My last post on the NASA "quantum vacuum plasma thruster" was mainly about the shoddy theory behind it - like how there's no such thing as a "quantum vacuum plasma".

But you could argue: hey, if the gizmo actually works, isn't that good enough?   

Unfortunately, the experiment has problems too.  In brief:

1.  They tested a device that was designed to work and one that was designed not to work.  They both worked.

2.  They tested the devices in a "vacuum chamber", but they didn't take the air out.

3.  They didn't carefully study all possible causes of experimental error... like their devices heating the air.

In a bit more detail:

1.  Their device, called the Cannae drive, was invented by a guy named Guido Fetta.  You can see a picture below.  It's not complicated!  It's a hollow container made of metal, about 11 inches in diameter and 4-5 inches long.  You pump radio waves in one end. At the other end, a copper wire serves as an antenna.  This lets you measure the radio waves bouncing around inside the container, and adjust their frequency until you hit a resonance.  Then this thing is supposed to generate thrust, for some unknown reason.

Fetta thought this device would work if you carve slots on one side of the flat part.  The NASA guys tried a version with slots and one without slots.  They claim both versions generate a thrust of 22-48 micronewtons when they pump 17-28 watts of radio waves into them:

Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the "null" test article).

So, basically they found evidence against Fetta's idea: the slots make no difference.  It's like giving someone a placebo and finding it works just as well as the drug you're testing.

They also tried a resistor instead of their device.  They claim this produced no thrust.  This rules out some possibilities of experimental error... but not others. 

For example, if parts of their flat metal can get hot and create air currents, that might create the force they saw.  It's a tiny force, less you'd get from 5 milligrams of mass pushing down due to gravity.

2.  Their paper goes into great detail about the "vacuum chamber" their experiment was done in - but in the abstract to the paper, they say they didn't remove the air.  This is important because of the issue of air currents. 

It's also just weird.  In their paper they say:

To simulate the space pressure environment, the test rig is rolled into the test chamber. After sealing the chamber, the test facility vacuum pumps are used to reduce the environmental pressure down as far as 5x10E-6 Torr. Two roughing pumps provide the vacuum required to lower the environment to approximately 10 Torr in less than 30 minutes. Then, two high-speed turbo pumps are used to complete the evacuation to 5x10E-6 Torr, which requires a few additional days. During this final evacuation, a large strip heater (mounted around most of the circumference of the cylindrical chamber) is used to heat the chamber interior sufficiently to emancipate volatile substances that typically coat the chamber interior walls whenever the chamber is at ambient pressure with the chamber door open. During test run data takes at vacuum, the turbo pumps continue to run to maintain the hard vacuum environment. The high-frequency vibrations from the turbo pump have no noticeable effect on the testing seismic environment.

They're working really hard to get a good vacuum, right?  But in their abstract they say:

Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure.

At ambient atmospheric pressure?   What's the point of the fancy vacuum chamber?  A sentence in their conclusions gives a clue.  Talking about future plans, they say:

Vacuum compatible RF amplifiers with power ranges of up to 125 watts will allow testing at vacuum conditions which was not possible using our current RF amplifiers due to the presence of electrolytic capacitors.

So it seems they couldn't actually test their device in a vacuum.

3.  If you're trying to find some small effect, checking the ways you could have screwed up is the most important thing.  The device they're testing is simple, but the test apparatus itself is very complicated, and lots of things could go wrong. 

Their paper should have a big section on this, but it doesn't.  Instead it has a section on how if the gizmo works, you could scale it up and do great things:

Figure 23 shows a conservative 300 kilowatt solar electric propulsion roundtrip human exploration class mission to Mars/Deimos. Figure 24 shows a 90 metric ton 2 megawatt (MW) nuclear electric propulsion mission to Mars that has considerable reduction in transit times due to having a thrust to mass ratio greater than the gravitational acceleration of the Sun (0.6 milli-g’s at 1 AU). Figure 25 shows the same spacecraft mass performing a roundtrip mission to the Saturn system spending over a year around two moons of interest, Titan and Enceladus.

This is called 'counting your chickens before the eggs have hatched'.

I would need to be more of an expert than I am to imagine all the things that could go wrong with their experiment.  But just so you see what I mean, here's one thing they do mention:

one visible effect to the seismic environment is the periodic (about one-third to one-quarter Hertz) perturbation created by the waves from the Gulf of Mexico (about 25 miles southeast of Johnson Space Center), especially on windy days.

The thrust they're measuring is so small that waves in the ocean 25 miles away could screw up the experiment!  They tried to deal with this... but it goes to show, you can't revolutionize physics until you carefully check all the sources of error.

I thank Greg Egan and +Matt McIrvin for their help, but of course they're not to blame for any mistakes I made. 

The paper I'm talking about was published here:

• David Brady, Harold White, Paul March, James Lawrence and Frank Davies, Anomalous thrust production from an RF test device measured on a low-thrust torsion pendulum, 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, http://arc.aiaa.org/doi/abs/10.2514/6.2014-4029.  

Unfortunately it's not free except for the abstract.  Luckily someone has liberated the paper and put a free version here:

http://rghost.net/57230791

Beware: the abstract in the paper is different than the abstract on the NASA technical report server here:

http://ntrs.nasa.gov/search.jsp?R=20140006052

This is where they say they didn't remove the air from the vacuum chamber.

There's a website about Guido Fetta's company and his device:

• Cannae Drive, http://cannae.com/about

It says:

The Cannae Drive is a resonating cavity with design features that redirect the radiation pressure exerted in the cavity to create a radiation pressure imbalance on the cavity. This differential in radiation pressure generates an unbalanced force that creates thrust. The cavity is accelerated without use of propellant. Don't believe it? Study the theory.  Replicate our numerical models.  Review our experimental results.  And draw your own conclusions.

Unfortunately, when I click on the links to theory, numerical models or experimental results, I get:

404 - Article not found

+Hamilton Carter pointed out another paper by the NASA team, which explains the wild optimism behind this experiment:

• Dr. Harold “Sonny” White, Paul March, Nehemiah Williams, and William O’Neill, Eagleworks Laboratories: advanced propulsion physics research,  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492.pdf

They write:

NASA/JSC is implementing an advanced propulsion physics laboratory, informally known as "Eagleworks", to pursue propulsion technologies necessary to enable human exploration of the solar system over the next 50 years, and enabling interstellar spaceflight by the end of the century. This work directly supports the "Breakthrough Propulsion" objectives detailed in the NASA OCT TA02 In-Space Propulsion Roadmap, and aligns with the #10 Top Technical Challenge identified in the report. Since the work being pursued by this laboratory is applied scientific research in the areas of the quantum vacuum, gravitation, nature of space-time, and other fundamental physical phenomenon [sic], high fidelity testing facilities are needed. The lab will first implement a low-thrust torsion pendulum (<1 uN), and commission the facility with an existing Quantum Vacuum Plasma Thruster. To date, the QVPT line of research has produced data suggesting very high specific impulse coupled with high specific force. If the physics and engineering models can be explored and understood in the lab to allow scaling to power levels pertinent for human spaceflight, 400kW SEP human missions to Mars may become a possibility, and at power levels of 2MW, 1-year transit to Neptune may also be possible. Additionally, the lab is implementing a warp field interferometer that will be able to measure spacetime disturbances down to 150nm.  Recent work published by White suggests that it may be possible to engineer spacetime creating conditions similar to what drives the expansion of the cosmos. Although the expected magnitude of the effect would be tiny, it may be a “Chicago pile” moment for this area of physics.

The "Chicago pile" was the experiment that demonstrated a nuclear chain reaction. 

#spnetwork doi:10.2514/MJPC14  #cannae_drive  
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It seems as though the abstract and the paper  are describing two different experiments ambient atmospheric pressure vs. vacuum, the experiment they did vs. the experiment they wanted to do. That in itself should be sending of warning alarms it would seem ... or am I missing something. +John Baez, thanks for the information
 
So basically, this thing acts sort of like a resonant chamber at microwave frequencies?  

Seems like a straight forward enough design to replicate as a "proof of concept" and to verify the experimental results. A senior in a EE program with a little bit of microwave training could make a project out of that. 
 
The Cannae Drive, as in "Ye cannae change the laws o' physics, Cap'n"?
 
I've been holding my breath on this one since extraordinary results require extraordinary evidence... Glad I haven't commented... Yet. 
 
+Tom Nathe wrote: "So basically, this thing acts sort of like a resonant chamber at microwave frequencies?"

Yeah, it's a funny-shaped metal can that acts like a resonant chamber for microwaves of a frequency of 936 megahertz.  (That's what we'd call UHF, or ultra-high frequency.)  

Roger Shawyer's original EmDrive was a tapered cylinder, smaller at one end than another.  He thought that shape was important.

Guido Fetta's Cannae Drive is a flattish disk with prongs poking out from top and bottom.  He thought it was important to cut slots on one side.

Somehow these gadgets are mysteriously supposed to generate thrust.  None of the theories for how they could work make any sense.  So someone who knows their microwave engineering might have fun replicating this experiment and finding what's wrong with it.
 
Goverment-sponsored pseudoscience is a big problem in Russia... One big mistake that you can make while opposing it -- too many discussion of the science behind it. They'll twist it into: "See? There is a debate in scientific community about my invention. We really need more money to figure it out. "
 
Who would have thought that the way to the stars was just a fancy microwave oven. [ Sarcasm ]
 
Wonder how good it is at nuking popcorn?
 
according to relativity, photos carry momentum, right? I mean E = pc so it is not MUCH momentum. But wouldn't that little bit of momentum from the photon emission in one direction create the thrust they invoke? That doesn't violate any physics . . .
 
+Cade Johnson I had the same thought, but 30 watts only gives you a tenth of a micronewton.  So their claimed effect is 100 times greater then what you'd get from just shining microwaves out the back of the thruster. 
 
. . . so photons can make some thrust but not enough to go to Mars in weeks. It is the old light-sail idea I guess: You need a pretty big area to catch enough solar photons to move some mass. Converting via solar panel just costs efficiency . . .
 
+John Baez are they using the Woodward device for thrust detection? It's got it's own set of issues.
 
So it works for very small values of "works".
 
Basically its exciting atoms. Providing thrust.
I reckon it will not work in a total vacuum.
 
+Cade Johnson They also insist that this is happening without any emission of radiation from the device. You couldn't get the thrust without some photons actually permanently emerging from the device to carry momentum away.
 
+Matt McIrvin yeah, I just picked up on that a while ago - no emission - but that's CRAZY! LOL
 
+Hamilton Carter - I don't know what a Yeh Woodward device is.  They're using a torsion pendulum:

"The Eagleworks Laboratories Low-thrust Propulsion Test Facility at NASA’s Johnson Space Center (JSC) is capable of measuring thrust down to the single-digit micronewton level. The central component for this facility is a horizontal torsion pendulum. The torsion pendulum is constructed primarily of aluminum structure that is mounted on a slide-out table within a 30 inch by 36 inch vacuum chamber. The chamber is subsequently mounted on a 4 foot by 8 foot optical bench. The pendulum arm pivots about two linear flexure bearings in a plane normal to gravitational acceleration. The flexure bearings provide an essentially frictionless and hysteresis-free interface between the static test stand fixed structure and the dynamic pendulum arm. Test article force is measured by measuring the pendulum arm displacement and calculating the force via the flexure bearing spring constants that were determined during test facility setup."
 
 
They are missing critical ingredient: popcorn ;o)
 
First the superluminal neutrinos, now this. The history books will have some strange things to say about early 21st century science.
 
There was chatter of flying, double-lenticular discs that now have surfaces of polished aluminum, and used to have polished nickel surfaces, and that could be powered up and sent hurtling across the sky using directed microwave energy, which superheated the surfaces and caused a thrust like you're describing here.

Ufo Crash in the Desert (High Quality)
 
Looks like the link to the paper no longer works.
Edit: Now it does.
 
+John Baez Thank you for your critique. I am a layman and quantum physics is not within my purview. While I give the opinions of experts great weight it is not something I can easily consider.

I do understand basic mechanical principles and this is something that I can apply when I'm judging the quality of an experiment involving mechanical things.

It seems to me that this paper shouldn't have been published as a paper. It should have been published as lab notes + a request for funding for further tests.

One test I can think of is to put power supply, rf generator and device in an airtight/thermally and electrically insulated/RF shielded container. Put the container on a scale inside of a structure suitably constructed to eliminate interference from stray air currents, vibrations and so on. Maybe even a large vacuum chamber if necessary.

If the device works as claimed it will produce thrust regardless of whether the container it's in has atmosphere.
 
+Daniel Estrada Future historian living in the 31st century, studying 21st century science, will have the most outrageous amounts of massive facepalms and the nosier belly laughs...
 
+Bill Reed that's not uncommon. The abstract is what funding was probably granted on, while the body is the actual experimental data. The fact that they published anyway is the unusual part...
 
+Daniel Estrada At least the folks at OPERA basically reported what they saw, what they had done to verify their detectors, and said "this don't make no sense, but it's what we got".

These "reactionless drive" guys are off into fantasy land already, and seemingly they haven't even stopped and paused about their control also producing an effect.
 
This gadget reminds me of the Crookes Radiometer.   Remember those?  Glass-bulb with 4 vanes, painted black on one side - Sat in the window sill and Spun with no (heh) apparent reaction?
It's been demonstrated the Crookes worked by micro air currents due to differential heating.  I.e. in hard vacuum the radiometer device stops spinning.   Air-currents.  Very small air-currents.   
 
