Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: yor_on on 10/09/2014 20:56:19
-
have a read.
http://www.news.cornell.edu/stories/2014/09/defying-physics-engineers-prove-magnetic-field-light
Then tell me what they mean :)
-
I read it, and was left scratching my head. Changing phase isn't anything special, but I didn't see how that's a magnetic field for light. Light is an electromagnetic wave, we make electrons (and positrons) out of light in pair production, and a magnetic field is a "curl" or "rotor" field. Have a look at some images (https://www.google.co.uk/search?q=electron+magnetic+field&biw=1366&bih=599&source=lnms&tbm=isch&sa=X&ei=t48RVMTsGfPo7AbYxoDICg&ved=0CAYQ_AUoAQ) showing electron motion in a magnetic field. The article doesn't seem to be much like that, or anything like Faraday rotation (http://en.wikipedia.org/wiki/Faraday_rotator) where light is rotated in a magnetic field. I am however reminded of Taming Light at the Nanoscale (http://mag.digitalpc.co.uk/Olive/ODE/physicsworld/LandingPage/LandingPage.aspx?href=UEhZU1dvZGUvMjAxMC8wOS8wMQ..&pageno=MzM.&entity=QXIwMzMwMA..&view=ZW50aXR5):
"Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras. These may all do different things but they have one thing in common: in the electronic circuits that drive these devices, charged particles flow through components and impart power via what is known as the conduction current. But is the motion of charged particles the only current we have available? Those with a good memory for Maxwell’s equations of electromagnetism will remember that in addition to the familiar electric field, E, there is also a displacement field, D..."
Light is essentially alternating displacement current (http://en.wikipedia.org/wiki/Displacement_current#History_and_interpretation), and you can contrive circuitry for displacement current in a similar fashion to the way you can devise circuitry for conduction current. The article you referred to is obviously something on those lines, but I didn't "get it". Maybe the work is reported elsewhere in a different fashion that makes things clearer?
-
Yep, confused me too. The heading of the article is "Defying physics, engineers prove a magnetic field for light." but that isn't what the article seems to be discussing? "Until now. Lipson, a leader in the emerging field of silicon photonics – sending light through waveguides instead of currents through wires – and colleagues have shown that an equivalent field for light does exist."
equivalent? as if optics bending light?
"When a light wave travels under normal conditions, its phase is proportional to how far it traveled, but it is unaffected by what path it has taken. Just like a magnetic field causes a current to switch direction, the researchers showed that by modulating the light with their device, ...... they could make the phase of the light change not only as a function of distance traveled, but also by the shape of its path....."
would that be what they mean, that you change phase by the path taken? And then imagining this equivalent to?? A electrons path inside a magnetic field?
I'm still confused :)
-
Me too. There's things out there like light bends itself round corners (http://physicsworld.com/cws/article/news/2012/nov/30/light-bends-itself-round-corners) and tying light in knots (http://physicsworld.com/cws/article/news/2013/oct/16/physicists-tie-light-into-knots) and how to turn light into matter (http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_16-5-2014-15-32-44). But this doesn't seem to be much like that. We need to find another report about this, or the original paper.
-
Here's the paper on arXiv: http://arxiv.org/abs/1309.5269
"Photons are neutral particles that do not interact directly with a magnetic field. However, recent theoretical work has shown that an effective magnetic field for photons can exist if the phase of light would change with its propagating direction. This direction-dependent phase indicates the presence of an effective magnetic field as shown for electrons experimentally in the Aharonov-Bohm experiment. Here we replicate this experiment using photons. In order to create this effective magnetic field, we construct an on-chip silicon-based Ramsey-type interferometer. This interferometer has been traditionally used to probe the phase of atomic states, and here we apply it to probe the phase of photonic states. We experimentally observe a phase change, i.e. an effective magnetic field flux from 0 to 2pi. In an Aharonov-Bohm configuration for electrons, considering the device geometry, this flux corresponds to an effective magnetic field of 0.2 Gauss."
I still don't get it. The Aharonov-Bohm experiment demonstrates four-potential. There's no electric or magnetic field outside the solenoid, but the electron wave is shifted. It was first predicted by Ehrenberg and Siday in their semi-classical paper. Here's a picture from it. If you've got a wall-mounted hosepipe, watch it rotate a little when you turn the water on. It's the electromagnetic equivalent of that. Hmmn. A magnetic field is a "rotor" field, maybe that's the connection.
