Totally agreeable, butwith 'α' as the angle between the longitudinal direction of the conductor and the direction of the magnetic flux density vec _B.I'm sticking with it since the electrical field component is negligibly small within the conductive wall, therefore the reason of the force acting on the electrons must the magnetic field and the associated Lorentz force which triggers the charge carrier movement to the first approximation. However, I fully agree with meberbs regarding the scattering conditions described in the message written by spupeng7.The electric field within the skin penetration depth exists but again - it is negligible - regarding its field strength.
Question:Where has the energy that we put into the initial ray disappeared? In this situation it is not transferred into another form or another particle.OK, both rays work towards each other, but no heat is generated or radiated.Will this energy vanish in a magical way or will it be added to the energetic background vacuum field?
Quote from: RERT on 11/06/2018 11:09 amQuote from: spupeng7 on 11/06/2018 12:26 amQuote from: meberbs on 11/06/2018 12:00 amQuote from: spupeng7 on 11/05/2018 11:39 pmThanks meberbs, you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?Edit: thanks also for the references.The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.I think the modeling software catches it at the moment of equilibrium and is time averaged. That moment the friction slowing the electrons matches the input energy keeping them at equilibrium. There might be some small effect due to the friction [inducing thermal effects where thermal radiation transmits through the entire material] but it's small compared to the stored energy of a high Q cavity. Edit:I almost forgot to emphasize that half of the energy in the cavity is in the magnetic field. The magnetic field is what's up against the skin of the cavity. A changing magnetic field induces an electric field. These electrons see the changing magnetic field has an electric field. In a sense they see both electric and magnetic field. They see this Electro-magnetic field as moving at the speed of light. During their acceleration the electromagnetic field they emit cancels the electric field of the incoming light while constructively enhancing the magnetic field when they are free to accelerate. The skin depth for this to happen is what contains the radiation inside the cavity. The time to reflect I think has to do with penetration depth which depends on the frequency. https://en.wikipedia.org/wiki/Penetration_depthalso related:googled "time to reflect penetration depth"https://www.fer.unizg.hr/_download/repository/1992_JQE_v28_n02_Babic_Corzine.pdfAnalytic Expressions for the Reflection Delay,Penetration Depth, and Absorptance ofQuarter-Wave Dielectric MirrorsDubravko I. Babic and Scott W. Corzine Quote...In this paper we derive expressions for the penetration depth and mirror reflection delay that are valid for arbitrary material refractive index combinations and any number of layers... ...the reflection delay adds to the laser cavity roundtriptime. So there does appear to be a time delay in reflection via skin depth where I think the first electrons are not capable of totally reflecting the entire signal via resistance and I think mass. As a new change in power or a beam of light coming in has both electric and magnetic field then yes there would be some electric field penetration into the surface of the material.
Quote from: spupeng7 on 11/06/2018 12:26 amQuote from: meberbs on 11/06/2018 12:00 amQuote from: spupeng7 on 11/05/2018 11:39 pmThanks meberbs, you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?Edit: thanks also for the references.The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.
Quote from: meberbs on 11/06/2018 12:00 amQuote from: spupeng7 on 11/05/2018 11:39 pmThanks meberbs, you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?Edit: thanks also for the references.The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.
Quote from: spupeng7 on 11/05/2018 11:39 pmThanks meberbs, you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?Edit: thanks also for the references.The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.
Thanks meberbs, you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?Edit: thanks also for the references.
...In this paper we derive expressions for the penetration depth and mirror reflection delay that are valid for arbitrary material refractive index combinations and any number of layers... ...the reflection delay adds to the laser cavity roundtriptime.