+John Baez Roger Shawyer's version makes more sense but he's still violating conservation of momentum so if his device works at all it must be because it's radiating losses anisotropically. And the efficiency from a "solar powered" version cannot be better than the radiation pressure you'd get from a perfect mirror the size of your solar panel.
 
>hey, if the gizmo actually works, isn't that good enough?

It's more than good enough; even if the technology would be useless (not the case here), an experimental result that's impossible by our current theories is very exciting!  Too bad that it doesn't work.
 
+Dr. Gary Rutledge : the Crookes' radiometer was exactly what I thought of when I read these results.  And it took about 50 years for people to sort out in a satisfactory manner exactly how the radiometer spins the way that it does; air currents can do surprisingly subtle things!

Another thing that gets me about such results: if conservation of momentum can in fact be violated in a macroscopic system, I would expect, without doing any math whatsoever, to find that it is violated all the time in really obvious ways.  In other words, I would expect to see violations all over the place.  Considering how fundamental COM is for all of particle physics, for instance, it shouldn't take a special resonating cavity to find something really weird going on.

This is one of my big guidelines in assessing systems like this: if you find a violation of a fundamental physics law, you have to explain to me why it hasn't been noticed in 200+ years of research before I'll spend a lot of time trying to understand your results.
 
Guido Fetta? How can something invented by a Star Wars character not work?
 
You say "there's no such thing as a 'quantum vacuum plasma'." But another NASA document talks about it as if its existence is a given, stating (referring to it as 'virtual plasma'):

"The virtual plasma is exposed to a crossed E and B-field which induces a plasma drift of the entire plasma in the ExB direction which is orthogonal to the applied fields."

Google document title: "Eagleworks Laboratories: Advanced Propulsion Physics Research"
Jay Cie
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Um, you are saying that the "free version" is where the errors are shown and it is also not the same paper as the pay one? You do see the problem there.

That said radiation pressure is an amazing if not that thrilling manse of propulsion. Using the relativistic mass of light as propellant is amazingly efficient if massively slow. It's also behind one of the biggest once mysteries of space exploration.
 
The theory is likely wrong but I have the position that most theories are likely wrong so that doesn't bother me; you can just strike the theoretical aspect away until later.

That there might be substantial pay-off is an argument which drives a lot of research, like quantum computers, so you might either care about it or strike it away.

They found an experimental effect in two devices which, as +John Baez pointed out, is likely due to heat. But the experimental effect is there.

There is nothing to do except for running the experiment once under clean conditions. Doesn't bother anyone, just makes the experimental physicists a bit better at their work. You'll likely won't find anything but maybe you do; there are reasons to assume we don't know everything.
 
Lot of speculation here without any empirical data. Perhaps you should actually perform the experiment and disprove them. That is how science works. 
 
Has anyone pointed out that there should be no energy dissipation in this device? A resonant cavity should not dissipate, yet they claim to be supplying 17 or 28 watts of power. This power has to go somewhere -- likely into heating the structure, presumably non-uniformly, leading to "thrust" in the air. One questions where the heat will go in a vacuum environment. Perhaps it just continues to get hotter, eventually producing photons and thrust that way ;-).
 
Sorry but this is how science (still) works:
http://goo.gl/E59fYw 
I rarely do attend conferences with real hard-core scientists (who won’t take artists seriously anyway) but the last time I happened to crash one, all sorts of outrageous clams defying common sense made me speechless  ...
One young researcher made it her habit to attend every auditorium once, ask a simple question to the board while promoting her latest research project: "funding very much appreciated" was the catch phrase I vividly remember: girl got to live.

Since I was too late to troll yesterday’s debate before comments had been closed here some enlightenment regarding ideology (in science):
Slavoj Žižek "Maybe We Just Need a Different Chicken"
 
This is still going around the internet as a true thing.
 
While we are talking about exotic forces and space-drive... What is your take on the Casmir Effect? Can it be used for propulsion?

https://en.wikipedia.org/wiki/Casimir_effect

Applications
It has been suggested that the Casimir forces have application in nanotechnology,[35] in particular silicon integrated circuit technology based micro- and nanoelectromechanical systems, silicon array propulsion for space drives, and so-called Casimir oscillators.[36]
On 4 June 2013 it was reported[37] that a conglomerate of scientists from Hong Kong University of Science and Technology, University of Florida, Harvard University, Massachusetts Institute of Technology, and Oak Ridge National Laboratory have for the first time demonstrated a compact integrated silicon chip that can measure the Casimir force.[38]
 
See note on page 6 of Classical Mechanics by Herbert Goldstein (1950)
 
+John Baez I've seen that NASA vacuum chamber in a doc with Michio Kaku. It was huuuuuuge. The chamber, not Kaku.
 
+Greg Gbur the law of conservation of energy is not being violated with this drive. 
 
If someone could produce a "thrust" by stripping transient/virtual particles out of the "quantum vacuum" then you should be able to repeat the effect in a simpler experiment. If someone at CERN was to get physical particles out of the quantum vacuum with microwaves, it would be Nobel material. It would be a spectacular discovery right up and possibly beyond the Higgs.
There should be some evidence apart from this anomalous "thrust". The energy being used is plenty enough to produce thrust by boiling off atoms/molecules/electrons from ordinary matter in the device and its interactions with the atmosphere.
The idea that the anomalous "thrust" is due to an effect that cannot be demonstrated in simpler experiments, when "ordinary" explanations  suffice, does not bear up to scrutiny. Basically jumping to extraordinary conclusions just because something stumps one, is the stock and trade of pseudo-science.
 
+John Baez, the 'yeh', was a phone typo.  They're using a force measuring apparatus originally described by Woodward at California State.  One of the earlier papers from the group you're discussing was particularly misleading/disappointing because a first reading gave the presumption that they had measured a force where, a more in depth reading revealed that Woodward had reported a force using the same apparatus for his 'thrust generating' capacitor stacks.

In a sense they have started out with one strike against them because they have used instrumentation developed for an earlier experiment that was supposed to have shown a novel thrust producing effect, but which was never accepted by the scientific community at large.  It's an interesting design choice to make.  It begs a few questions:
1.  Did they do it on purpose to appeal to people that might have been fans of Woodward's work?
2.  Did they do it to save time?  Rhetorical since it looks like they rebuilt the Woodward apparatus.
3.  Did they just not think through the implications?

I think this is the paper I read that involved the Woodward instrumenttion
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492.pdf
 
+Matthew Yeager - physicists are mostly divided into experimentalists and theorists.  Experimentalists design and do experiments.  Theorists invent theories, do calculations, and discuss experiments.  I'm a theorist.  The last time I did an experiment I dissolved part of my coat with battery acid.  But experimentalists need critiques from theorists - theorists can be good at spotting mistakes.  Someone should redo this experiment while avoiding the 3 mistakes listed here.
 
+Daniel Estrada wrote: "First the superluminal neutrinos, now this. The history books will have some strange things to say about early 21st century science."

Actually this sort of stuff has always happened.  +Johnathan Gross mentioned N-rays.   Then there's polywater, the fifth force, the pentaquark (well, that was in 2003), the DAMA 'discovery' of dark matter, the cygnet...

Most really surprising new discoveries in physics turn out to be wrong. It's easier to find something amazing by screwing up than by actually finding something amazing.  What's new is that thanks to the internet, the public hears about the false discoveries before they've been weeded out. 

In my posts I'm trying to provide some of the skepticism that any physicist would automatically feel for a 'discovery' such as this.   I'm saying what almost any physicist would think.  Nonphysicists may not realize what a low batting average 'amazing new discoveries' have.
 
+John Baez Yeah well. I find you a bit too negative too. It is far more likely they kind-of rushed the experiment since they didn't expect to find anything too.

But they did. So I would say they're somewhat stuck with doing the experiment properly.
 
+John Baez I'm not even sure the Internet changes the situation much apart from speeding up the exposure-to-explosion-to-debunking cycle, and providing long-running fora for true believers. Popular science magazines and newspapers have spread around half-baked science stories since forever.

And the really grade-A nonsense, the stuff that is not so much half-baked science as outright pseudoscience, has always proliferated in popular books.
 
+Jay Cie wrote: "Um, you are saying that the "free version" is where the errors are shown and it is also not the same paper as the pay one?"

I was a bit confused.  The abstract in the paper:

http://rghost.net/57230791

contains dramatically different information than the abstract on the NASA technical report server:

http://ntrs.nasa.gov/search.jsp?R=20140006052

The latter says the experiment was done when the "vacuum chamber" was full of air.   This is strange. 
 
+GoddardsJournal wrote: "You say "there's no such thing as a 'quantum vacuum plasma'." But another NASA document talks about it as if its existence is a given, stating (referring to it as 'virtual plasma')."

Yes, this was put put out by the same lab, the Eagleworks Laboratories.  That's part of the problem: these guys are living in an alternate universe when it comes to the laws of physics.  Google "virtual plasma" and "quantum vacuum plasma" and see what you get.   Mainly just these guys, and people talking about these guys.  I'm pretty much an expert on quantum field theory, which is where people study the quantum vacuum and virtual particles.  But nobody in that subject talks about "virtual plasma" or "quantum vacuum plasma".  It's not a thing. 
 
+Greg Gbur You said, "Another thing that gets me about such results: if conservation of momentum can in fact be violated in a macroscopic system, I would expect, without doing any math whatsoever, to find that it is violated all the time in really obvious ways."

You mean like the entire universe actually accelerating away instead of gradually slowing down? 

I am not saying this experiment means much. Most likely some sort of unknown measurement error. But there is the slightest chance something new to physics is just on the verge of reveling itself. Possibly an emergent force like buoyancy, but in space instead of a liquid or gas? You really can't just assume measurement error until you find it, any more than you can assume it works either.  There are 3 independent teams of people that got measurable thrust from similar type systems. This one, the British team and the Chinese team. (and rumors the Russians may have but unconfirmed) That's not proof, but it is enough to merit a serious attempt to actually find that measurement error instead of just assuming it must be there somewhere.
 
In the paper:

"How much energy is in the Quantum Vacuum? The theoretical calculation for the absolute zero ground state of the ZPF can be calculated using the following equation[6]:
Using the Plank frequency as upper cutoff yields a prediction of ~10114 J/m3 . Current astronomical observations put the critical density at 1*10-26 kg/m3. The vast difference between QED prediction and observation is not currently understood. "
It can be readily "understood" if one realizes that it is somewhat dubious that one can extend the equations of non-relativistic QM (photon/matter energy levels and interactions) to radiation alone, in the same way. There is a whole raft of assumptions behind the calculation of the energy in the quantum vacuum. The fact that the  calculation returns a result that diverges to infinity until one arbitrarily adds an ad-hoc limit at the Planck length, simply shows that the assumptions don't work. 
The situation is very akin to cold fusion. The power of the thrust is billions of times less than the power input, too much wriggle-room.
 
Scott Strough said: "You mean like the entire universe actually accelerating away instead of gradually slowing down?"

I don't think anybody believes that is the result of violation of conservation of momentum.  This is where the term "dark energy" comes from.  And it's beside the point.  This isn't an experiment on a cosmological scale: if it were so trivial to violate conservation of momentum, it would cause trouble at all levels of physics.

Azure Mallone: "the law of conservation of energy is not being violated with this drive. "

Did I say it was?  I believe I said "conservation of momentum," which is a completely different law.  Symmetry of physical law in space = conservation of momentum.  Symmetry of physical law in time = conservation of energy.
 
+Greg Gbur Actually, the general-relativistic mechanism involved in cosmic acceleration through dark energy does do funny things to conservation of energy/momentum. The easiest way to describe it is that energy is just not conserved in that situation for the case of the whole universe.

Unfortunately it's still nothing you could exploit to build a free-energy or free-momentum machine, since it's still possible to define sensible versions of energy and momentum that are strictly conserved for any system that is confined to a limited area of space.
 
+Asbjørn Heid wrote: "At least the folks at OPERA basically reported what they saw, what they had done to verify their detectors, and said "this don't make no sense, but it's what we got"."

Yes, the superluminal neutrino experiment at OPERA did most things right.  Their paper did not, for example, contain a section on how superluminal neutrinos would revolutionize interstellar communication.  They didn't make up goofy buzzwords to "explain" why neutrinos went faster than light.  They said a lot about possible sources of error, and asked people to confirm their work.

They didn't sufficiently apply the first law of engineering: when in doubt, check the cables

And they suffered:

In the months after the initial announcement, tensions emerged in the OPERA collaboration.  A vote of no confidence among the more than thirty group team leaders failed, but spokesperson Ereditato and physics coordinator Autiero resigned their leadership positions anyway on March 30, 2012. In a resignation letter, Ereditato claimed that their results were "excessively sensationalized and portrayed with not always justified simplification" and defended the collaboration, stating, "The OPERA Collaboration has always acted in full compliance with scientific rigor: both when it announced the results and when it provided an explanation for them."
 
+John Baez Thanks for your reply! What about quantum plasmadynamics (QPD)? It appears to be a recognized field, or concept, in physics. Does it not involve vacuum fluctuations being understood in some way as a plasma?
 
