 

Offline lightarrow

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Re: How does a 'field' become observer dependent?
« Reply #5 on: 07/08/2013 22:32:09 »
Let's make it even simpler. If I turn on the light, is that a EM field? Does it propagate at 'c'? When I switch it of, is the EM field still propagating from its origin, towards infinity? And if I let it be on then? Is a EM field constantly leaving that lightbulb, or is it a 'static' field, staying put? If it is, what part of it is propagating?
I try to answer this post only otherwise I get a headache. If we could convert your thoughts into an exploitable form of energy, the energetic problems of Sweden would be solved ;)

<<If I turn on the light, is that a EM field? Does it propagate at 'c'? When I switch it off, is the EM field still propagating from its origin, towards infinity?>>

It keeps propagating away from its source, the lamp.

<<And if I let it be on then? Is a EM field constantly leaving that lightbulb, or is it a 'static' field, staying put?>>

In that case of a lamp switched on and then off in a free space, the em field generated varies with time in every fixed point of space you choose, so it can't be static.
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #6 on: 09/08/2013 17:46:23 »
What would a observer dependence mean for a observer in this field? Maybe the point I'm trying for is that every observer should have a uniquely true definition of what they measure. Does it matter that they can't define a (common) 'patch of space' and 'time' for this? As long as it is unique, belonging to the observer?
« Last Edit: 09/08/2013 17:48:04 by yor_on »
 

Offline lightarrow

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Re: How does a 'field' become observer dependent?
« Reply #7 on: 09/08/2013 20:31:25 »
I don't know if I interpreted your answer correctly, but, for example, a vector in 3D space doesn't change if we choose another cartesian frame of reference, for example translated and rotated with respect to the first. Yet the components of the vector changes!
With fields is something similar: they changes but there is something "bigger" made of them wich doesn't.
 

Offline Bill S

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Re: How does a 'field' become observer dependent?
« Reply #8 on: 09/08/2013 20:58:44 »
Quote from:  yor_on
…. observers will define it, distorting this common field somehow through their observations

My understanding is that the EM field is present everywhere, but it can be “switched on, (non-zero) or off (zero)”.  If you switch on a lamp it causes excitations in the EM field which propagate at “c”, and may be considered as ripples in the EM field, or as particles (photons).  At this point the field can be observed through observation of the effect these excitations have on objects that react with them. 

This seems to leave open the question: does observation distort a field, or does the field have to be distorted in some way before it can be observed?



 

Offline JP

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Re: How does a 'field' become observer dependent?
« Reply #9 on: 09/08/2013 23:04:39 »
This seems to leave open the question: does observation distort a field, or does the field have to be distorted in some way before it can be observed?

Both.  Observation absorbs energy from the field.  To do so, the field must be carrying energy to begin with.  But in doing so, it also takes energy out of the field, which necessarily disturbs it.  We see this everyday.  When you use a camera to take a picture, the light enters the front of the camera and is absorbed.  The camera has changed the field by blocking/absorbing some of the light--if there were no camera present, the field would be different (namely, there wouldn't be a shadow of the camera).
 

Offline Pmb

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Re: How does a 'field' become observer dependent?
« Reply #10 on: 10/08/2013 04:08:51 »
I don't know if I interpreted your answer correctly, but, for example, a vector in 3D space doesn't change if we choose another cartesian frame of reference, for example translated and rotated with respect to the first. Yet the components of the vector changes!
With fields is something similar: they changes but there is something "bigger" made of them wich doesn't.
It's the same with fields. Especially the EM field and the gravitational field. For example; the Faraday tensor (aka EM field tensor) is defined here
http://home.comcast.net/~peter.m.brown/em/faraday_tensor.htm
As measure in an inertial frame the E field forms the spatial portion while the rate of change of energy with respect to proper time forms the time component.

See also http://www.phy.duke.edu/~rgb/Class/phy319/phy319/node135.html

To find the electric field measured by a particular observer one forms the observer's 4-velocity and contracts it with the Faraday tensor. One then obtains the electric field 4-vector. A similar process is done using the magnetic field (See Wald's text page 64). While the electric and manetic field can be expressed as Cartesian 3-vectors they can also be expressed as 4-vectors in this way. A similar thing happens with relativistic mass as well as energy.

As a good example consider the EM field of an electromagnetic wave. Obviously there is no preferred frame of reference for such a field and to measure the field means to measure its components in a particualar frame of reference. Once that's done one has the complete description of the "invariant" geometric object "Faraday tensor."
« Last Edit: 10/08/2013 04:35:08 by Pmb »
 

Offline lightarrow

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Re: How does a 'field' become observer dependent?
« Reply #11 on: 10/08/2013 12:42:00 »
Thanks, I didn't remember of the "Faraday tensor", I only remembered there was something invariant ;)
The difficulty for me to remember this concepts is in translating mathematically in which sense can be invariant an object whose components are not.
 

