what does it take to reflect a microwave? A metal? Or will another microwave reflect a microwave?
Quote from: scienceguy on 07/08/2018 02:06 amwhat does it take to reflect a microwave? A metal? Or will another microwave reflect a microwave?Microwave photons do not reflect nor bounce.
Question to be experimentally proved is can a tapered resonant cavity generate an assymetric force? If it can be shown to happen, then it follows why and how CofM and CofE are conserved without expelling mass. Ie the wavelength lengthened photons, with lower momentum, are what carries away the required Newton 3 momentum gain of the accelerated mass.
Would be interesting for someone to ray trace an averaged photon pathway, from say big end plate to small end plate and back to big end plate, in a TE013 resonant cavity. Some may be very surprised what that exercise will reveal. Can share that for a round trip there will be 8 side wall & end plate impact and emit events.
Even more interesting to work out the radiation pressure that will be generated at each impact and emit event. Thoughts the radiation pressure will be the same at each impact and emit event site are very wrong. Likewise thoughts that the overall force will be zero are also very wrong.Such a simple exercise but after so many years, as far as I know, no one here has ever actually done the calculations but instead made statement, without any proof, the overall force would be zero.
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Meberbs -Noether's theorem regarding energy conservation relates to space(time) which is translationally invariant. It's quite difficult to arrange an experiment containing physical objects which is translationally invariant. One is probably left arguing that translational invariance is the correct approximation when some small test apparatus is much smaller than the translations you care about. The immediate proximity of a tapered copper can is definitely not.Others -My guess on the physics discussions: we won't get anywhere with linear theories. Having said that, there are opportunities for interesting non-linear calculations just by letting the skin resistance in the copper depend on temperature ~ current ~ field, though the MEGA concept seems to finger GR as the obvious non-linear starting point.I'm not wildly concerned about energy or momentum conservation. 120 years ago we thought mass was conserved, until we figured out it wasn't. We will have to follow where the data leads, though at the moment that doesn't look to be very far !
Having said that, there are opportunities for interesting non-linear calculations just by letting the skin resistance in the copper depend on temperature ~ current ~ field,
...How many times do you have to be told that the photons are part of the system? They never leave the cavity and all momentum they have originally came from the cavity. If the drive were to work as you claim, by the time you turn it off, it will have changed momentum, and there is nothing remaining in the universe that has corresponding opposite momentum. That is the definition of breaking conservation of momentum....
Meberbs -Noether's theorem regarding energy conservation relates to space(time) which is translationally invariant. It's quite difficult to arrange an experiment containing physical objects which is translationally invariant. One is probably left arguing that translational invariance is the correct approximation when some small test apparatus is much smaller than the translations you care about. The immediate proximity of a tapered copper can is definitely not.
Quote from: meberbs on 07/08/2018 08:29 am.....When a photon impacts an orbital metallic electron, the photon energy and momentum are gained by the orbital electron. As it is not enough energy to alter the electron orbit, the absorbed energy and momentum are remitted as a newly created photon with either the same freq as impacted or a lower freq if the atom gained energy and momentum from the impact. Well established physics and what happens with a solar sail.The photons in a resonant cavity have energy and momentum that was created by the Rf energy that flowed in the coupler and resulted in the creation of the photons. So Rf electrial energy is converted into photon momentum and energy. If some of those photons lose some of their energy and momentum via inelastic events, the emitted photons having a longer wavelength. Well estabished physics.Only question is can a tapered resonant cavity generate an assymetric force?
Quote from: meberbs on 07/08/2018 08:29 am...How many times do you have to be told that the photons are part of the system? They never leave the cavity and all momentum they have originally came from the cavity. If the drive were to work as you claim, by the time you turn it off, it will have changed momentum, and there is nothing remaining in the universe that has corresponding opposite momentum. That is the definition of breaking conservation of momentum....meberbs, Part of this argument has always bothered me, but first remember that I do not believe that bouncing anything inside a frustum generates any net anomalous force/acceleration.The part that bothers me is the emphasis on conservation of momentum, where it seems obvious that a significant amount of the electromagnetic energy introduced into the frustum is converted to and dissipated as heat, and for the EmDrive as a whole, Lorentz forces etc., which moves the problem to one of conservation of energy rather than just momentum.Even in classical everyday mechanical systems like a vehicle moving down a roadway a portion of the initial momentum generated by an engine never makes it to an end stage transfer of momentum. Except in hypothetical situations it is almost always a conservation of energy balancing act and situation, while if all you follow is momentum in and out, conservation of momentum will always appear to be broken.This is part of what has lead to so much focus on improving experimental design, an account of energy in vs. energy out. And the possibility that some as yet undetermined mechanism might generate some useable force/acceleration... or not.
I'm not wildly concerned about energy or momentum conservation. 120 years ago we thought mass was conserved, until we figured out it wasn't.