+GoddardsJournal - A plasma is a gas so hot that the atoms in it are mostly ionized: many of their electrons are stripped off.  A candle flame is just barely a plasma; an aurora or the interior of the Sun is a full-fledged plasma.  As with all other forms of matter, if you want to understand plasma very deeply you need to take first quantum mechanics and then quantum field theory into account.  Very roughly, quantum mechanics is the application of quantum ideas to particles, like atoms, while quantum field theory is the application of quantum ideas to fields, like electromagnetism... and the realization that there's no fundamental difference between particles and fields.  The classic example of quantum field theory is quantum electrodynamics, which applies to the electromagnetic field and its interaction with charged particles.

In his 2008 book Quantum Plasmadynamics, Donald B. Melrose writes:

The idea of synthesizing quantum electrodynamics (QED) and the kinetic theory of plasmas first occurred to me in the early 1970s. The project to do so has been carried out bit by bit over the subsequent years. The name “quantum plasmadynamics” (QPD) is my own jargon for the synthesized theory.

This makes perfect sense.  It's not about "virtual plasma" or "understanding vacuum fluctuations as a plasma", whatever those would mean.  It's about studying plasmas - honest-to-goodness, real plasmas! - with the help of quantum field theory (QED in particular). 
 
+Marco Devillers wrote: "It is far more likely they kind-of rushed the experiment since they didn't expect to find anything too."

On the contrary, I believe this team plans to develop new methods of interplanetary travel based on their device.  Here's something else they wrote:

NASA/JSC is implementing an advanced propulsion physics laboratory, informally known as "Eagleworks", to pursue propulsion technologies necessary to enable human exploration of the solar system over the next 50 years, and enabling interstellar spaceflight by the end of the century. This work directly supports the "Breakthrough Propulsion" objectives detailed in the NASA OCT TA02 In-Space Propulsion Roadmap, and aligns with the #10 Top Technical Challenge identified in the report. Since the work being pursued by this laboratory is applied scientific research in the areas of the quantum vacuum, gravitation, nature of space-time, and other fundamental physical phenomenon [sic], high fidelity testing facilities are needed. The lab will first implement a low-thrust torsion pendulum (<1 uN), and commission the facility with an existing Quantum Vacuum Plasma Thruster. To date, the QVPT line of research has produced data suggesting very high specific impulse coupled with high specific force. If the physics and engineering models can be explored and understood in the lab to allow scaling to power levels pertinent for human spaceflight, 400kW SEP human missions to Mars may become a possibility, and at power levels of 2MW, 1-year transit to Neptune may also be possible. Additionally, the lab is implementing a warp field interferometer that will be able to measure spacetime disturbances down to 150nm.  Recent work published by White suggests that it may be possible to engineer spacetime creating conditions similar to what drives the expansion of the cosmos. Although the expected magnitude of the effect would be tiny, it may be a “Chicago pile” moment for this area of physics.

The "Chicago pile" was the experiment that demonstrated a nuclear chain reaction.

The whole paper is worth reading - I thank +Hamilton Carter for pointing it out:

• Dr. Harold “Sonny” White, Paul March, Nehemiah Williams, and William O’Neill, Eagleworks Laboratories: advanced propulsion physics research,  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492.pdf.
 
+Matt McIrvin wrote: "I'm not even sure the Internet changes the situation much apart from speeding up the exposure-to-explosion-to-debunking cycle, and providing long-running fora for true believers."

Someone should do a careful empirical study on this.  I feel as if more people are getting exposed to this incident than would have happened 20 years ago.  For example, yesterday (Aug. 3) NBC News did a story on it:

http://www.nbcnews.com/science/weird-science/impossible-space-engine-might-work-nasa-test-suggests-n171201

This story says it was based on the Aug. 1 story in Space.com:

http://www.space.com/26713-impossible-space-engine-nasa-test.html

which says it was based on the July 31 story in Wired.co.uk:

http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive

So clearly stories travel faster, but sometimes they seem to get bigger, too.  Or maybe nobody looks at NBC News anymore.
 
Could they could put the amplifier outside the chamber?
 
+John Baez I have to admit one thing. The media is very quick to report anything fantastic in science and give the impression that the results are immutable. However, I find theoretical physicists are in the same ball park as philosophers. Nice to listen to but 90 percent of what they come up with sounds much like a guy on acid trying to tell you about religion..... BTW don't take that personally I'm just joking around.
 
I guess I'm thinking from personal experience: 30 years ago, this would have been something I'd have read an excited, fairly uncritical article about in Omni magazine or The People's Almanac or something, and then vaguely wondered about for the next ten years.
 
Ah well. I still believe QM is a discretization of a continuous phenomenon so there might be something there. Not holding my breath though.
 
+Matthew Yeager - unless you get into technical details and equations, there's no way to really understand theoretical physics.  Matt McIrvin studied particle physics in grad school at Harvard so you can trust what he says.  Anyone else, take with a grain of salt.   Journalists especially.
 
For people keeping careful score, I should admit I was mixed up about something.  It's the abstract on the NASA technical report server:

http://ntrs.nasa.gov/search.jsp?R=20140006052

that says the experiment was done when the "vacuum chamber" was full of air.   Not the abstract on the journal website here:

http://arc.aiaa.org/doi/abs/10.2514/6.2014-4029

Maybe they managed to evacuate the chamber before they actually wrote the paper, which you can get for free here:

http://rghost.net/57230791

Maybe not.  The NASA technical report server lists a date of July 28, while the paper is from a conference held July 28-30.

I have fixed my mistake on the blog article and a comment above.
 
+John Baez Thanks again! You're right, that use of 'plasma' refers to known plasma. A wiki entry indicates that the "plasma" allegedly involved with these thrusters is theoretically generated from quantum vacuum fluctuations. So ever-present quantum fluctuations are allegedly being used as a fuel / propellant source.

So 'quantum vacuum plasma' generation may be a core hypothesis here such that tests for this technology amount to tests of the 'quantum vacuum plasma' hypothesis.

The wiki entry reads: 

The Q-thruster operates on the principles of magnetohydrodynamics (MHD), the same principles and equations of motion used by a conventional plasma thruster. The difference is that the Q-thruster uses the atomic particles spontaneously produced by quantum vacuum fluctuations as its propellant. The atomic particles produced by the fluctuations are subsequently electrically ionized to form a plasma. The now electrically charged plasma is then exposed to a crossed electric and magnetic field, inducing a force on the particles of the plasma in the E×B direction, which is orthogonal to the applied fields.

Wiki entry: Quantum_vacuum_plasma_thruster
 
+GoddardsJournal wrote: "So ever-present quantum fluctuations are allegedly being used as a fuel / propellant source."

Yes, that's their idea. Unfortunately while you can use energy to "turn virtual particles into real ones", this is just another way of talking about creating particle-antiparticle pairs from energy, e.g. energy in an electromagnetic field.  This process is well understood and well studied in the lab. It most definitely does not let you create a "reactionless drive".  It's also not something you can do by bouncing microwaves inside a metal container.

The Eagleworks team writes:

"[...] even though QED is one of the most experimentally successful theories to date, the community’s understanding of the vacuum is only just beginning as this is a new field, and the study of the quantum vacuum is at the leading edge of science with a wide open horizon to explore."

This is not true: experts know a lot about the quantum vacuum, much more than these guys, and it is not a "free lunch".

The wiki entry you cited was written by someone without much expertise.  For example, it mentions "atomic particles".  Experts talk about subatomic particles (like electrons, protons), but what's an "atomic particle"?  An atom?  Okay, but those are called "atoms".

More importantly, atoms aren't "spontaneously produced by quantum vacuum fluctuations".  You can create atoms (together with anti-atoms) if you put in enough energy using E = mc².  But is someone really planning to create matter from energy in order to shoot it out the back of a rocket?  Making 0.7 grams of matter (and antimatter) takes the energy of Hiroshima bomb.
 
I blame poor math teaching. Those people should learn surface integral, if they don't want to learn momentum conservation.
 
Well that shoots my whole explanation behind how I time-traveled to the lesser Magellanic Cloud in the ass... thanks a lot!  (sarky)
 
+John Baez I really don't think that's what they are saying John. Granted it may well be wrong what they are saying, but at least attack their hypothesis instead of making up some new thing. They are not talking about using the energy to create matter/antimatter pairs and shoot them out the back. They are talking about pushing against the virtual pairs, which supposedly are popping into existence  and annihilate all the time and don't leave the system.

As a thought experiment.....imagine a normal reaction thrust engine that spits out a material with a 1/2 life of 1 hour. It provides thrust.....but 1 hour later most of it goes poof. Several hours later the traces of the propellent are negligible. Now imagine the propellent has a 1/2 life of 1 minute. 1 second...... The trail of propellent behind the rocket is ever shorter. If you keep reducing the 1/2 life of the propellent, eventually the plume behind the rocket will be so short it actually disappears before leaving the rocket exhaust pipe. The 1/2 life of a matter /antimatter pair is very short indeed. If the team actually is using that somehow as the reaction mass, there would be an "exhaust" so short it would appear to be nothing at all.
 
+Scott Strough wrote: "They are talking about pushing against the virtual pairs, which supposedly are popping into existence  and annihilate all the time and don't leave the system."

Maybe that's what they want to do.  But that's not possible.  So I turned my attention to something that is.  You can't push against virtual particles unless you turn them into real particles, because momentum is conserved, and at the end of the day, if you accelerate in one direction, something real has to accelerate in the opposite direction.

"The 1/2 life of a matter /antimatter pair is very short indeed. If the team actually is using that somehow as the reaction mass, there would be an "exhaust" so short it would appear to be nothing at all"

Actually you'd get gamma rays, and other forms of light, and other particles: that's what happens when matter and antimatter annihilate.  They don't just go away invisibly.  It takes energy to make particle-antiparticle pairs, and you get energy back when they annihilate.

(Virtual particle-antiparticle pairs are free, but for that very reason you can't use them to push yourself.)
 
I find it really scary that they are letting a bunch of NASA Eagleworks amateurs loose with the stuff for  'creating conditions similar to what drives the expansion of the cosmos.'
I think people should take this up immediately with their Republican representative in Washington.  Get some reality into the science conversation.
 
Great article, John.  Truly humbling to see your mind at work on this topic. 

Nonetheless (and apropos of nothing), I still assert that my original contention that I participated in an FTL NASA mission in 1966, which was fueled by 'dark matter' procured from the Lesser Magellanic Cloud (100,000 light-years distant).  We simply used the dark matter from the Magellanic Cloud to fuel the super-rocket that went there, to pick up and collect the dark matter, and then merely traveled faster-than-light (back into the past, before the launch had occurred), so that we could use the dark matter as fuel for our mission.  Obviously, it worked, or I wouldn't be here.  RIght???
 
+Nick James wrote: "I find it really scary that they are letting a bunch of NASA Eagleworks amateurs loose with the stuff for  'creating conditions similar to what drives the expansion of the cosmos'."

Are you serious?  If so, don't be scared.  They are bouncing 28 watts of microwaves around inside a copper can. Your microwave oven is more dangerous.
 
+John Baez  :-)
I'm vastly more scared by the potential reaction from the intellectuals in the Republican party. Maybe they will pull the funding plug again, just to stop this nasty expansion stuff being proposed by NASA.  Oh, no, wait... Republicans are in favour of expansion, right?  Give it more funding NOW.
 
+Nick James - okay, whew.  Sometimes people actually mean what they say on the internet. 

You do, however, suggest a nice way to shut this operation down.
 
Much of what sustains this is that a lot of people seem able to suspend disbelief in some strange thing when it's explained as interaction with virtual particles in the quantum vacuum.

But, really, "interaction with virtual particles in the quantum vacuum" is a way of describing almost everything that happens in the world. It's not as if this is some special phenomenon off to the side that works by completely different rules.

I've been pondering why the characterization has this effect, and I think part of it is the general "quantum = magic" notion that you see about in mass media.

But, more specifically, there's this idea that virtual particles are things that are exempt from normal conservation laws. There's a way of describing them that you often see in popular articles, that the uncertainty principle allows the "borrowing" of energy from nowhere for a short time, so they're not really subject to conservation of energy. The world does some kind of temporary sneaky trick while you weren't looking.

That's roughly inspired by the way perturbation theory was handled mathematically in nonrelativistic quantum mechanics; sometimes it's called the "pre-war" handling of perturbation theory because it preceded such things as Feynman diagrams.

Actually, though, nothing quantum is specially exempt from normal conservation laws.

You can see that even with Feynman diagrams: energy and momentum are conserved at every interaction vertex, just like every other quantity. What's suspended is the need for a virtual particle to be "on-shell", that is, for its energy and momentum to exactly obey the normal laws of motion for a particle. And that's because it's not actually a traveling wave corresponding to a real particle; it's some other field configuration. I suppose you could describe it as the uncertainty principle allowing the "particle" to conform to the necessary supply of energy, rather than vice versa.
 
Dear John, that wasn't actually the control. I found this here:

http://www.reddit.com/user/dalovindj

You've still got it wrong. There weren't two controls. The RF load was the single control over multiple tests of two different designs (the two test articles). You have to pay the $25 to read the paper to see the elaboration on the control, but surely if the control produced the same amount of thrust there would be nothing to publish. It would be immediately clear to everyone that it was a measurement error. What you are suggesting is nonsensical and is directly contradictory to what is in the paper and to what was reported by people who attended the presentation.
The null configuration (not the RF load - not the control but the central subject of a test) was one of two test articles. There are two competing theories as to how the phenomenon works. Fetta believes that it works based on asymmetry in the design, while White believes it works by pushing against the quantum vacuum.
They tested an asymetric and a symetric design. The symmetric design (neither were "broken") is what they refer to as the null. It was meant to test a prediction of Fetta's theory on how the device produces thrust. He believes that the force is produced by an imbalance of the lorentz force caused by the asymmetric chamber. This test seems to indicate that Fetta's theory is incorrect (or at the very least innacurate). Dr. White's theory on how thrust is produced (pushing against the quantum vacuum), however, predicted that both test articles should produce thrust, which they did. It would seem an endorsement of White's theory over Fetta's.
Pony up the $25 and read the paper yourself. I don't know how to explain it in any clearer terms. You are entirely off base.
 