Offline Bill S

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Re: How does a 'field' become observer dependent?
« Reply #12 on: 10/08/2013 19:00:46 »
Thanks JP.  Is my understanding of the EM field anywhere near the mark?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #13 on: 18/08/2013 16:39:26 »
The problem is that a (assumed universal) field becomes something different to me, considering it from how there is a discrepancy in both distance and time relative once local observation, to then describing it 'universally', if this now makes sense? And I mix them up a little here too. Vectors described in a EM field isn't about that really, and I can see how it confuse you Lightarrow. My sole excuse is that when I think of a field it is EM that comes to mind :) And I need something to go out from.

Does a Higg field have a inertia? The field may explain some constituent of what gives a mass, but I don't see it explain a atom of rest mass? Assuming that 'motion' creates a mass (quarks gluons etc) internally doesn't really makes it easier to see to me either?

Assuming 'motion' to create it, or accelerations macroscopically? I don't know, what is that 'motion'? But that's not the question really. For now I just want to understand how observer dependencies is explained away in a 'universal Higgs field'? Then again, we have those with a EM field too?
« Last Edit: 18/08/2013 16:46:05 by yor_on »
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #14 on: 18/08/2013 17:00:44 »
In a isolated atom, are the 'forces' keeping it in a static, or a dynamic, equilibrium? Is there anything 'moving' at all? Or is the different probe answers we get a result of a probability, having very little to do with any definition of a macroscopic motion?

And that is a question of rest mass, in a 'inertial' object I guess :) But it too must relate to a 'field concept' in my mind.

 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #15 on: 08/09/2013 12:09:06 »
Think of gravity.
Assume that it represent a field.

It follows that either you need to assume a field, no matter what, to be observer dependent, or to represent some other definition, outside observer dependencies. So, which one is it?

Einstein thought of both photons and gravity as fields, if I get him right.

" I must have expressed myself unclearly in regard to the light quanta. That is to say, I am not at all of the opinion that one should think of light as being composed of mutually independent quanta localized in relatively small spaces. This would be the most convenient explanation of the Wien end of the radiation formula. But already the division of a light ray at the surface of refractive media absolutely prohibits this view. A light ray divides, but a light quantum indeed cannot divide without change of frequency.

As I already said, in my opinion one should not think about constructing light out of discrete, mutually independent points. I imagine the situation somewhat as follows: . . . I conceive of the light quantum as a point that is surrounded by a greatly extended vector field, that somehow diminishes with distance. Whether or not when several light quanta are present with mutually overlapping fields one must imagine a simple superposition of the vector fields, that I cannot say. In any case, for the determination of events, one must have equations of motion for the singular points in addition to the differential equations for the vector field.
(Einstein to Lorentz, 23 May 1909, Einstein 1993, Doc. 163) "

To make me understand a field I need to understand observer dependencies. And it's not enough transforming one point in a space (and time), relative a observer, to another point, as using a Lorentz transformation.

You can either assume that, if a degree of freedom is a 'dimension', then there should be some more degree, as I suspect Einstein to have assumed, in where those observer dependencies can be translated away, presenting us with 'one common universe'. That way of looking on it assume that what we 'instinctively' presume, also must be what it is. It's about from where you look.

Or as I think, that what we have, always is a local definition, joined through constants. Each way of looking at it I, and you, meet the same difficulty though, explaining what a observer dependency should mean for this universe.

A field, and constants?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #16 on: 08/09/2013 12:24:15 »
Think of a coordinate system, in where you have a ball situated. That ball exist, it has a individual existence, but your coordinate system is a artifact, dependent on mass energy and 'motion'. The 'motion' you measure for yourself is relative a constant.
=

Is lights speed in a vacuum observer independent?
If it is, what then is observer dependent, as you measure other frames of reference.

Should all constants be observer independent?
They should, shouldn't they?

So, if you now presume a constant able to have changed?
Would it be a constant, from such a definition?
=

It's all about from where you stand looking at it as I think, can't stress that one enough. But if you as me think of it all, as being able to relate to some least principles, creating all we see. Then there should be something a universe rests on, agreeable for, and hopefully to, us all.
« Last Edit: 08/09/2013 12:35:33 by yor_on »
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #17 on: 08/09/2013 12:46:04 »
If a constant is allowed to change, although still being defined as a constant, then that should be from an idea of this 'field/universe' etc representing something alike that commonly same space Einstein thought of, having a existence outside observer dependencies. Myself I would like constants that does not change at all. Because assuming a field, you define it as a reality relative something outside this field. You must do so to allow constants to change. As long as you do so a universe are bounded, and even if infinite from a definition in where a straight line never is found to end (your 'forward motion'), it still is finite from my view.

