Finnish Scientist Provides Another Explanation For The 'Impossible' EM Drive (examiner.com)

MarkWhittington quotes a report from Examiner: Ever since the EmDrive entered the news about a year or so ago, it has sparked considerable controversy. The device is alleged to work by using microwaves that produce, in some fashion as yet unknown to science, thrust. Many scientists suggest that the EM drive is impossible as it violates known physics. However, a number of tests conducted in Great Britain, Germany, China, and at NASA's Eagleworks at the Johnson Spaceflight Center have resulted in thrust that cannot, as yet, be explained by experimental error. The International Business Times reported that a Finnish scientist has published an article in a peer-reviewed science journal with a possible explanation as to how the drive works. International Business Times writes, "A new peer-reviewed paper on the EmDrive from Finaland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting photons that leak out of the closed cavity, producing an exhaust. The research, entitled "On the exhaust of electromagnetic drive," is published in the journal AIP Advances 6 and is the brainchild of Dr Arto Annila, a physics professor at the University of Helsinki; Dr Erkki Kolehmainen, an organic chemistry professor at the University of Jyvaskyla; and Patrick Grahn, a multiphysicist at engineering software firm Comsol."

Comments

If this is correct it should be easy to check

[Crashmarik]

Unless the photons are perfectly out of phase and co linear you will get interference patterns on all three axes. Seeing as they are microwave photons that should make them nice large and obvious.

Re:If this is correct it should be easy to check

[flyingfsck]

Well, maybe you should read the article. They postulate that the exhaust is indeed paired photons, which are impossible to observe. I'm just not convinced that such an EM drive will be more efficient than simply placing a lump of decaying matter at the focus of a reflector and using ordinary infrared photons as the drive.

Re:If this is correct it should be easy to check

[jeepies]

That's not how destructive interference works in the EM field. The photons at a point of destructive interference are diverted to area of constructive interference. They don't continue on as an unobservable photon pair. A point of destructive interference in a wave means the photons aren't there. In terms of the wave equation it means the probability of finding a photon at that location is 0. That's not because photons masking each other, it's because physically they are never present at that point.

Re:If this is correct it should be easy to check

[Martin S.]

Large and obvious elementary particle, what sort of Universe do you live in?

Re:If this is correct it should be easy to check

[silentcoder]

Assuming the theory is correct, you may be right. But this is a new theory - and key to it is that it means the EM-drive does, in fact, have an exhaust - it's just that the exhaust is mass-less photons rather than matter. But the whole reason we have the name 'photon' is because light behaves so much like a particle to begin with - and photons are known to have momentum after all.

That said, since it's apparently able to convert something like sunlight into useful thrust without fuel - it could, in theory, keep providing thrust for many centuries (well until something hits or damages it). Your decaying matter will be useful only as long as the fuel remains(but may provide more thrust since the particles it exudes have mass which hugely increases their momentum). Then again - depending what you use, quite a lot of decaying matter have half-lives in the thousands-of-years category.

All that said - assuming both technologies prove viable, you can expect more prosaic and immediate concerns to dominate the decision - like what happens if something goes wrong and the damn thing crashes to earth. Space agencies tend to be rather reticent about putting things in orbit which, if they crash, could spread highly reactive material around the area they land in. This is why RTG's tend to only be used on long-range space-probes, the only risk of spreading that plutonium on the planet is if it crashes during launch.

Having said all that - if we imagine an EM-drive which uses solar-power to produce microwaves to produce photons to produce miniscule levels of thrust - well magnetrons are fairly heavy, and the parts in there are quite pricey... would you not be able to do it more cheaply for about the same weight (if not volume) by skipping all the intermediary steps and just fitting the satelites with solar sails ?

Re: If this is correct it should be easy to check

[silentcoder]

Well thats a factor for long range missions but not for orbital satelites just trying to compensate for decay. If you make a long range em-drive probe with solar as the electricity source you have the same problem. Solar panels are subject to the same inverse square law as solar sails.

Re: If this is correct it should be easy to check

[oobayly]

There's also the energy consumption to consider - will it require solar cells large enough to act in a manner of solar sails? And will the thrust on the solar panels negate the thrust generate by the EM drive?

Pre-edit:
TLDR: No
According the fountain of knowledge (Wikipedia), the EM drive generates thrust in the region of 0.1 to 0.3 mN/W. Solar energy is about 1361 W/m2, and a solar sail generates about 7.81 uN/m2, which is the equivalent of 5.7 nN/W. Plus, thrust isn't ways going to be opposing sunlight.

Re:If this is correct it should be easy to check

[Anonymous Coward]

The thrust of a solar sail drops exponentially as it moves away from stellar bodies though, whereas the thrust of an EM drive could remain constant as long as it had a supply of energy.

Could you explain why exponentially? I would have thought it would be as 1/d^2, the rate at which solar flux drops.

Re: If this is correct it should be easy to check

[orlanz]

But wouldn't the solar panels also lose collection capability? I think a direct conversion of momentum would always be more efficient than hopping through multiple energy states.

Re: If this is correct it should be easy to check

[rgbatduke]

Ah, but this drive is MAGIC, and doesn't obey the laws of conservation of momentum and equal action/reaction and all that. It pulls itself up by its bootstraps. It gets rich by selling itself rocks. And if it violates momentum conservation it almost certainly violates energy conservation too. Chaos ensues. The Universe collapses in a puff of physical inconsistency.

Or, as it moves forward, it kicks something else backwards. There really aren't a lot of choices here that don't require a fairly complete rewrite of physics. Even at the quantum level, outside of irrelevant borrowings at the scale of hbar, these conservation laws hold and it is pretty well believed that they hold globally for closed systems and that energy and momentum and angular momentum are in detailed balance in interactions. That's the entire basis of field theory. You're talking about a nearly complete rewrite of field theory (along with everything else).

Or, it kicks something backwards. Or, something else is going on. I'll take a heap 'o convincing, though, before I throw out physics in favor of "magic".

rgb

Re: If this is correct it should be easy to check

[Dr_Barnowl]

I said "a supply of energy" not "solar panels". My presumption was that any really long-range vessel (to which an EM drive would be well suited) would be nuclear powered in one form or another.

Re: If this is correct it should be easy to check

[silentcoder]

If its a nuclear powered craft an em-drive is pointless. You just changed the type of fuel not the need for fuel.
In that case a chunk of uranium and a funnel will do the same job much cheaper.

Re: If this is correct it should be easy to check

[Weaselmancer]

Your signature line is funny, considering the nature of your post. ;)

That being said, you should read McCulloch's paper on his emdrive theory. It isn't a complete rewrite of physics, just an additional term added in to momentum. It struck me as very similar to when Einstein amended momentum with the gamma factor. Everything we saw up to Einstein's time was correct for p=mv. Mostly because velocities near the speed of light hadn't been considered yet. If McCulloch is correct, we get another gamma-like term added in for small accelerations in the form of quanta. If he's correct, of course.