@allI have a small energy paradox in my head... I hope someone can explain it?!To generate an EM wave, we have to pump energy into a generator, for example a laser. Imagine a perfect interferometer device without any loss where the initial beam is divided into two beams. Both beams carry exactly half the energy of the initial beam. Let us now add a phase delay of exactly 180 degrees to one of the individual beams. Finally, let both carriers overlap.The related formulas tell us that the rays will cancel each other out. There is nothing left, as far as i understand it.Quote from: https://en.wikipedia.org/wiki/Conservation_of_energy In physics, the law of conservation of energy states that the total energy of an isolated system remains constant, it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.Question:Where has the energy that we put into the initial ray disappeared? In this situation it is not transferred into another form or another particle.OK, both rays work towards each other, but no heat is generated or radiated.Will this energy vanish in a magical way or will it be added to the energetic background vacuum field?If it is true that we can put energy into the vacuum field this way it may be possible to harvest some energy from it in a similar way to get thrust (a net force against a proper device).
In physics, the law of conservation of energy states that the total energy of an isolated system remains constant, it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another.
Unlike a fermion inelastic collision, bosons are super-positions of fields. Now what is the phase-relationship between the E & M fields for counter-propagating waves? And the spin/polarization? The momentum, defined by the fields, just keeps on propagating as super-positions of the fields. I suppose then, it could be considered as instantaneous angular-momentum.
Thanks All, reflection with any delay at all, means that the momentum of the reflected radiation is retained in the surface during that delay... Question: is the speed of conduction across a surface a product of its refractive index?
Quote from: RERT on 11/06/2018 11:09 amIt's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.I believe it is, in Meep anyways. See the Lorentz-Drude model. It models the plasma-frequency (cut-off) and plasmons, IIRC, which are a result of the mass of the charge carriers.
It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.
I do not know what you mean by "speed of conduction," but since the refractive index of a metal is irrelevant to most of its conductive properties, the answer is probably "no." (Unless you define a complex index of refraction that combines conductivity and standard linear permittivity effects into a single term, but even then, it has little to no relation to many things you might be referring to)
Quote from: mwvp on 11/08/2018 01:25 amQuote from: RERT on 11/06/2018 11:09 amIt's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.I believe it is, in Meep anyways. See the Lorentz-Drude model. It models the plasma-frequency (cut-off) and plasmons, IIRC, which are a result of the mass of the charge carriers.Thanks!Quote from: meberbs on 11/08/2018 03:11 amI do not know what you mean by "speed of conduction," but since the refractive index of a metal is irrelevant to most of its conductive properties, the answer is probably "no." (Unless you define a complex index of refraction that combines conductivity and standard linear permittivity effects into a single term, but even then, it has little to no relation to many things you might be referring to)If you model classically a plane wave incident on a conductor such as copper, the fields only penetrate the skin depth. But the variation in the incident fields causes variation in the fields at the surface, which propagate inwards into the metal dissipatively. So an incident peak moves in with a given speed, admittedly shrinking rapidly.So there is definitely a 'speed of light' in copper, namely the speed of motion of those peaks through the skin - though when I tried, Googling 'speed of light in copper' gave no joy. As far as I can tell, the speed is very low, and the refractive index therefore very high, though I don't know if the concept of a refractive index is helpful.Hoping I have done the sums right...
Quote from: X_RaY on 11/07/2018 09:00 pmQuestion:Where has the energy that we put into the initial ray disappeared? In this situation it is not transferred into another form or another particle.OK, both rays work towards each other, but no heat is generated or radiated.Will this energy vanish in a magical way or will it be added to the energetic background vacuum field?The problem is built into an assumption in your setup. After you split the beam, there is no way for you to perfectly recombine them on top of each other. When you attempt to do so what you end up with is a set of interference fringes. There will be dark spots, but for every dark spot where fields cancel, there will be a light spot where fields add so the energy still exists.This exact setup can be done with a Michelson interferometer.
Supernovae... This is because gravitational waves are generated by a changing quadrupole moment, which can happen only when there is asymmetrical movement of masses.
It would be better to ask what the speed of an electromagnetic wave through a copper conductor is... Rather than the speed of light in copper.The result would be close to but less than the speed of light in vacuum. A google search phrased as indicated above, returns an answer of c x 0.951 (for 12 gauge copper wire), but I am sure there are other variables that would affect the issue as it involves the discussion here.
http://theoryofsuperunification-leonov.blogspot.com/http://leonov-leonovstheories.blogspot.com/Results of measurement of the specific thrust force of the quantum engineIf anyone has looked at this? Is this similar to EM Drive? Is this pseudoscience? Profile says Dr. V. Leonov was awarded a Russian government prize in the area of science and technology and in 2007 was included in 100 leaders of science and technology of CIS countries.