+Daniel Rocha - I read the free version of the paper here, and pointed everyone to that:

http://rghost.net/57230791

Is this the same as the version that costs $25?  I imagine so.

In my article, I said that the the slots making no difference was "evidence against Fetta's idea" - not evidence against all variants of this scheme.  I said that the RF load feeling no thrust was "rules out some possibilities of experimental error... but not others".  Nothing you just said makes me feel I was wrong about this.  My only mistake, perhaps, was in the summary version of point 1.
 
+Miguel Carrion Alvarez Maybe I will... There's a whole other aspect, probably more important, that I didn't get into, which is the notion of "something" existing in empty space, and how this resembles and does not resemble the old luminiferous aether.
 
...I've spent a lot of time thinking about these issues, and the reason is kind of embarrassing: I basically flunked Sidney Coleman's quantum field theory class the first time I took it, and I did a lot of pondering in the process of getting myself deconfused.
 
+Matt McIrvin - I think another big stumbling block for layfolk is the blurry division between physical reality and our mathematical formalization of it.  Virtual particles seem to hover in a no-man's land between "real thing" and "mere calculational trick"; it takes quite a while to understand their role.

For example, if you say there's a "pre-war" version of perturbation theory in which virtual particles violate conservation of energy and momentum, and a "post-war" version in which they don't, ordinary folks will want to know which one is "right". Saying that they're just different calculational techniques that both give the same final answer won't go over well... though I would want to push that lesson.
Georg S
 
I miss Lucius Aemilius Paullus and Gaius Terentius Varro among
the authors names.
Hannibal
Translate
 
"Quantum vacuum virtual plasma"
My cat barfs this stuff up all the time. It has strings in it too.
 
+John Baez Top commenter of Wired article suspects experimentalist might find how to resonance a dark matter by chance.  And many people supports this comment.
http://www.wired.co.uk/news/archive/2014-07/31/nasa-validates-impossible-space-drive
WDYT? Is it possible that this phenomenon is beyond standard model or QED that human has?

"I believe that they might be hitting a dark matter resonance: microwave photons have approx. 10^-23 Joules = 10^-4 eV. Josephson-Junctions experiments discovered an axionic dark matter resonance at.. 0.11 meV. This cavity is tuned to 10^-25 Joule photons, if this connection I suspect is correct, the maximum thrust should occur at 100 Ghz frequencies"
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.231801
 
With all due respect, I think you're doing these charlatans a favor by trying to disprove their nonsense quantum whatever ZOMG PATENTED!!!11 engines. Just remember Russell's teapot. 

Everywhere around the net all I see from regular people is that the evil scientists are bullying these "geniuses" into silence and submission. This gives them undeserved publicity and weight into the eyes of the general public. 

In my opinion, nonsense "scientific" work should be completely ignored by the mainstream science and engineering. Without publicity their "genius" ideas will simply wither and die. 
 
+John Baez +Matt McIrvin The magical properties of vacuum and particles has echoes of the business about 6 weeks ago about the speed of light.  That has almost vanished, I think.

I am impressed that they claim to detect waves on the shore 25 miles away.  Does all hell break loose when a large truck passes the door?
 
+John Baez
Well why not? I'm able to make my car go by pushing against the steering wheel. Fund me!
 
A lot of people have been asking me about this (I'm the physicist of my circle of friends). All I could say, without actually diving into this stuff, is that it sounds like baloney. But it's good that some people take the time to seriously analyze these claims. And then say "sounds like baloney" over 251 lines, but still! 
 
+John Baez If you read between the lines of their online abstract, what happened was they spent several days achieving vacuum conditions (which takes days as described in the full study) only to run into "technical issues." Read: they discovered that their RF amplifiers were not vacuum compatible. D'oh! Then they "resolved" that issue by taking the "test article" back out of the chamber, and then putting it back in (as they state) albeit at atmospheric pressure (as they also state later). 

Well, that's not actually resolving the technical issues!
 
+Miguel Carrion Alvarez +Nick James This cat is way too big (25lb) and clever to be trapped in a paradox box and I believe he...um...knows things. Can't say more now...he's standing at the door with that look. ;)
 
+Scott Strough When you say "They are talking about pushing against the virtual pairs, which anialate and don't leave the system" :
Surely this would mean that the "virtual pair" would decay to a Photon with the momentum that was added by the microwave photon. Hence, a photon would still leave the system.
If I read Feynman right, the intermediate step of a "non-virtual" photon interacting with a virtual particle pair, which then annihilate, will return a photon again.
To say that the annihilation does not return "anything" flies in the face of the physics that we have on virtual particle mediation in quantum processes.
 
+John K N Murphy - you've read your Feynman correctly.  At a more basic level, if some particles don't "leave the system", then you can't use them to accelerate your system. 

I can accelerate a rocket by throwing a tennis ball out the back end.  But if I throw it and a net attached to the rocket catches it, that won't accelerate the rocket.  More precisely, the rocket will accelerate when I throw the tennis ball, and decelerate again when the net catches it.  If the rocket is initially at rest, the center of mass of the rocket will never move throughout this whole process.

This is all due to 'conservation of momentum'.   Tennis balls are easier to understand than virtual particles, but conservation of momentum applies equally well to both.  If someone claims they have a new machine that violates conservation of momentum, they can't use virtual particles to justify how it works.  They are trying to overturn everything we know about physics, and the only way to do that is by doing experiments, getting skeptical people to replicate them, and making sure all sources of experimental error are eliminated.
 
+John Baez  I like to take a "special" relativistic view of momentum, (as in the special relativity treatment of the Compton Effect) where momentum is mathematically equivalent to conservation of the "light-like" component of an object's mass-energy being conserved as a vector in space-time. I know its not a common way of looking at momentum, but it does appear consistent and allows one to treat collisions in a relativistically consistent manner. All one does is treat a photon's momentum as its energy, and then treat a particle with mass as having a "momentum" "with time" and "across time" (the latter photon-like). 
The total "with time" energy is conserved as a magnitude, while the "across time" component is conserved as a vector. From that, you can describe all of classical mechanics, and illustrate particle interactions (such as pair creation/annihilation from photons) provided one attributes matter as having a "sense" in 4D space-time (matter/antimatter).
Applying that slightly unconventional, (but I would argue completely equivalent to the conventional), way of representing energy/momentum gives a clear way to visualise the interactions in question WRT momentum.
 
Another idea for "free thrust"

Is it theoretically possible to harness/capture cosmic particles and use them for thrust?

This is an itch I cannot scratch.
 
+David Edenden - yes, in theory one could catch cosmic rays (meaning high-energy protons and atomic nuclei hurtling through space) and use them for propulsion.  But it sounds tough for various reasons; mainly:

1) They don't provide much thrust compared to, say, sunlight.

1) Unlike sunlight, they tend to come from many different directions in the sky.  So, to get a net thrust in one direction you'd want to figure out how to catch more coming from a given direction than the opposite direction.

Both these problems go away if you use sunlight.  People are already testing out solar sails for propulsion in outer space.  This is an elegant idea that actually works - check out the movie here:

https://plus.google.com/u/0/117663015413546257905/posts/JecnDz1zR7a
 
Could it be that they forgot to make a vacuum in the chamber and they are just ionizing the air?
 
+David Edenden  Some science fiction stories use versions of a fusion "ramjet" that used a vast electromagnetic "funnel" to scavenge hydrogen from space to get both fuel and mass for a spaceship's drive.
 
+John Baez Surely the Cannae drive should be bidirectional and just as likely "brake" virtual particle pairs as "accelerate" them, which would give no net thrust, where do they get the asymmetry from?
 
+Kam-Yung Soh - thanks!  Yes, we've been talking about this stuff over email in the last few days.
 
+John K N Murphy wrote: "Surely the Cannae drive should be bidirectional and just as likely "brake" virtual particle pairs as "accelerate" them, which would give no net thrust, where do they get the asymmetry from?"

First of all, you can't accelerate or brake using virtual particles, as I've explained earlier in this thread.   So we can forget about that.

But they seem to be observing some asymmetrical effect even if it has nothing to do with what they claim: e.g., asymmetrical air currents.  So it makes sense to ask your question: where do they get the asymmetry from?

This is a good question.  In the device designed by Fetta there are slots on one side but not the other.  But they also tried a device with no slots on either side, and still reported a force! 

The obvious remaining asymmetry is that they pump the microwaves into one end of the device and let them go into an antenna (a wire) at the other end.  So I guess that has something to do with it.
 
John Baez
Thanks ... now I can sleep at night.

But if you could capture them, then propulsion can be done in the far reaches of the solar system where the sun's rays are very weak.

Also because propellant is not needed on board, then approaching the speed of light may be possible  ... I think.
 
+David Edenden
See: https://en.wikipedia.org/wiki/Bussard_ramjet

This was discussed in the original Cosmos by Carl Sagan along with other possible designs for interstellar travel.

The kinematics is not very practical, but if you can use the captured cosmic rays to fuel a nuclear reactor and use the nuclear waste as propellant it might have a decent efficiency.
 
I'll just add that 'cannae' is the usual transcription for the way we Scots pronounce "can't". Not strictly relevant but humorous nonetheless.
 
+John Baez wrote: "The obvious remaining asymmetry is that they pump the microwaves into one end of the device and let them go into an antenna (a wire) at the other end."  

And also of course one end is longer than the other, as the picture shows!
 
+John Baez
I fjust found more detail:

"To start, if we add all the energetic charged particles originating at the Sun and stellar explosions, we find that the energy striking the Earth is about 5 joules/sec/km2 (where 1 joule/sec = 1 watt). That means that were you to collect all the energy of cosmic rays over 12 square kilometers, you would have enough energy to power a 60 watt light bulb"

http://helios.gsfc.nasa.gov/qa_cr.html

Scientific facts are soo annoying!
 
I keep seeing the 'nothing leaves the drive' meme. Surely at least thermal photons leave the drive, even if the microwaves don't?

Of course that wouldn't get you the sort of thrust they're talking about, only the maximum of 3.3 microNewtons per megaWatt that John has posted in a comment in the earlier article. https://plus.google.com/117663015413546257905/posts/WfFtJ8bYVya

And that's assuming you could coax all of those (thermal) photons to scoot out the back.

So something leaves. In equilibirum as much power as you put into the cavity will be leaving it.

But the physics we know won't explain the thrust they see. So yes: either new physics or botched experiment and history thus far favours the latter.
 
Ok, so it violates the conservation of momentum because in these devices they tested, none of them allowed the em waves to exit the resonating chamber?
 
+John Baez Given a particle/antiparticle pair can, at least transiently, form an "atom" as has been observed in experiments, then a photon should be able to couple to one, and give it linear momentum, as happens in recoil of spectral emission.
My earlier point, is that should this happen, then when the 'moving' particle pair annihilates, (as by the work Feynman, and others) it would then leave a 'real' photon again.

What I intended to ask is perhaps better put as: Do a thought experiment. Just suppose that they are coupling to virtual particle pairs, that as they indicate, subsequently annihilate.
Then if that is so, then a) the coupling and annihilation transaction is (according to QED) photon in, photon out. Which is technically the same as having the "thrust" being radiation pressure. b) There is no apparent asymmetry in such a mechanism, the radiation field is symmetric in the forward/back direction, any resultant momentum transfers would cancel out regardless.
Now as you pointed out, a) given the power of the supposed "thrust" higher than the power of the thrust form EM radiation pressure, then it comes from somewhere else.
In this regard, the experimental system is dissipative (eddy currents) and losses in amplifiers etc. mean that it is very inefficient. There is far more power going in to the system, than the power of observed the "thrust" by what, a factor of a billion? So other effects, heating, gasses boiling off surfaces, transfer of heat to gasses etc, could well be the cause, as in the Crookes Radiometer (which goes the opposite way that one would expect if the rotation were due to radiation pressure).
 
+John K N Murphy wrote: "What I intended to ask is perhaps better put as..."

I don't see a question after that, except for this:

"There is far more power going in to the system, than the power of observed the "thrust" by what, a factor of a billion?"

Power and thrust are in different units: power is energy per time, while thrust is momentum per time so there is general no numerical answer to your question here. 

However, if we obtain thrust by shooting out photons (= electromagnetic radiation), we can say more: one kilowatt of power provides 0.33 micronewtons of thrust.   So, the NASA experiment is getting much more thrust than could be explained by converting all their power into electromagnetic radiation and shooting that out.
 
Cannae optimised their cavity design based on an e/m simulator (perhaps COMSOL) which was showing an unbalanced net Lorentz force - of course disallowed by standard physics. The details are on Cannae's website. Puzzling is that the sim designers could not find the error.
 
+Andrew Palfreyman - when Greg Egan calculated the force produced by microwaves bouncing around in a conical cavity he got a nonzero answer until he did the calculation right:

http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html

To do the calcuation right, he needed "to be careful, because some modes of the cavity radiation will induce a redistribution of electric charge in the cavity walls, and there will be an additional force due to the interaction of the electric field and that charge distribution."