-
Not to mention that "direction-dependent phase" is well known in optics (anisotropy of the index of refraction). The press release is poorly written and misleading.
What they appear to be doing is using the fact that matter can interact with a magnetic field, and that light waves passing through that matter will depend on the matter's properties. Therefore, by changing the magnetic field, you can indirectly influence light (by acting on whatever matter its passing through). It seems a bit overblown to say this is demonstration of the Aharanov-Bohm effect for light, but its cool that the same mathematics describes the light waves in this experiment and it may be useful in designing photonic circuits.
The original paper that did this experiment, which is much clearer on what's going on, is here:
http://www.nature.com/ncomms/2014/140130/ncomms4225/pdf/ncomms4225.pdf
-
So what exactly is the magnetic flux from 0 to 2pi referring to?
-
So what exactly is the magnetic flux from 0 to 2pi referring to?
When you are measuring phase and/or angles, you can use degrees, where there is 360 degrees in a circle. This was invented by the Babylonians (if not earlier), and is taught to students at school.
Mathematicians, physicists and engineers often prefer to measure phase and/or angles in units called "radians", which is shown by the abbreviation "RAD" on a scientific calculator. In this scheme, there are 2pi radians in a circle. Radians have some useful mathematical properties when you combine them with imaginary numbers - for example there is a close relationship between the ex function and sin(x)+cos(x).
This results in one of the neatest results in mathematics eπi+1=0, which combines 5 of the fundamental constants of mathematics. (I think it was discovered by Euler?)
-
Ok, downloading pdf:s here :) Hopefully they will make sense to me.
==
Found a really interesting effect from the Aharanov-Bohm effect for light, also explaining it somewhat. http://phys.org/news/2014-05-breakthrough-paper-aharonov-bohm-effect-published.html Further down there's a link to "Aharonov–Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap", which may fit your ideas of how the news release interpreted it John?
Or maybe not?
It's the same, just got stuck on this Quantum rotor, rereading you :)
-
Not to mention that "direction-dependent phase" is well known in optics (anisotropy of the index of refraction). The press release is poorly written and misleading.
What they appear to be doing is using the fact that matter can interact with a magnetic field, and that light waves passing through that matter will depend on the matter's properties. Therefore, by changing the magnetic field, you can indirectly influence light (by acting on whatever matter its passing through). It seems a bit overblown to say this is demonstration of the Aharanov-Bohm effect for light, but its cool that the same mathematics describes the light waves in this experiment and it may be useful in designing photonic circuits.
The original paper that did this experiment, which is much clearer on what's going on, is here:
http://www.nature.com/ncomms/2014/140130/ncomms4225/pdf/ncomms4225.pdf
Thanks for that, JP.
You know, I think this might be more important than the authors realise, in that in gamma-gamma pair production there's photon-photon interaction. Not a photon-phonon, interaction, a photon-photon interaction. One for another day though.
-
Wouldn't it be better to call it a localized field, set under certain conditions, that will produce photons acting a specific way? Gives me a headache thinking of it as a, constantly existing, photon propagating, interacting with a phonon.
=
Maybe one could call it a 'constantly existing photon potential' propagating inside that field instead :)
Luv that
-
No, field is the wrong word. This is "an Aharonov-Bohm effect for light", and the Aharonov-Bohm effect is where there's no detectable E or B field, but there is detectable effect. Have a look at the Aharonov-Bohm effect (http://en.wikipedia.org/wiki/Aharonov%E2%80%93Bohm_effect#Global_action_vs._local_forces) on Wikipedia:
"Thus the Aharonov–Bohm effect validates the view that forces are an incomplete way to formulate physics, and potential energies must be used instead. In fact Richard Feynman complained[citation needed] that he had been taught electromagnetism from the perspective of electromagnetic fields, and he wished later in life he had been taught to think in terms of the electromagnetic potential instead, as this would be more fundamental."
Potential is more fundamental than field. Have a look at the Wiki derivation from electromagnetic theory (http://en.wikipedia.org/wiki/Electromagnetic_radiation#Derivation_from_electromagnetic_theory): "the curl operator on one side of these equations results in first-order spacial derivatives of the wave solution, while the time-derivative on the other side of the equations, which gives the other field, is first order in time". It's like four-potential A is the height of the hill, the electromagnetic field Fμv is the outline of it, the electric field E is the slope of it, and magnetic field B is the rate of change of slope. But in the Aharonov-Bohm effect there's a plateau all round the solenoid, only it's twisted around. Does that make sense? JP can you offer a better analogy to deliver some understanding?
