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#2780 by SeeShells on 11 Feb, 2016 18:12
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I confirm that the experiment by G. Nimtz and A. A. Stahlhofen was conducted at frequency of 9 GHz as I calculated based on the wavelength:
Quote from: G. Nimtz and A. A. StahlhofenThe experimental set-up is illustrated in Fig.1. We have investigated double prisms of Perspex with a refractive index n = 1.6 with microwaves at a frequency of 9.15 GHz, i.e. at a wavelength of 32.8 mm. The sides of the right triangle prisms are 0.4 x 0.4 m^2, which is of a macroscopic dimension for a quantum mechanical experiment. The experiment was carried out with a symmetrical beam path as sketched in Fig. 1. The beam has a perpendicular incidence at the first prism and is reflected at the Perspex/ air boundary under an angle of 45°, which is above the critical angle of total reflection. (The critical angle for the Perspex prism is 38.7°.) The dish antennas had diameters of 350 mm; the receiver antenna was movable parallel to the prism's surfaces. The microwave polarization was TM, with the electric field in the plane of incidence. The measured Goos-Hänchen shift in this experiment is of the order of a wavelength.
Also, as I correctly supposed, they measured the well-known Goos-Hänchen shift.
The prisms they used were made of Poly(methyl methacrylate) (PMMA), also known as acrylic or acrylic glass as well as by the trade names Plexiglas, Acrylite, Lucite, and Perspex, a transparent thermoplastic often used in sheet form as a lightweight or shatter-resistant alternative to glass.
Thus, Nimtz experiment consisted of the well known surface evanescent wave that takes place at angles greater than the total reflectance angle, inside acrylic thermoplastic.
They used an angle of 45°, which is above the critical angle of total reflection. (The critical angle for the Perspex prism is quoted as 38.7°).
Also notice that they used dish antennas with diameters of 350 mm (13.78 inches); the receiver antenna was movable parallel to the prism's surfaces. The microwave polarization was TM, with the electric field in the plane of incidence.
This experiment is similar to the one briefly discussed in the textbook by Panofsky, dating to 1955.
Also, as I expected, there is nothing "unusual" in this effect, or needing Quantum Mechanics, since such surface waves also take place in solid and liquid interfaces due to elastic waves (instead of electromagnetic waves), and they can be explained by wave theory:
the authors themselves confirm my expectation:QuoteThis universal tunneling time seems to hold even for sound waves (i.e. phonons) as measured by Yang et al. at 1 MHz and by Robertson et al. at 1 kHz in a sound tunneling experimental set-up
I find the claims of the authors about superluminal travel very perplexing since this effect is well known, it is discussed in most textbooks, and it can be simply explained.
There was NO copper sheet involved, the evanescent waves occur at the surface due to the difference in electric permittivity between the acrylic and air.
The fact that there are evanescent waves in the surface of the acrylic at angles equal or greater than the total reflectance angle is fully expected (this is discussed in most books in electromagnetism: Jackson, Collin, etc.). I don't see any possibility that this can occur with a fully sealed EM Drive with copper walls mm thick at ~2.45 GHz, since the skin depth is only ~ micrometer.
Even if one would have an EM Drive with a very thin wall of less than 1 micrometer I don't see how these surface evanescent waves even if they would occur would be able to explain the claims of EM Drive researchers of force/Power exceeding a perfect photon rocket.
So I shouldn't even test the drive for them?
Shell -
#2781 by mwvp on 11 Feb, 2016 18:33
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I wanted the near field to propagate at the speed of light so I could use it for propulsion but I keep seeing these hints that for long wavelengths (cm range and longer) it appears to be super-luminal (less than a wavelength I think, err maybe further) which seems to throw a monkey wrench in the works if it's true. I'm still not sure exactly what to make of it. I know waves can superimpose to give the impression of waves that propagate faster than light but these are some links that suggest it may be more than just superposition of waves.
First link: "ASPECTS ON THE PHASE DELAY AND PHASE VELOCITY IN THE ELECTROMAGNETIC NEAR-FIELD"
2nd link:"Nearfield Electromagnetic Effects on Einstein Special Relativity" by William D. Walker
3rd: "Near-field Analysis of Superluminally Propagating Electromagnetic and Gravitational Fields" by William D. WalkerQuoteIn the above referenced paper it has been shown that dispersion is nonlinear in the
Not sure I agree with this guy that space/time is really Galilean but I'm open to the idea that the near field might behave as such.
nearfield of a dipole and only linear in the farfield.
4th "Do Evanescent ModesViolate Relativistic Causality?" by G. NimtzQuoteThe detector receives the tunneled signal earlier than the signal, which traveled the same distance in vacuum...
