So you're saying that a magnet interacting with a magnetic field does not conserve momentum? Of course it does!
QuoteQuoteThe photons that are exchanged between the two magnets causes them to "attract" not repel, so conventional "logic" would say they are conveying the momentum in the wrong direction.To understand this, you must consider not only the Amplitude of the field, but also the Phase, North vs South. This is where everyone is missing the mark, like Greg Egan using time averaged sin and cos, ignores the relative instantaneous phase and resulting interference pattern of the superposition.ToddYou see, this is where I still don't understand where you are coming from. To use your two magnets pulling towards one another analogy, the apparent gain in momentum from one magnet was exactly cancelled when we chose a larger, more inclusive boundary with which to perform our momentum accounting. So with the emdrive moving forward, what is it in your theory that moves back? Our is it that the whole universe is not a large enough circle with which to account for momentum, and thus momentum is gained in another dimension/exotic field?At the end of the day, phase, superposition and interference are all classical effects. Nothing special there. So what circle do I need to draw around the EMdrive, and what fields do I need to consider, such that I end up with a momentum that is equal and opposite the physical momentum of the drive?Nothing is moving "backwards". Momentum is flowing INTO the boundary, NOT OUT of the boundary. It works both ways. Divergence is not zero when the source is turned on. The Poynting vector is not zero. The momentum put inside is then attenuated asymmetrically, and the resulting forces and amplitudes depend on the relative phase of the waves, not simply their time-averaged pressure. The conservation law says is that there must be divergence through the boundary, it can be in either direction, in or out. It isn't ONLY expelling something out that satisfies this condition.Todd
QuoteThe photons that are exchanged between the two magnets causes them to "attract" not repel, so conventional "logic" would say they are conveying the momentum in the wrong direction.To understand this, you must consider not only the Amplitude of the field, but also the Phase, North vs South. This is where everyone is missing the mark, like Greg Egan using time averaged sin and cos, ignores the relative instantaneous phase and resulting interference pattern of the superposition.ToddYou see, this is where I still don't understand where you are coming from. To use your two magnets pulling towards one another analogy, the apparent gain in momentum from one magnet was exactly cancelled when we chose a larger, more inclusive boundary with which to perform our momentum accounting. So with the emdrive moving forward, what is it in your theory that moves back? Our is it that the whole universe is not a large enough circle with which to account for momentum, and thus momentum is gained in another dimension/exotic field?At the end of the day, phase, superposition and interference are all classical effects. Nothing special there. So what circle do I need to draw around the EMdrive, and what fields do I need to consider, such that I end up with a momentum that is equal and opposite the physical momentum of the drive?
The photons that are exchanged between the two magnets causes them to "attract" not repel, so conventional "logic" would say they are conveying the momentum in the wrong direction.To understand this, you must consider not only the Amplitude of the field, but also the Phase, North vs South. This is where everyone is missing the mark, like Greg Egan using time averaged sin and cos, ignores the relative instantaneous phase and resulting interference pattern of the superposition.Todd
Quote from: sghill on 06/02/2015 07:57 pmQuote from: phaseshift on 06/02/2015 07:00 pmQuote from: deltaMass on 06/02/2015 06:50 pmIn conventional physics, it is clear that the momentum of the radiation injected into the cavity produces a back reaction upon the source of that radiation. Therefore if you put a box around [source + cavity], where the source includes a portable power supply (e.g. battery) - then the net momentum of the system is zero forever as viewed from outside the box.If there is a radiation leak, thrust no greater than P/c ("equivalent photon rocket") may result from such a system, including thermal effects originating from the input power P.Clearly here the claim being made is not conventional physics because:1. The claim is made that the box as a whole will moveand2. The claim is made that the magnitude of the thrust causing this movement exceeds the maximum expected thrust of the equivalent photon rocket by orders of magnitude.Thus any successful attempt at explanation will not use conventional physics.There is a