I've got to dash, but I've just seen your update, and noticed this in the article:
"This purely quantum effect, verified in a multitude of experimental set-ups, is at the heart of much of modern physics".
It isn't a purely quantum effect. It was predicted by Ehrenberg and Siday in their 1949 paper "The Refractive Index in Electron Optics and the Principles of Dynamics". The Aharonov-Bohm effect was predicted in an optics paper, and here we are sixty five years later with an Aharonov-Bohm effect for light.
-
So what exactly is the magnetic flux from 0 to 2pi referring to?
When you are measuring phase and/or angles, you can use degrees, where there is 360 degrees in a circle. This was invented by the Babylonians (if not earlier), and is taught to students at school.
Mathematicians, physicists and engineers often prefer to measure phase and/or angles in units called "radians", which is shown by the abbreviation "RAD" on a scientific calculator. In this scheme, there are 2pi radians in a circle. Radians have some useful mathematical properties when you combine them with imaginary numbers - for example there is a close relationship between the ex function and sin(x)+cos(x).
This results in one of the neatest results in mathematics eπi+1=0, which combines 5 of the fundamental constants of mathematics. (I think it was discovered by Euler?)
That was not what I meant although very interesting answer. I meant are they saying the wave of the photon can be shown to exhibit magnetism when non-symmetrical.
-
Yeah, you're right John. I also think so, but it's the first time I've seen someone define it here :) potentials are expressions that we later, after a outcome, can define as a product of a presumed 'field'. But if we lift forward somethings potential we also seem to be leaving a materialistic reality, in where stuff as EM exists. A potential is no boson. Anyone seeing a cave here :)
-
There's a lot of problems with the way electromagnetism is taught and understood, yor_on. I quite like this paper (http://arxiv.org/abs/0803.2596) myself, wherein the photon is a "pulse" of four-potential. It's something like a lemon (http://physicsworld.com/cws/article/news/2012/aug/10/photon-shape-could-be-used-to-encode-quantum-information), and the space and time derivatives of potential gives you the archetypal sinusoidal waveforms. By the way, we maybe referred to the wrong paper above, see this:
http://www.nature.com/nphoton/journal/v8/n9/full/nphoton.2014.177.html
-
Don't know , defining a point like particle as some sort of 'wave-train' containing a number of oscillations/waves seems a tricky assumption to me. Doing so a photon can't be point-like (as well as dimension less) anymore as I think of it? Then again, I need to read the whole paper, don't I :) then there is the other link that speaks of "The photon and the laser pulse interfere and either reinforce or cancel one another out, depending on their shapes. "
Not sure how I should read that, waves do cancel and reinforce each other, but a light quanta (photon) doing it? We can send singular photons so it should be possible to test if you can get two photons to cancel each other? But if we could it seems to me that a photon can't be a final state, aka a discrete energy quanta any more. It also say that "Single photons and other quantum light states can also be generated in a variety of complex shapes." without defining how we can know this?
-
It may just be the way it is expressed through words (nomenclature). you have https://en.wikipedia.org/wiki/Wave_packet
There it states
"Quantum mechanics ascribes a special significance to the wave packet: it is interpreted as a "probability wave", describing the probability that a particle or particles in a particular state will be measured to have a given position and momentum.
It is in this way related to the wave function.
Through application of the Schrödinger equation in quantum mechanics, it is possible to deduce the time evolution of a system, similar to the process of the Hamiltonian formalism in classical mechanics.
The wave packet is thus a mathematical solution to the Schrödinger equation. The area under the absolute square of the wave packet solution is interpreted as the probability of finding the particle in a given region. The dispersive character of solutions of the Schrödinger equation has played an important role in rejecting Schrödinger's original interpretation, and accepting the Born rule."
I like that one better, than me imagining a photon as consisting of 'physical waves' making up a 'discrete' energy quanta.
=
Heh, finally reading the paper through it seems as the guys writing it agrees with me ::))
Just got stuck at the beginning there. and yes, I think it's a nice paper.