He might be, and he might not be. But I think his paper is pretty interesting and it doesn't seem to me like it would take a massive rewrite of everything we know. It feels more like the transition from Newtonian physics to relativistic physics. More of a "Oh, for these unique and less common cases, here's another thing you need to consider." No magic necessary.

Re: If this is correct it should be easy to check

[lgw]

if the directional emission of photons creates thrust why can't we create an em drive from a flashlight?

Every flashlight is an EM drive. The thrust is quite small, of course, as is the efficiency. Light has momentum, and every physics student has probably calculated the thrust of a solar sail, both black and reflective, for some test or assignment.

Re:If this is correct it should be easy to check

[lgw]

The thrust of a solar sail drops exponentially as it moves away from stellar bodies though, whereas the thrust of an EM drive could remain constant as long as it had a supply of energy.

I don't think that word means what you think it means.

Assuming we're talking about a "solar sail" that works by reflected sunlight, both the thrust of the solar sail and the power from your solar panels drops off identically, as the square of the distance from the Sun.

Re:If this is correct it should be easy to check

[Anonymous Coward]

That's not how destructive interference works in the EM field. The photons at a point of destructive interference are diverted to area of constructive interference. They don't continue on as an unobservable photon pair. A point of destructive interference in a wave means the photons aren't there. In terms of the wave equation it means the probability of finding a photon at that location is 0. That's not because photons masking each other, it's because physically they are never present at that point.

You're using vector math put forward by Heaviside (whether you realize it or not.) The original form of Maxwell's equations are based on quaternions and fully allow for both longitudinal and scalar EM fields in addition to the standard transverse ones all of known EM physics is based on. TL;DR: Heaviside reformatted Maxwell's equations because quaternions are hard to work with and he dropped the scalar component when converting to vector form.

Most pairs of photons fit the pattern you described because they aren't actually aligned perfectly, the angles are very slightly offset so they go from "not existing" to "existing" in the wave equation because the wave equation fits the observations of inadequate experimental designs.

In the EM drive there is the potential due to the geometry of the cavity that two photons may attenuate into a pair of photons of a different frequency occupying the same exact space and direction of travel, when that happens you achieve the pair as described.

Re: If this is correct it should be easy to check

[funwithBSD]

So the theory is that it is a solar sail with a portable sun?

That actually makes some kind of sense... I must have screwed it it up.

Re:If this is correct it should be easy to check

[cbhacking]

The bigger problem is the question of trust-to-power ratio. Specifically, the fact that the EMDrive exhibits way too much thrust-to-power to be a photon drive unless the photons are *way* more energetic than microwave photons. The momentum of a photon is a function of the photon's frequency (or, inversely, wavelength), and the momentum is also proportional to the energy. This means it's pretty easy to compute the maximum possible force from a given frequency of EM radiation at a given power level (assuming perfect focus and zero losses, which are of course unrealistic); take the energy per second (power), divide by the energy per photon (determined by frequency), multiply by magnitude of the momentum vector per photon (determined by frequency, and remember we're assuming all photons are perfectly focused out the back so the direction of the momentum vector is built into our assumptions) and get the total impulse per second (which is force). The EMDrive produces about three orders of magnitude too much force to be a pure photon drive; at the energy levels used in EmDrive tests so far, a photon drive's thrust would be completely undetectable to the test apparatus.

Re:If this is correct it should be easy to check

[ceoyoyo]

I think he means "exponentially" in the common vernacular, where it's a synonym for "really fast."

You're correct, solar sail thrust follows the inverse square law, i.e. it drops of quadratically.

Re: If this is correct it should be easy to check

[rgbatduke]

Oh, I was just being facetious. As you say, physics has undergone multiple "complete rewrites" (not really, but yeah, aristotelian->newtonian, newtonian->quantum, galiliean->lorentz are at the very least very, very serious revisions of the way we think even if they do eat their predecessors and continue to support their successful results).

However, the law of conservation of momentum is one of those things that it is difficult to muck with, without requiring a pretty complete rewrite. If you put this thing in deep space and it just moves (accelerates) without shooting mass/energy/momentum out in some form, it would make me -- and physics -- pretty sad. I have to put it in the same category as the prior reports of transluminal neutrinos and the like. Always possible that they are true, but claims that will change everything require the most solid of evidence, and so far this is in the category of any number of famous "marginal" results that turned out to be accidents of one sort or another.

At the end of the day, of course, physics is KNOWN to be incomplete. Maybe the damn thing is acting as a darkon drive and is through a process we do not understand converting microwaves to darkons to momentum through some unknown resonance process. Maybe it is evidence for a dual universe where charge and spacetime are reversed, and the cavity somehow couples the two so it is pushing off against its shadow twin. Maybe we can make up a dozen theoretical explanations for it -- eventually, if necessary.

But for the moment it, like transluminal neutrinos, is still in the "probably magic" category pending extraordinary evidence to back up the extraordinary claim. Maybe if NASA launches one into orbit with its own solar power system and runs it for a few years, during which time it promotes its orbit in unmistakable ways. It doesn't look like it needs to mass more than a few hundred kilograms total, solar panels ought to be able to provide it with at least a kilowatt or three, so getting a thrust of around a newton should be possible. A newton may not sound like much pushing 100+ kg, but an acceleration of 1 mm/sec^2 over a day adds 84600 mm/sec, or roughly 90 m/sec, or (multiplying by 9/4) roughly 200 mph. It wouldn't take many days to make a clear, unmistakable alteration in the orbit. With modern instrumentation, I would think "one" (or even less) would suffice. Even 20 m/sec/day acceleration at a tenth of this ought to show up almost immediately.

In space, there is nothing nearby to push against. One can actually use the observed thrust itself to measure the mass of the satellite and see if it varies over time (eliminating the possibility that mass is being thrown out somehow assuming that it does not, as it should not). With solar cells with a cross-sectional area of at most a few square meters, radiation pressure is utterly incapable of producing this acceleration because you have at most Pr = S/c to work with, and S is order of 1400 W/m^2 and by the time you divide by c you have basically nothing left (as observed elsewhere in the thread).

At that point, if it accelerates as advertised, Classical Electrodynamics is dead as a doorknob, and QED is walking wounded as it still works off of CED and at the microwave level and high power, "photons" ought to be irrelevant anyway. Note well: you are converting a substantial amount of incoming electromagnetic energy directly into work "with no other effect" if it works as advertised. So even the second law of thermodynamics is going to be very sad. I'm tempted to quote Eddington:

"The second law of thermodynamics holds, I think, the supreme position among
the laws of nature. If someone points out to you that your pet theory of the
Universe is in disagreement with Maxwell's equations - then so much the worse
for Maxwell's equations. If it is found to be contradicted by observation -
well, those experimentalists do bungle things up sometimes. but if your theory
is found to be against the second law of thermodynamics I can give you no hope;
there is nothing to do but to collapse in deepest humiliation."

