Talk:EmDrive/Archive 2

This is an archive of past discussions about EmDrive. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.

Archive 1

Archive 2

Archive 3

Archive 4

Archive 5

An "open system" from which no energy or matter leaves or enters

The article Lead says "no detectable energy leaves the device" but a later section explains that momentum is still conserved because relativity makes this an "open system". The wikilink to open system is about thermodynamics and makes no mention of relativity; also the defining characteristic of an open system is that energy and matter enter and exit the system. So, we have a terminology problem. Also, this isn't a credible answer to the momentum conservation objection. A rocket looks like an open system, but when one includes the propellent in the analysis, momentum is conserved. Spiel496 (talk) 15:18, 24 July 2014 (UTC)

True but if one includes the propellant, the system is no longer open. The rocket alone is an open system in which momentum is not conserved; the propellant is an open system in which momentum is not conserved. But the combination of the two is a closed system in which momentum is absolutely conserved. -- Derek Ross | Talk 19:16, 24 July 2014 (UTC)

Yes, I agree. In the case of a rocket, if one includes everything, then momentum is conserved. Understandably, the first criticism levied at the EmDrive idea is that it looks like momentum would not be conserved. So if Shawyer has a rebuttal to that, it makes sense to include it. But contradicting the first paragraph by saying "it's an open system" doesn't help anybody understand. Spiel496 (talk) 20:36, 24 July 2014 (UTC)

Under normal circumstances such as the rocket the momentum exchange is accomplished by changing the velocity of the propellant and of the rocket and it's not too difficult to visualise what's going on and to see how the momentum is conserved. In the case of the EmDrive it's more difficult to visualise because (as far as I can see and of course I may have misunderstood) the resonator changes its velocity but the photons in the resonator do not. Instead they change their mass (or to be more accurate their energy), so the system is rather different from that of a rocket but it is still possible to construct an equation in which momentum is conserved because the resonator's momentum (which is mv) is increased by as much as the photons' momentum (which is E/c since photons have no rest mass) is reduced even though no photons actually leave the resonator: their energy just drops to zero at which point they no longer exist. That's my understanding anyway but I'm no waveguide expert. -- Derek Ross | Talk 04:33, 25 July 2014 (UTC)

Speaking about the theoretical explanations. I am under the impression that Shawyer tries to explain the net thrust obtained in lab in term of classical electromagnetism, and then he adds bits of special relativity to fix the issues logically raised about conservation of momentum and energy, sometimes using weird wording for scientists, that does not help. The problem is, and I tend to agree with that, no net force should be possible if only Maxwell's equations and special relativity are the basis of the theoretical explanation. Chinese's maths also involve classical electromagnetism and thus have the same problem. When they show the energy and the momentum are separately conserved and correspond to Newton's second law, for example in the equation (8) of their fourth paper, a non-zero average thrust is not compatible with their explanation:

{\frac {\partial }{\partial t}}\int _{V}(\mathbf {g} _{f})\mathrm {d} V=\oint _{S}\mathbf {n} \cdot \mathbf {T} \mathrm {d} S

In this equation they correctly identify the thrust with the right-hand side of the equation, but the time average of the left hand side is zero, since

\mathbf {g} _{f}

is a periodic function of time. But should the actual theory be incomplete, does not mean the EmDrive must be thrown out with the bathwater. That's why physicists like Fernando Minotti addressed those issue with clean equations. He thinks for example that when the Chinese numerically evaluated the right-hand side of the equation above, the precise cancellations that should occur in an exact treatment did not happen, and a spurious residue of the order of magnitude of the measured forces may have appeared, giving a wrong idea of a classical explanation. He proposed a better way to handle the momentum and energy conservation, to be verified. That what is needed: more theoretical work providing verifiable predictions in lab, which will show falsifiability of the theories. A very interesting behavior predicted by Minotti is thrust reversal at some resonant frequencies (thrust vector in the direction from the big end toward the small end plate). Tokamac (talk) 09:49, 26 July 2014 (UTC)

I hesitate to be critical of Tokamac and Derek because you're doing your best to answer my concerns, and I realize it isn't your job to defend this technology. However, it seems to me that none of us is able to understand Shawyer's analysis fully enough to explain it to another person. The best one can do is to repeat his equations and terminology, so that other readers can also fail to follow the logic. I'm not convinced that is preferable to just providing a link to Shawyer's paper.

Regarding the conservation of momentum: the nice thing about this law is that it lets you skip all the intervening analysis and ask "did the momentum change?". I don't need to understand all the thrust formulas. If the entire system changes momentum, then momentum was not conserved. If there's some question about the momentum of the electromagnetic radiation inside the cavity, fine; wait until the EmDrive has been shut off and ask the equivalent question: If the center of mass has changed, i.e. the system moved to a new location, then momentum was not conserved. Spiel496 (talk) 18:16, 26 July 2014 (UTC)

We can say the same thing of Woodward's Mach Effect Thruster and Alcubierre's warp drive. They both violate conservation of momentum if you look at them without taking the physics involved into account. But if so they don't violate general relativity. Woodward effect relies on plain GR including Sciama's work over Mach's Principle, with momentum exchange between the local mass and the chiefly distant matter in the universe through a Wheeler–Feynman type field. Alcubierre drive relies on warp drive physics, which is standard GR with a negative energy source and thus is a reactionless drive as first noted by Lobo and Visser in 2004. The work of Lobo and Visser is the third most important work in warp drive physics after the works of Miguel Alcubierre in 1994 and José Natário in 2002. For resonant EM cavities, the scalar-tensor theory of Mbelek and Lachièze-Rey (of the Brans-Dicke type), cited by Minotti, behaves also as standard GR with a negative energy source. There is no violation of conservation of momentum in those works (theoretically speaking; if they are physically at work is another story).

But I agree with you that if Shawyer is wrong and say, Minotti is right, that Shawyer's theoretical explanations take currently too much place in the article. Tokamac (talk) 21:42, 26 July 2014 (UTC)

Spiel, I take no position on whether Shawyer's analysis is right or wrong. As you say, none of us is able to understand Shawyer's analysis fully because of our lack of expertise in the area. However, we all know that the system as a whole must obey conservation of energy and momentum at all times. The difficulty for me lies in identifying what the system actually comprises. If we could do that we could then sum up the component momenta to see what is really going on. Unfortunately I do not believe that even Shawyer himself understands what the full system is and what is going on with momentum at the most detailed level. So all we can do is describe his analysis fairly and to the best of our understanding and point out the problems with it. We have to leave it to our readers to realise just how speculative this is. I hope that our current article describes the controversy well enough to do that. -- Derek Ross | Talk 22:22, 26 July 2014 (UTC)

3kN is not equivalent to 3 tonnes (assuming Earth)

"would allow static specific thrust of about 3 kN/kW, that is 3 tonnes of thrust per kilowatt of input power" — Preceding unsigned comment added by 199.64.72.252 (talk) 18:04, 1 August 2014 (UTC)

Corrected. The source stated 30 kN, not 3 kN. Tokamac (talk) 19:52, 1 August 2014 (UTC)

Misleading analysis

The article states:

Should the EmDrive produce a real thrust, various conjectures have been made to explain the underlying physics. Shawyer claims the thrust would be caused by radiation pressure imbalance due to group velocities of electromagnetic waves within the framework of special relativity. Dr. Yang from NWPU predicts a resulting net force using classical electromagnetism. A more complete theory has been proposed in 2013 by Argentine physicist Fernando Minotti from CONICET, who explains the alleged forces on asymmetric electromagnetic resonant cavities by a particular class of scalar-tensor theory of the Brans–Dicke type...

This makes the attempts to explain this (probably bogus) device sound much more credible than they are - at least to layfolk. Saying Minotti's theory is "more complete" than Yang's is silly, because it's completely different from an attempt to explain the EmDrive using classical electromagnetism! A Brans-Dicke theory is a theory - for which there's not a shred of evidence - saying that electromagnetism and gravity interact in a nontrivial way. If you could explain the drive using classical electromagnetism you wouldn't need to explain it using the vastly more speculative Brans-Dicke theory.