-
Don't pay too much attention to all that probability stuff. It's something of a popscience myth associated with the Copenhagen Interpretation and "quantum mysticism". It just doesn't feature in classical electromagnetism, or QED, or optics. The photon isn't some point particle, instead E=hf applies, because it has a wave nature. Long wave radio-wave photons can have a wavelength of kilometers. Have a look into weak measurement (http://physicsworld.com/cws/article/news/2011/dec/16/physics-world-reveals-its-top-10-breakthroughs-for-2011) on physicsworld. The photon is no more a point particle than a seismic wave. See The secret lives of photons revealed (http://physicsworld.com/cws/article/news/2011/jun/03/the-secret-lives-of-photons-revealed) and look at this picture:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fimages.iop.org%2Fobjects%2Fphw%2Fnews%2Fthumb%2F15%2F6%2F4%2Fdouble1.jpg&hash=da4cb37b9a845040a714f1d541491915)
3D plot of a single photon showing wave-like behaviour
-
I don't know John. I enjoyed it when the pdf you linked here wrote "The single photon must not necessarily be a wave train containing intrinsic oscillations, but it is rather a single pulse and it may be viewed as such one."
That is my view too. I don't see how it becomes a wave, behaving 'photon like'. What I can accept so far is the duality, that combined with the setup will give you one or the other. and maybe ? A field that uses both? But that field is one he* of a mystery to me.
-
to see why consider it such as both time dilation and length contractions are true statements. That's what I think they are at least :) The world becoming observer dependent. Now create a system, let's call all objects in it moving 'observers' of each other, inside some common space. Motion exist and is easy to prove logically, so they are indeed moving. Each one of them will define this 'common space' differently. and all of them will be correct. there exist no (common) gold standard experimentally. Now try to put up a unitary field that take all this into consideration, giving us one practical description of that space, I will be pleased if you succeed. You cannot use Lorentz transformations for it, because they are simply logic, knitting together my description of a reality with yours. The space in where a Lorentz transformation exist is purely mathematical, but the universe you meet exist, and will always be locally true for you.
=
you might say that a Lorentz transformation, in itself, is neither here nor there. It's a link between two observers, giving a necessary logic and causality to a universe. because that is what physics are, a logic, or several depending on how you look at it. Same with everything else, all sciences assume logic to exist.
=
you could look at it this way. what do you need to construct a 'common space'?
Causality should be there, if you want it to be understandable.
Causality is a primary logic you need. Break it and the common space we define, our 'universe' becomes something else. What causality need to exist is a arrow. That arrow need a direction. Each one of us have a locally true, four dimensional reality, with a locally true arrow pointing us from our birth to our death. Then we have causality that knits together my local reality with yours, into that 'common space' or universe, as described through a Lorentz transformation.
==
The 'gold standard' that do exist, and create our physics are all local definitions, as 'c' and other constants. We use those for all sciences, and when we assume the universe to have the same physics, laws etc we go out from such local definitions, expecting them to be true wherever we go to measure them. So locally no ambiguities exist, there we can agree on that my time is yours too :) If it wasn't we wouldn't have 'repeatable experiments' and a computer would consist of 'black magic', as would the universe, or 'white' for those preferring that.
So relativity could be seen as a 'wrong statement', in a sense, as everything isn't relative, not when locally defined. But observing that common space it becomes relative, observer dependent.
-
If you would treat the universe as some matrix consisting of points, 'observers', of each other. Then each point have a adjustable slide, consisting of mass, relative motion and acceleration, versus all other points. All points exchangeable with each other, meaning that locally you never will experience any 'time dilation' or 'Lorenz Fitzgerald contraction'. Those present themselves only when comparing between frames of reference, and when you compare you presume your local reality to be the gold standard from where all other frames are defined.
Doing so, also using a logic resting on local measurements we automatically get a gold standard valid for us all. That's a primary reason why your clock won't 'stop' locally, or 'change its pace', you hovering over some event horizon.
It's easy to see why Einstein spent a lot of time looking for that 'fifth dimension' in where you could join observer dependencies, into one whole description of a 'common space' containing us all. And a 'field' needs that description too I think.
A added complexity to a description of that common space should be that for each observer (ideally) agreeing on observing a same frame of reference (point) no one will agree on the others description of a time or distance. If that was a illusion it wouldn't be as hard to digest. But it's no illusion, as I see it, at relativistic speeds your speed is not enough to explain how a universe can shrink for you.