corollary to all this:If you attempt to explain this effect with conventional physics alone, you have made an error.Thank you, thank you, thank you. Exactly.But we've covered all of this literally dozens of times up thread. Pretty please, don't rehash what we've already covered ad nauseum, and instead focus on what we haven't covered so that the thread doesn't loose meaning or focus. Every few weeks this thread has a collective breather when someone yells "Unicorns don't exist!" then the lurkers ask a bunch of newbie questions, and then we go back to researching while the audience listens quietly. Agreed! Yes, we keep going in circles rehashing the same stuff over and over - and every time that an attempt is made to go outside of the dogmatic circle the thread is jerked back 'into place'. There are a few that manage to keep bringing their ideas up for discussion (thank you Todd and others) but the ideas get lost in all the 1/4 wavelength vs 1/2 wavelength kind of discussions. The answers lie outside the circle and it is certainly constructive to have such discussions. We need a phase shift in thinking
Quote from: phaseshift on 06/02/2015 07:00 pmQuote from: deltaMass on 06/02/2015 06:50 pmIn conventional physics, it is clear that the momentum of the radiation injected into the cavity produces a back reaction upon the source of that radiation. Therefore if you put a box around [source + cavity], where the source includes a portable power supply (e.g. battery) - then the net momentum of the system is zero forever as viewed from outside the box.If there is a radiation leak, thrust no greater than P/c ("equivalent photon rocket") may result from such a system, including thermal effects originating from the input power P.Clearly here the claim being made is not conventional physics because:1. The claim is made that the box as a whole will moveand2. The claim is made that the magnitude of the thrust causing this movement exceeds the maximum expected thrust of the equivalent photon rocket by orders of magnitude.Thus any successful attempt at explanation will not use conventional physics.There is a corollary to all this:If you attempt to explain this effect with conventional physics alone, you have made an error.Thank you, thank you, thank you. Exactly.But we've covered all of this literally dozens of times up thread. Pretty please, don't rehash what we've already covered ad nauseum, and instead focus on what we haven't covered so that the thread doesn't loose meaning or focus. Every few weeks this thread has a collective breather when someone yells "Unicorns don't exist!" then the lurkers ask a bunch of newbie questions, and then we go back to researching while the audience listens quietly.
Quote from: deltaMass on 06/02/2015 06:50 pmIn conventional physics, it is clear that the momentum of the radiation injected into the cavity produces a back reaction upon the source of that radiation. Therefore if you put a box around [source + cavity], where the source includes a portable power supply (e.g. battery) - then the net momentum of the system is zero forever as viewed from outside the box.If there is a radiation leak, thrust no greater than P/c ("equivalent photon rocket") may result from such a system, including thermal effects originating from the input power P.Clearly here the claim being made is not conventional physics because:1. The claim is made that the box as a whole will moveand2. The claim is made that the magnitude of the thrust causing this movement exceeds the maximum expected thrust of the equivalent photon rocket by orders of magnitude.Thus any successful attempt at explanation will not use conventional physics.There is a corollary to all this:If you attempt to explain this effect with conventional physics alone, you have made an error.Thank you, thank you, thank you. Exactly.
In conventional physics, it is clear that the momentum of the radiation injected into the cavity produces a back reaction upon the source of that radiation. Therefore if you put a box around [source + cavity], where the source includes a portable power supply (e.g. battery) - then the net momentum of the system is zero forever as viewed from outside the box.If there is a radiation leak, thrust no greater than P/c ("equivalent photon rocket") may result from such a system, including thermal effects originating from the input power P.Clearly here the claim being made is not conventional physics because:1. The claim is made that the box as a whole will moveand2. The claim is made that the magnitude of the thrust causing this movement exceeds the maximum expected thrust of the equivalent photon rocket by orders of magnitude.Thus any successful attempt at explanation will not use conventional physics.There is a corollary to all this:If you attempt to explain this effect with conventional physics alone, you have made an error.