So, I'm going to say "alternative" instead of "more complete".

Also, the article neglected to mention that the 2014 NASA experiments claim to detect a force about one thousandth as big as the Chinese claimed. This is what we'd expect from experimental errors: the harder you look, the smaller they get. I'll fix this.

John Baez (talk) 08:20, 2 August 2014 (UTC)

You forgot to point out that the input power used at Eagleworks was 17 watts, while the Chinese magnetron provided 2500 W, and that any nonlinear effect should be accounted for before stating the above. Please take note of the Chinese diagram showing the evolution of thrust generated as a function of input power, from 300 W to 2500 W. After knowing this, you can't compare the force produced by Chinese high power test with the force produced in NASA low power tests, before NASA high power tests are undertaken in the coming months. For this reason the statement "a force about one thousandth of that claimed by the Chinese" in the beginning of the wikipedia article, which states about half these facts, is misleading because not NPOV. Tokamac (talk) 18:23, 2 August 2014 (UTC)

I'm not at all sure that dropping ALL descriptions of possible theories -- https://en.wikipedia.org/w/index.php?title=EmDrive&diff=619592982&oldid=619592388 is helpful to the article. (I deleted an un-cited speculative paragraph that tried to fill the gap). The article, by omission, now implies that there are NO attempts at an explanation, rather than that there ARE attempts, mostly by the inventors, but that they are disputed. In any case, the current tests are only about the results, with no actual explanation, so theory doesn't belong there. Alanf777 (talk) 02:37, 3 August 2014 (UTC)

The only current paragraph on theory is in the lead (or in the criticisms). But the information in the lead should be a summary of what's in the body of the article. Maybe put that paragraph in a short theory section, with an even shorter summary in the lead. Alanf777 (talk) 02:41, 3 August 2014 (UTC)

Links to More Info (Cannae & EmDrive)

Some links:

... hope this helps! Radical Mallard (talk) 13:03, 3 August 2014 (UTC)

Thank you. That does help.- Mr X 15:21, 3 August 2014 (UTC)

Criticism section: Neutral point of view, due weight and original research

I have tagged this section as it seems WP:UNDUE given the relative treatment of the subject in the sources. I am going to try to copy edit the section to remove some of the WP:OR/WP:SYNTH. Please let me know if anyone objects to any specific edit so that we can work toward an accurate summary of the sources.- Mr X 14:50, 3 August 2014 (UTC)

The entire 'Experimental errors, evaporation' section is someone's unsourced analysis of a primary source which is strictly forbidden according to WP:OR.- Mr X 15:16, 3 August 2014 (UTC)

Experimental errors, evaporation

Possible effects of moisture evaporation, or evaporation of the cavity materials have to be ruled out. While EmDrive has been proposed to work in vacuum, both NASA and Chinese experiments work in atmosphere, at ambient atmospheric pressure, though NASA experiments were done both on the bench and "within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure".[26] No comparison of mass and control for loss of mass due to evaporation has been done in the experiments. A slight evaporation of order of micrograms per second (in the case of NASA experiment) due to heating of inside walls of the cavity might cause experimental errors larger than the observed effect. The larger previous claimed result of a force of 720 mN, could be explained by a much higher degree of evaporation, of hundreds of miligrams per second, possibly due to moisture, but other experimental errors need to be ruled out first.

source

And now it seems that Ashenai has reverted all of my edits. I await their detailed defence of this content (and in the section below) that violates several of our policies.- Mr X 16:20, 3 August 2014 (UTC)

I'm afraid I feel almost all of your edits were unwarranted and seemed to have a very noticeable tilt towards making the drive's operation seem more plausible. I do agree with you that a large section in the Violation of Conservation of Momentum heading was OR/SYNTH (and also the Evaporation section), so I kept those parts removed as per your edit. I reverted the rest. Please establish a consensus before further contentious edits of this nature! --Ashenai (talk) 16:18, 3 August 2014 (UTC)

Thank you for joining the conversation. The section 'Violation of conservation of momentum' is entire;y original research. In other words, it's some editors analysis of a primary source. WP:OR does not allow this.

No, the 'Violation of conservation of momentum' section simply restates the (sourced) criticisms in the second paragraph of the article. --Ashenai (talk) 16:47, 3 August 2014 (UTC)

Claiming that a non-attributed source said "it's a load of bloody rubbish." is entirely WP:UNDUE as if an editor cherry-picked a single to support their personal belief that the EmDrive is, well, rubbish. This misleads our readers and is sensationalistic.- Mr X 16:26, 3 August 2014 (UTC)

I agree, that did read like a pointless, contentless cheap shot. I removed it, thanks. --Ashenai (talk) 16:37, 3 August 2014 (UTC)

Since Ashenai restored the potential WP:BLP content and WP:SYNTH (see below), I would like to also ask what their argument is for retaining content that clearly violates our policies. Perhaps I'm missing something.- Mr X 16:33, 3 August 2014 (UTC)

As I've stated in my response to the section below, I do not currently see WP:BLP and WP:SYNTH issues in the article. --Ashenai (talk) 16:47, 3 August 2014 (UTC)

Skeptic Weighs In

From the comments section of http://theness.com/neurologicablog/index.php/nasa-tests-em-drive/:

"# Gborron 02 Aug 2014 at 10:01 am

I just registered because this thing is driving me nuts, mostly the boundless lack skepticism I see everywhere (or worse yet, the amount of flak skeptic get for “being negative assholes”).

The amount of disinformation on the web is also getting out of hand. By now most headlines refer to the machine as “fuel-less engine” instead of propellant-less, casually “deduce” that the effect is because of quantum physics, the three questionable tests by the same Chinese researchers are always cited as “three independent research groups” and any kind of skepticism is generally dismissed by saying “But these are NASA researchers you are criticizing! Are you telling me you are smarter than people working for NASA?”

Seriously, I have no problem with the test results themselves. If they are correct, hooray, if not then the scientific method will figure out where they made a mistake. The way the news media and the Average Joe gobble it all up without even a hint of critical thought on the other hand just gets under my skin…"

...let me add to this persons remarks that people also keep confusing the Cannae Drive and the EmDrive and vice-versa... ---Radical Mallard (talk) 22:32, 3 August 2014 (UTC)

While I don't disagree with what you wrote, please be aware that talk pages are for discussing edits to the article, not for discussing the subject itself. Articles are built from whatever reliable sources exist as opposed to editors' personal knowledge. Verifiability is one of our foundational principles.- Mr X 22:52, 3 August 2014 (UTC)

Original research

The issues template asserts that the article may contain original research. I feel I now understand (although I do not agree with) the assertion of BLP violation, so let's look at this one. Where do you feel original research still exists in the article? --Ashenai (talk) 17:56, 3 August 2014 (UTC)

"New Scientist has drawn great criticism from the scientific community due to this uncritical treatment of EmDrive in its article." The phrase "scientific community" is found nowhere in the source. This violates WP:OR.- Mr X 23:04, 3 August 2014 (UTC)
First paragraph, 'Shawyer's New Scientist article' section: "You can use high school physics to find the correct angles and reach the conclusion that momentum is conserved and the drive can't work as postulated." Technically, this is in the self-published paper, but as presented, it makes the statement in Wikipedia's voice and serves to instruct the reader (there is a guideline that proscribes doing this, but I can't remember the name of it). It's also rhetorical.- Mr X 23:12, 3 August 2014 (UTC)

Self-published sources

WP:SPS says:

Never use self-published sources as third-party sources about living people, even if the author is an expert, well-known professional researcher, or writer.

Costella's self-published paper should be excluded then, especially given its WP:BLP implications ("Why Shawyer’s ‘electromagnetic relativity drive’ is a fraud"). GregorB (talk) 15:31, 3 August 2014 (UTC)

I agree. I've removed the unpublished criticism and the attempted fraud claim. Note that the paper written by Shawyer did not mention Costella. Perhaps some of this content can be salvaged and reintroduced, but we must be careful not to use WP:SYNTH to connect facts together and lead readers to a conclusion not made in the sources.- Mr X 16:15, 3 August 2014 (UTC)

OK. Costella's views can still be reintroduced as long as there are properly sourced. GregorB (talk) 16:21, 3 August 2014 (UTC)

More information Content removed as WP:BLP violation and WP:SYNTH. ...