Quote from: TheTraveller on 07/08/2018 10:16 amQuote from: meberbs on 07/08/2018 08:29 am.....When a photon impacts an orbital metallic electron, the photon energy and momentum are gained by the orbital electron. As it is not enough energy to alter the electron orbit, the absorbed energy and momentum are remitted as a newly created photon with either the same freq as impacted or a lower freq if the atom gained energy and momentum from the impact. Well established physics and what happens with a solar sail.The photons in a resonant cavity have energy and momentum that was created by the Rf energy that flowed in the coupler and resulted in the creation of the photons. So Rf electrial energy is converted into photon momentum and energy. If some of those photons lose some of their energy and momentum via inelastic events, the emitted photons having a longer wavelength. Well estabished physics.Only question is can a tapered resonant cavity generate an assymetric force?TT,I believe this implies a simplistic and inaccurate situation. If the microwaves inside of the frustum interacted as you describe there would be no degradation of the conductive walls. I am pretty sure that past DIY experimental attempts have shown pitting of the inside copper surface(s). That alone proves that there is enough electromagnetic energy to alter electron orbits even to the point of ionizing atoms resulting surface pitting...Then again maybe those ionized (charged) copper atoms flying around inside the frustum under the influence of an asymmetric electromagnetic field is the source of an anomalous thrust... but then, if this were the case, wouldn’t the surface pitting degrade the Q, affect the over all efficiency and limit the drives usesful life cycle/span?Point is contrary to your comment above, ”As it is not enough energy to alter the electron orbit,...” microwaves inside a frustum have been shown to interact destructively with the conductive walls of the frustum.
You are lying here. You have been shown the calculations many times:http://www.gregegan.net/SCIENCE/Cavity/Cavity.html
So people that proclaim left to right symmetry fail to take into account time.Greg Egan's analysis assumes a sinusoidal change with time. Clearly this is not the case. There is TIME-ASYMMETRY left to right. The origin of the asymmetry is the RF feed, that Greg Egan does not take into account. There is an interaction between standing waves and the travelling waves from the RF feed.As Notsosureofit said: steady state standing waves by themselves never occurs as long as the RF feed is on.
YES, they contradict Egan. http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.htmlEgan assumed that the time variation of the fields was symmetric, given by a sinusoid in time. His weakness is that he failed to consider the effect of the RF feed travelling wave. Greg Egan's results only apply for the RF feed being OFF.
NEW INFORMATION: We show here that those (Greg Egan, etc.) that pontificate that the electromagnetic fields inside the EM Drive produce a Poynting vector that sums up to zero over integer periods of time are plain wrong. The reason is that the Poynting vector sums up to zero over integer periods of time only when the electromagnetic fields are standing waves (waves that do not travel in the longitudinal direction). The RF feed antenna disturbs what would otherwise be a standing wave frozen in space and results in waves that travel in the longitudinal direction back and forth and a time variation of the amplitude electromagnetic field that is not a simple sinuosoid, as long as the RF feed is on. This results in a non-zero Poynting vector with a net pointing from the small base to the big base over integer periods of time (probably due to geometric attenuation of the travelling waves due to the conical taper). During EM Drive experiments, the RF feed is on: it is only with the RF feed on that forces have been measured. Notice that the period of this non-sinusoidal variation of the Poynting vector is half the period of the electromagnetic field (as expected from theoretical considerations).
It's right to be very sceptical of all claims with no mechanism of action within known physical laws.It's also wrong to lose sight of the fact that those laws change from time to time, eg conservation of mass.
Quote from: meberbs on 07/08/2018 08:29 amYou are lying here. You have been shown the calculations many times:http://www.gregegan.net/SCIENCE/Cavity/Cavity.htmlPlease, not this page again…Rodal explained back to the EM Drive Thread #3 (three years ago!) that aero's simulations (as predicted by Notsosureofit BTW) showed how Greg Egan's "demonstration" you quoted, involving standing waves only, was wrong as it didn't reflect the reality of what is going on in a real asymmetric cavity, when considering the flow of time and the presence of an antenna constantly feeding new RF energy:...See here, here and there. Of course, as also pointed out obviously by Rodal (miss you a lot José, long time no see…) such an asymmetry does not explain on itself how propellantless propulsion could be achieved, bus since Egan's oversimplistic explanation has been contradicted, we should definitely stop referring to it. More especially when using such a flawed explanation (incomplete and far from reality) to prove someone's quote is flat wrong or that he would even lie.
Theoretical calculation for ideal cavities that fail to predict several real experimental phenomena, as well as discrete and incomplete simulations involving Maxwell equations only, can't account for any propellantless thrust. This is true.However as Rodal also pointed out many times on these boards, such calculations and simulations fail to take into account the possibility that the EmDrive is not a closed system. If there is any kind of field propulsion making the EmDrive an open system, propellantless propulsion (not reactionless propulsion!) becomes non-impossible. No current calculation or EM simulation based on Maxwell laws only can predict such an effect.On the other hand I agree that Shawyer's simple explanation about the radiation pressure imbalance between the two end plates as the cause of thrust does not correctly fall in the true definition of an "open system".But Mach effects, quantised inertia, scalar–tensor theories -among others- qualify for the possibility of an open system and a field-effect propulsion for the EmDrive.