And there seems to be more. It was sort of a mixed feeling for me of diasppointment and wonder. I'm still not sure what to think of it. On the other hand, phased arrays work and the antennas are within 1/4lambda.
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1489915#msg1489915
I'll try to have a look at those links later; Rodal seems to share my take on the matter, perhaps not for the same reasons, and is expounding on it well enough. A few years back I read about the superluminal and evanescent stuff, and concluded that some physicists had indulged in too much hemp or granola, or were stirring up the pot to get published, or were cruelly teasing their students.
I don't know really know the motives and heartfelt beliefs, but I know if I take the metal waveguide away from the space enclosed, light/RF propagates through the vacuum at C, without any dispersion as measured up to TeV cosmic gamma rays. Which is interesting when you consider DeBroglie/matter wave dispersion.
Maxwell's equations don't describe matter waves. One great point about taking the ee5303 EM FTDT simulation course is getting thoroughly familiar with how Maxwell's equations really work, and where and how dispersion comes into the picture. You need resonant atomic systems or resonant cavities/waveguides to make observations about collective and time-averaged phenomina, some of which appear to violate causality.
There really is only the time-domain. All references to frequency are about time-averaged collective phenomena.
That's my take, FWIW. -
#2782 by mwvp on 11 Feb, 2016 19:02
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...Bottom line is that I am now more optimistic that I know a systematic method to eliminate negative Q. Now if I could just get Harminv to calculate realistic Q values ... But maybe it will when all the Q's are positive.
You know Meep has a frequency-domain solver:http://ab-initio.mit.edu/wiki/index.php/Meep_Reference#Frequency-domain_solver
It doesn't do Drude, but using a fixed, real (not complex) conductivity at the frequency of interest is faster anyways.
I understand FDTD isn't very fast for highly-resonant systems, unless necessary, which it wouldn't seem to be if Q is what's desired.
The prof. in the course I keep raving about also stated, numerous times, that reducing symmetry is always good practice. And to make trial runs using coarse space & time resolution.
Probably nothing you don't know. Just trying to help. Good luck. -
#2783 by Rodal on 11 Feb, 2016 19:18
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...So I shouldn't even test the drive for them?
I think that you should measure the electromagnetic fields on the external surface of the EM Drive, 1) foremost for safety reasons, 2) to verify how hermetically sealed is your EM Drive (and therefore how sealed other EM Drive experiments have been: NASA's frustum was also DIY in a living room) and 3) to verify the expectation that there should not be any surface evanescent waves not associated with holes or gaps.
Shell
But I'm most interested, and looking forward to a response concerning what methods of detection of evanescent waves have you investigated so far, and which method you are planning to use
1) are you planning to use a prism or a lens to achieve frustration of total reflectance ?
2) are you going to try to measure with a subwavelenght sized antenna at a subwavelength distance from the surface
3) some other method?
4) the evanescent surface wave has constant phase planes perpendicular to the surface, measuring phase is one thing you could do
5) constant amplitude planes of the evanescent surface wave are parallel to the surface
Remember that the evanescent surface wave carries no power in the direction normal to the surface, it is a travelling surface wave.
http://tristantech.com/microwave-near-field-measurementsQuoteThe instrument presented here is an example of a resonant cavity near field microwave system. Here, the energy from a resonant cavity is coupled outside the cavity via a small hole or a conductive wire, producing evanescent fields. The size of the hole or the wire is usually much smaller than the wavelength. The hole or wire size (not the wavelength) sets the spatial resolution for the imaging of materials. Depending upon the probe configuration, a spatial resolution on the order of l/1000 (where l is the resonant wavelength) can be achieved. The important parameters of the resonator are the resonant frequency (fo) and the quality factor (Q). A sample coupled into a resonator can change fo and / or Q. A change in Q is associated with surface resistance and dielectric losses. A shift in fo is caused by the material’s dielectric constant. Probes of this type are also called evanescent microwave probes (EMP). The main probe features include the following: - See more at: http://tristantech.com/microwave-near-field-measurements#sthash.29YCPHlv.dpuf
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#2784 by SeeShells on 11 Feb, 2016 19:46
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Thanks for the link. I've seen their probes and have looked into them Dr. Rodal....So I shouldn't even test the drive for them?
I think that you should measure the electromagnetic fields on the external surface of the EM Drive, 1) foremost for safety reasons, 2) to verify how hermetically sealed is your EM Drive (and therefore how sealed other EM Drive experiments have been: NASA's frustum was also DIY in a living room) and 3) to verify the expectation that there should not be any surface evanescent waves not associated with holes or gaps.