Content removed as WP:BLP violation and WP:SYNTH.

Shawyer's New Scientist article

Shawyer's article in the New Scientist was indeed almost immediately challenged^[1] by Dr. John P. Costella, a theoretical physicist and electrical engineer who works for the Australian Department of Defence, whose Ph.D. is in relativistic electrodynamics, the field of physics that Shawyer relies on to support his theory. According to Costella, the angles of the force vectors are calculated incorrectly. You can use high school physics to find the correct angles and reach the conclusion that momentum is conserved and the drive can't work as postulated. He says that the rest of of the paper has theory that is correct, but which doesn't demonstrate anything about how the drive works.

Shawyer says that Dr. Costella didn't disprove his derivation of the static thrust equation (related to the law of conservation of momentum) nor the dynamic thrust equation (related to the law of conservation of energy), and didn't comment about thrusts measured in the experiments either. According to Shawyer, what Dr. Costella criticized as being "a fraud" in Shawyer's founding theoretical paper was some vectors pointing the wrong direction in a diagram of Shawyer's theoretical paper by then (version 9.3, fig. 2.4) still available on New Scientist web site:^[2]

“

Look at the arrows that Shawyer labels Fs1 and Fs2 on his Figure 2.4. These are supposed to be the forces that the particle imparts to the wall of the conical part of his contraption. But hang on a minute! When a particle bounces elastically off a wall, doesn't the wall feel a force that is perpendicular to the wall? Of course it does: if you remember your high school physics, you subtract the initial momentum vector from the final momentum vector, and the resultant force points into the wall. (OK, it's actually called the impulse, not the force, but it's effectively the same thing for what we're talking about here).

Now look back at Shawyer's Figure 2.4. He has Fs1 and Fs2 pointing perpendicular to the axial direction, not perpendicular to the cone's walls. His arrows are wrong. This is the fundamental blunder that renders Shawyer's paper meaningless. There is no 'drive'. [...] Shawyer's 'electromagnetic relativity drive' is a fraud.

”

— Dr. John Costella, Why Shawyer's 'electromagnetic relativity drive' is a fraud (in reference to version 9.3 of Shawyer's theory paper).^[1]

Shawyer has since published an updated theory paper (version 9.4) where the diagram criticized by Costella is simply omitted.^[3]

References

[1]
Costella, John P. (2006). "Why Shawyer's 'electromagnetic relativity drive' is a fraud" (PDF). John Costella’s home page.
[2]
[3]
Shawyer, Roger (March 2007). "A Theory of Microwave Propulsion for Spacecraft (Theory paper v.9.4)" (PDF). SPR Ltd.

Close

I do not see how Costella's paper is problematic: it is not a source about Shawyer at all, but about Shawyer's work. WP:BLP does not apply. --Ashenai (talk) 16:48, 3 August 2014 (UTC)

Giving so much weight to an unpublished paper is itself problematic. I believe that WP:BLPSPS applies. Throughout this article, there seems to be a great deal of original research in a fairly transparent attempt to discredit the subject. For example, discussing reasons why the concept violates various physical laws when such content does not appear in sources is not allowed. Also, GregorB gave a very clear example of a BLP violation.

Yes, you already quoted WP:BLPSPS, and I still do not understand how on earth it would apply. All the criticism in the article is regarding the EmDrive, not Shawyer. WP:BLPSPS only applies to claims made about a person. The EmDrive is not a person. I don't see GregorB's example as a BLP issue either, the quote was talking about the EmDrive. I am truly baffled as to what you mean. --Ashenai (talk) 17:26, 3 August 2014 (UTC)

Look at the title of Costella's paper: "Why Shawyer's 'electromagnetic relativity drive' is a fraud". Not merely "bogus", but a "fraud", i.e. a "deception deliberately practiced in order to secure unfair or unlawful gain." That's a fairly clear WP:BLP issue and is precisely what WP:SPS warns against. GregorB (talk) 17:37, 3 August 2014 (UTC)

If it said "Why Shawyer is a fraud" I'd be right on board, but as is I think this is definitely reaching. That said, I don't pretend to be an expert on Wikipolicy, and I'd be amenable to asking WP:BLPN for advice. --Ashenai (talk) 17:52, 3 August 2014 (UTC)

I do think we should take that particular issue to WP:BLPN for advice. I'm also concerned that we have used Costella's unpublished paper in four citations. I think we need to either find supporting secondary sources, or remove some, or possibly all, of the material. This may be something that WP:NPOVN can help with.- Mr X 17:59, 3 August 2014 (UTC)

I hope that we can get other editors involved to review and copy edit this article so that it conforms to our policies. If not, WP:ORN and possibly WP:BLPN may be able to offer help.- Mr X 17:11, 3 August 2014 (UTC)

I have raised the Costella concern at WP:BLPN here.- Mr X 18:09, 3 August 2014 (UTC)

Alrighty, I responded with my own thoughts. Off to bed now, hopefully we'll get more people looking at this article soon (and not just from a BLP point of view.) --Ashenai (talk) 18:20, 3 August 2014 (UTC)

I have also asked for opinions about Costella's self-published paper at RSN.- Mr X 20:18, 3 August 2014 (UTC)

Costella

While we wait for more input on whether or not Costella's blog and unpublished paper are reliable sources, I would like to point out a few serious concerns about using him as a source at all. Currently 23.7% of the article is devoted to Costella's self-published criticism. This is extraordinarily unbalanced for a reliable source, and much more so for an unreliable source.

A few notes:

No reliable secondary source has published Costella's paper, although Wired magazine briefly commented on it here.
Costella seems to be active on the internet as a debunker/critic. See his his analysis of the Zapruder film, questioning its authenticity, his analysis of Climategate and his criticism of the NTSB.
Costella claims that the EmDrive is a perpetual motion machine, which seems odd since, the EmDrive clearly relies on energy being put into the system.- Mr X 14:20, 4 August 2014 (UTC)

On the 'perpetual motion' assertion—that's just fundamental physics. Any theoretical framework that allows violation of conservation of momentum (like the EmDrive) also permits the creation of perpetual motion machines of the first kind.

Worse still, any theoretical device that violates the law of conservation of momentum actually requires that the laws of physics – not just the physical conditions, but the underlying physical laws themselves – vary between different points in space. (This is a consequence of Noether's theorem, which is so astonishingly powerful because the mathematics apply no matter what those physical laws are: Newtonian or relativistic, flat or curved space, classical fields or quantum particles, even something completely different and as-yet-undiscovered.) TenOfAllTrades(talk) 15:56, 4 August 2014 (UTC)

We don't call a source reliable because we personally think what it says is true. This sort of criticism need to be sourced more reliably to be included. This is giving Costella (as a specific source of those objections) wildly undue prominence. (If another self-published blog from a random academic says Costella is wrong, do we add that? How many wrongs make a right in this case?) And whether or not this theoretical device would imply that perpetual motion machines were also possible, it is needlessly misleading to say this specific proposal is being presented as a "perpetual motion device". It's not and saying so confuses the issues. __ E L A Q U E A T E 16:15, 4 August 2014 (UTC)

Of course, we use self-published pages from Shawyer's (or his company's) own websites fairly extensively, including for the claim that the EmDrive doesn't violate conservation of momentum. WP:PARITY applies. TenOfAllTrades(talk) 16:56, 4 August 2014 (UTC)

We should not be using self-published sources for much of anything in this article. Two wrongs don't make a right.- Mr X 17:24, 4 August 2014 (UTC)