Maybe Cannae forgot that?
 
The theoretical arguments are always irritating; it's like taking a mathematical world in which manifestly 2+2=4 and insisting that through some elaborate, pages-long calculation process you can come up with 5. Or those joke "proofs" people always post on Facebook that 1=0.

With those, everyone knows there has to be a problem somewhere, even if they can't find exactly where it is. This is really the same kind of thing, except that the intermediate steps get pushed far enough out of the realm of most people's expertise that it doesn't seem as clear, and the burden of proof shifts.
 
I see a conspiracy in the making. When this is proven to be ill founded, which it most probably will, internet rumors will start of the mysterious powers that be stifling the next best thing to sliced bread.
 
+John Baez My apologies for the apparently garbled mix-up with thrust and power, I do understand the physics and the units.
I was thinking at the time of conventional thrust, where a stream of mass is accelerated. In that situation there is a clear link between the power required to produce the thrust, i.e. the rate at which kinetic energy is transferred to the "jet" and the resulting thrust. A tethered rocket/jet engine has a relationship between thrust, and the power required to produce that thrust.
The only thing about the Cannae drive in this respect, is that the power required to produce a "conventional" thrust of 30 micro Newtons, by say, heat transfer to gases, is many orders of magnitude less than the power being fed into the unit. Much of the power is possibly being dissipated (e.g. by eddy current) so there could well be a variety of ways that thrust is produced, and at the very least, a good experiment should outline, and characterise, the "uncertainty" due to such extraneous means.
If one calculates the uncertainty, in calibrating the "zero thrust" condition, then the measurement may be insignificant.
 
+Matt McIrvin The EmDrive is like those silly proofs. The tapered can has supposedly more radiation pressure force on one end  to the other. This is just as silly as saying I can make a "free energy" tapered can elevator motor by filling it with high pressure gas, it will rise or fall according to whether large end is up or down.
 
What about Noether's theorem which seems to imply -- correct me if I'm wrong +John Baez-- that if momentum is not conserved than the very laws of physics would be dependent on location. If this were so it would actually mean the end of Experimental physics.
 
+Bill Reed Either that, or the laws of physics can't be described by a Lagrangian interaction (contrary to everything else that seems to be the case).
 
+Matt McIrvin
Thank you for the clarification! I amend my conclusion to: "If this were so it would actually mean either the end of Experimental physics. or the end of theor3etical physics as we know it." :-)
 
+Bill Reed - to me, a better wording of the amended statement is given in the second paragraph of +Greg Gbur first comment. Same point, same zero meaning to the fans, but being less dramatic may get you further with a genuine layman who wants to find out why it's really not worth talking about scientifically and then to ask how was it funded over other projects.
 
+Colin Gopaul
I am a laymen and the comment I made has been on my mind since shortly after I began commenting on this post. Tired of waiting for the comment, I made it. Again, I am a layman ... but apparently not a layman like some.
 
+John Baez I found some 'heavy-duty maths' from one of the NASA scientists undergirding the Q-drive and quantum plasma talk here : forum.nasaspaceflight.com/index.php?action=dlattach;topic=13020.0;attach=173105 They're saying that mathematical models based on known physics predict the ability to achieve propulsion by pushing off of the quantum vacuum. They also refer to other supporting experimental observations @ California State University, Fullerton and ARC Seibersdorf Research, Austria.
 
+Bill Reed
I think I get your perspective now on your preference for your choice of words, not by your words themselves, but by the force of your defense of them.
Interestingly, I too get impatient with getting the type of comments we sometimes want. I guess we are just enjoying google plus and this particular user's post. 
 
A NASA document states: "The idea of pushing off the quantum vacuum has been in the technical literature for a few decades, but to date, the obstacle has been the magnitude of the predicted thrust which has been derived analytically to be very small, and therefore not likely to be useful for human spaceflight." Google quote or fragments for the source. 

Sounds like one possibility is these devices do in fact produce quantum thrust, but the phenomenon won't produce very much thrust. 
 
+GoddardsJournal
The problem is the whole "momentum is not conserved" thing. A law of nature is not allowed to break just a little bit. Either this is bunk or we have been pursuing the wrong track for 400 years.

"Extraordinary claims require extraordinary evidence" and not just some theoretical just so story.
 
+Bill Reed The documents I just cited by the NASA scientists derive predictions of Q-drive propulsion from known mathematical physics. I'm not able to evaluate that math, so I can't explain why that's the case. 
 
+Bill Reed .... just so story and dodgy, unreproducable, experiments, first published in the media. Cold fusion was better...
 
The quantum vacuum giveth, and the quantum vacuum taketh away again, in equal measure ...
Leaving your engine very hot and bothered and zero net momentum.
 
+GoddardsJournal wrote: "I found some 'heavy-duty maths' from one of the NASA scientists undergirding the Q-drive and quantum plasma talk here forum.nasaspaceflight.com/index.php?action=dlattach;topic=13020.0;attach=173105"

Thanks!  This is fun to see.  I wouldn't call it "heavy-duty math" - and it's nothing like standard physics, that's for sure!  The slides aren't self-contained; for example they introduce a scalar field ϕ without defining it.  They seem to be based on a far-out theory of James Woodward:

https://en.wikipedia.org/wiki/Woodward_effect

After all, the slides say "Enter a relativistic gravitational wave equation derived from first principles by Jim Woodward and Tom Mahood."  This equation is nothing ordinary physicists believe - and also, they don't show how to derive any sort of thruster design from this equation.
 
+John Baez I'm no physicist, so for me it's one physicist's word against another (who by his background appears qualified) who isn't present to defend himself. But then it seems the Q-thruster researchers have gone into hiding, even the Cannae website has gone down after the news. So their response to scrutiny doesn't betray confidence. 

What puzzles me is why are they devisings ever-more sensitive means to detect infinitesimal quantities of thrust? Why not just crank up the juice on these gizmos and produce an effect nobody can dispute?!
 
+GoddardsJournal By reproducible, I simply mean being able to isolate and reproduce the actual effect that they say is causing the thrust, not some spurious "thrust" that is in effect a conventional physical "thrust" side-effect generated by the effects of the heat and power being put into the device.
Right now, it seems that any pseudo-science becomes "real science" to the credulous if you put "quantum" in and ten times more so, if you add "vacuum energy", and then stratospheric if you can show people a load of equations that look sufficiently abstruse. Its as if one could say the leprechauns are a subtle effect of "quantum vacuum string metric tensor", and people would start taking you seriously.
In my book, it doesn't get to first base as reproducible evidence of thrust from "pushing" off the quantum vacuum, because they don't have evidence of anything out of the ordinary.
 
+GoddardsJournal - you don't need to be a physicist to tell which physicists are doing work that most physicists believe in.  You just need some common sense and detective work.  For example:

1) Look carefully at that "relativistic gravitational wave equation derived from first principles by Jim Woodward and Tom Mahood" in the slides you showed me:

forum.nasaspaceflight.com/index.php?action=dlattach;topic=13020.0;attach=173105

2) See if you can find it in any published papers or Wikipedia articles on physics.  If it's as important as they say, it should be all over the place!

3) Look for references to Woodward's work on the arXiv, the main repository of physics papers.  So far I just see one, by Woodward himself:

http://arxiv.org/abs/1301.6178

4) Convince yourself that for any idea physicists take remotely seriously, you can find dozens or hundreds of papers on the arXiv.  For example, "quark stars" - hypothetical stars made of quarks:

http://arxiv.org/find/all/1/all:+EXACT+quark_star/0/1/0/all/0/1  
Or "strangelets" - hypothetical blobs of strange quarks.  Compare "virtual plasma":

http://arxiv.org/find/all/1/all:+EXACT+virtual_plasma/0/1/0/all/0/1

(These are probably coincidental hits; check them out.)

5) Talk to various reputable physicists, experts on gravity, and ask them if this "relativistic gravitational wave equation" is something they know about and believe in.

6) Check to see if I'm a reputable physicist or an expert on gravity.  See how many books and papers I've published on the subject. 

And so on.  You can't tell if any idea is right by this kind of test, but you can tell if it's widely accepted or only studied by a very small group of people.

I could demolish Woodward's ideas directly myself, but it's good for you to develop your own "bullshit detection" strategies.
 
+John Baez I found two peer-review studies supporting Q-trusters published in the journal of the Chinese Academy of Sciences (I presume, perhaps in error, that the CAS has reasonable standards). One study reports positive results for tests of a Q-drive (the same Chinese test we've heard about) and the other was published prior to that and predicts thrust from the device based on "classic theory of electromagnetic fields."

Those studies can be found googling their titles:

"Net thrust measurement of propellantless microwave thruster"

"Thrust prediction of propellantless microwave thruster operating on variational power"

The studies are in Chinese, but the abstracts are in English. The EmDrive site as a translation of at least one of them.

So there are two independent groups of scientists both associated with highly reputable scientific institutes and both claiming to have mathematical models that predict outcomes they've thereafter reported to have detected, but this is all a comedy of errors? I mean sure, maybe it is. But this isn't what typical 'junk science' looks like. 
 
 
+John Baez Your general argument seems be an appeal to tradition, that if there's a radically new theory or technology, it should be rejected if there are not already "dozens or hundreds of papers" on it. That would be a reliable argument if all that can be known is known, but there's good reason to assume there's more to be known about the universe. 
 
My replies frequently don't appear. Do you see then to approve them?
 
+John Baez You don't take into account conspiracy way of thinking. Actually  you can not argue with/convince any person with non-scientific-method way of thinking, because "scientific common sense" argument make sense  only in scientific method context. And even more complex, sometimes for some persons scientific method/critical thinking turned off only for specific areas. 
 
+GoddardsJournal wrote: "Your general argument seems be an appeal to tradition, that if there's a radically new theory or technology, it should be rejected if there are not already "dozens or hundreds of papers" on it."

No, the reason I reject the theoretical work of James Woodward and Harold White is that I understand physics well enough to know these ideas are idiotic.  (The device might work, but not for the reasons they describe.)

I was just trying to show you what you could do without learning physics.  I said  "you don't need to be a physicist to tell which physicists are doing work that most physicists believe in."  I also said "You can't tell if any idea is right by this kind of test, but you can tell if it's widely accepted or only studied by a very small group of people."  

This is the situation you're in.  You seem to be saying you can't tell if their ideas are right, because you can't understand the equations in those slides.  You're saying it's "one physicist's word against another".  I'm saying
it's not really like that: it's more like 1000 physicists word against another.  This is something you can confirm without learning more physics.   The only way you can improve your ability to tell if a complicated-sounding physics idea is actually right is to learn more physics.
 
+GoddardsJournal wrote: " My replies frequently don't appear. Do you see then to approve them?"

For some reason your comments are starting to get classified as spam by the automatic G+ system.  I have to see them and mark them as "not spam" to make them visible to everyone else.
 
I've complained to +Yonatan Zunger about this phenomenon before.  It's not just you; a lot of comments on my threads get marked as spam, and about 5% are actually spam.  I think it may tend to happen when people include links in their comments.  I think it started for you when you included a link in your comments, though now it's happening to comments you didn't include links in.
 
+Sergey Ten wrote: "You don't take into account conspiracy way of thinking. Actually  you can not argue with/convince any person with non-scientific-method way of thinking, because "scientific common sense" argument make sense  only in scientific method context."

You're right.  I've had a lot of dealings with physics crackpots, since I used to moderate a physics newsgroup.  I learned that some people will never be convinced by the arguments that convince most scientists.  I try not to waste time on such people.   But sometimes I act like I'm wasting time on them!  I do this for the benefit of other people reading the conversation.

In the case of this Woodward/White theory, I haven't yet met anyone who would benefit from a detailed analysis of that theory. 
 
+GoddardsJournal wrote: "I found two peer-reviewed studies supporting Q-thrusters published in the journal of the Chinese Academy of Sciences." 

Okay.  You say one of them predicted thrust based on the "classic theory of electromagnetic fields", by which you must mean "classical electromagnetism".  So this has nothing to do with quantum effects: this is something more like Shawyer's claim that he could get thrust by bouncing microwaves in a can purely using classical electromagnetism.  (I hope you know that "classical" means "not quantum".)

So what theory does the other paper invoke?  Does it use that "relativistic gravitational wave equation derived from first principles by Jim Woodward and Tom Mahood"?  I am trying to convince you that only a very tiny group of physicists take this equation seriously.   (I am not trying to convince you it's wrong, because you say you're "no physicist", so it would be a lot of work.)
 
+John Baez Indeed, in another thread here I've been having a discussion with a guy who basically regards physicists as devotees of an obsolete religion who are now fighting a desperate, unscientific rear-guard action as their dogma disintegrates. I'm not gonna convince that guy.

But when this story first broke, it seemed as if almost everyone who mentioned it was treating it (in its breathless Wired incarnation) very uncritically, and now most of them aren't, so I'm happy about that.

There's still some more along the lines of "why all the attacks? Why don't you wait for replication to criticize? Aren't anomalous results how progress in science works?" which all sounds perfectly reasonable until you get into the details.
 
+John Baez Well, I have consulted expert advice, your advice in this conversation. And I've accepted almost everything you've told me above. But I also want to make sure I'm not just blindly agreeing with you and thereby being unfair to the other side. 