QuoteSo you're saying that a magnet interacting with a magnetic field does not conserve momentum? Of course it does!I don't believe such a situation conserves momentum. Imagine a universe in which only a single charged particle and a single electric field, defined over the entire universe, exist. This particle will accelerate endlessly, gaining momentum, with no creation of any opposite momentum, either physical or EM. This is no different than a magnet in a magnetic field. Without a field source, there is no guarantee that the interaction of an arbitrary field and some object being acted upon conserve momentum. By drawing a boundary such that a field source is ignored, a net gain in momentum seems possible.
Hahaha, well I'm sorry to hound you like this, but I suppose my immediate question is: From where does this momentum that flows into the boundary come from? There is still momentum that is not accounted for. Does it come from the microwaves? Then the force on the cavity is balanced by the force on the magnetron, so no net force for the entire device. A non-zero divergence to the poynting vector, when averaged over time, is correct, but the poynting vector is a flow of power (hence the non-zero divergence ought to be rather intuitive). When we divide the poynting vector by c2, we have the linear momentum of the EM field. For a constant force on the emdrive, it is not enough to have non-zero poynting vector. You must have a poynting vector that grows such that its time derivative is equal to and opposite the force on the emdrive. Without that, I do no understand how there is any sustained force from any EM field, no matter if it is radiative/reactive or constructive/destructive.
Quote from: wallofwolfstreet on 06/02/2015 11:52 pmQuoteSo you're saying that a magnet interacting with a magnetic field does not conserve momentum? Of course it does!I don't believe such a situation conserves momentum. Imagine a universe in which only a single charged particle and a single electric field, defined over the entire universe, exist. This particle will accelerate endlessly, gaining momentum, with no creation of any opposite momentum, either physical or EM. This is no different than a magnet in a magnetic field. Without a field source, there is no guarantee that the interaction of an arbitrary field and some object being acted upon conserve momentum. By drawing a boundary such that a field source is ignored, a net gain in momentum seems possible. Contrary to what you believe. QED tells us otherwise. A charged particle in it's ground state has a zero point energy. The vacuum EM field in it's ground state also has a zero point energy. Neither is "zero". They exist in equilibrium with a constant exchange of power. Power in = Power out. This is text book physics and it is true of every sub-atomic particle, even quarks "inside" a proton. That is CoM and CoE at the quantum scale. So yes, the interaction of a single particle obeys CoM and CoE with the field it is immersed in.QuoteHahaha, well I'm sorry to hound you like this, but I suppose my immediate question is: From where does this momentum that flows into the boundary come from? There is still momentum that is not accounted for. Does it come from the microwaves? Then the force on the cavity is balanced by the force on the magnetron, so no net force for the entire device. A non-zero divergence to the poynting vector, when averaged over time, is correct, but the poynting vector is a flow of power (hence the non-zero divergence ought to be rather intuitive). When we divide the poynting vector by c2, we have the linear momentum of the EM field. For a constant force on the emdrive, it is not enough to have non-zero poynting vector. You must have a poynting vector that grows such that its time derivative is equal to and opposite the force on the emdrive. Without that, I do no understand how there is any sustained force from any EM field, no matter if it is radiative/reactive or constructive/destructive. So far, what I've come up with is the following. I'm still learning, but this makes sense to me;Suppose we start with a perfect cylinder, that is perfectly conducting such that there are no losses at all. I then input microwaves at the resonant frequency, 50W for 100sec = 5000J of energy stored. I turn off the microwaves and since there are no losses and no attenuation in a cylinder, this 5000J of energy is stored like a perfectly tuned LC resonator. The linear momentum you are referring to, has been reflected bazillons of times over, resulting in a NET zero momentum. However, the standing wave that persists has a forward and a backward wave, each having momentum > 0, but in opposite directions. So can we agree we have a cylinder that has 0 NET momentum but has 5000J of energy stored as an oscillating EM wave