John Costella seems to generally promote conspiracy theories rejected by the scientific and academic mainstream and, despite an academic credential, does not seem to be an established expert otherwise. This seems to be a case of "My enemy's enemy is my friend." Just because some people have understandable cause to question this theory, is no reason to use an analysis from a source with no reputation for fact-checking and accuracy as a source in a Wikipedia article. I think it's somewhat embarrassing to elevate this voice above others. This is not the "verifiable and reliable criticism" described in WP:PARITY nor does it seem to be used with the care described in the sourcing and attribution section of that guidance. In the case of obscure fringe theories, secondary sources that describe the theories should be carefully vetted for reliability. Basically, if you consider something a Bigfoot theory, you shouldn't source the lion's share of criticism to someone whose main career is giving credence to unicorns.__ E L A Q U E A T E 18:18, 4 August 2014 (UTC)

Group velocity

It doesn't seem appropriate to talk about group velocity in this context. According to the article on that concept, it has meaning only when the radiation is modulated (pulsed). The modulation envelope moves at the group velocity. The EmDrive is driven (I think) with a constant amplitude, constant frequency; there is no group. Elsewhere in this article, the term "phase velocity" is used. If "group velocity" was intended to be synonym, that was a mistake, and we should replace it with "phase velocity" throughout the article. Phase velocity does make sense in this context, and in waveguides it can take on values other than c. Spiel496 (talk) 19:06, 9 July 2014 (UTC)

Okay, now the article uses the bogus term "group velocity" throughout. The group velocity terminology originates from Shawyer's own paper. We can be NPOV without letting the fringe scientist dictate our terminology. I don't know what he means by "group velocity" but he doesn't mean dω/dk. We need to be clear about what v_g is, or just omit the math altogether. Spiel496 (talk) 01:10, 10 July 2014 (UTC)

No group velocity? Well, you seems mistaken by what you read in the article Group velocity.

Microwaves in a waveguide have a wavelength:

\lambda _{g}={\frac {\lambda _{0}}{\left[1-(\lambda _{0}/2a)^{2}\right]^{1/2}}}

where a is the width of the waveguide. This shows a wider waveguide makes the wavelength smaller.

The phase velocity u in a waveguide is given by:

u=\lambda _{g}f={\frac {c}{\left[1-(\lambda _{0}/2a)^{2}\right]^{1/2}}}

whereas the group velocity v in a waveguide is:

v={\frac {df}{d(1/\lambda _{g})}}=c\left[1-{\frac {\lambda _{0}}{2a}}^{2}\right]^{1/2}

Phase velocity can be higher than the speed of light but carry no information; whereas group velocity is always lower than the speed of light and conveys power. See this reference on Wikibooks for example. It is indeed group velocity which contributes to the radiation pressure. You can check this fact in any microwave engineering text book, in which you can read that the group velocity (sometimes referred to as the guide velocity) carries the energy and momentum of the electromagnetic waves along a waveguide. The equations for group velocity are well defined and show that the velocity decreases as the guide dimensions decrease until cut off where propagation stops. The equations are very non linear but a practical example of their effectiveness is the grid dimensions on the window screen of a microwave oven.

As for the Chinese papers they have been peer-reviewed (three times) and also use group velocity:

"For electromagnetic wave, energy of quantum is transferred at the group velocity v_g, its momentum is p = m v g = h f v_g / c². When the electromagnetic wave in the waveguide is transmitting in travelling-wave state, v_g= c λ_o / λ_g √µ_re_r, where µ_r and e_r are the transmission medium relative permeability and relative permittivity respectively, the wavelength of the electromagnetic wave within the waveguide is λ_g = λ_o / √µ_re_r - (λ_o / λ_c)², λ_c is the waveguide cut-off wavelength."

I don't think you can treat Dr. Yang and her team, as well as the referees of the Journal of Astronautics, the Journal of Northwestern Polytechnical University and Acta Physica Sinica of "fringe scientists".

Tokamac (talk) 12:20, 10 July 2014 (UTC)

Alright, you've convinced me; group velocity is the quantity related to energy transfer. I appreciate the time you put into your response. It still strikes me as counter-intuitive that group velocity matters in a situation where there are are not groups (pulses) in the waveform, but I can't argue with waveguide theory. Spiel496 (talk) 17:32, 10 July 2014 (UTC)

While what has been said may be true, it opens up another question, as the narrowing of the waveguide alters the the group velocity, it will also change the impedance thus there should be some reflection and there will be a component of the radiation pressure of that in the axial direction. Nowhere does this seem to be addressed. Ultimately, if conservation of momentum is to be preserved, it must exactly cancel the difference between the end-plate forces. Thinking of the operation in terms of photons, some must hit the tapering sidewalls which means they would no longer be moving axially and their reflection will again result in a reaction force which is not considered. While it is possible that the design might conserve energy (the power input being converted to kinetic energy of the payload), the author claims that it is not a reactionless drive but never explains where the balancing momentum change occurs. George Dishman (talk) 20:54, 4 August 2014 (UTC)

criticism section

New sources

Diagram?

Tinkerer?

Minotti's paper

Colin Johnston

Armagh Planetarium’s Science Communicator has this to say about the emDrive: http://www.armaghplanet.com/blog/no-nasa-has-not-verified-an-impossible-space-drive.html

Despite the tiny measured thrusts, this is a startling announcement. The NASA researchers seem to have found a flaw in a central dogma of science, opening the possibility of a wonderful new era of interplanetary travel. This seems to be news worthy of the attention it is receiving. Sadly it is not as simple as that. In fact I am rather dubious and here are my reasons to be sceptical.

The test was not conducted in a vacuum, rather with the vacuum chamber “door closed but at ambient atmospheric pressure”. This was because the capacitors used in the test devices could not survive vacuum conditions, I presume this was a last minute discovery. Not performing the tests in a vacuum is a serious blow to the experiment’s credibility. The slightest air current could interfere with so slight a measurement. (UPDATE: I originally suggested that the electrical current fed to the drive device was generating heat which caused convectional air currents, moving the device on its pendulum. The paper seems to indicate thrust occurs instantly when the power is applied and drops immediately to zero when the power is cut off. That seems to suggest the device is not effected by self-generated convectional currents.)

The research team also tested a Cannae device designed to accept electrical power but not to function as thrust-generating unit. To make it inoperable it was manufactured without the slots its inventor believes to be essential for its operation.Yet the team measured a force generated from this device too! This non-functional device was not an experimental control, instead the researchers also tested an RF load with no functioning components -a resistor, and measured zero thrust for that test. It is extremely odd that a device designed by its creator to be inoperable works just as well as “functional” devices.

The team suggest this is not actually reactionless propulsion (suggesting that they know how outrageous this would be) but rather momentum is being transferred “via the quantum vacuum virtual plasma”. This sounds profoundly impressive but also scarily like Star Trek-style technobabble. To the best of my knowledge quantum mechanics predicts that all space is permeated by “sea” of virtual particles but I have never seen this described as “plasma” before. Harold White, a team member, has, shall I say, form in presenting his research in a prematurely positive way.

Most damning in my opinion, is the reported “power to thrust ratio” of 5.3 micro-Newtons per watt. Say the device was not a closed cavity after all and instead just squirted out microwaves. As mentioned earlier, the microwave beam would actually act a rocket exhaust. You can calculate the power to thrust ratio of such a beam, it comes out as 0.33 nano-Newtons per watt . This very low efficiency is a consequence of physical law and is the best that can ever be achieved. Yet the NASA team claim to have observed an efficiency about 15 000 times greater! This is seems impossible.