It's not easy for me to accept that two teams of qualified professional scientists, one from NASA and one published by the Chinese Academy of Sciences, are crackpots. For some reason I feel that I have a duty to try to represent them or at least respect them as human beings. 

I haven't seen papers / studies from 1,000 physicists who disagree or disprove those scientists. I've only seen a handful online such as yourself, fewer than the number of scientists they're disagreeing with. And I don't expect a new concept and alleged invention to have a massive body of prior research and community support. However, on that score, it does seem that a likely core weakness is the "Woodward effect" and the failure for many years to confirm it.  
 
+Bill Reed and +Matt McIrvin:  I think that you're exaggerating the danger that this result, if somehow true, would pose to physics as we know it.  You might as well say that, because the magnetic forces exerted by two moving charged particles on one another violate Newton's third law, that physics as we know it had ended before it began!  But in that case, the missing momentum is transferred to the magnetic field, and we would conclude something similar here.  (Perhaps the quantum virtual plasma has the momentum?)  It's even easier to find interactions that seem to violate energy conservation.

It's quite unlikely that this effect is real, of course, and we know that those who claim to derive it from standard physics are wrong; but if it turns out to be real and we do get a correct theoretical understanding of it, then it will be the discovery of a previously unknown field, or of a new interaction with a known field, or something like that, not the end of physics as we know it.
 
+GoddardsJournal wrote:

"It's not easy for me to accept that two teams of qualified professional scientists, one from NASA and one published by the Chinese Academy of Sciences, are crackpots."

It's very easy for me to accept, because I know several similar cases.  You might be amused to read the case of the Bogdanoff brothers, twins from Russia who live in France:

https://en.wikipedia.org/wiki/Bogdanov_affair

They wrote theses that were mostly just crazily strung-together buzzwords.  Their original thesis advisor died, and his successor said that to get their PhD they needed to publish a certain number of papers in respected journals.  So they sent the same papers to a large number of journals.  They were rejected from most - some of the referee's reports have been made public! - but as I would expect, they were accepted by some.  (Not all referees bother to do their job well.) 

They succeeded in publishing papers - in some cases nearly identical papers! - in these journals:

Classical and Quantum Gravity
Annals of Physics
Nuovo Cimento
Czechoslovak Journal of Physics
Chinese Journal of Physics

The first three are or were highly respected journals, though Nuovo Cimento has gone downhill.  Some of these journals have subsequently published letters of apology.  It's quite a tale!  (The Wikipedia article tells a fraction of the full sordid story... see the references and talk pages for more.)

You might also be interested in the case of a physicist who published over 400 crazy papers in a superficially respectable journal he himself edited:

https://en.wikipedia.org/wiki/Mohamed_El_Naschie

So, you should never think that because one or two papers on a subject have appeared in a reputable-sounding journal that these papers are correct, or even make sense at all!  If you don't know a subject, you need to rely on a more statistical approach.  This is why I asked you to take a far-out-but-still-somewhat-respectable subject like 'quark stars' (or pick your own), and count the references to that topic.  This will give you a kind of baseline.  Or, pick a subject you feel sure is crazy and count the papers on that!  This would be even better.
 
+Toby Bartels My opinion, as a layman with some mathematical education and an interest in physics, is that these physicists got caught thinking out loud and now are looking for any out they can so as not to look like fools. (Perhaps they should think more before they publish.) This has been exacerbated by the yellow journalism which passes for scientific these days. I don't believe these results are a danger because I'm quite sure they are false ... just like the other breathless headlines about scientific result that turned out to be just wrong.

Really, resorting to virtual world to justify these results is just a desperate last ditch effort, in my opinion. Virtues fields, particles, etc. are not magic. When everything is sais and done the laks of physics end up balancing out here in the real world. An example of this is Hawking Radiation ... yes a virtual particle gets "de-virtualized" but in the end the mass that has appeared has been subtracted from the mass of the Black Hole. If they are going to give us an explanation that the Momentum has magically been extracted from the "virtual plasma" then they owe an explanation of where else the momentum has been changed in order that the books balance out. "The devil is in the details," not in clever meaningless phrases.

+Matt McIrvin 
 
+GoddardsJournal wrote: "I haven't seen papers / studies from 1,000 physicists who disagree or disprove those scientists."

Right, and you never will, because the main reaction of physicists to bad work is to ignore it. 

If the NASA team started getting lots of money from NASA to do their research, physicists would pay attention.  But I believe that team is doing it "on the side", without funding for this project.  So, they're not causing much trouble, and they will be ignored - except when popular magazines make a big deal of it.  Then scientists who enjoy popularizing science will try to pour cold water on the frenzy.   So far the main people who have bothered are me, Sean Carroll, David Goldberg, Mika McKinnon:

http://space.io9.com/a-new-thruster-pushes-against-virtual-particles-or-1615361369/1615513781

and Brian Koberlein:

http://briankoberlein.com/2014/08/03/hype-drive/

If you want to see thousands of physicists, look at the physicists who are ignoring what would be the biggest development in the last 5 decades if it were true.

Or else just wait and see: this will never completely die out, but it will also never amount to anything significant.
 
From Forbes: "The authors of the paper said it was intended to 'demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma,' but they declined to say what that meant."

"Other scientists, however, are lining up to pour cold water on the paper, noting that if asked to bet on overturning physical laws or a lab error, they’re putting their money on the latter."

Indeed!

http://www.forbes.com/sites/paulrodgers/2014/08/04/ye-cannae-change-the-laws-of-physics-or-can-you/
 
+Toby Bartels You're right, of course: things only really stop making sense if you take the theoretical arguments of the advocates seriously. If it turned out the thing actually worked, it would very likely not be because of anything they're suggesting, but because the momentum went to some other unknown place, call it X.

There's a famous historical example of this happening before. When it appeared that energy and momentum conservation were being violated in nuclear beta decay, Niels Bohr's preferred resolution was that they were only approximately correct. Really, there was another, weakly interacting particle carrying off the rest: the neutrino. When it was theorized, that seemed to some like a pure concoction to save appearances, but of course neutrinos were eventually detected, with some difficulty.

So what could X be? In this case X would still be pretty weird by present standards. The device couldn't just be creating and emitting something like a neutrino, since the momentum change is too large for the power involved; any pure emission (or pure absorption) would have to be some kind of tachyon, which is a whole other can of worms.

Either that, or (more likely, I'd say) X would have to be some pre-existing stuff we never knew about before that was getting, not emitted or absorbed, but somehow pushed against: its momentum gets changed. This is sort of what people are imagining when they're thinking of the device pushing against the electromagnetic vacuum. But it couldn't be the electromagnetic vacuum as described by any standard theory, it'd have to be something else. Something not Lorentz-invariant.
 
...Were I taking this seriously, I'd be tempted to say "hey, dark matter!!" (Not dark energy.)

But then we can put lower limits on the density of dark matter required to support the claimed effect, and ask whether that's consistent with other things. Considering that not even the creators of these devices are claiming they can somehow interact with dark matter, I'd wait for more anomalies before getting too excited...
 
Ok. So what's the big problem? The heard from some unbelievable stuff (that could be REALLY useful for propulsion systems for spaceships).
And it is not scientific to claim that something can't work because it can't be explained right no (remember, we can't explain high temperature super conductance either but it clearly does exist!)
So they do some experiments on it and find an effect (and yes, it has been tested in vacuum and a can't see "shoddy practices" in the paper).

So shouldn't we be excited that they maybe found something exciting new instead of calling them all idiots?
Maybe they are all wrong, but even than, we have learned something!
 
Wait. They tested something which dumps a few hundred watts into a small object in an atmosphere, and they are surprised that it moved?

Seriously?

OK, I'm now shifting my opinion of this to "the people who did this experiment are idiots."
 
Some people are reacting to any skepticism towards the miraculous magic reaction-less drive as if the schoolyard bully has stolen their lollypop.

<Sarcasm Philip K. Dick defined reality as "that which kills you if you don't believe in it." So, how'bout we build you a reaction-less space ship, provision it for a trip to mars, and start you from earth orbit. If you make it, bonus, new physics. If you simply starve in orbit, it wasn't real and we're done with it. Win-win! /Sarcasm>
 
+Bill Reed great, thank you for the link.
So, I still say: Just because it sounds improbable, it does not mean that it is impossible. And testing it is the only way of getting results. NOT testing it would have been stupid!

And as to the scientific journals: Just remember the latest blunder with "easy stem cell rejuvenation by acid".
 
+Marco Tedaldi
I just meant that we are probably dealing with people who have a degree in journalism and got this nice gig writing about science.
 
+Bill Reed I'm definitely not smart enough to consider myself knowledgeable about the subject.
I'm just trying to not dismiss something just because it does not have a nice, smooth explanation attached.
As I mentioned earlier: We can't explain high temperature superconductivity. But we're using it anyway and it works.
My BS detector mainly starts tingling if someone wants to make money off of something funny and does not disclose stuff... like rossi with his eCat.
 
Poking around the Interwebs, it seems that at least some who have been developing these devices have started companies. As for the rest "Extraordinary claims require extraordinary evidence," if they are going to make claims that are nonsensical to our current theories they need to be doing a better job of convincing the rest of us.
 
Here's another very similar idea that got some attention from the popular science crowd but trained physicists knew enough to ignore: a quantum propeller for pushing on the vacuum.  http://arxiv.org/abs/0912.1031
 
One thing that bugs me is there's a world of difference between scientists daring to 'think outside the box' (and who might in so doing pursue paths that prove to be dead ends) and crackpots (ie, people operating from real mental defects). But if that big difference isn't carefully appreciated, an environment is created that shames and thereby stands to suppress exactly the kind of daring thinking that could foster breakthroughs that lead humanity to new previously unimagined levels of development, as prior breakthroughs have. 
 
+GoddardsJournal - yes there is, and I don't complain about scientists who think outside the box while maintaining some basic level of smarts about what they're doing.  For example, if scientists did experiments searching for a reactionless drive without making up completely lame pseudo-explanations for how it was supposed to work, I would never complain in the way I've been doing in this instance.  But Shawyer claimed classical electromagnetism could violate conservation of momentum, which is as false as 2+2=5: it's a fact about math that momentum is conserved in classical electromagnetism.  And the NASA people we're talking about now are flinging around words and equations without any sign of serious thought, or any sign of understanding the usual well-established theory of the quantum vacuum and virtual particles.  There are good people proposing radical new theories on these topics - but those people understand the existing theories, and can explain what aspects they are trying to change.
 
+Marco Tedaldi wrote: "the point is, in the paper (despite different information in the abstract) they seem to have evacuated the chamber."

As I mentioned, in one version of the abstract they wrote:

Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure.

So, no vacuum.   Then in the paper they write:

To simulate the space pressure environment, the test rig is rolled into the test chamber. After sealing the chamber, the test facility vacuum pumps are used to reduce the environmental pressure down as far as 5x10E-6 Torr. Two roughing pumps provide the vacuum required to lower the environment to approximately 10 Torr in less than 30 minutes. Then, two high-speed turbo pumps are used to complete the evacuation to 5x10E-6 Torr, which requires a few additional days. During this final evacuation, a large strip heater (mounted around most of the circumference of the cylindrical chamber) is used to heat the chamber interior sufficiently to emancipate volatile substances that typically coat the chamber interior walls whenever the chamber is at ambient pressure with the chamber door open. During test run data takes at vacuum, the turbo pumps continue to run to maintain the hard vacuum environment.

This makes it sound  like they did the experiment in vacuum - contradicting the abstract.   But wait!  In the conclusions of the same paper:

Vacuum compatible RF amplifiers with power ranges of up to 125 watts will allow testing at vacuum conditions which was not possible using our current RF amplifiers due to the presence of electrolytic capacitors.

Now they're saying it wasn't possible to actually do the experiment in vacuum! 

This fuzziness on an absolutely crucial issue does not breed confidence.  If they really did the experiment in vacuum, why did they say in the abstract and conclusions that they couldn't?
 
+Yonatan Zunger wrote: "They tested something which dumps a few hundred watts into a small object in an atmosphere, and they are surprised that it moved?"

To be clear, they used just 17-28 watts of power and measured a force of 22-48 micronewtons.

In 2012, some Chinese physicists claimed they could get a force of 0.720 newtons from a power of 2,500 watts using a version of Shawyer's device.  I don't know if there was air around.

xkcd seems a bit mixed up about the power too, alas:   http://xkcd.com/1404/
 
+John Baez Ah, that makes much better sense -- with a few hundred watts, I would be fairly surprised if the force were only a few tens of µN. Nonuniform heating of the air alone should produce more than that.
 
...Were I taking this seriously, I'd be tempted to say "hey, dark matter!!"

To be clear, even this "pushing against ambient dark matter" hypothesis I came up with doesn't make a whole lot of sense. Why would there be an interaction with dark matter that only happens in a specially-shaped microwave cavity? That's not how anything else in the world seems to work.

It's just the only exotic-physics explanation I could come up with that is even consistent with conservation laws and relativity, and involves things that might exist.
 
Well the neutrino was predicted because energy-momentum was observed to not be conserved in beda decay, so Pauli postulated that it was being carried away by an unseen particle.

But yeah, in this case postulating dark matter interactions is grasping at straws.
 
There seems to be this widespread idea that the virtual particles in the quantum vacuum are a thing you can push against.

One way to put it is that, well, you can push against them all you like... but the virtual particles in the quantum vacuum have a very, very specific spectrum, such that it's collectively unchanged by a Doppler shift.