There's some wisdom there...

Re: If this is correct it should be easy to check

[rubycodez]

except it takes 300MW to produce a newton of thrust, which is why I don't buy the argument of exhaust photons causing EM drive thrust, the level of photons (they're all contained in any practical sense) leaving the device, if any, are far far too tiny to produce thrust. so if something is really going on, it isn't simple photon propulsion

Re: If this is correct it should be easy to check

[fahrbot-bot]

Ah, but this drive is MAGIC, ...

On the other hand, perhaps the code for this phenomenon, like quantum mechanics, is just inadequately developed in the computer simulation in which we and our universe exist.

Re: If this is correct it should be easy to check

[Weaselmancer]

I wouldn't be sad, personally. There's a quote somewhere that says that all the best science doesn't start with "eureka" it begins with "hm, that's odd..." I've always liked that quote.

FYI, there is a person who feels exactly as you do (put it in space, turn it on, see what happens). The project is a 24Ghz microsatellite version, currently being funded on gofundme. It doesn't look like he's going to get the cash for it unfortunately, but it's a step in the right direction.

Personally I'd like to see more designs put forward before we put one in space. We now have 3 competing theories on how this might work (Shawyer's wave group velocity idea, McCulloch's inertial quanta, and now Kolehmainen's paired photon idea). Personally my next step would be to simulate all three as heavily as possible and see if we can experimentally test and match those simulations to indicate which might be the best theory. These theories make predictions about how an emdrive should behave. Let's throw some test cases at them and see which ones still hold water. Do some science, you know? Then figure out the most likely description of what's going on, use that to make the best emdrive we can, and launch it. I'd love to see that.

And you're correct, of course. It's best to be skeptical of such an extraordinary claim. But McCulloch makes a compelling case how it could come to be (my personal pick of the 3 theories so far), and despite the worries about how a functioning emdrive would fit into our current knowledge, to me it still looks like a pretty minimal addition. If momentum were quanta, to me it just looks like a deeper understanding of already well known phenomena but with a new set of corner cases added to the picture. Read McCulloch's paper - it really is an interesting notion.

Re: If this is correct it should be easy to check

[lgw]

No, no, if you drag the Sun along with you that's called a Shkadov thruster (which should actually work, if you could build it).

Re: If this is correct it should be easy to check

[lgw]

Yup, the paper about escaping photons is rubbish. But then, I'm assuming this drive is as well, unless someone can manage to get thrust out of it above the hard-to-isolate background noise.

The gravity wave detector guys have the same isolation problem, but they can use correlation between detectors to prove results. Extreme claims require, well, more than "this might be something other than noise".

Re:If this is correct it should be easy to check

[Crashmarik]

One where the wavelength of photons can be kilometers. Which one do you live in ?

Re: If this is correct it should be easy to check

[joe_frisch]

the gravity wave detectors take GREAT pains to make sure that noting touches the test masses except the suspension cables (which are single crystal fibers). Testing the EM drive requires power cables, or microwave waveguides - either of which can produce substantial forces when it warms up from power running through it.

You could do the experiment, but it would be a lot of work, and its certain to fail.

Re: If this is correct it should be easy to check

[lgw]

From what I hear, the LIGO guys see data every time a heavy truck drives by on the nearest highway. One detector by itself can't be too confidant of any result, but there are two observatories and when their results correlate, that's a strong signal. Once we have several around the world, we'll be able to add direction to the observations. (Currently we only know direction if the source happens to line up with the two observatories).

For the EM drive - if someone has a solid guess at how it works, we should be able to build one that produces a lot more thrust based on that guess, and thus test the hypothesis cleanly. Very exciting if it ever makes it that far.

Re: If this is correct it should be easy to check

[joe_frisch]

LIGO does get a lot out of looking for common signals between detectors but it also has exceptionally good isolation from ground motion. Of course it is looking for very much smaller signals. It also only looks at non DC effects. Its really a completely different animal. (BTW I worked on the predecessor to LIGO in 1983....awesome to see those guys finally succeed!)

The problem with the EM drive is that if it generate more thrust than a photon drive would for the same input power, without using any propellant, it violates basic physics and cannot work. If it uses propellant, then it is just a rocket. If it generates the same thrust as a photon drive, then it has the same problem of requiring an impractical amount of power to produce useful thrust.

Re:If this is correct it should be easy to check

[lgw]

That be "geometrically". It's only "exponentially" when the variable is the exponent.

Re:If this is correct it should be easy to check

[david_thornley]

No. We already knew about photon drives, and the fact that a flashlight produces thrust. The problem is that photons are a very energy-inefficient way of generating thrust, and the observed results reported a lot more acceleration than is possible for a photon drive of that energy.

Solar sails are another technique, in which the ship uses photons and particles produced outside the ship to accelerate.

The PU-238 power sources NASA uses are designed to survive being in an exploding rocket and falling to Earth. IIRC, it happened once. The problem with them is that they're heavy and expensive (I read something about having only a limited supply of the isotope), and solar panels are a much lighter and cheaper energy source if the spacecraft is staying reasonably close to the Sun.

Re: If this is correct it should be easy to check

[lgw]

I love the LIGO observatories, myself. Each new kind of observatory we get working is wondrous - look at all that came from the CMBR observatory satellites. I'm hoping we get a dark matter detector soon, and an CNBR observatory in my lifetime (though I couldn't even guess how you'd make such a thing).

without using any propellant, it violates basic physics and cannot work

Ahh, but "violates basic physics and cannot work" would be the best experimental result, if only it were high-confidence. Much like this observation turned all of physics on its ear the last time people were thinking there was only minor work left in the field.

Re: If this is correct it should be easy to check

[joe_frisch]

Black body radiation was measured a long time ago, back when we were just stating to be able to do complex quantitative measurements. It was measured in the late 1800s, and explained by quantum mechanics.

The problem with the EM drive and new physics is that it is operating under very normal conditions - modest frequencies, field strengths and length scales. There is a huge amount of experimentation, intentional, and as a side effect of normal engineering in this parameter range. There really is no reason to expect this particular experiment to find new physics because they are not doing anything particularly new.

Re: If this is correct it should be easy to check

[lgw]

The specific curves were measured in 1860. The first real explanations were in 1900, inventing an entire field of physics that was essentially re-written in 1920, and it's still doing new work today. That measurement was one heck of a "this can't quite be explained by current theories".

The new experiment is probably nothing, but if it isn't it would also likely be one heck of a "this can't quite be explained by current theories". It's at least beyond mere charlatanism now.