Quote from: OnlyMe on 11/08/2018 05:05 pmIt would be better to ask what the speed of an electromagnetic wave through a copper conductor is... Rather than the speed of light in copper.The result would be close to but less than the speed of light in vacuum. A google search phrased as indicated above, returns an answer of c x 0.951 (for 12 gauge copper wire), but I am sure there are other variables that would affect the issue as it involves the discussion here.The speed of conduction along the skin is a different question, and not surprising to be a large fraction of c. I was referring to the speed of transmission of disturbances across the skin when the copper is reflecting an incident wave.
OK, so we may need to define terms for this question. If the mechanism of reflection involves conduction in the reflector surface, and the incident radiation causing that current has a component of inertia in the direction of incidence, is that inertia not a dynamic component of that surface until the process of reflection is complete?
Quote from: spupeng7 on 11/09/2018 11:15 pmOK, so we may need to define terms for this question. If the mechanism of reflection involves conduction in the reflector surface, and the incident radiation causing that current has a component of inertia in the direction of incidence, is that inertia not a dynamic component of that surface until the process of reflection is complete?Lets start with the simplest case where the wave is incident normal (perpendicular) to the surface. Currents will be present parallel to the surface, so will not contain the momentum from the wave. The currents are circular in nature due to the magnetic field and therefore have no net momentum. The momentum of the fields that penetrate into the conductor is still present as part of the fields by the Poynting vector. (There are a couple ways to book keep the effects on the fields due to material permittivity, but that is a separate discussion, and wouldn't change anything, relative permittivity is close to 1 in most metals to my knowledge anyway.) Some tiny bit of the momentum from the fields overlaps into the material, but it is still momentum in the form of electromagnetic fields as it finishes turning around.Note that I am using some loose language here for descriptive purposes. Since everything is happening continuously and waves are propagating in both directions, the momentum density due to the fields can be roughly 0 at points in a resonant cavity, while the energy density is actually non-zero.
Thanks meberbs, forgive me if I labor the question; if there is any inertia from the reflecting energy, present in the reflector with any duration, then the difference in scale between the opposing reflectors in our resonant cavity would alter those durations bringing the inertia of the waveguide itself out of balance. We are assuming Machian interactions but talking about nothing more complicated than radiation pressure.
Quote from: spupeng7 on 11/12/2018 11:06 pmThanks meberbs, forgive me if I labor the question; if there is any inertia from the reflecting energy, present in the reflector with any duration, then the difference in scale between the opposing reflectors in our resonant cavity would alter those durations bringing the inertia of the waveguide itself out of balance. We are assuming Machian interactions but talking about nothing more complicated than radiation pressure.You seem to have still misunderstood, the momentum of the fields inside the conductor is still momentum of the fields. Just because the fields overlap with matter does not transfer the momentum to the matter. (And here I repeat the previous caveat I mentioned about bookkeeping due to some of the fields existing due to the polarization of the material in the presence of the externally applied field.)The size of the endplates has no relation to the field penetration depth, so the durations are unaffected.Even if you made the endplates out of materials with different conductivities, this would in no way bring the inertia of anything out of balance. At all times the sum of the momentum in the fields and the momentum of the cavity walls is constant (and zero for simplicity.) You can set up a situation such as a short pulse emitted in the cavity from a directional antenna, which would briefly cause the cavity to move in one direction, while the fields move in the other direction. The center of energy (relativistic equivalent for center of mass) would not move. The fields would get to one end, and then the reflection would reverse the momentum between the fields and the cavity.I have trouble figuring out what kind of logic you are using sometimes. In just this post you made 2 or 3 gigantic leaps concluding relations between things that are unrelated. For example, your incorrect claims that "the difference in scale between the opposing reflectors in our resonant cavity would alter those durations" and "alter(ing) those durations bring(s) the inertia of the waveguide itself out of balance." Neither of these are supported by any kind of logic that I can see, yet you treat them like facts.