Do anything to disturb that, by transferring momentum to some of those virtual particles, and you don't have a vacuum state any more; you have a final state with some real particles in it.

So "pushing against the virtual particles in the vacuum" is just a fancy way to talk about emitting real photons. There's no way to push against the vacuum without emitting something in the end, and no way to get more momentum shift in this way that you get by emitting electromagnetic radiation.

Now, the next step in these arguments is usually to say, "Well, physicists don't know everything. We all know there are open mysteries associated with this, like dark energy, and why there isn't a huge cosmological constant. How do you know virtual particles don't act in some different way than your theories say?" Well, for one thing, the existing theory makes exquisitely correct predictions for things involving interaction with virtual photons, like the magnetic moment of the electron.

But I think a more pertinent objection is that once you throw out existing theory, you've lost the right to use existing theory as a justification for your speculations. Most of these arguments tend to claim at least initially that the effect can actually be justified by well-established theory, which is clearly not the case.
 
... Another potential objection did occur to me, which is: "Suppose you just temporarily borrow some momentum from the vacuum somehow, move a short distance, then give it back? Momentum is conserved, but you went on a little trip anyway."

But that's actually not possible for a different reason: it's the answer to one of John's and my favorite physics trivia puzzles: the conservation law you get by applying Noether's theorem to a relativistic change in velocity. As long as relativity is true, the center of mass (more properly, "center of momentum") of an isolated system has to not move around in the reference frame where it has zero total momentum. 
 
+Matt McIrvin wrote: "Why would there be an interaction with dark matter that only happens in a specially-shaped microwave cavity? That's not how anything else in the world seems to work."

Yeah.  One proponent of the NASA drive suggested that it could be pushing on dark matter and pointed out this paper as evidence:

http://arxiv.org/abs/1309.3790

It doesn't seem very relevant, and I haven't read it, so I don't know if it makes any sense, but it's the only thing I know that involves dark matter (more specifically axions), microwaves vibrating at a specific frequency, and an experiment that claims to detect a mysterious effect:

We provide theoretical arguments that dark matter axions from the galactic halo that pass through the earth may generate a small observable signal in resonant Superconductor/ Normal Metal/ Superconductor Josephson junctions. The corresponding interaction process is based on uniqueness of the gauge-invariant axion Josephson phase angle modulo 2pi and is predicted to produce a small Shapiro step-like feature without externally applied microwave radiation when the Josephson frequency resonates with the axion mass. A resonance signal of so far unknown origin observed in [C. Ho ffmann et al. PRB 70, 180503(R) (2004)] is consistent with our theory and can be interpreted in terms of an axion mass m_a c^2 = 0.11meV and a local galactic axionic dark matter density of 0.05 GeV/cm^3. We discuss future experimental checks to confi rm the dark-matter nature of the observed signal.

They claim axionic dark matter would most likely form a Bose-Einstein condensate under current conditions... is that true?
 
+John Baez wrote: "But Shawyer claimed classical electromagnetism could violate conservation of momentum, which is as false as 2+2=5."

Where does he say that? All I've heard and read him saying is his EmDrive does not violate conservation of momentum. I too can't understand how that could be , but I've never seen him saying his contraption violates laws of physics. In fact, he seems to go out of his way to deny that. 

Also, the peer-reviewed Chinese paper I cited claims that a Q-thruster can be predicted to work based on the mathematics of classical electromagnetism. I'm not saying they're right, but simply pointing out that they too are not proclaiming to violate laws of physics. 
 
+GoddardsJournal - Shawyer says that bouncing microwaves inside a funny-shaped can is able to push the apparatus forward without the need of propellant.  This violates conservation of momentum unless something leaves the can.  He claims this is possible using just classical electromagnetism.  So - without putting in those words, of course, since that would make the idea sound dumb! - he is claiming that classical electromagnetism can violate conservation of momentum.

Special relativity is a basic ingredient in classical electromagnetism, and it's a mathematical fact that you can't use these theories to build a device that pushes itself forward without something shooting out of the device, but Shawyer mistakenly believes that special relativity can provide an "end run" around conservation of momentum:

http://www.newscientist.com/data/images/ns/av/shawyertheory.pdf

He writes:

Relativity theory implies that the electromagnetic wave and the waveguide assembly form an open system. Thus the force difference results in a thrust which acts on the waveguide assembly."

This stuff is false, and more importantly his calculation of the thrust is wrong.  A correct calculation appears on Greg Egan's website, but as Egan notes we don't even need to do this calculation, because conservation of momentum is a general theorem in classical electromagnetism. 

http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html
 
Speaking of shoddy science...and perception bias.

First and worst, you completely fail to separate the observed phenomenon from the inventor's wild theories on why it happens. Invalidating the latter does not invalidate the former.

The focus on the air in the chamber by the so called debunkers is mostly grasping at straws to have something hard to point at and say "Ah hah! See, it's a sham!"
But if you do apply a little actual reason to your argument you'd have to ask where, in a sealed chamber, would air currents come from? 
I for one am willing to give NASA scientists enough credit to think they could find and eliminate any artificial sources of airflow inside a sealed chamber.
Secondly, why didn't your magical air currents also affect the control device?
So far the only source of strong winds I can see is coming out of the mouths of the nay-sayers.
NASA on the other hand is doing acutal science here. They have an observed phenomenon. They threw out the silly theories of the inventor, which the nay-sayers instead choose to focus on in order to falsely bolster their argument against the actual phenomenon. NASA clearly stated that they are not bothering with the supposed theory of operation. Now that they have a reasonable, valid, experimental result they are doing the good science of refining the experiment to eliminate possible sources of false results. They are also going to have multiple other labs independently perform their own experiments to further confirm or deny the results. That's how real science is done.
The only claim NASA has made so far is that their experiment produced a result that tended to confirm the existence of the phenomenon enough to warrant further tests. They have not claimed anything about how this phenomenon works nor have they validated the wild theories of the various "EmDrive" proponents. If anything, the wording of their results paper implies that they are very politely saying they are ignoring those theories because they are bunk.

People used to think there was an aether through which various forces like magnetism, gravity etc. were transmitted. While that theory was wrong, gravity, magnetism, etc. still exist.
Right now  +John Baez +Yonatan Zunger and other's are wasting their time arguing that the aether doesn't exist and therefore there's no such thing as gravity or magenetism etc, all the while ignoring the apple's falling on their heads and the magnets stuck to their fridges.
NASA meanwhile are doing real science. Dropping hammers and feathers.
 
+Christopher Gaul wrote: "First and worst, you completely fail to separate the observed phenomenon from the inventor's wild theories on why it happens."

In fact I deliberately did separate these.  First I wrote a post on their "wild theories".  Then I wrote this second post, which focuses on their experimental techniques. 

"Invalidating the latter does not invalidate the former."

That's true... though if someone makes crazy claims about how something works, it can't help but reduce our degree of belief that it works.  Conversely, if these guys came up with a great explanation of how their device worked, it would increase our belief that it actually works.

"The focus on the air in the chamber by the so called debunkers is mostly grasping at straws to have something hard to point at and say "Ah hah! See, it's a sham!""

No: the air is the simplest explanation of the force.  The experimenters must have known this, which is why they used a vacuum chamber in the first place, and why they plan to actually remove the air from it in future experiments.

"But if you do apply a little actual reason to your argument you'd have to ask where, in a sealed chamber, would air currents come from?"

Sorry, I should have explained that - I thought it was obvious.  They are pumping at least 17 watts of power into their device.  Most of this ultimately goes into heat. It's very hard to prevent one side of the heated device from being a little hotter than the other.  This can create air currents that push the device.  Not very much - but we're talking about a tiny force here, at most 48 micronewtons.  That's less than .0002 ounces.

"Secondly, why didn't your magical air currents also affect the control device?"

That's a great question.  To answer it, we'd have to think about the difference between pumping microwaves into a resonance chamber and pumping electricity through their other device.  Better yet, they should repeat their experiment in a vacuum.

"The only claim NASA has made so far is that their experiment produced a result that tended to confirm the existence of the phenomenon enough to warrant further tests. They have not claimed anything about how this phenomenon works."

Sorry, that's false.  In this post I linked to a paper by 3 of the experiment's authors, which discusses their overall game plan and their theory of how this device works:

• Dr. Harold “Sonny” White, Paul March, Nehemiah Williams, and William O’Neill, Eagleworks Laboratories: advanced propulsion physics research,  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492.pdf

It's worth reading!
 
+Christopher Gaul the NASA team does endorse the quantum-plasma-thrust theory. And the object they expressly call the control (for the Cannae drive) also seemed to produce thrust. Assuming there might be something I don't understand, last week I sent a query to Dr White asking why the success of the control doesn't refute the theory. I've gotten no reply to date. 

Like you, I also don't see their work as pseudoscience (a pseudoscientific claim is unfalsifiable whereas their claims are falsifiable) but rather scientists thinking outside the box, on the boundaries of theoretical physics, which is bound to draw fire. And in this case their study was also very sloppy. If you're going to try to 'do the impossible', you better do it with the utmost care or you're going to be pilloried by traditionalists.

Their failure to achieve vacuum conditions despite their objective to do so, their failure to make that shortfall clear up front, and their failure to explain why the success of the Cannae control can be listed as evidence for the theory alone are reason to trash this study. I guarantee you that it would not pass peer review in any reputable physics journal. 
 
 
+GoddardsJournal You're mistaken about the control device. It's seems that everyone eager to debunk this misreads that part of the test. 
There were THREE devices tested.

Device one - A device built as per the inventor's specifications. This device produced thrust

Device two - A version of device on that was modified to remove slots that the inventor believed were necessary. This device also produced thrust.

Device three - The actual control device which did not produce thrust.

Because of the wording of many of the reports and summaries and false debunkings, many people have mistakenly taken device two to be a non-functional control device. They are wrong about that. It is merely a modified version of the test device intended to be a control against the functionality of the slots, not a control against the functionality of the entire device!
 
+John Baez Once again you have, like everyone else on team debunk all the thingz, have made arguments based on assumptions and attempted to discredit NASA's work by attacking methodologies which they have already themselves acknowledged as problematic and which they have already addressed with their plans for future experimentation.

In everyone's eagerness to jump on the debunking bandwagon, they have completely ignored what NASA is doing. It is their stated goal to examine and test many wildly fringe science propulsion devices with the intention of either discrediting them or proving them to be worth further experimentation.

In that light, the methodology NASA used to test the EmDrive device initially is perfectly reasonable. It makes perfect sense to test the device as built, and with the least amount of setup cost. No point is wasting time and taxpayers money to construct a new device and test rig capable of being tested in ideal conditions. Because of the test device's use of non vacuum capable components, it was tested as is, in a sealed, but non vacuum chamber. They acknowledged this as an issue and clearly attempted to mitigate the influence of air as much as possible. 
Once they got positive results from this initial test, they stated in their release that they were already planning to re-test with a vacuum capable version of the device, in a vacuum, and at multiple labs. 

Crying foul on the initial test at this point given those facts serves no useful purpose.

This is how science is done! 
I applaud NASA for being able to think outside the shackles of conventional wisdom and explore the unknown in a reasonable, scientific, and cost effective manner.
That kind of thinking will serve science and mankind orders of magnitude better than the attitude displayed by the debunkers.
 
+Christopher Gaul They're controls for two different things. The positive result for device two entirely falsifies the Cannae drive inventor's hypothesis about how the thing works. The negative result for device three, the simple load, indicates... what? There's some kind of revolutionary physics going on that doesn't correspond to anybody's theory? Who knows?

The problem with insisting on a total divorce between theory and experiment is that theory motivates experiments in the first place; otherwise, you're just casting about in the dark, trying completely random things in the hope of striking gold. (Suppose the microwave cavity is shaped like a bowling pin? Suppose it's shaped like an octopus? Suppose we keep it the same shape but paint it green? On the inside? Maybe that's important! Etc.) If you do that, you might strike gold eventually, but you'll probably get spurious results much more often. Without a sufficiently definite hypothesis to test, you can paint just about anything you get as a positive result, but it's not going to be very convincing.

What you especially can't say is that this experiment constitutes a replication of a couple of other experiments with a completely different configuration and a different theory of operation, just because the experiments, while quite different, are similar in spirit and the results, while wildly different, were in some sense positive. And that's what the popular coverage has been like: "people said Roger Shawyer was wrong, but now NASA has confirmed that he's right!"
 
+Matt McIrvin You're demonstrating the problem that all the debunkers so far have in common. You are arguing the wrong thing.

Separation of the inventor's theory is important because it's irrelevant to this experiment and distracts people like yourself from the actual point which is...
To demonstrate that the device produces a measurable phenomenon.  Period.
This is the theory in question. And NASA has done a great job of testing that theory. They can now move on to other theories related to the device and test them as well. In fact they already are working on doing so.

Stop getting yourself worked up over the wrong theory and applying it to the experiment.
 
+Christopher Gaul That's not correct. First there were FOUR, not three, devices. You didn't mention the tapered cavity device (section IV). Second, the authors called the unslotted Cannae test article the control, which is what I said. They called it the control in this excerpt:

"Prior to testing, Cannae theorized that the asymmetric engraved slots would result in a force imbalance (thrust). As a result, a second (control) test article was fabricated without the internal slotting (a.k.a. the null test article)."