that does carry momentum? The momentum of this wave is much larger than the 50W input, but it's not doing any work because a standing wave has 90-deg phase shift between the E and B fields. The "power factor" is zero.Now, suppose with the flick of a switch we can reduce the diameter of one end by 50%, turning the cylinder into a frustum. Suddenly the dimensions of the cavity have changed and the waves must phase shift to restore the boundary conditions. The phase shift of the forward wave is opposite the phase shift of the backward wave. This causes the power factor to shift away from zero, and causes an interference pattern that is required to do work on the boundary to equalize the pressure again.This was an extreme example, but what I'm trying to illustrate is how the momentum of thrust is decoupled from the momentum input. The input energy is stored as a standing wave. The attenuation of that standing wave favors one side over the other and as the phase shifts, the field does work on the boundary to balance the pressure. I'm working on the paper. What I posted the other day was a rough first draft. Thanks for helping me to attack the questions people will have.Todd
...Yang is closer than anyone and simply didn't disclose the details, and used a poorly constructed example to explain it, but her force equation is correct "IFF" you plug in the correct field amplitudes AND phases. Simply put, it moves because inside there is an EM stress energy tensor that is skewed to one side by constructive and destructive interference with the source. It would have a lot more thrust if the balance were 50/50, but as it is, only a small percentage of the waves walk out of phase to cause the interference. So the standing waves dominate, and there is very little thrust. The percentage results in higher NET thrust for higher Q, but it would be a more efficient thruster if the percentage were higher and the Q were lower.Todd
...We can definitely agree that the cylinder has 0 NET momentum but has energy stored as an oscillating EM wave that carries momentum. And that this oscillating EM wave is made up of the superposition of waves, each containing more momentum than the single 50 W photon rocket equivalent, we can also agree. But at the end of the day, all of the momentum within the cavity can be accounted for as coming from an equal and opposite momentum that must have been imparted to the magnetron or feed cable/antenna, because everything stated is just classical EM, and classical EM obeys COM.
So when the end is shrunk, and the waves phase shift into a state with non-zero power factor and a subsequent non-zero poynting vector, surely you can realize no more force on the boundary from this attenuation than you originally supplied to those waves with your magnetron? In other words, averaged over some arbitrarily long time period, shouldn't your hypothesis result in a total thrust no greater than the equivalent photon rocket?
If you had just opened one end of your cylindrical cavity, instead of flipping the switch of your diameter reduction device, wouldn't the result be the same? The sudden release of stored momentum gives a momentary thrust greater than a photon rocket, but time-averaged, nothing is gained.
... You stated the EM drive may have trouble optimizing this imbalance in phase. What do you think of having two separate cavities near each other but out of phase such that the top cavity appears to be destructively interfering with the bottom while the bottom cavity appears to be constructively interfering with the top? See figure "EM propulse proposal.png" . Is this the same as your proposed separation of the (top and bottom) cavity for the EM drive or different? In reference to http://emdrive.wiki/List_of_Suggested_Experiments 7. Separate resonance and attenuation chambers. Purpose: Proposed by WarpTech as a test of his theory.9. Measure the force on two cylindrical resonant wave guides (lowest transverse electric mode) tuned to resonate at the same frequency (one is adjustable) with their flat plates separated by a quarter wavelength. The current in cavity one is out of phase with cavity two by 90 degrees. [6]What do you think of this paper that suggests such EM propulsion may be possible using light speed delayed information of the near field? http://arxiv.org/abs/1502.06288Another hypothesis of mine is that if we are pushing off the near field then if it works and is greater than light pressure then we may be instead some how pushing off space and time since we are taking advantage of the fact that information must travel at finite speed (space/time) to get such a push. As far as I knew space time waves are different from electromagnetic waves in that space time waves are related to gravitational objects but maybe there could be a connection.