So each observer have its own, very real, description of a common space as I think. If we now use QM to define it, presuming this to be real effects, which they are (NIST) then it has no end that I can define. And that is a question about discreteness too, to me. Is there a discreteness to the universe? Can I use some matrix with 'points', locally equivalent? The logic we use presume a local equivalence (as repeatable experiments) so? If there is a 'point' existing, how does it relate to those other points?
And that is decoherence, I suspect :)
and now I will stop mumbling in my beard ::))
-
Relativity isn't wrong, yor_on. What's wrong is the way people misunderstand it and make it complicated.
Have a read of The Other Meaning of Special Relativity (http://www.classicalmatter.org/ClassicalTheory/OtherRelativity.pdf) by Robert Close. The crucial thing to throw into the mix is the wave nature of matter. The universe isn't some matrix consisting of points. The universe consists of waves. Or fields and waves if you prefer. But it doesn't much matter because there's not much difference between a field-variation and a wave, or between a standing wave and a field. That's why quantum field theory works.
-
The questions above is not answered John, the equivalence we define physics from need to be answered in a 'wave universe' too.
-
Can you rephrase that please?
And do read that paper. It explains why you always measure the speed of light to be the same.
-
The equivalence creating physics, repeatable experiments. To get to it you need to make all 'points' equivalent relative constants. As for Robert Close, he's new to me. had a look and read.
"A Dirac-like equation is derived by factoring the one-dimensional wave equation and then generalizing with rotations of velocity and polarization. The general vector wave equation can then be derived from the resulting 'bispinor' equation. The general solution of the one-dimensional wave equation is a superposition of forward- and backward-propagating waves. These two independent states are separated in space by a 180 degree rotation and therefore form a spin 1/2 system. Complex spinors (Dirac spinors or bispinors) are required in order to rotate the wave velocities in three dimensions. Waves can propagate along curved paths (e.g. spirals) with mass proportional to the velocity rotation rate."
He seems to use some sort of geometric definition of why mass (matter) exist, or would that be dimensional definition? It's a lot of theory to digest there actually :) As for the paper I found it confusing. How does he define relative motion? How does he define the boundaries of this wave universe?
-
The equivalence creating physics, repeatable experiments. To get to it you need to make all 'points' equivalent relative constants.
I'm sorry yor-on, I'm still not clear what you mean.
As for Robert Close, he's new to me. had a look and read.
"A Dirac-like equation is derived by factoring the one-dimensional wave equation..."
That's not in the paper I said you should read. The paper I said you should read starts off saying this:
"Einstein’s special theory of relativity postulates that the speed of light is a constant for all
inertial observers. This postulate can be used to derive the Lorenz transformations relating length
and time measurements by different observers. In this paper it is shown that the Lorentz
transformations can be obtained for any type of wave simply by defining distance to be
proportional to wave propagation time..."
-
'Locality' versus observer dependencies. One assumption physics make is that you can place yourself anywhere in this universe and find constants locally equivalent. How would a wave universe define (explain) it, in your own words please.
=
We can put it this way, assume it is a wave universe. How do you define positions to it? What should 'dimensions' be seen as? In what way should every position in 'time and room' be considered equivalent? That as it needs to build on a equivalence too, unless it is a new logic system, defining it otherwise than from any idea of constants. And what would a arrow be? And gravity?
-
'Locality' versus observer dependencies. One assumption physics make is that you can place yourself anywhere in this universe and find constants locally equivalent. How would a wave universe define (explain) it, in your own words please.
You define your second and your metre using the local motion of waves, then you use them to measure the local motion of waves, so you always measure the same value. It looks like the speed of light is absolutely utterly constant, even though it's not. Hence you have the tautology described by Magueijo and Moffat in http://arxiv.org/abs/0705.4507 :
"Following Ellis [1], let us first consider c as the speed of the photon. Can c vary? Could such a variation be measured? As correctly pointed out by Ellis, within the current protocol for measuring time and space the answer is no. The unit of time is defined by an oscillating system or the frequency of an atomic transition, and the unit of space is defined in terms of the distance travelled by light in the unit of time. We therefore have a situation akin to saying that the speed of light is “one light-year per year”, i.e. its constancy has become a tautology or a definition."
We can put it this way, assume it is a wave universe. How do you define positions to it?
Using the motion of waves.
What should 'dimensions' be seen as?
As now, the motion of waves through space over time.
In what way should every position in 'time and room' be considered equivalent?
Because you measure both using the motion of light.
That as it needs to build on a equivalence too, unless it is a new logic system, defining it otherwise than from any idea of constants.