Re: If this is correct it should be easy to check

[rgbatduke]

C'mon, if they can program experiments that prove that there could be no hidden variables that explain the randomness in quantum mechanics (using, of course, hidden variables that simulate the randomness in quantum mechanics in their computer) they ought to be able to fix this bug...

rgb

Re: If this is correct it should be easy to check

[rgbatduke]

My biggest concern is the free lunch thing -- second law violation is -- unlikely. Literally. Energy quanta and attendant uncertainty is all great, but it can't be used to generate free energy. Momentum uncertainty doesn't seem as though it could be used to generate free momentum. And finally, I am deeply skeptical of violating the relativistic relation between (massless) energy and momentum.

But sure, anything is possible. And no doubt, a reactionless drive would be very cool and enormously useful, maybe even enough to permit the exploitation of near-earth space. As I said, even mm/sec^2 accelerations are plenty to get around if you can afford to take your time to get places and all your ship needs to run is sunlight. Light sails would be equally cool, except for that pesky E/c bit, and even so NASA is testing using those to at least overcome high orbit drag and keep satellites up longer without an expensive boost (at whatever acceleration they can produce, maybe microns per second squared, dunno).

I love science fiction, and would like nothing better than to see new physics that enables all the things that forty years of studying, doing research in, and teaching physics have taught me are just plain impossible (barring new physics). But at the same time, I can't suspend my disbelief the way I do with e.e. smith's space opera (with its TERRIBLE physics) when it is the real world. Either way, time will tell. It usually does.

rgb

Re: If this is correct it should be easy to check

[Keith Henson]

If someone can make a reactionless drive, then they have solved our energy problems as well. It's a simple thought experiment to see how a constant force can generate arbitrary amounts of power since the energy you can get out of a moving object is the product of the force and the velocity. Unless the power input goes up related to velocity, you can let it accelerate till it is going fast enough to tap for whatever amount of power you want. If the power input does depend on velocity, velocity with respect to what? And how would the device know how fast it is going?

Someone made a comment that EM drives could move power satellites to GEO. They didn't think it through. If they work, we can use them to create energy and not bother with power satellites.

Re: If this is correct it should be easy to check

[lucien86]

You forgot some basic physics. Take an example : An electric motor produces a rotary force, but the motor only spins if it is supplied with a source of electric power. Useful Input Energy > Useful Output Energy. Some of the energy is always wasted, usually converted to noise or waste heat.
In the same regard the EM drive (if it works) consumes power to do work, and more useful power goes in than comes out. No free energy anywhere.

Where the EM drive does appear to fail (in theory) is on the conservation of momentum. So if the machine does work then no doubt there will be something somewhere that does balance the conservation of momentum. Being interested in FTL physics I might suggest that one mechanism that might explain such is some kind of FTL interaction.

Re:Good

[BitterOak]

Finns get a lot of media considering it is an icey wasteland.

An icy wasteland that gave us Linux!

Must be a first for slashdot RTFA skimmed summary

[Crashmarik]

Recent reports about propulsion without reaction mass have been met on one hand with enthusiasm and on the other hand with some doubts. Namely, closed metal cavities, when fueled with microwaves, have delivered thrust that could eventually maintain satellites on orbits using solar power. However, the measured thrust appears to be without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired-photon conclusion.

Relevant portion of abstract bolded

This could be exciting

[jenningsthecat]

If the theory is correct, then researchers will actually know how the damned thing works. That should allow allow them to make the drive much more efficient.

Re:This could be exciting

[wierd_w]

There's one problem though...

I seem to recall that the net thrust exhibited by the em-drive is greater than the photon pressure of the microwaves. if the thrust was being produced by cancelling photon pairs escaping the system, then it would be some fraction of that potential, not greater than.

I can see this explaining SOME of the thrust, but the deal breaker is the thrust being higher than the photon pressure of the microwaves it runs on. (Else, it would be easier and more efficient to just aim the magnetron's waveguide out the back of the ship.)

Shawyer's non-peer reviewed "quantized inertia" explanation that abuses unruh radiation is more likely to explain the greater thrust values (and also makes some testable predictions.)

Re:This could be exciting

[wierd_w]

It's very simple, AC.

You see, when you touch your little red rocket, and make the fuel spray out, it makes daddy god very angry. Especially if it gets on the floor.

When daddy god gets angry, he makes poor little jesus have to strike you blind, so you cant find it anymore.

Really, it's all in the bible, which everyone knows is the leading authority on everything. /sarcasm

Re:This could be exciting

[c9brown]

For anyone interested, the "quantized inertia" explanation was proposed by McCulloch, and is here: http://dx.doi.org/10.1209/0295-5075/111/60005

Re:This could be exciting

[RockDoctor]

That should allow allow them to make the drive much more efficient.

You have some reason to think that this is not already working at maximum efficiency? It's natural efficiency may be low - like the efficiency of the conversion process of potassium nuclei plus an electron into argon nuclei.

Re:This could be exciting

[RockDoctor]

When daddy god gets angry, he makes poor little jesus have to strike you blind, so you cant find it anymore.

Are you implying that ACs are so stupid that without looking they can't find their sex organs to masturbate?

Actually, you may have a point there.

Re:Good

[ChunderDownunder]

Really, I thought it was summer up there?

No No No

[Greyfox]

Clearly running the microwave creates a virtual quantum burrito. As long as there's a burrito in the microwave, thrust is guaranteed to be generated,shortly!

Re:No No No

[wierd_w]

I dont see "quantum burrito" on the standard menu-- Is this something you have to ask the universe for directly?

Re: No No No

[wierd_w]

Ahhhh! So THAT explains why the enterprise is always looking for gaseous anomalies!

Do the phartons exhibit any kind of tunneling behavior? I'd expect them to be quite difficult to contain...

Re:No No No

[istartedi]

Yes, but until you eat the burrito you are not sure exactly how much thrust there is going to be.

Re:what's that word

[wierd_w]

That's not nice!

I am sure this poor soul just tried many times to gain tenure, and ended up having to take a real job in software instead.

This stuff is cool

[GoodNewsJimDotCom]

I love when we find stuff that defies what we know about the known universe. It could open up all sorts of new discoveries if found to be legit. I wonder if Elon will plop one of these things in space with an on switch hit.

Re:This stuff is cool

[Anonymous Coward]

Nope, but there is already a project to send small emdrive to space, https://hackaday.io/project/10166-flying-an-emdrive

Awesome

[fred911]

Next we need research on how the flux capacitor works.

Re: Must be a first for slashdot RTFA skimmed summ

[wierd_w]

More, photons are massless, and only interact strongly with matter because they are the force mediating particle for electromagnetism.