Quote from: dustinthewind on 06/03/2015 03:11 am... You stated the EM drive may have trouble optimizing this imbalance in phase. What do you think of having two separate cavities near each other but out of phase such that the top cavity appears to be destructively interfering with the bottom while the bottom cavity appears to be constructively interfering with the top? See figure "EM propulse proposal.png" . Is this the same as your proposed separation of the (top and bottom) cavity for the EM drive or different? In reference to http://emdrive.wiki/List_of_Suggested_Experiments 7. Separate resonance and attenuation chambers. Purpose: Proposed by WarpTech as a test of his theory.9. Measure the force on two cylindrical resonant wave guides (lowest transverse electric mode) tuned to resonate at the same frequency (one is adjustable) with their flat plates separated by a quarter wavelength. The current in cavity one is out of phase with cavity two by 90 degrees. [6]What do you think of this paper that suggests such EM propulsion may be possible using light speed delayed information of the near field? http://arxiv.org/abs/1502.06288...I had similar ideas nearly 20 years ago! The conclusion I came to back then was that there is always the "hidden momentum" creating an equal and opposite force. If you use a 1/4-wave coupling of the electric field and the charge, you will have an opposite force between the magnetic field and the current, and in the end you have a photon rocket resulting from the leakage inductance and capacitance....It will take me a while to read Dr. Pinheiro's paper. I usually agree with what he writes about, we've had correspondence in the past. I have not read this paper. Thank you....Todd
... You stated the EM drive may have trouble optimizing this imbalance in phase. What do you think of having two separate cavities near each other but out of phase such that the top cavity appears to be destructively interfering with the bottom while the bottom cavity appears to be constructively interfering with the top? See figure "EM propulse proposal.png" . Is this the same as your proposed separation of the (top and bottom) cavity for the EM drive or different? In reference to http://emdrive.wiki/List_of_Suggested_Experiments 7. Separate resonance and attenuation chambers. Purpose: Proposed by WarpTech as a test of his theory.9. Measure the force on two cylindrical resonant wave guides (lowest transverse electric mode) tuned to resonate at the same frequency (one is adjustable) with their flat plates separated by a quarter wavelength. The current in cavity one is out of phase with cavity two by 90 degrees. [6]What do you think of this paper that suggests such EM propulsion may be possible using light speed delayed information of the near field? http://arxiv.org/abs/1502.06288...
Is there anything that can be gained from looking at Shawyer's superconducting frustum experiment? That has hardly been mentioned at all. This is his 2nd generation thruster (TheTraveller correct me if its not) that he claims is far more powerful and he has gone to a squared off frustum. Is this simply for ease of doing some of the math? Is it because working with superconductors is too difficult in a conical frustum? I could come up with a dozen more questions.
"Scientists have argued for more than a century about the momentum of light in materials," Leonhardt told Phys.org. "Is it Abraham's, is it Minkowski's? We discovered that momentum is not a fundamental quantity, but it is made in the interplay between light and matter, and it depends on the ability of the light to move the material. If the medium does not move, it is Minkowski's, and if it moves, Abraham's. This was not understood before."Read more at: http://phys.org/news/2015-06-physicists-pressure.html#jCp
The findings have both fundamental and practical significance. Fundamentally, the results help scientists gain a better understanding of the nature of light. While it has long been known that light carries both energy and momentum, and that the energy of a photon is quantified by its frequency f times Planck's constant h, the momentum of light has not been so easy to describe. Does the momentum increase or decrease as the refractive index of the medium increases? The results here suggest that the answer depends on whether or not the light can put the fluid into motion: if it can, its momentum decreases and it exerts Abraham's pushing force; otherwise, its momentum increases and it exerts Minkowski's pulling force.
I have been following and looked up the term for evanescent waves and it appears to be the same as the near field.