You don't need a new logic system, you just need to appreciate how the wave nature of matter relates to special relativity. Read that paper.
And what would a arrow be? And gravity?
The arrow of time is an abstract thing. Gravity is where light curves and matter falls down because a concentration of energy in the guise of a massive star conditions the surrounding space altering its properties such that motion through it is modelled as curved spacetime.
-
Maybe it's about where we stand looking at it, I stand locally anchored. This mean that the common universe we see becomes somewhat of a mirage to me, at least as defined from any 'commonality', aka a seamlessly existing 'same for us all' universe. Presuming this universe to be the exact same for you as for me, ignoring what time dilations and Lorentz contractions tell us, the problem could be reduced to what the 'stuff' inside it is made of.
Most people probably do so, and so they do not see it as I see. You might put it as they have their minds made up. 'This universe exist, I can 'touch it', and so can you, therefore we exist in it together'. If you don't use that prerequisite, the 'field' becomes open for other interpretations. When Einstein looked for that fifth dimension I see it as he used that prerequisite, the definition of a 'container' in where we all exist. That container then ruled by logics, and causality. One of the reasons Einstein found 'spooky action at a distance' so uncomfortable too, as another guess of mine. The funny thing is that those people thinking purely in QM terms tend to look at this universe much the same. I don't agree to that.
-
Don't want to be rude, but I think we need to move this one to 'new theories' John. You should really read that article I linked, about lights duality. That one contradicts any pure wave theory as I see it. But I need to look more at his paper on special relativity.
=
Here it is http://www.mpg.de/511738/pressRelease20051011
-
Let us define it such as I did before, this ideal system of observers, observing each other uniformly moving in a 'common space'. There I stated that each observer, ideally now, would find his relation time and lengthwise, relative the point observed, to differ from any other, although they all observed the same 'point'. Assume this to be true, then apply it on a idea of waves communicating creating it.
at the same time allow all of them to keep constants equivalent. If we assume it to be some 'containing space' I actually believe we also have to assume each point, between the observer and the observed, also to contain those same constants, and so define a own relation relative all other points.
so each point would then define the waves coming and leaving differently, also, those agreeing on observing one specific point should then each one give a unique definition of what types of waves communicating between that agreed on 'point' and themselves. If I'm thinking right here :)
-
What does it presume?
Well, first of all a absolute space, secondly I would expect to need some ground state from where those waves emanate, and then differ depending on relations. That should mean absolute motion.
-
In relative motion, as in Earth moving, it shouldn't matter what speed we define to it, as I gather. The energy (waves) measured from a light bulb should be the same, no matter what uniform speed I define relative something else. In a acceleration it is different though, there I will find a blue respective redshift emanating from that light bulb, depending on my position relative the light bulb, versus the overall direction of acceleration.
-
Alternatively we can forgo any demand of a 'ground state', instead assuming it all to build on the relations between the objects (points) involved, as if there would be no building blocks for defining a energy.
=
But I don't think we can do that.
(Now it's definitely belonging to new theories John:)
-
Above all, it's hard trying to see how all points simultaneously hold those constants, keeping them equivalent to each other, at the same time as they define unique relations with each point existing in a universe, or maybe we should call those points 'space time positions'. And none of them (ideally) agreeing on the others measurement. Then again, the same can be said for relativity as it is. The difference seems to me to be that where Einstein used a duality, your idea uses waves. I need to think more about this one :)
-
Ah well, there's another aspect there, but that one is not as obvious maybe? You also assume a variable light speed. Now, if you do and also connect 'c' to your local clocks oscillations, you automatically define it as we must grow old differently 'fast' depending on mass, relative motions, accelerations.
Then you, being stationary relative a event horizon, still measuring 'c', must define that as a lie. Also defining yourself to grow old much slower that you would on Earth :) But allow me to differ there. You will not, and that one I guarantee, notice any difference locally. Your local lifespan won't allow you any more reading, or writing, than if you had stayed on Earth.
-
Using my brand of locality it doesn't matter how one want to define the common universe, not for what is measurable, and what create the sciences we relies on. Locally 'c' will be 'c', your life span the same, no matter where you go, no matter what mass. And only when comparing frames of reference to your local, will you define time dilations and Lorentz contractions. And they won't be yours.
-
Don't want to be rude, but I think we need to move this one to 'new theories' John.