Shell
But I'm most interested, and looking forward to a response concerning what methods of detection of evanescent waves have you investigated so far, and which method you are planning to use
1) are you planning to use a prism or a lens to achieve frustration of total reflectance ?
2) are you going to try to measure with a subwavelenght sized antenna at a subwavelength distance from the surface
3) some other method?
4) the evanescent surface wave has constant phase planes perpendicular to the surface, measuring phase is one thing you could do
5) constant amplitude planes of the evanescent surface wave are parallel to the surface
Remember that the evanescent surface wave carries no power in the direction normal to the surface, it is a travelling surface wave.
http://tristantech.com/microwave-near-field-measurementsQuoteThe instrument presented here is an example of a resonant cavity near field microwave system. Here, the energy from a resonant cavity is coupled outside the cavity via a small hole or a conductive wire, producing evanescent fields. The size of the hole or the wire is usually much smaller than the wavelength. The hole or wire size (not the wavelength) sets the spatial resolution for the imaging of materials. Depending upon the probe configuration, a spatial resolution on the order of l/1000 (where l is the resonant wavelength) can be achieved. The important parameters of the resonator are the resonant frequency (fo) and the quality factor (Q). A sample coupled into a resonator can change fo and / or Q. A change in Q is associated with surface resistance and dielectric losses. A shift in fo is caused by the material’s dielectric constant. Probes of this type are also called evanescent microwave probes (EMP). The main probe features include the following: - See more at: http://tristantech.com/microwave-near-field-measurements#sthash.29YCPHlv.dpuf
That said...
You need to start with the basics on the build and whether it holds air.
I pressurized my frustum after sealing it. Inserted a one way valve, pressurized it to 5psi then monitored the pressure level changes over a 96 hour period on a digital gauge. No pressure changes showed. This was done through the hole for the quartz rod with one end sealed and the other small end with the fitting and digital gauge.
This is a paper by NIST that I'm currently working through in the setting of this basic research.
NIST Technical Note 1536
Measuring the Permittivity and Permeabiiity of Lossy Materials: Solids, Liquids, Metals, Building Materials, and Negative-Index Materials
James Baker Jarvis
Michael D. Janezic
Bill F. Riddle Robert T. Johnk Pavel Kabos
Christopher L. Holloway Richard G. Geyer Chriss A. Grosvenor
Electromagnetics Division National Institute of Standards and Technology Boulder, CO 80305
PDF warning
https://www.gpo.gov/fdsys/pkg/GOVPUB-C13-c122c633217fc0f9e59285da3726a436/pdf/GOVPUB-C13-c122c633217fc0f9e59285da3726a436.pdf
Back to work, lost yesterday because of Jury duty. Lots of fun .... not.
Shell
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#2785 by rfmwguy on 11 Feb, 2016 20:48
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Data recording for emdrive experiments -
Congrats to LIGO today. I did follow their disclosure a bit. One of their charts is below. A couple of things struck me:
1) Signal to noise is low.
2) Nice residual channel....will steal that idea for my next data set.
3) Space propagated what is effectively an acoustic frequency for billions of light years.
4) It was a one-time event of a very short duration and very low energy (here on earth).
5) A definitive statement was made about the discovery of gravitational waves and immediately accepted by the press.
I'm sure a peer-reviewed paper published in a leading journal will appear shortly and look forward to reading it.
This does illustrate (to me anyway) the differences between proving a widely accepted theory and proving a new theory such as the emdrive.
Far more rigorous testing and standards are required of new ideas. So be it. Think that's the way it needs to be
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#2786 by Mulletron on 11 Feb, 2016 20:58
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I don't know man. That seems like a bit of a stretch. LIGO's data exactly matched prediction calculated from theory.
Added:
EmDrive doesn't even have a theory and the data is...ahem sparse. -
#2787 by rfmwguy on 11 Feb, 2016 21:05
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I don't know man. That seems like a bit of a stretch. LIGO's data exactly matched prediction calculated from theory.
Don't get me wrong, I believe it 100%. I've followed that system for a while and am fascinated with it. They did a great job.
My point was it did confirm a theory and there was no instant call for lack of data or additional testing. I full well believe they detected gravitational waves.
On the emdrive side, people here have always said extraordinary claims require extraordinary proof on new physics and its understandable why...so, if anyone plans to DIY the emdrive, like shell says...data, data and more data.
Sparse data and no theory on emdrive? Yep, you got that right, my friend.
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#2788 by tchernik on 11 Feb, 2016 21:14
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Data recording for emdrive experiments -
Congrats to LIGO today. I did follow their disclosure a bit. One of their charts is below. A couple of things struck me:
1) Signal to noise is low.