Photons are their own antiparticle, so when they interact strongly with each other, the force drops to zero, so the pair doesnt interact with anything else. This allows them to pass through the wall of the cavity like it wasnt even there. They still have energy, and a mathematical equivalent of momentum, so when they leave the system, an equal and opposite change in momentum of the system occurs.

That's my layman's understanding anyway.

The problem is that this is just a convoluted form of light pressure. The thrust exhibited by the em-drive is supposedly higher than the expected momentum change from simply radiating the microwave photons, and only some of the photons bouncing around inside the cavity will perfectly pair up to form neutral photon pairs that can escape the system. That means this mechanism cannot explain the anomalous nature of the thrust.

Re: Must be a first for slashdot RTFA skimmed summ

[joe_frisch]

The electromagnetic field strength is linked to the energy density of the field. If the electric fields from the photons cancel in some location, then there is no energy density in that location and no probability of finding a photon there. If the photon fields cancel at the metal, then there is nothing to escape. eg. the article doesn't make any sense at all.

Conservation of (relativistic) momentum is conserved in all particle interactions - even in quantum mechanics. The only way the EM drive can work is if there is entirely new physics. There is no reason at all to expect new physics - frequencies and microwave intensities in the system are not at all unusual. Accelerator cavities have fields thousands of times stronger at similar frequencies and there is no behavior seen that isn't predicted by E&M. Particle interactions have fields enormously stronger (though at higher frequencies) and the divergence from standard electromagnetism match the predictions of electro-weak interactions which also conserve momentum.

Accurately measuring these small forces is technically very difficult, it is not at all surprising that uninteresting effects (thermal radiation pressure, cable distortion, magnetic fields, etc) are difficult to factor out of the equation.

It is as certain as anything is in science that the EM drive cannot work. Electromagnetism (with electro-weak included) has been tested over an enormously wide range of conditions, with no deviations from theory found.

Re: Must be a first for slashdot RTFA skimmed summ

[flyingfsck]

Photons are not really mass less. They have mass due to their enormous speed: E=mc^2

Kinda sounds like how a LASER works

[fzammett]

You've got a cavity. Inside you pump some energy. The energy is nominally trapped and bounces around. Eventually, some of it finds its way out in a coherent way. Seems like the paper is describing a similar explanation as to how LASERs work, roughly-speaking. Sounds plausible for sure.

Re:Kinda sounds like how a LASER works

[Anonymous Coward]

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

Re:Kinda sounds like how a LASER works

[afxgrin]

Lasers have the cavity to increase gain through a medium. We have no gain medium in this case, it would be far more efficient to just strap a pringles can on the end of a magnetron and call it a day if it worked like that.

Re:Kinda sounds like how a LASER works

[thegarbz]

It's like a LASER with microwaves. Dare I say a MASER? :-)

Re:Kinda sounds like how a LASER works

[turp182]

I have a cavity. I pump energy into it, in the form of some small bits of food (chewing would be a better term than pumping). This energy is trapped, but it sticks rather than bouncing around.

Eventually it finds its way out, via a dentist, in some coherent way. The cavity is also filled.

Please, dear god, please don't let there be lasers involved!

Anyway, I apologize, I just had to...

Re:Kinda sounds like how a LASER works

[cbhacking]

Yeah... except that even a perfectly-efficient microwave-frequency laser would produce much less than 1% the observed thrust of the EmDrive, at the power levels that have been used in testing it. Either our understanding of photon momentum is completely wrong (which seems unlikely, since we can directly observe the thrust from photon drives) by roughly three orders of magnitude, or the measured thrust is completely wrong (which gets less plausible with every replication, though it's still a leading theory), or the EmDrive is doing something that produces a lot more thrust than merely spitting microwave photons out its ass.

If photon drives could produce meaningful thrust at usable power levels, we'd already be using lasers or parabolic reflectors - whichever turned out to be more efficient in terms of thrust-to-mass ratio - to drive our satellites. The principle has been known for a long time. We aren't doing that, because the thrust produced is unusably tiny for the power levels a spacecraft has available. The EmDrive's observed thrust-per-energy ratio would be much more usable, especially if we could refine the design to be more efficient. Remember, with the EmDrive we're working from observations and trying to build a model; until we have the correct model we won't know the maximum efficiency. For photon drives, we're working with models and verifying them in the lab; the maximum efficiency is already well-known.

Re:Kinda sounds like how a LASER works

[ArsenneLupin]

Fortunately the trapped energy didn't come out from the other end...

Re:Kinda sounds like how a LASER works

[turp182]

Actually, a considerable amount of the energy I consume does come out of the other end, and thus propels me.

Re:Good

[aliquis]

forestry wasteland?

Not making any sense to me

[goombah99]

Their claim, to my ears, is even more ludicrous than the EM drive itself. What they say is that if two photons co-propogate with opposite phase they exist in the sense of carrying momentum and energy but they can't intereact with anything like say the wall. Isn't his bananas? the dark nodes of an interference pattern don't contain any ray-like photons. they seem to be saying it does. Now one can argue what's a photon? ie. can we really talk about ray-like photons (photons going along an axis), or do we need to talk about full 3D modes which are the eigen modes of the cavity. However in either case this seems bananas to me. if two photons are canceling it's the same as no photons. the energy didn't disappear, it just was reflected at the time you injected the second photon. you do not get two photons co-propagating out of phase like they claim.

Some one please explain this seeming madness.

Re:Not making any sense to me

[jeepies]

Your understanding is correct. There are no photons at a point of destructive interference. Co-propagating out of phase photons makes no sense what so ever.

Re:Not making any sense to me

[lindseyp]

If two out of phase photons, carrying momentum, cancel each other out and 'cease to exist', what happened to the momentum?

If that, too, ceased to exist, and all the cancelled photons were going in the same direction, it would have a net effect on the momentum of the drive.

Re:Not making any sense to me

[Anonymous Coward]

If two out of phase photons, carrying momentum, cancel each other out and 'cease to exist', what happened to the momentum?

If that, too, ceased to exist, and all the cancelled photons were going in the same direction, it would have a net effect on the momentum of the drive.

Let's assume that you are right. What happens to the energy used to emit those cancelled out photons? Does that also cease to exist?

Re:Not making any sense to me

[Z00L00K]

Go to ludicrous speed.

Re:Not making any sense to me

[rgbatduke]

Elementary E&M. The EM field, quantum or not, "particle like" or not, is a FIELD. If you set up the two slit experiment there are places on the screen where the fields from two coherent sources (slits) are out of phase and no energy or momentum is transferred. Even if you turn the intensity down to where one "photon" at a time goes through the pair of slits (yes, it goes through BOTH slits, or at least the FIELD does) the photons appear only in the BRIGHT bands where the fields are IN phase. No energy or momentum is transferred to the dark bands.