Deserves inclusion.

jps (talk) 20:24, 6 August 2014 (UTC)

I don't think that a planetarium employee's blog post is worthy of inclusion in any form unless it is also cited by some reliable sources.- Mr X 00:04, 7 August 2014 (UTC)

His profession is to communicate science. As such, he is the best source I've seen on the subject so far. jps (talk) 04:46, 7 August 2014 (UTC)

I integrated the first two points made by the source into the article. I'm not sure the third and fourth points are worthy of inclusion: they sound more like a personal expression of disbelief than legitimate criticism. --Ashenai (talk) 11:39, 7 August 2014 (UTC)

With respect, I have removed your bold addition. Let's please wait until there are some expert criticisms published in reputable sources.- Mr X 14:49, 7 August 2014 (UTC)

With respect, I have reverted your removal per WP:PARITY and WP:FRINGE. If this is a notable fringe claim, we need to be willing to include the 3rd party commentary as it comes. This is as good as we can get. Your inarticulate rejection of the source is not convincing. jps (talk) 15:22, 7 August 2014 (UTC)

Agreed. We don't know what the Hell this thing is. And certainly the "fringe" speculation will become part of its history, whether its the Piltdown Man of space propulsion or not. Kortoso (talk) 16:29, 7 August 2014 (UTC)

Please follow WP:BRD and seek consensus. No, we do not need to include 3rd party commentary "as it comes", if it comes from unreliable sources such as blogs without editorial oversight or Google+ pages (yes, there really is such a citation on the article). WP:FRINGE is not a license to use questionable sources. "Anyone can create a personal web page or publish their own book, and also claim to be an expert in a certain field."... "Self-published material may sometimes be acceptable when its author is an established expert whose work in the relevant field has been published by reliable third-party publications. Colin Johnston does not seem to meet these criteria. From WP:PARITY: "Of course, for any viewpoint described in an article, only reliable sources should be used; Wikipedia's verifiability policy is not suspended simply because the topic is a fringe theory."- Mr X 16:33, 7 August 2014 (UTC)

I believe criticism that accurately represents the mainstream scientific position has a weight behind it that makes it appropriate to include in the article. I think these sources are acceptable, given that they're the best available. --Ashenai (talk) 16:49, 7 August 2014 (UTC)

RS doesn't necessarily mean not self published. As with all things, context is important, such as expertise etc: "Parity of sources may mean that certain fringe theories are only reliably and verifiably reported on, or criticized, in alternative venues from those that are typically considered reliable sources for scientific topics on Wikipedia". Second Quantization (talk) 17:24, 7 August 2014 (UTC)

Experts are experts no matter where their contributions are made. We merely need to verify what the experts say, which is pretty straightforward when it comes to GooglePlus or Blogs. When the personal page is that of a verifiable expert on the topic, we can treat that as though they've been interviewed. In fact, it's better than that because they've been able to present their own commentary without an editorial filter. No one is going to mistake that for a peer-reviewed reference, but right now the WP:REDFLAG revolutionary claims being made by EmDrive proponents are essentially ignored by the scientific community otherwise because they are either unwilling or unable to publish their work in Science or Nature or Physical Review Letters, for example, where breakthrough work is normally published when it is of high quality. If that doesn't occur, if publications are either self-published or published by low-impact, in-house, or fringe journals (as is the case for both the Eagleworks and the Chinese groups), the WP:PARITY playing field shifts to the discourse of expert commentary. This is the most fair we can be because high-quality journals will not publish refutations of low-quality work, and high-quality researchers won't bother publishing in low-quality journals. If we've truly found a notable fringe claim, then what we need to do is find independent evaluation of the claim and that comes from experts.... and those experts are under no obligation according to our sourcing rules to subject their critiques to shoddy peer review in low-quality journals. That's the rule for WP:FRINGE. That's always been the rule for WP:FRINGE. Note that independent evaluation should be paid close attention to when it is found as that is the best way to write WP:FRINGE articles. jps (talk) 19:21, 7 August 2014 (UTC)

Dielectric section

Pseudophysics

My removal of Category:Pseudophysics was reverted by QTxVi4bEMRbrNqOorWBV. As I tried to explain in my edit summary, we can't place pejorative categories on articles without impeccable sourcing. To do so violates WP:CAT which states "Categorization of articles must be verifiable." and "Categorization must also maintain a neutral point of view." Can anyone produce (reliable) sources that unambiguously places EmDrive in the pseudophysics (or pseudoscience) category?- Mr X 03:31, 5 August 2014 (UTC)

The only expert sources I am seeing that are not connected to the advocates clearly label it as having the properties of pseudophysics. Are there any independent sources that I'm missing which dispute this? jps (talk) 04:32, 5 August 2014 (UTC)

I'm not seeing the sources that claim most/many/all scientists label the EmDrive as pseudophysiscs or anything similar. Could you be specific and list them here so that we can discuss the appropriateness of this category? Thank you.- Mr X 11:49, 5 August 2014 (UTC)

Are there any sources which discuss what most/many/all scientists think regarding this subject at all? The relevant sources are those who are academic physicists commenting on this subject. jps (talk) 12:40, 5 August 2014 (UTC)

No, and that's kind of the point. We can't characterize this subject based on our own assumptions that this concept is pseudoscience. If someone can't produce sources (citations to published reliable sources, not a vague wave to "academic physicists"), then the category must be removed. Please let me know if you see anything in our policies or ARBPS that refutes that.- Mr X 13:07, 5 August 2014 (UTC)

We have plenty of sources which identify it as having the characteristics of pseudophysics. WP:ARBPS is not a content policy. This was just recently clarified by the arbitration committee. I'm not making a vague wave here. I'm saying that every single source written by an academic physicist demonstrates in one way or another that this subject involves pseudophysics. jps (talk) 13:13, 5 August 2014 (UTC)

Great! Let's just start with one. Please tell me which citation supports your assertions. (and I do realize that Arbcom does not mediate disputes, but the case does clarify that the verification policy must be followed.- Mr X 13:34, 5 August 2014 (UTC)

The New Scientist imbroglio is an excellent start. jps (talk) 13:35, 5 August 2014 (UTC)

That's also not very helpful. Where in the New Scientist article is the the declaration that scientist regard this idea as pseudoscience? Please be very specific.- Mr X 16:51, 5 August 2014 (UTC)

blink I'm not sure what you want. Jeremy Webb stated, "We should have made more explicit where it apparently contravenes the laws of nature and reported that several physicists declined to comment on the device because they thought it too contentious." However, we now have a number of physicists commenting including John Baez and Sean M. Carroll. jps (talk) 20:56, 5 August 2014 (UTC)

That's weak sourcing for categorizing this subject as pseudophysics. I'm going to disengage now as I have little tolerance for passive aggressiveness.- Mr X 23:21, 5 August 2014 (UTC)

Sean M. Carroll is a credentialed expert, but all I see from him is a tweet before he obviously had a chance to actually look at the paper. He's repeating that false meme about the control having a thrust result. Adding that makes Carroll look uninformed. I don't think a tweet should be taken as his most considered word on the subject, or we're reporting tabloid-style. The early Baez stuff looks like it's was based on an analysis of the abstract. I'd use that stuff with care, or we risk repeating early distracting mistakes on a Google+ home page and twitter as the final consensus opinion of the scintific community. This stuff should be sourced cleanly.__ E L A Q U E A T E 23:37, 5 August 2014 (UTC)

Actually, I think the quote that MrX just removed is the most telling. The issue Carroll takes is with the theorizing. The poor argumentation is a feature of pseudoscience. John Baez makes a similar point. I think that the sourcing is as good as we generally require for WP:FRINGE ideas -- namely that the experts who have commented are indicating it is such. jps (talk) 19:28, 6 August 2014 (UTC)

Pseudophysics generally involve non-falsifiable predictions or situations where people have been proven to falsify results to only appear to be science (water-fuel engines etc.). This seems to involve a specific completely falsifiable prediction where people are questioning the quality of specific tests, not that it's a claim about physics that can not be tested. I don't think anyone (even the strongest critics) has claimed that a good test is not possible here. The category for fringe physics is arguably fine, per the multiple meanings of Fringe science. It's an extraordinary hypothesis, but it is offered and being tested within the scientific method by non-pseudo scientists and physicists. It's Fringe science and a "controversy in science" but there's an argument that it's only potentially pseudoscience at this point.__ E L A Q U E A T E 15:51, 5 August 2014 (UTC)

Perpetual motion violates 1st or 2nd law of thermodynamics and can be characterised as pseudoscience. How about "Conservation of momentum" argument? In case there arises any contribution: Wikipedia:Fringe_theories/Noticeboard#EmDrive. Logos5557 (talk) 16:39, 5 August 2014 (UTC)

Again, original research is not allowed. Can you please point to a reliable source that claims that the EmDrive is a perpetual motion device or that it is based on the conservation of momentum? Please quote directly from a source. Note that the inventor specifically denies that the EmDrive violates the conservation of momentum principle.- Mr X 16:59, 5 August 2014 (UTC)