2) Nice residual channel....will steal that idea for my next data set.
3) Space propagated what is effectively an acoustic frequency for billions of light years.
4) It was a one-time event of a very short duration and very low energy (here on earth).
5) A definitive statement was made about the discovery of gravitational waves and immediately accepted by the press.
I'm sure a peer-reviewed paper published in a leading journal will appear shortly and look forward to reading it.
This does illustrate (to me anyway) the differences between proving a widely accepted theory and proving a new theory such as the emdrive.
Far more rigorous testing and standards are required of new ideas. So be it. Think that's the way it needs to be
Yes, but the difference that matters is that they knew where to look, what to look for and how to get it. A big body of largely accepted theory supported them too.
With the Emdrive, we are still at step 1: it's still not clear if the signal exists as a separate entity from thermal/EM noise without the shadow of doubt. Some emerging models are starting to appear and make predictions, but there isn't any accepted theoretical framework making very precise predictions of measurable signals as specific as LIGO's.
Nevermind. The signals pursued by Emdrive experimenters are way above those of LIGO in terms of strength. So much in fact, that this community owes its very existence to the possibility of having DIYers checking them out, without the need of huge LIGO-like experiments.
What Emdrive still needs is the compromise and commitment to pursue the facts. That is, more experiments, better experiments, more data.
The truth will appear in the end, whatever it is. -
#2789 by JasonAW3 on 11 Feb, 2016 21:16
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I don't know man. That seems like a bit of a stretch. LIGO's data exactly matched prediction calculated from theory.
Added:
EmDrive doesn't even have a theory and the data is...ahem sparse.
Actually, from the graphs I've seen, it wasn't an EXACT match, but pretty close to what was predicted. -
#2790 by rfmwguy on 11 Feb, 2016 21:24
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@tchernik Good thoughts there. It certainly helps me and maybe others frame what emdrive is trying to do and the uphill battle it faces.
While Einstein's theory was eventually accepted without experimental evidence, it took a century to prove the theory. This is quite a sobering fact and perhaps many expect the emdrive to be resolved quickly.
To tell you the truth, I did. When first experimenting, I thought I'd see nothing and quickly dismiss it in my own mind. When things didn't work out that way, I expected to be able to resolve it within a year.
Now I realize DIY will probably never be able to resolve it and it will need to go to a higher level of experimentation and thinkers. This is fine, its still fun to experiment and build and perhaps I'll add a little info to the longer term effort.
Emdrive is too early to announce total success and too early to announce total failure IMHO. -
#2791 by 1 on 11 Feb, 2016 21:32
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I'm sure a peer-reviewed paper published in a leading journal will appear shortly and look forward to reading it.
Paper's up, along with one of the longest lists of et al. peers I've ever seen
In all fairness in regards to acceptance time, the amount of indirect evidence for gravitational waves was already outstanding. Mentioned in on the first page of the paper is the well known PSR B1913+16 binary pulsar system who's orbital periods have been decaying in exact agreement with GR for the last 40+ years.
Black line is sans-GR, blue line represents GR predictions moving nicely through the center of the actually-observed red dots.
Think of it this way. Gravitational waves were simply the last leg of a 100 year long marathon; but even with nobel prize-winning indirect data, the desire for more was enough to fund a bunch of expensive interferometers! Things that are in uncharted territory, like the EM drive, usually evoke reactions more along the lines of 'get-the-hell-out-of-my-office' rather than 'hmm, what else can you show me?' IMHO, any requests for more data should be seen as encouraging. You have at least one more friendly, if skeptical, ear. -
#2792 by Rodal on 11 Feb, 2016 21:33
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...
This does illustrate (to me anyway) the differences between proving a widely accepted theory and proving a new theory such as the emdrive.
Far more rigorous testing and standards are required of new ideas. So be it. Think that's the way it needs to be
DISCLAIMER
The views expressed in this EM Drive thread by the NSF EM Drive Moderator/Global Moderator do not reflect the views of others that regularly posts in this thread, including me.
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#2793 by tchernik on 11 Feb, 2016 21:35
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@tchernik Good thoughts there. It certainly helps me and maybe others frame what emdrive is trying to do and the uphill battle it faces.
While Einstein's theory was eventually accepted without experimental evidence, it took a century to prove the theory. This is quite a sobering fact and perhaps many expect the emdrive to be resolved quickly.
To tell you the truth, I did. When first experimenting, I thought I'd see nothing and quickly dismiss it in my own mind. When things didn't work out that way, I expected to be able to resolve it within a year.