So the correct answer is that if there is a volume of space where the photons are out of phase and cancel, there is another volume of space (at a different angle) where they are IN phase and do NOT cancel, they add. Energy and momentum are conserved. The light just goes only to places where the FIELD addition is coherent and at least partly in phase. QED.

The photon is its own antiparticle, BTW.

This drive is (so far) like a hypothetical box in space containing a kid with a basketball. He keeps bouncing the ball off of one wall so that it recoils off and he catches it. Every time he bounces it off the wall, however, the box recoils away from the kid, and gradually builds up an appreciable momentum.

So all we need to explain this drive is a way for the kid to catch the ball, inside the box, and not just transfer the exact same momentum back to the other side of the box that he's standing on in order to be able to throw the ball in fhe first place.

rgb

Re:Not making any sense to me

[jeepies]

Photons don't cancel each other out. A point of destructive interference in the EM field is a place where photons are not physically present, not a place where they met and ceased to exist. Where do the photons go? They go to points of constructive interference.

Interference just causes the photons to be somewhere else: points of constructive interference, not oblivion. I was going to type up the double slit experiment but someone beat me to it. Their explanation is correct.

Simply put the article is nonsense. Photons can't travel in destructively interfering pairs because they never exist at points of destructive interference in the first place.

Re:Not making any sense to me

[jwillis84]

That is an interesting ideal.

Intereference patterns being a rotation out of phase with the observable universe.

Just as electric fields and magenetic fields oscillate in perpendicular directions to a line of travel.

An interference pattern could be another direction in which we know little about.

Re:Not making any sense to me

[WhiplashII]

It's actually a dark matter generator. It generates dark matter, and throws it out the back.

Re:Not making any sense to me

[rgbatduke]

Well, I am a theorist that teaches graduate level CED and a science fiction author, so I'm really good at making stuff up that sounds plausible. But let's maintain perspective, please. The point of my post is that energy and momentum are strictly conserved in the two slit experiment in the observable universe. Sure, the missing energy/momentum "could" be in a direction we know nothing about, but that is pretty implausible, basically just science fiction so far. We would need way more evidence before we started to take that sort of hypothesis seriously.

Put it up in space, power it with solar cells. One ought to be able to build one that should produce an acceleration of 1 mm/sec^2, "forever", off of sunlight. That's a delta-v of around 200 mph/day, unmistakable, and if it can produce this without losing mass and using only sunlight as energy input, CED, QED, and the second law of thermodynamics are going to all be very sad... as we will have built a machine that violates the second law of thermodynamics, (electrical) energy into work "with no other effect".

Until then, let's remain just a bit skeptical, shall we?

rgb

Re:Not making any sense to me

[jabuzz]

Hold your horses there. The device cannot violate the second law of thermodynamics because for starters no magnetron is 100% efficient. So first step converting electrical energy into microwaves is less than 100% efficient. To claim otherwise is regrettably unfortunate from someone teaching at a leading US university..

In addition as far as I am aware the conversion of microwaves into movement is also substantially less than 100% efficient. That is if I have 100J of energy in microwaves (which remember I can't get from 100J of electricity) and use it to lift 1kg it should in a vacuum rise U=mgh, or roughly 10m on earth. Now last time I looked the EM drive was not remotely that good.

Also if we are collecting photons from the sun converting them to electricity and then converting the electricity to motion, to claim the device in space is an isolated system is another massive fail. The isolated system would have to include the sun for starters...

Clearly the second law of thermodynamics is alive and kicking with an EM drive.

What is sad is someone teaching physics at a leading US university making basic high school physics errors in their claims. How am I supposed to take your arguments seriously in light of such basic errors?

Now like you I am highly sceptical of the EM drive. However unlike various cold fusion devices and the like there are two fundamental differences. Firstly there is nothing secret in the EM drive. Anyone can go an make one if they want. Secondly and highly importantly so far all experimental analysis of the device by multiple independent labs indicates it does indeed produce thrust. So while I remain highly sceptical until proved otherwise I have to give it the benefit of the doubt unlike Mr. Rossi's E-Cat which is nothing more than a scam from a fraudster.

Remember Fleischmannâ"Pons cold fusion claims? Well by the equivalent time from the claim now there where numerous labs reporting being unable to repeat the results. The same has not happened to the EM drive, in fact the total opposite.

Remember boys and girls verified observations whether experimental or natural always and I mean *ALWAYS* trump all theories no matter how sacred the theory is.

Right now however the observations for the EM drive could be experimental error so I remain sceptical but equally I am unwilling to dismiss it out of hand either and feel more investigation is clearly justified.

Re: Good

[Anonymous Coward]

And a git!

Re:what's that word

[Required Snark]

RTFA. They ran Matlab (or some equivalent) code to verify the distribution of the EM radiation in the microwave chamber. It's likely that this guy worked on that part. There are the resultant images in the technical paper.

Do you think that your primary care doctor invented all the drugs and tests you get? Do architects design and build the entire building by themselves? Does the CEO of a cable company personally bring the fiber or cable to your door?

Sometimes stupid can be cute. This does not apply to you.

Re: Must be a first for slashdot RTFA skimmed summ

[jeepies]

The author of that paper clearly does not understand how constructive and destructive interference work in the EM field. He's correct that the photons do not simply disappear when there is destructive interference, however they are diverted to areas of constructive interference and this would not allow them to leave the cavity of the device if they otherwise couldn't.

What they wrote in the paper may sound good to someone who has a passing knowledge of EM fields and constructive/destructive interference in waves, but to someone who understands this more clearly it makes about as much sense as asking a mechanic to change your blinker fluid.

Re:But what if we fed it more power?

[Required Snark]

No, it's different the cold fusion. The people who discovered this do not claim any magic sauce. No information is being withheld.

This is proceeding the way that scientific progress normally works. An experimenter found an effect that did not fit in the current paradigm. Other experimenters found similar results. Now theoreticians are coming up with hypothesis that may explain the result. Other theoretical types will either agree or disagree. Other experiments will be done to test the hypothesis. Eventually a general consensus will emerge. It's all completely normal.

Remember it was 100 years ago that Einstein predicted gravity waves, and they were just detected. Eventually can be a long time.

Re:what's that word

[dargaud]

Yup, as a software engineer working in research, sometimes I've had my name in papers because there was no way they could get their results without specifically crafted software. Of course they had to explain to me many times and very slowly what they wanted...

Re: Must be a first for slashdot RTFA skimmed summ

[Ramze]

Actually, it depends on how you define "mass."

Physicists used to use the terms "rest mass/invariant mass" and "relativistic mass," but most have since thrown out the term "relativistic mass" because it means the same thing as "energy of motion relative to an observer."

https://profmattstrassler.com/...

Most physicists would define a photon as having no mass, yet it would carry momentum proportional to its energy. Mass is seen as a property of a particle that makes it resist changes in speed, but photons always travel at the speed of light (in a vacuum) -- never speeding up, or slowing down... and never at rest.