This hypothesis has nothing to do with perpetual motion. There is also no claim that this drive turns lead into gold or cures cancer or picks racehorses with 100% success. The armchair science is clouding actual issues out of view. We probably won't have a useful article until the hype and anti-hype dies down.__ E L A Q U E A T E 17:04, 5 August 2014 (UTC)

Come now, the hypothesis has at least something to do with perpetual motion inasmuch as the proponents are trying desperately to say that it is not perpetual motion. But we cannot rely just on the proponents for such an argument. Claims of being able to extract zero point energy are not exactly new, and are properly part of the larger perpetual motion family. Understanding of what zero point energy actually is shows that it cannot be a workaround from the Laws of Thermodynamics and, thus, the proponents who claim ability to harness it are essentially engaging in perpetual motion claims. jps (talk) 19:32, 6 August 2014 (UTC)

It has nothing to do with perpetual motion. (Your logic is that because people say it's not, then it must be? Really?) Even the critic you think is valuable says so: While I’m at it, can I also clarify some misconceptions about this technology: It is not designed to be a “free energy device” The main extraordinary part of this theory is that we can push against virtual particles with electromagnetic radiation. That's a wild enough claim by itself, but there's no claim to perpetual operation without energy input, or "harnessing" zero point energy. The theory has a lot to be skeptical about with adding claims it doesn't make.__ E L A Q U E A T E 04:42, 7 August 2014 (UTC)

(edit conflict)@Elaqueate: Yes, that is my view as well. This idea certainly challenges the boundaries of science, but to call it pseudoscience at this point is would require original research. It's very simple. We require reliable sources, and have yet to see any declaring that scientists regard the EmDrive as pseudoscience.- Mr X 16:51, 5 August 2014 (UTC)

I'm neither in favor nor against pseudoscience characterisation; also did not claim that emdrive had something to do with perpetual motion. I just tried to point out that, if it violates conservation of momentum, this can be a basis for pseudoscience categorisation. On the other hand, it seems that Costella had raised some strong arguments which were not refuted exactly/completely. Logos5557 (talk) 17:33, 5 August 2014 (UTC)

There's controversy and we should reflect competing theories and prevalent criticism as given in RS. (And Costella seems to be known for JFK conspiracy theories and work done to attack the scientific mainstream on climate change. There should be better sources for criticism than that, it's like using Ken Ham as a source in a scientific article.)__ E L A Q U E A T E 18:04, 5 August 2014 (UTC)

Well, of course, Logos. If it violates conservation of momentum it is pseudoscience. However in order to prove or disprove conservation of momentum, one needs to identify the entire system. A solar sail appears to violate the conservation of energy and of momentum principles, if one considers the sail and nothing else. It is only when one considers the sail plus its incident photons that one can show that no violation is taking place. In a similar fashion, the fact that the EMDrive appears to violate the conservation of momentum principle might mean that we are not considering the whole system. or it might mean that the experiments so far are in error. The latter is more likely but the former is not impossible. And so until someone can show which explanation of the apparent violation is correct, it would be premature to categorise the EMdrive as pseudoscience. -- Derek Ross | Talk 20:36, 5 August 2014 (UTC)

The best debunkers of pseudoscience are often those who support other pseudosciences. For example, the best debunking of geocentrism comes from Answers in Genesis. This doesn't mean that we take their points as gospel, only that when they are approaching a subject without their blinders on they can more easily see the pitfalls (having themselves fought against slings and arrows in other subjects and on other sides). jps (talk) 21:01, 5 August 2014 (UTC)

The best debunking of geocentrism does not come from Answers in Genesis. There is an assumption in your statement that have no blinders and I think many sources would disagree with your assessment. (More simply, they do not have a reputation for fact-checking and accuracy.) This is probably an off-topic topic.__ E L A Q U E A T E 21:12, 5 August 2014 (UTC)

Oookay.... yes, it's off-topic, but AiG's debunking of geocentrism is perhaps more thorough than any other that can be found because, frankly, most everyone else simply dismisses such charlatans out-of-hand while AiG considers other religious fundamentalists making outrageous claims to be threatening to their position as an outsider making outrageous claims. This is how Costella's letter could be endorsed by many mainstream physicists in spite of his documented lunacy vis-a-vis JFK assassination conspiracy theories and global warming denialism. Physicists don't care what your motivation is for explaining the correct answer -- only that you provide the correct answer. I've seen the same thing with astronomers who will quote Hugh Ross in defense against AiG. This is an old story but perhaps you're right that it is off topic. In any case, I don't think we need to delve into Costella too much. He has an oversized internet presence, and I would prefer we stick to Baez and Carroll's more recent critiques. jps (talk) 21:23, 5 August 2014 (UTC)

"..by John P. Costella, a theoretical physicist and electrical engineer who works for the Australian Department of Defence, whose Ph.D. is in relativistic electrodynamics, the field of physics that Shawyer relies on to support his theory". How does this -now removed- statement match to Costella's linkedin profile? It seems that the article was not well curated previously. Egan, on the other hand, whose letter was posted on Baez's blog, does not look more qualified than Costella. Logos5557 (talk) 00:16, 6 August 2014 (UTC)

Wow.- Mr X 00:58, 6 August 2014 (UTC)

The difference is, of course, that Egan was commenting on reporting while Costella was commenting on the claims themselves. Criticism of the reporting is relevant to this article as it was the New Scientist piece that established notability and is part of the reason that people have taken note in a WP:FRINGE way (though, I will point out, this subject is bordering on the non-notable and a case could be made for merging the lot of these claims into reactionless drive....). jps (talk) 13:45, 6 August 2014 (UTC)

The pitfall of this invention may be the assumption of radiation pressure's being one-directional only. That is, magnetron is supposed not to have a reaction force/pressure while producing microwaves. Otherwise, this "hypothesis" collapses onto itself. Let's assume that the sun is cut into half, and that half sphere can preserve its shape, and does not radiate photons from its flat surface. Does it move (as a reaction to the radiation pressure from half sphere surface) in the direction normal to the flat surface or not? Is Radiation_pressure#Radiation_pressure_by_emission the answer to this? All of these are OR, of course, and we need to wait some real physicists/engineers to take care of this matter. Logos5557 (talk) 01:33, 6 August 2014 (UTC)

You may be right. However as you say, your speculation is Original Research. If you wish it to be included in the article you will need to have it published by a Reliable Source. There is no point in discussing it on this talk page. -- Derek Ross | Talk 05:25, 6 August 2014 (UTC)

Shawyer's qualifications are also important. Does he have a degree in aerospace/aeronautical engineering, mechanical engineering, physics, or in other disciplines like electrical, electronic, computer engineering? Logos5557 (talk) 10:20, 6 August 2014 (UTC)

It seems that I had overlooked this statement in the lead: "The device uses a magnetron producing microwaves directed inside a specially shaped, fully enclosed tapering high Q resonant cavity whose area is greater at one end" which confirms this sketch. Now, this question arises; isn't the "radiation pressure imbalance" gained by (through area difference between the two ends/faces) the wider end having greater area, cancelled by the "radiation pressure imbalance" gained by the narrower end (having smaller area) by means of reflected waves/photons? All of these are OR, of course, let's wait. Logos5557 (talk) 15:50, 6 August 2014 (UTC)

Apart from the losses by reflected waves/photons which impart momentum to other faces, there seems a very basic flaw with the shape of the cavity. Despite his "oversize presence in internet", I guess Costella was able to discover the flaw in "radiation pressure" explanation, though being not so clear:

"This is the fundamental blunder that renders Shawyer’s paper meaningless. If you remember your high school physics, it is simple enough to draw a diagram to prove to yourself that, when a particle bounces off the wall of the cone, the increase in the particle’s momentum in the axial direction is exactly balanced by the impulse imparted to the cone in the opposite direction."