Either that or we define motion and distances as artifacts. In that case it becomes meaningless defining a 'size'.
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #18 on: 08/09/2013 14:35:35 »
Constants that are unchanging should be like principles, to my mind, ideal representations defining something behind this universal veil. Defining them as changing, although not observer dependent, also relating them to a 'field' changing, assuming that concept, then that field needs a boundary from where it can be seen to change. I'm not discussing if there are one, or several, 'fields', as I don't see how that would matter for this. If you want fields, interacting with fields, you also need to define their boundaries, and as that also must make them observer dependent, you can't. You should only be able to translate observer dependencies for them.

And the point with a constant, is that it should not be observer dependent, it does not change in interactions. It's the same from any observer. And preferably stays the same under a universes existence.

It doesn't matter if you define constants as local representations, or as commonly shared although 'universal constants', if distance and motion would be artifacts, because then you can refer to a universe as a 'point like' existence. The discrepancy that allows life and a universe though is just those weird frames of reference, interacting, including finding different 'fields'.
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #19 on: 08/09/2013 16:16:42 »
I haven't mentioned 'time' here. But as I see it we build physics on a existent 'objective' time. The time for a repeatable experiment is defined as being a 'objective reality', presenting us proofs of physical laws existing, objectively. Defining it from relativity that only can be true in a local definition. My 'time' should extremely seldom be the exact same as yours, assuming mass (gravitational time dilations) and motion. Being 'at rest', as sharing a exact same definition of a arrow, is a approximate definition practically, as far as I can see, only able to define if using 'identical test particles', in a 'flat space', being at absolute rest with each other. But ideally we can define being 'at rest', and so it's not a meaningless concept.

So, what makes those test particles share a same arrow? And do we need them to define a arrow?
« Last Edit: 08/09/2013 16:19:35 by yor_on »
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #20 on: 08/09/2013 16:22:46 »
Split all particles, define it at some smallest common nominator as a 'grain of time'. You consist of those particles, I do too. Would that define a 'commonly existing objective' arrow?

If it does, what then define the time dilations we measure?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #21 on: 21/09/2013 20:13:51 »
On the other tentacle, there is proofs for a objective 'time', as a arrow, existing, same for us all. We just need to join a same frame of reference, in all aspects naturally, down to be of the exact same distribution of mass. And then there is the fact that, wherever you compare, it won't matter for your own measurement of your life span. It will be the same relative your local clock. You do not gain any extra years by hiding at some neutronstar, not locally measured. And you can't avoid aging, it's a fact of life.

So a arrow exist, and possibly able to be defined as being of a locally same duration, relative your also local lifespan. That becomes a local proof, not unlike the way we define a repeatable experiment to my eyes. And as physics builds on those?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #22 on: 03/10/2013 08:54:08 »
What if I would assume 'time' to be a homogeneous 'field? How would we then define the way energy, mass and motion distort our measurements of other frames. How would you go about measuring your own frame of reference in such an idea. Microscopically we must meet time dilations, and if a Lorentz contraction is a complementary part of a time dilation?

Is there any way to measure on 'one frame of reference', what you measure with, and in, being part of it? We get our measurements comparing between frames of reference, don't we?

But if I now assume that there is a homogeneous 'field' defining 'grains of time'? Some smallest common nominator for a arrow?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #23 on: 03/10/2013 08:59:05 »
To make that work I think we need more dimensions. Because somehow mass as well as motion, and 'energy', whatever that is, should twist those to give us what we call mass? Or can you do the same with fewer dimensions than what we measure?
 

Offline yor_on

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Re: How does a 'field' become observer dependent?
« Reply #24 on: 03/10/2013 09:08:20 »
Then we might have a 'field', and dimensions as in unmeasurable 'degrees of freedom', twisting it all into what we define as our four dimensional reality, the common universe. With our measurements expressing just a part of it. It's a weird idea, but it's also one making sense to me when it comes to thinking of a field. Because you need to find the homogeneity of that field, in its smallest expression, to have something to stand on as I think. Alternatively you might be able to relate it to a 'projection' of a universe, coming from some simple principle of how a few 'dimensions' create something more, for us existing in it. Or you want to stay inside the dimensions we can measure on, in which case this becomes trickier to define.
 

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Re: How does a 'field' become observer dependent?
« Reply #24 on: 03/10/2013 09:08:20 »

 

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