You, not the authors, are calling the "RF Resistive Load" the control. They never called it a control device. Though I agree that it does seem to be playing that role in some capacity. However, and I think John pointed this out, it's not a reasonable control, it appears to be a solid block-like object. A control needs to have some similarity to the tested item minus the 'active ingredient' (in this case slots). The placebo control in a drug trial isn't a clock you put on the wall, but a pill similar to the drug being tested minus the (hypothetically) active ingredient. 

The Cannae-propulsion theory appears to be falsified. Atmospheric phenomena are a more likely explanation for the trust both the active and control Cannae-drives experienced. 
 
+Christopher Gaul the authors said this: "Q-thruster test articles are going to be tested in a vacuum to reduce possibility of air currents polluting the thrust signal during testing." [*] Therefore, because they in fact did not test in vacuo, the air-currents hypothesis is a possible explanation. 

Now, given two explanatory hypotheses, one being "anomalous" (by the author's own admission) and one non-anomalous, it seems to me by Occam's Razor we're wiser to assume the non-anomalous hypothesis.

[*] ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140005831.pdf
 
+Christopher Gaul wrote: "In everyone's eagerness to jump on the debunking bandwagon, they have completely ignored what NASA is doing. It is their stated goal to examine and test many wildly fringe science propulsion devices with the intention of either discrediting them or proving them to be worth further experimentation."

Actually if that's all they were doing I would be much happier, even though I'd still want them to test their gizmo more carefully, for example by evacuating the vacuum chamber.

What irked me was two things.  First, they're advocating some crackpot theories of physics, which scarcely qualify as "theories" because they're so sketchy:

• Harold White, Paul March, Nehemiah Williams, and William O’Neill, Eagleworks Laboratories: advanced propulsion physics research,  http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110023492.pdf

• Harold White, STAIF 2007: inertial mass dependency on local vacuum fluctuation mean free path, forum.nasaspaceflight.com/index.php?action=dlattach;topic=13020.0;attach=173105

Second, in their report on the experiment they did, they have a section where they are optimistically scaling up the effect and talking about how we could use it to go to Mars and Titan.

If they focused on their experiments and focused on trying to do them well, I'd have no complaints.   Of course I still wouldn't believe the device worked until more tests were done, but I wouldn't have felt the need to pour some cold water on their claims.
 
I think instead of focusing mainly on the boolean presence/non-presence of air in the chamber, and automatically making a conclusion based on that alone, it would be much more useful to focus on quantifying the effects of air on the chamber given heat transfer from the experimental apparatus.  The question is a simple mechanical engineering problem of heat transfer of natural convection on a vertical wall of temperature Tw.  This is a well-defined problem from which there is a well-defined answer that can directly shed light on what wall temperatures are required to produce the velocity necessary to reproduce the thrust observed.  
 
+Jerry Vera It sounds like you're saying the burden of proof falls on those who are skeptical of an extraordinary claim. 
 
As a practicing engineer, I'm just trying to add my two cents and sprinkle some attention towards something with definite metrics to being more clarity to the problems in the experimental setup so we can all have a better understanding of what to focus on when deciding how much-or how little-the affect of atmospheric air actually is. 
 
+Jerry Vera - it sounds like a good idea; can someone here do the calculation?  Removing the air from that chamber would also be nice.
 
Yes it would be.  

One of the interesting aspects about this particular design is that the geometry is symmetric.  A faulty thrust measurement consistent with surface buoyancy would have to result from non-uniform heating, which would create a faster velocity profile on one side over the other.  Along that line of reasoning, a uniform heating would result in buoyancy on both sides that cancel one another.  That being said, the geometry may not be perfect.  

Another factor to consider is that buoyancy resulting from heating would be a transient effect running over several seconds.  That is, the internal surface impedance that creates heat would have to conduct through the metal (initially at ambient temperature), heat up the metal, then the metal would have to heat up the adjacent air on the outer wall.  As the air heats up, its velocity would steadily grow until a thermal steady state is achieved  This may take 10-30 seconds.  An erroneous thrust consistent with this theory would present itself as a longer term, growing phenomena, not a quick jerk on the device when powered.  So this is something I would keep on eye out for.  

Lastly is the case where buoyant air makes its way up and around the chamber, then back down again striking the device.  I suspect that this, too, would occur several seconds into the run, not immediately at power up.
 
Here's a message I got from Greg Egan:

Hi John

The following should be treated as a crude, back-of-the-envelope, order-of-magnitude calculation!

I assume an environmental temperature of 20 degrees C, a density of air of 1.2 kilograms per cubic metre, and a specific heat for air of 1000 joules per kilogram per degree.

Using the formulas from http://www.engineeringtoolbox.com/convective-air-flow-d_1006.html, I find that a vertical surface with a height-to-centre of 0.1 metres and a width of 0.1 metres will generate an air flow of about:

  S = 3.6×10^{-5} dT^{2/5} kilograms/second

where dT is the difference in temperature between the surface and the environment (in degrees C).  The speed of the air flow will be:

  v = 0.038 dT^{1/2} metres/second

and the force exerted by the air flow will be:

  F = S v = 1.4×10^{-6} dT^{9/10} Newtons

If the air being transported by this flow is heated to the mean of the surface temperature and the environmental temperature, the rate at which it is dissipating thermal energy will be equal to:

  P = 0.018 dT^{7/5} watts

If we solve for the temperature difference in terms of the power, and substitute that back into the formula for force, we get:

  F = 18.5×10^{-6} P^{9/14}

For P = 28 watts, F = 157 microNewtons.

Of course not all of the force exerted by the air flow would result in a net thrust, but it seems reasonable to conclude that the forces measured (e.g. 40 microNewtons for 28 watts) are of the same order of magnitude as convective forces.
 
Very good analysis!  Thank you! I suspected it would indeed be of the same order of magnitude, which clouds the results and makes going to higher powers (in vacuum) like you say, all the more necessary.

I say it clouds the results only because (I suspect) the equations pertain to steady state conditions, and if a phenomena was reported in the seconds before thermal equilibrium was achieved (i.e. 28 watts going in and going out, and no longer contributing to raising the temperature of the copper), then it would mean that in these first few moments, the thrust cannot be attributed to convection.

Alternatively, if we use these equations the as we approach the 28 W steady-state condition (say 1- 27 W of energy fed to the air), then I think we can deduce that a force attributed to convection would increase during the duration of operation, then plateau at 157 mN.

Thanks, John and Greg!
 
Way back in 2001 Evgeny Podkletnov claimed to produce a 1000 g "impulse", that lasted 1/10,000th of a second, from an electrically shocked YBCO superconductor.  Quite understandably, no physicist took him seriously, any more than in his earlier claim of a .05% drop in the Earth's gravity, above a rotating YBCO disc in 1996.  Major labs, including NASA, attempted to replicate his earlier experiment with negative results.  But, apparently, no one ever tried to duplicate his later experiment in which a YBCO disc was shocked with 2 million volts.

But a similar experiment, conducted by the Austrian Research Center (ARC), in 2003-2006, had one aspect in common with Podkletov's later experiment.  Both experiments would have momentarily accelerated the Cooper pairs, within their respective superconductors.   The ARC team applied a mechanical acceleration to their niobium ring of 7.33 g's yielding 100 micro-g's acceleration signal.  So, out of curiosity I did a back-of-the-envelope calculation how much a free electron would accelerate under the conditions of Podkletnov's experiment.  The result was rather curious.  Instead of the signal yield being a linear function of how much a free electron would be accelerated, it was a very close linear function of how much a proton would be accelerated.  But protons are tightly bound within nuclei, at the superconductor's lattice sites, so it didn't make any sense.

Nonetheless, my curiosity was sufficiently piqued to try to replicate Podkletnov's experment, though on a much smaller scale.   I shocked small, commercial YBCO discs with about 600 volts, and once saw a signal that disappeared once the superconductor rose above its critical temperature.  But, I'm almost certain I was picking up the acoustic 'pop', when the capacitor bank was discharged through the superconductor, due to the expansion of the liquid nitrogen.  Recently, with some electronic wizardry, I've isolated the acoustic signal from the hoped-for anomalous acceleration signal, on the assumption that the anomalous signal propagates at light speed.

My hope is to continue testing with liquid helium and niobium, if I can find a lab that will accommodate me, as there is no way an amateur could work with liquid helium.  What I've done so far is described here:  http://starflight1.freeyellow.com

 
 
Greg's analysis seems close to the mark. Another effect is electron emission from the dielectric being excited by the microwave field. Apparently no thrust is measured when the dielectric is absent. If so, that makes Shawyer's claimed results (and the Chinese who claimed replication) somewhat suspect. Not deliberately so, but clearly buoyancy and convection effects have been difficult to control for.

For a bit of historical insight, Paul March, who presently works with Sonny, has also worked with Jim Woodward on his Mach Effect Thruster. I think Paul has a 'theory neutral' attitude, working to see actual positive experimental signals from the test rigs that he has worked on over the years, and avoiding arguments over theory.

I think the only reasonable position on this is to "wait and see" what the results of the pending vacuum chamber tests are. If the thrusts persist or can be intensified, without any atmosphere to confound things, and electron emissions can be mitigated, then there's something going on.

Of course, the theory that White has proposed means if it works, then it's not acting as a rocket, with an on-board reaction-mass, but as a "jet" that gets its working fluid from the 'vacuum'. It's adding energy to that 'fluid' and throwing it out the back. The problem with all jets is that eventually the energy-adding process becomes harder and harder as the speed of the vehicle relative to the working fluid gets higher. The thruster might produce a much smaller top-speed than hoped for...
 
Not vacuum spawned electrons, just plain old cathode rays from hitting the dielectric with the microwaves. It's a possibility I will have to mention to Paul March.

Sent from my iPhone
 
That'll teach me for not checking another person's calculations. Greg's figures require a rather high temperature difference, based on the equations he uses.

If P = 0.018.(dt)^(7/5)

Then dt = (P/0.018)^(5/7)

which means dt = 190 degrees to get the thrust he computes. Paul March, in a different forum, says the observed temperature rise was ~1 degree.

Using the observed temperature rise and Greg's  F = S v = 1.4×10^{-6} dT^{9/10} Newtons, then the thrust is just 1.4E-6 N. They consistently observed much higher thrusters, which appeared immediately when the power was on. Thus no time for thermal effects to build-up and insufficient temperature difference to be due to air-flow.

Need another explanation guys.
 
Greg Egan replies:

The only reason I bothered estimating the convective force was because a previous commenter suggested that someone ought to do this to check whether or not the presence of air had any potential to make a difference.  Personally I remain completely agnostic as to whether the thrusts White et al measured are thermal in origin, or due to an (entirely conventional) electromagnetic effect that they have not accounted for.

The only published data from which it was possible to estimate the convective force was the power consumption, 28 watts.  If the experimenters really did measure a temperature rise of 1 degree, why isn't that in their paper, along with details of how it was measured, and what data (if any) they also measured about the distribution of the temperature across the surface?  All of these things should have been published as part of the description of the experiment, not asserted later "in a different forum".
jeff h
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Hmm, I haven't noticed anyone mentioning the fact that they got a positive result (~10 uN) from the RF load when testing the tapered cylinder.  They guess that it's due to the 5.6A current in the power cable running from the liquid metal contacts to the RF amplifier interacting with the magnetic damper system.  I first thought about air currents being the culprit, but they've got (unshielded?) neodymium magnets to dampen harmonic motion, and who knows how the various cables were routed/adjusted during testing, and how well shielded they were?
 
+John Baez
I briefly skimmed your article and your responses to the questions in the comments. As a lay person who is interested in seeing how far this idea goes. I dropped the 25 bucks needed to get access to the paper, since no one had liberated it at that point. So I really appreciate the fact that your updated your critique after gaining access to the actual paper.

However, your initial analysis was correct that the experiment was not run in vacuum even though the description of the experimental protocol, makes it sound like all the tests were run in vacuum. This is because the RF amplifier they were using had capacitors that were not rated for vacuum. The rumor is, they should have already started another test run with the experiment inside a fully evacuated chamber; towards the end of last year. So hopefully there will be an update some time this summer with new results.

I do have a question for you. It is my interpretation that your critique of the Woodward effect stems mostly from how White referenced it in the deck you reviewed. Is my interpretation accurate? I ask because I have read at least one paper that Woodward wrote where he outlines an argument for why the QVPT theory is not right. So I do not believe that Woodward would personally support White's usage.

Another question I have for you is. Have you reviewed any of Woodward's work? I would love to hear your comments on it outside of its usage to justify QVPT.
 
+David Taylor-Fuller - there are two separate issues here: the experiment, and White's theories attempting to explain it.  The latter are goofy and half-baked, perfectly suited to bringing disrepute on the whole business.  So, to be charitable, we can completely ignore those theories and focus on the experiments.  Let's do that.

There's no reason to think an effect of this sort they're looking for should exist, and every reason to think it doesn't.  Thus, the experiments should be done in a way that carefully rules out all possible errors.  Then people should criticize the experiment and the experimenters should do another round of experiments, etcetera, until some other teams of experimentalists become interested enough to replicate the experiments.  This is how it always works: compare the history of experiments to detect things like dark matter, proton decay, a fifth force, and so on.

Until they remove air from the chamber, the best thing for me to do is think about something else.

I haven't studied Woodward's work except for this one paper.
Rep0007
 
...but the main thing is, the device looks cool.  Whatever its value as a science experiment, it's excellent art, and the whole thing can perhaps best be interpreted as entertainment, rather than research.
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