Since Shawyer updated his paper in reply to Costella's "article", we're not able to see the diagram in its initial version. However, still, the figure in page2 of his paper seems erroneous. Shawyer calls cone side face/wall as "waveguide", perhaps to "imply"/claim that cone side wall is "different" than end faces. However, when cone side wall(s) "guides" the wave/photon, it still will have a reaction force exerted by the wave/photon afterwards. And that reaction force will always be normal/perpendicular to the cone side surface, as sketched here. When that reaction force is decomposed into horizontal and vertical components (let's take horizontal as the direction perpendicular/normal to the end faces/walls), horizontal component of the reaction force exerted to the cone side wall(s) will add up to the reaction force exerted on narrower/smaller end face, and as a result there will practically be no "radiation pressure imbalance". No need to mention that vertical components of the force exerted on cone side wall(s) will cancel out, because of opposite directions. There is no difference between the resultant horizontal forces exerted on a fully enclosed conical cavity and a fully enclosed cylindrical cavity. The "effective" areas (i.e. end areas) perpendicular to the direction of "motion" are the same in each case. Perhaps Shawyer raised below argumentation in order to "prevent/refute" this way of thinking:

"We note that if the forces had been the mechanical result of a working fluid within the closed waveguide assembly, then the resultant force would merely introduce a mechanical strain in the waveguide walls. This would be the result of a closed system of waveguide and working fluid. In the present system the working fluid is replaced by an electromagnetic wave propagating close to the speed of light and Newtonian mechanics must be replaced with the special theory of relativity."

If there is a paper or discussion out there, bringing these matters into the focus, other than simply rejecting by referring to the conservation of momentum, then the rest will be to turn the eyes on other explanations such as gravity interaction or quantum vacuum mumbo jumbo. Nevertheless, it seems that there will always be people rejecting pseudoscience characterisation. Logos5557 (talk) 06:57, 7 August 2014 (UTC)

Shawyer's patent filed in 1999 ~~seems a bit different than later version(s) of the invention~~ seems to have a different presentation than the latest version of the invention. From the link to the patent file given in Talk:Quantum_vacuum_plasma_thruster, it is seen that there is a "section 6" towards the narrower end of the cavity, containing a "dielectric resonator or ferrite material". He claims that:

"the momentum of the electromagnetic wave decreases, because the propagation velocity decreases as the wave enters into section 6; and this decrease in velocity is due to two effects: the first effect is decrease in propagation velocity due to the increased relative permeability or due to the incrased relative permittivity or due to the increase of both relative permeability and relative permittivity of the material in section 6; the second effect is a reduction in the group velocity of the electromagnetic wave due to the increase in guide wavelength as the cross section of the waveguide decreased."

In theory paper he introduces dielectric medium in page 6, not page1:

"Returning to a stationary waveguide, we now let the waveguide include a dielectric-filled section at the smaller end of the taper and choose the dimensions to ensure a reflection-free transmission of the beam from the vacuum-filled section to the dielectric-filled section. Note that the reflection-free interface, with matched wave impedances , will ensure no forces are produced at the interface."

Perhaps, the "aim" of that dielectric medium is to damp out the reflected waves. However, is it any different than removing the narrow end wall/face completely?

Additionally, the figure in the patent does not address any force exerted on cone side walls. Logos5557 (talk) 08:39, 7 August 2014 (UTC)

Shortcut to the similar discussion 8 years ago: Talk:EmDrive/Archive_1#The_Obvious_Criticism. Logos5557 (talk) 14:47, 7 August 2014 (UTC)

Support User:MrX. NASA validated this technology, so I see no reason for it to be categorized as Pseudophysics. Dmatteng (talk) 15:09, 6 August 2014 (UTC)
- "NASA" did no such thing. A research group at a NASA center put out press release and an un-reviewed technical report. jps (talk) 20:08, 6 August 2014 (UTC)
  - Thanks for a clarification. A question though: NASA and "NASA center" are not the same? And, should we consider the research group as a not reliable one? Dmatteng (talk) 03:23, 7 August 2014 (UTC)

This is from the Engineering Directorate of NASA. It's NASA. The "center" is the Johnson Space Center a.k.a. "Mission Control" a.k.a. "Houston" a.k.a NASA. It's NASA work done in NASA headquarters by people with NASA on their golf shirts. I am having trouble thinking how it could be more NASA. NASA/JSC is implementing an advanced propulsion physics laboratory, informally known as "Eagleworks". I will agree that NASA has not "validated the technology", that's an overstatement. But it's NASA scientists under NASA auspices in a NASA lab that performed the tests we're discussing.__ E L A Q U E A T E 04:12, 7 August 2014 (UTC)

Well, according to NASA report the technology is found to work. Is it not a validation? (ie, a validation that it works). Dmatteng (talk) 06:31, 7 August 2014 (UTC)

The particular set of tests showed anomalous thrust. It's interesting and relevant to this topic, but I don't think they consider it a validation of any of the specific theories all by itself. If the set of tests can be replicated, I think it could be a part of later possible validation. They've provided some experimental evidence that could be interpreted to support a theory. The main point is that NASA considers the idea testable and is putting work into testing it. That's not endorsement of the theories, but their attention is not completely dismissible either. They seem to be treating it as an idea that is potentially compatible with what we understand about physics, rather than as pseudophysics.__ E L A Q U E A T E 13:37, 7 August 2014 (UTC)

I agree with what you are saying, however I would probably not call it "anomalous thrust", but simply "thrust", or "anomalous thrust" with attribution to NASA. I think though that we can say that NASA validated the fact that there is a thrust. Also articles such as http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive use the word validates. Dmatteng (talk) 14:48, 8 August 2014 (UTC)

so jsp is basically workers at NASA with engineering degrees comparing to some new age pseudoscience charlatans. and your claim about Sean M. Carroll's claims who has no proof of device being hoax you take as reliable source and reason for not to remove this article from this category. and of course there is presumption that theory dont works, but experiments of multiple team researchers have been confirmed at china, UK... — Preceding unsigned comment added by 188.127.97.194 (talk) 22:22, 7 August 2014 (UTC)

Peculiar citation

Fernando Minotti, a researcher at CONICET, in a 2013 paper published in a peer reviewed scientific journal noted that the thrust attributed to the EmDrive may be explained by certain theories of gravity.Minotti, F. O. (July 2013). "Scalar-tensor theories and asymmetric resonant cavities". Gravitation and Cosmology. 19 (3): 201. arXiv:1302.5690v3. doi:10.1134/S0202289313030080.

Gravitation and Cosmology is a journal with an impact factor of 0.491 and whose editorial provenance out of Russia is not associated with the major Russian research associations or typical names in the field. The journal is a questionable outfit at best.

I would recommend keeping it out until it receives some citations to people outside the cadre: http://adsabs.harvard.edu/cgi-bin/nph-ref_query?bibcode=2013GrCo...19..201M&refs=CITATIONS&db_key=AST

jps (talk) 20:02, 6 August 2014 (UTC)

I agree that some of these are "low-level" citations, but I think it's relevant to say that people other than Shawyer and Fetta have attempted explanations. Alanf777 (talk) 21:54, 6 August 2014 (UTC)

Why is that relevant? We should only find relevance for points that are discussed in 3rd part literature. jps (talk) 22:15, 6 August 2014 (UTC)

Why is that not relevant then? The theory section is here for that purpose, to list all conjectures and theories trying to explain how an RF resonant tapered cavity could produce thrust. And doing that, of course we do not reference any obscure idea on blogs, we are talking of the inventor of the device, the people who repeated the experiments, and everyone who produce a peer reviewed work. Still you let references to Shawyer's radiation pressure idea, Yang's EM explanation and White's QVF conjecture, but Minotti's paper about the consequence of scalar-tensor theories on those microwave cavities keeps being removed, although he is the only one among the four that has an explanation that has been published through peer review. Once we say it's peer-reviewed, you're talking about impact factor, an so on… but what is the impact factor of Sonny White's non peer-reviewed papers about Quantum vacuum fluctuations? Minotti's work is based on Brans–Dicke theory, not on pseudophysics, and his conclusions comes directly from the work of noted physicists like Matt Visser and fr:Marc Lachièze-Rey.

Minotti's paper is very new to have much citations. But how about citations of work that Minotti's basing his paper upon?