Re:Good

[Anonymous Coward]

I think the Finish summer is next weekend, not this one.

Universal Equation

[CrashNBrn]

What do you think this is?

Now they just need to figure out how Pi and Planck's constant fit in and we'll should get the Universal Equation.

Re:Good

[nicnet]

He's not Swedish, just comes from a Swedish speaking family in Finland (very common).
According to your principal 50 million Americans are "actually Spanish".

Re:what's that word

[cryptolemur]

Here's the man's dissertation: https://aaltodoc.aalto.fi/hand.... Check that first, then jump to conclusions...

Re:Good

[quenda]

That was a bit flippant, so let me explain. "American" is a nationality, but Swedish is also an ethnicity.
In North America you have borders with barbed-wire fences and long queues where you smile at idiot homeland security drones who can really ruin your day.
In Europe there is a sign at the side of the road "Welcome to Finland" in 3 or so languages.
Ethnicity and language there is more relevant than the nationality on your passport.

Actually

[IdeaMan]

The explanation is that it works by Swimming through Spacetime.

Or we may ask its inventor

[m.alessandrini]

How did he conceive it in the first place? I mean, surely he didn't invent it by accident, provided that its effects are so little that they must be measured by NASA in their labs, so I presume he knew what he was doing and what physical laws he was looking for. Unless he is an alien or a man from the future and he can not tell us the truth, of course.

Re:Or we may ask its inventor

[rubycodez]

the inventor was thinking of asymmetric bits of metal (such as wedge shaped) used in "thrusters". However thrusters just move ionized air, nothing magical about them though tin foil hat sites get very excited about them.

Re:Good

[nicnet]

Th word I was looking for was "Spanish", not Hispanic or Latin American.
The point is that speaking a language does NOT define one's nationality.
Most of my (mother-tongue) Swedish speaking friends here in Finland, would without a doubt call themselves Finnish. The exceptions are those that come from Sweden. Pretty sure that if Linus was my friend, he would be be in the non-exceptions.
Finland has 2 official languages.

Re:But... but... the 'experts' say it's impossible

[abies]

Unfortunately, brains have already fallen out of the heads of all open minded idiots, so they cannot contribute much to the discussion.

Re:Good

[Z00L00K]

Finland has two main seasons - Mosquitoes and Mosquito-free.

Outdoor activities are preferred in the mosquito-free season, indoor activities are aside from Koskenkorva consumption also a lot of thinking and preparations for the mosquito-free season.

Re:Good

[silentcoder]

But Finland has had a significant Swedish-speaking minority for a very long time (long before the EU opened the borders). They have no herritage with Sweden and the only thing they have in common with the Swedes is that they speak a dialogue of the language. They are no more Swedish than the entire population of Switzerland is German (despite speaking a variant of German as their language).

Re:Good

[silentcoder]

No, next weekend is Canadian summer.

Oxymoron?

[Anonymous Coward]

impossible as it violates known physics

After centuries of new discoveries and scientific revolutions, I would have thought we were done with that meme.

Re:Oxymoron?

[gweihir]

You misunderstand. Nobody with an actual clue claimed the device violates known physics (there are a lot of clueless morons in the discussion whenever "magic" devices are the subject though), the claim is that the theory of operation offered by the creators of the device violates known physics and that does make the explanation exceptionally unlikely to be true.

As this new paper now shows, it seems no known physics is violated, there is just some tiny extension of it that is consistent with what was already known. Unlike the bogus explanation of the EM drive creators, this paper is actually science as it should be done: Observe an effect that is surprising and then carefully search for an explanation. Here they carefully searched for a way that something could escape from the device and generate the trust, which is what any competent physicist would have expected right from the start. And it seems they found something.

Re:Oxymoron?

[angel'o'sphere]

Unlike the bogus explanation of the EM drive creators,
Could you point out what is bogus on the "explanation" of the original "inventors"?

Because so far on /. no one did, and I find the articles I read about it very plausible. Thank you.

Re:Oxymoron?

[Cochonou]

Just have a look at the older articles (circa 2010) from this site. You will not have too look for very long to find very bogus physics.

Re:Oxymoron?

[gweihir]

What I was pointing at (or at least trying to) is that either the phrasing of TFA is incorrect or TFA is quoting clueless people.

I certainly agree to that.

Re:Oxymoron?

[gweihir]

My guess is that this person did not even try. "I find the articles I read about it very plausible." already says it all, as does the classic fallacy of trying to make the proponents of the established facts prove their position instead of the proponents of the extraordinary claims. (The systemd-sect is known for using this tactics aggressively as well.) A certain sign of an idiot.

Re: Must be a first for slashdot RTFA skimmed summ

[wonkey_monkey]

Photons are not really mass less. They have mass due to their enormous speed: E=mc^2

That's an old way of thinking. These days they are treated as purely massless.

The full version of Einstein's formula is E^2=(mc^2)^2+(pc)^2 where p is the momentum, which in photons is related to the frequency. The (mc^2)^2 bit remains 0.

Just a thought....

[Eric Freyhart]

Why can't we just plug up a light bulb behind a satellite and drive it? I mean, photons have mass, and can be directional (laser). It would seem to be a much better propulsion method than even an ion drive.

Re:Just a thought....

[wierd_w]

Emitted photons DO provide a thrust, but the thrust is very minimal, and only noticeable after long periods of time.

Several deep space probes have "anomalous" trajectories that have since been attributed to the IR photons being emitted from the heat sinks of their RTGs.

The EM-Drive is only generating all this press hoopydoo, because the thrust it exerts on the tortion pendulum is greater than that expected from this light pressure alone. If it could be explained handily by light pressure, it would have been swept under the rug years ago as uninteresting.

Re:Just a thought....

[Eric Freyhart]

Hmmm. Ok, that seems logical (sorry for stealing your line Mr. Nimoy. We miss you!).

pfff..

[SuperDre]

All it shows is that our knowledge of physics is just very limited.. Laws of physics are only a template to try to explain stuff, it isn't set in stone, it's just our (lack of) understanding of physics..

Re:pfff..

[Anonymous Coward]

All it shows is that the uneducated I-want-to-believe masses can work a comment field. Viva the coming idiocracy!

Re:But what if we fed it more power?

[silentcoder]

>Remember it was 100 years ago that Einstein predicted gravity waves, and they were just detected. Eventually can be a long time.

And worth noting that, in science, 100 years can be enough for the "laugh-you-out-of-the-room" crazy idea to become the mainstream consensus theory. A perfect example:
1912 - Wegener proposes continental drift. He gets laughed out of the room. Firstly he's not a geologist but a botanist and he basis his ideas on the agreement of the fossil records between Africa and South America but he has no real explanation for what can move a whole continent. He suggests forces in the mantle but every geologist "knows" those forces are far too weak (today we have a completely different model of those forces that's more than capable of it).