Now I realize DIY will probably never be able to resolve it and it will need to go to a higher level of experimentation and thinkers. This is fine, its still fun to experiment and build and perhaps I'll add a little info to the longer term effort.
Emdrive is too early to announce total success and too early to announce total failure IMHO.
Personally, I'm not convinced DIY efforts can be completely ruled out as game-changers.
For example, if someone finds a way to obtain a greater thrust than would be physically possible with thermal or EM noise effects.
On this, people working on superconductive versions or higher power ones (hard to do, not cheap) could bring fresh new data.
Of course, we could get our act together and simply test it in a vacuum (for removing the convection/thermal effects) and later, do a test in space.
If it moves in space, then it's hard to dismiss it as an experimental error.
But then again, nobody will spend significant money in something they aren't nearly certain it will work. Something as big as LIGO could be funded precisely because the theory behind it was very solid, and success was pretty much expected.
Because of this, institutional experiments as Dr. Rodal calls them are of the utmost importance: they represent probably the only way a space test could happen, unless some benefactor billionaire decides he wants to put one Emdrive in space. -
#2794 by Mulletron on 11 Feb, 2016 21:47
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I suspect that as long as people keep testing the Shawyer hypothesis, they'll keep coming up with inconclusive or null results.
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#2795 by rfmwguy on 11 Feb, 2016 21:47
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That always goes without saying. Remember, I was prepared to be a non-posting mod to help the effort here and Chris encouraged me to keep on posting as a regular member. Nothing changed, I try to make that clear as often as I can....
This does illustrate (to me anyway) the differences between proving a widely accepted theory and proving a new theory such as the emdrive.
Far more rigorous testing and standards are required of new ideas. So be it. Think that's the way it needs to be
DISCLAIMER
The views expressed in this EM Drive thread by the NSF EM Drive Moderator/Global Moderator do not reflect the views of others that regularly posts in this thread, including me. -
#2796 by rfmwguy on 11 Feb, 2016 21:54
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I suspect that as long as people keep testing the Shawyer hypothesis, they'll keep coming up with inconclusive or null results.
EMDrive in general or Shawyer Hypothesis? Not sure I could tell you the Shawyer Hypothesis. -
#2797 by Rodal on 11 Feb, 2016 21:58
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The designer of the LIGO Gravitational Wave experiment, MIT Prof. Weiss wrote up his design in the spring of 1972, as part of his laboratory’s quarterly progress report. Prof. Weiss great design did not appear in a scientific peer-reviewed journal.
According to Prof. Kip Thorne, Professor at Caltech , MIT Prof. Weiss article on the design of the LIGO experiment “ is one of the greatest papers ever written.” Thorne said “If I had read it (at the time), I had certainly not understood it” .
The following year, 1973, one of the most famous books on Gravitation was published: co-authored by Thorne, Charles Misner and John Wheeler (under whom Feynman got his PhD, as well as Thorne and Misner)
John Wheeler's Ph.D. Students (look at all these famous names !):
Jacob Bekenstein
Claudio Bunster
Demetrios Christodoulou
Ignazio Ciufolini
Hugh Everett
Richard Feynman
Kenneth W. Ford
Robert Geroch
John R. Klauder
Bahram Mashhoon
Charles Misner
Milton Plesset
Benjamin Schumacher
Kip Thorne
Jayme Tiomno
Bill Unruh
Robert Wald
Katharine Way
Arthur Wightman
Paperback: 1279 pages
Publisher: W. H. Freeman (September 15, 1973)
ISBN-10: 0716703440
ISBN-13: 978-0716703440
which contained a student exercise designed to demonstrate the impracticability of measuring gravitational waves with lasers. 
That's how great the design of Prof. Weiss is !: designed a year before one of the most famous books on Gravitation was published by one of the most famous General Relativity experts (John Wheeler) stating that it was not possible to detect gravitational waves. -
#2798 by Mulletron on 11 Feb, 2016 22:10
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I suspect that as long as people keep testing the Shawyer hypothesis, they'll keep coming up with inconclusive or null results.
EMDrive in general or Shawyer Hypothesis? Not sure I could tell you the Shawyer Hypothesis.
High Q, empty copper cans excited with microwave radiation. Heck, Eagleworks disproved that one already. -
#2799 by rfmwguy on 11 Feb, 2016 22:17
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IOW, dielectric needed?I suspect that as long as people keep testing the Shawyer hypothesis, they'll keep coming up with inconclusive or null results.
EMDrive in general or Shawyer Hypothesis? Not sure I could tell you the Shawyer Hypothesis.
High Q, empty copper cans excited with microwave radiation. Heck, Eagleworks disproved that one already.