Brans & Dicke 1961: 2021 (ADS base does not even know this one!)
Bekenstein 1982: 257
Visser & Barcelo 2000: 83
Visser & Lobo 2004: 39
Lachièze-Rey & Mbelek 2002: 17
Lachièze-Rey & Mbelek 2003: 10

Anyway, this is a waste of time. Judging the quality of a work explaining very novel ideas under the scope of its citations whereas the paper has been published only a few months ago… Removing it from Wikipedia is the best thing you can do to not interest other people pursuing in the same direction and improve the work. Tokamac (talk) 23:31, 6 August 2014 (UTC)

Wikipedia is WP:NOT for inspiring people. It is a non-innovative reference work. jps (talk) 04:48, 7 August 2014

"The theory section is here for that purpose, to list all conjectures and theories trying to explain how an RF resonant tapered cavity could produce thrust. " We don't discuss points not brought up in the sources about the "EmDrive". Read WP:OR and WP:FRINGE, Second Quantization (talk) 17:20, 7 August 2014 (UTC)

Minotti has published over 60 papers, see:

http://www.conicet.gov.ar/new_scp/detalle.php?keywords=&id=22231&articulos=yes

still you refer to his work as "dubious" and "questionable". You talked of a weak "impact factor", but at the same time preferred quoting someone else who never published anything outside of his blog instead. It's not about WP:OR actually. The subject is scientifically controversial and under this aspect you're making a wonderful job as advertising the whole thing as cranky and "seeming not peer-reviewed". Tokamac (talk) 00:24, 9 August 2014 (UTC)

He should publish it in a real journal then. Until then, it's unusable here. I also notice he's publishing outside his general area of expertise (industrial plasma modelling) where he did publish in good journals, Second Quantization (talk) 09:45, 9 August 2014 (UTC)

Ablation

Is there no one considering that this impulse is created by ablated particles from the truncated frustum? Kortoso (talk) 21:46, 7 August 2014 (UTC)

I haven't heard that one; if it's the case, it should be more noticeable at the higher power done in the Xian experiments. 98.233.40.74 (talk) 23:50, 7 August 2014 (UTC)

Well, duh. If thrust, through equal and opposite reactions, is classically derived from material being driven in the opposite direction from the desired path, then you've got to rule out that there's no material being driven in a convenient direction by the microwave. I'm not convinced that increasing the power will rule that out. It's bothersome that nobody is asking these questions. Kortoso (talk) 16:41, 8 August 2014 (UTC)

Yes, there was criticism in the article, suggesting evaporation as the source of the thurst. However, it was (together with all criticisms) removed/censored by POV pushing editors. No control for mass was done in either experiment, and evaporation of order of less than microgram per second could easily explain the effect (especially in the NASA case); even more so, if there is some moisture. What you are essentially doing, is microwaving the interior of a cone, and - surprise surprise - there is a small force in the opposite direction. Then you turn off the heating, but your interior is still at higher temperature, measure it again, and there is still a force - yet smaller. Nothing to do with exotic physics, everything to do with experimental error due to unforeseen effect of evaporation, i.e. ablation (though some moisture might play an effect, especially if there are parts other than metal; this is, in my opinion, the most likely explanation - EM radiation cannot cause such effect at these power/force ratios (that part was also removed from the article, though all was sourced). So, if there is no some weird effect (and QED effects, virtual plasma included, boil down to EM radiation reaction, there is no violation of impulse conservation there, so that is excluded too), it should be reaction from some loss of mass - and evaporation is an obvious source. However, they did not check for that. Also, some of experiments were done in atmosphere (at atmospheric pressure, even in chamber?! according to brief paper), so other possibility is interaction with heated air. However, in vacuum, ablation seems to be most likely explanation. Why all this sourced material and all criticism was removed, beats me. 213.198.221.171 (talk) 19:34, 8 August 2014 (UTC)

Your criticism titled "Experimental errors, evaporation and possible non-vacuum effects" was completely unreferenced. If you provided a reference to a reliable source maybe it would have stayed. Brian Everlasting (talk) 20:17, 8 August 2014 (UTC)

In facts, references were given, but even where they were present, you removed material, to suit your pro-NASA crackpots arrogant viewpoint. For instance, a relevant paper by physicists about dynamic Casimir effect, and its negligible effect, and the fact that relies on EM radiation for thrust, that can produce at most 1/c ratio, was removed, while references of some NASA engineers that scream of quackery were left. The paper that was published now completely (experimental), looks more serious, and it now does cover both for vacuum procedure, and heating off volatiles - but then they (apparently some junior who did all the work) put dielectric material that evaporates all over. No mass check was done, however. This is all present in their, and other papers. You, however, remove all critical materials, and this is the combination of arrogance and ignorant crackpottery that is particularly harmful. The many ways in which experimental error can creep in should be discussed in any article covering such topic, be it cold fusion, homeopathy water memory, neutrino super-light speed, hollow earth or your other pet pseudoscience. At least the CERN and the Italians figured out the error; perhaps NASA will figure it too, in the meantime, they may keep borrowing a lift to ISS from the lesser engineer quack or two.— Preceding unsigned comment added by 213.198.221.171 (talk • contribs) 10:19, 9 August 2014

Eagleworks tested a closed resonant tapered cavity, like Shawyer's EmDrive:

with a dielectric material (thick disc of polyethylene) put inside, near the small end reflector, and they filled the cavity with microwaves: thrust about 100 micronewtons for ~ 20W of input power measured.
they removed the dielectric material from within, and filled again the same cavity lacking the dielectric with microwaves at the same power: no thrust detected.

It's in the paper, so again: read it. Now you know that 1/ something VERY important is going on with this dielectric, and 2/ no ion wind nor heated air current nor evaporation of the metallic walls outside of the cavity are a possible spurious consequence of thrust. Tokamac (talk) 00:14, 9 August 2014 (UTC)

If "with and without dielectric" tests were performend on EMdrive, not on (or not only on) Cannae, then why don't you edit EmDrive#RF_resonant_tapered_cavity_thruster_.28EmDrive.29 accordingly. Logos (talk) 09:51, 9 August 2014 (UTC)

Probably because some wannabe NASA crackpots keep removing valid info. This page is a shed for nasty POV pushers. 213.198.221.171 (talk) 10:19, 9 August 2014 (UTC)

Logos, it's more complicated than just saying that in the article. Shawyer used a dielectric material only in is first prototype model, but never in all his following test articles. The Chinese didn't use any dielectric in the cavity neither. But both measured net thrusts. And both used high power microwaves. The presence of a dielectric resonator is because it would increase the force created. In private conversations, Paul March from Eagleworks Labs thinks their RF resonant tapered cavity could all the same produce thrust without the dielectric in it, but since they used very low power input (17W), this lower thrust signal could be buried below the resolution of their torsion pendulum (which can detect a force above the range of 1-to-5 micronewtons, depending on the fine tuning and environmental conditions). So with their upcoming high power experiments in the coming months, this apparent anomaly will hopefully be settled. They could detect some thrust without the dielectric disc inside of the cavity, and a higher thrust with the dielectric within. But for now this is pure conjecture. For now the low power results only contributed to settle the dispute about ion wind and ambient convectional air currents. Tokamac (talk) 10:40, 9 August 2014 (UTC)

Theoretically, dielectric resonator should make no difference, because as stated in its article "The microwaves are confined inside the resonator material by the abrupt change in permittivity at the surface, and bounce back and forth between the sides", and while bouncing back & forth between the sides (at a speed close to the speed of light), microwaves exert forces on those sides in equal amounts.

I don't know what the actual experimental setups of eagleworks and others were, but monitoring only the force could be misleading; because the force exerted might very well be intermittent/dynamic or sinusoidal in direction. Therefore, they both need to couple force measuring devices on both reflectors/sides of the cavity, and need to measure the real displacement in vacuum. If there happens positive force measurements on each side, then the invention fails. Accelerometers ~~would~~ could reveal the picture better than the "force sensing", but I'm not sure ~~whether or not any accelerometer can pick near light speed fluctuations~~. Logos (talk) 11:35, 9 August 2014 (UTC)