It isn't some new theory. Have a look at the Baez article (http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html):
"Einstein talked about the speed of light changing in his new theory. In 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 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 [Einstein means speed here] of propagation of light varies with position." This difference in speeds is precisely that referred to above by ceiling and floor observers..."
Most people just don't know about it, that's all.
-
Yeah, I like Baez too, but the modern definition is still 'c' as I think. It's you measuring that light, and it should be 'c' when counted on 'path taken' according to your measurement. But it's a interesting idea, although one I tend to veer from as it contain so many difficulties in defining how it should work for a whole concept of a 'common universe'. Locality has a simplicity making it attractive, although it has nothing to say, as I see, about how frames of reference connect, or whether a light path consist of a variable speed. We have 'c' though, and those other locally measured constants. they are what makes our world go round, and my computer work. If you can make that idea work, I think you will find it to become very complicated, which doesn't state it has to be wrong because of that though. But if you have two equivalent theories, one complicated, and one simpler, which one would you go for?
=
That's also why I refer to decoherence as some principle for what makes our common universe. It seems to come into play automatically in all macroscopic definitions of clocks and rulers.
-
There is another point where I differ, I don't like light paths :)
Never have, I much rather prefer light to be expressed through a 'field', even though I don't understand how that exist. The duality expressed through a field should make it simpler, if just someone could explain how observer dependencies can be in-cooperated in such an idea. Maybe that is where your ideas might have a relevance? Although, even if it is a field we still should find a arrow, and causality, to it. The really weird universe, to me that is, would be one where causality disappear.
-
Yeah, I like Baez too, but the modern definition is still 'c' as I think. It's you measuring that light, and it should be 'c' when counted on 'path taken' according to your measurement.
It isn't a modern definition so much as a popscience myth and a tautology that contradicts Einstein. Look at the Irwin Shapiro quote (http://en.wikipedia.org/wiki/Shapiro_delay) on Wikipedia: "The proposed experiment was designed to verify the prediction that the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potential".
There is another point where I differ, I don't like light paths...
You should. But you should remember the light takes many paths. I think a good analogy is a seismic wave moving from A to B. It isn't just the houses sitting on the AB line that shake.
-
heh, should what? Like light paths, or not like light paths? If you make a sheet, then light it up from under we have that rule, that for 'meaningful information' you have to use 'c'. Doesn't state that you can't move that flashlight faster, just that it is not allowed to contain any information. As for gravity and 'c', well, defined locally 'c' is 'c'. You might think of it as wondering where 'locality' reside. Magnifying a spot, will gravity disappear?
=
the sheet should be a simplified idea of a field here, with us inside the sheet, following the light path. Although, take away the flashlight, but keep the 'light path'.
-
That one wasn't that good. In reality you have light only in your measurements. There are no paths other than those we define through causality. So you have a source, and a sink, from that follows, over time, a path. But it's no ball propagating.
-
The Shapiro delay is fascinating. Seen it defined both as an example of time dilation as well as a result of the path taken in a gravitational potential. This one though refer to it as a result of the path, maybe you could define a path as result of the time dilation, observed by you measuring, too? http://physicspages.com/2013/08/08/delay-of-light-passing-a-mass-shapiro-delay/
==
Actually you should be able to apply this to the NIST experiments with synchronized atomic clocks too, finding them starting to differ at centimeters (placed height wise). Now we can make our pick, the light path changing due to your observation of a differing gravity, or the time dilation you define from your frame of reference, slowing the 'photon' down, or maybe both? And then one can walk over to that table, putting both clocks beside each other, comparing them to ones (formerly synchronized atomic-mechanical) wristwatch, finding the time to be 'synchronized' again.
(Eh, that should preferably be read as the oscillations from all three clocks becoming equivalent, at close proximity. Otherwise we need to move this to New Theories asap..)
It is interesting, isn't it :)
-
Hi all
Just caught up with you. Went to a IET presentation at Surrey uni on Wednesday on EM transmission band and the lecturer say that we can now get up to 8 messages on K, Ku and Klow bands because of using not just quadrature phase shift keying but 8-PSK . There was an article in IET magazine dated 20 February 2010 explaining this way of modulation.
This technology requires exact synchronisation of the start switching of the carrier wave magnoflux helix. The article you read I would think is trying to show how this could be possible using existing physics.
If we can 8-PSK all the micro-wave fibre optic cables under the sea then I think you can see how important it is to implement this and understand the new electro-magnetic physics involved
CliveS