Hello all. I have been following these threads for months but kept my silence, happy to watch the enthusiastic sharing of ideas brought forward. I just wanted to add my voice to phaseshift's post.Quote from: phaseshift on 06/02/2015 08:45 pmIs there anything that can be gained from looking at Shawyer's superconducting frustum experiment? That has hardly been mentioned at all. This is his 2nd generation thruster (TheTraveller correct me if its not) that he claims is far more powerful and he has gone to a squared off frustum. Is this simply for ease of doing some of the math? Is it because working with superconductors is too difficult in a conical frustum? I could come up with a dozen more questions.My background is in electrical engineering so I have been mainly focused on the efforts of the experimenters in this thread. To me the Shawyer v2 superconducting frustum is vital in making or breaking this device. It's success would help settle concerns arising regarding experimental artifacts as well as help prove a direct relationship between the Q-factor and thrust. It would also help break some of the circular conversation by reframing the discussion from IF to HOW (and would help direct a LOT of the scientific community's attention to this phenomenon).I had some questions:What detective work has been done on this device? Any experimental data from Shawyer or others?At least, has Shawyer said unequivocally that it works and is in line with his expected results?How feasible is it for us to deduct it's construction and replicate one? I am assuming it is an order of magnitude more complicated to build.The lack of results about this device is driving me crazy I assume that is intentional and at the very least we will hear a result maybe this year but maybe we can do something in between.
Quote from: dustinthewind on 06/03/2015 03:11 am I have been following and looked up the term for evanescent waves and it appears to be the same as the near field. Evanescent Fields Inside a Cut-off Waveguide as Near Fieldshttp://file.scirp.org/Html/34978.html"Usually, electromagnetic evanescent waves are some kinds of near fields (e.g., the ones in total internal reflec-tion). However, it looks as if the evanescent waves inside a cut-off waveguide had nothing to do with any near field. In this paper, by means of another way of looking at the guided waves, we will show that the evanescent fields inside a cut-off waveguide can be regarded as the near fields of an aerial array."
the near field propagates faster than light? I'm not sure I can bring myself to swallow that just yet.
Could be of interest:Conical waves producing longitudinal power flowshttp://rd.springer.com/article/10.1134%2F1.1307823"A conical electromagnetic wave converging to its axis is studied theoretically. It is demonstratedthat the wave produces an intense self-accelerating flow of energy (momentum)."
June 2, 2015 new buzzkill paper: http://arxiv.org/pdf/1506.00494.pdf FYI only"IV. CONCLUSIONSThe fact that the EM drive, or any other reactionless drive that has a thrust-to-powerratio greater than a photon-emitting device, would enable a perpetual motion machine of thefirst kind suggests that such a device cannot exist. This objection is not as easily explainedaway as the conservation of momentum objection to a reactionless drive, because this resultsuggests than a source of free and infinite energy is already at our technological disposal.Any conditions placed on the operation of the hypothetical “space drive” in order to makeis consistent with the First Law would also render it useless as a propulsion device; if it canwork as a propulsion device, it can also function as a perpetual motion machine of the firstkind. Further investment into investigating this concept should be tempered by the historyof attempts to realize perpetual motion machines."One does wonder if much of the buzzkill is a thinly disguised funding suggestion
Quote from: rfmwguy on 06/03/2015 11:56 amJune 2, 2015 new buzzkill paper: http://arxiv.org/pdf/1506.00494.pdf FYI only"IV. CONCLUSIONSThe fact that the EM drive, or any other reactionless drive that has a thrust-to-powerratio greater than a photon-emitting device, would enable a perpetual motion machine of thefirst kind suggests that such a device cannot exist. This objection is not as easily explainedaway as the conservation of momentum objection to a reactionless drive, because this resultsuggests than a source of free and infinite energy is already at our technological disposal.Any conditions placed on the operation of the hypothetical “space drive” in order to makeis consistent with the First Law would also render it useless as a propulsion device; if it canwork as a propulsion device, it can also function as a perpetual motion machine of the firstkind. Further investment into investigating this concept should be tempered by the historyof attempts to realize perpetual motion machines."One does wonder if much of the buzzkill is a thinly disguised funding suggestion It looks like a repetition of all the arguments already published by @frobnicat's in his discussions in these NSF EM Drive threads, but fails to give any credit to @frobnicat.