1930s - Arthur Holmes proposes an early version of plate-tectonics theory that at least makes Wegener's ideas sound a bit more plausible. Most geologists remain unconvinced to say the least.

1955 - Two scientists show up at a geology conference to rehash Wegener's idea. But they are armed with two key new weapons. One - they didn't used the land-shorelines but the shorelines about 50miles into the sea where erosion is less prevalent. Two, they used a computer to model the pieces - and the fits were just too damn perfect to ignore. They also propose a new mechanism for what could actually provide the force to move the continents - the theory we now call plate tectonics, basically an updated version Holmes's ideas. The conference ends up just as divided but, somehow, moving continents are now the consensus theory.

1990s - the new theory of plume tectonics explains most of the remaining questions about the subject, and what has long been mainstream science with a lot of unanswered bits suddenly makes tremendous sense. This is the prevailing theory today.

But look at that timeline - in a matter of about a hundred years an idea that probably occurred to many people over the centuries but was dismissed as fantasy by any serious scientist goes from ridiculous to mainstream - because we develop ever better technologies to gather data and test theories in simulations which gives us information not previously available. Now we've even got strong evidence that plate tectonics happen on other planets (notably Mars).

Re: Good

[Anonymous Coward]

The quality of trolls is really slipping around here

Re:Good

[quenda]

They are no more Swedish than the entire population of Switzerland is German.

Come on - the Swiss are even more German than the Germans. Swiss visitors to Germany complain about the inefficiency, lawlessness and excessive frivolity.

Re: Must be a first for slashdot RTFA skimmed summ

[gweihir]

Well, if they are right then something good came from this thing after all. This is also the first explanation that at least sounds as it could hold water.

Re:what's that word

[gweihir]

No. And if you were able to use Google, you would have found very fast that this is a specialization in Physics: "Multiphysics treats simulations that involve multiple physical models or multiple simultaneous physical phenomena." Or are you implying a simulation expert physicist working at a software firm suddenly loses his credentials? That would be even more stupid.

Re:what's that word

[gweihir]

What does tenure have to do with it? You become a Physicist when obtaining a Ba or Ma in the field. You become a scientist when obtaining a PhD. This person has one. It is immaterial what you do after.

Dirk Gently

[mlwmohawk]

Sherlock Holmes: "Once you have discounted the impossible, then whatever remains, however improbable, must be the truth"
Dirk Gently: "The impossible often has a kind of integrity to it which the merely improbable lacks."

I'm not ready to give up on a plausible answer based on physics we understand, it may be that it is doing something we understand and we are simply not realizing it.

Re:Dirk Gently

[Megol]

But they (the experimenters) have systematically removed measuring errors so... I guess as you are so smart you should help them? /s

Re:Dirk Gently

[joe_frisch]

I don't believe that they have corrected for all the external effects. Its a really tricky problem to get right.

I'm an experimental physicist and I can imagine how to do this experiment, but it would be a lot of effort and expense to do it correctly. There are a huge number of effects to take into account. The basic problem is that you are changing the power to the device by a lot, which can cause heating, and then trying to measure an extremely tiny force as a result.

Re:Dirk Gently

[NotAPK]

I too am an experimentalist and I was thinking about how to do it cheaply...

I think the simplest approach is to run the experiment twice, once with the device "on", and once with the device "off", and look for differences in the thrust, rather than trying to take a direct measurement of the thrust since as you correctly point out, there is heaps to take into account.

But I put scare quotes around "on" and "off" since how to do this will have an obvious impact on the device and the coupling to the device. Running power through cables will change their temperature, and thermal expansion may change the way they tug on the device. Same goes for the microwave guide tubes. My only idea worth sharing at this time is to set everything up as standard and then run it, and then replace one end of the cavity with a material transparent to microwaves and run it again. A high density plastic should do the trick, so replace 1mm of copper (or whatever the cavity is made from, brass? Aluminum? I don't think it matters...) with 10mm of plastic and the mass should be about the same. The only difference I would expect is that the cavity may run cooler in the second run. It should definitely be monitored for temperature, and if different by more than a degree (C) then some active cooling should be applied, which would then be the same for each run. Of course blowing a fan on it will probably produce more thrust than the device is generating :)

The thrust measurement can be directly measured against a very light spring scale provided the linear bearing has sufficiently low stiction. I'd recommend porous graphite air bearings to take the load of the device, most particularly because they have low stiction. The absolute position of the device can be read using an optical encoder, or a microscope viewing an appropriately fine vernier scale or grating: such a system should be able to measure a displacement of 10um with confidence: F = kD, so to measure a mN of thrust, the spring constant needs to be around 1000 N/m. I'm not a spring expert, but scouting around online this seems to be easily doable.

If I wasn't working so much at the moment, I'd even consider setting up the rig in the basement, since this is a cool experiment that with appropriate skill and care can actually be reproduced by an amateur, since no specific or crazy equipment should be needed.

Re:Dirk Gently

[joe_frisch]

A wire pendulum suspension (like used on LIGIO) is probably the most sensitive. do it in hard vacuum to get rid of convection currents. Power the device with batteries, and put it all in an insulated box whos outside temperature doesn't change significantly during a short run. Then pulse the engine at the pendulum frequency . Its a doable experiment but quite a lot of work to get right.

Re:But what if we fed it more power?

[wbr1]

I can claim I made an ICE powered automobile that gets 3000 MPG. The fact that my claim is bunk does not make all internal combustion engines stop working.

Re: Good

[Anonymous Coward]

And to them, germany is a poor country.

Convert energy into photons?

[Bohnanza]

So, all we need to do is shine a flashlight out the back of the spaceship and we are good to go?

Re: Must be a first for slashdot RTFA skimmed summ

[necro81]

Photons are their own antiparticle, so when they interact strongly with each other, the force drops to zero, so the pair doesnt interact with anything else.

[pedantic]
Be careful how you phrase that - photons have no interaction via the strong force. They cannot "strongly interact" in the way that, say, quarks strongly interact to create protons and the like.
[/pedantic]

I understand what you meant - that the photons are interacting with each other in a strong (i.e., powerful, tightly bound, significant, etc.) fashion. But since we're talking physics here, we should be careful about word choices.

Re:But what if we fed it more power?

[Megol]

First: magic? Nobody claims it have anything to do with magic. Well except idiots and trolls.

Second: how the fuck do you know? IF the em-drive does work it requires _very_ specific circumstances to work, do you expect that those circumstances would be common in the neighborhood so that people could trivially detect the effect?

Third: continuing your line of reasoning would lead a reasonable person to conclude that semiconductors and the field effect are "magic" and doesn't naturally exist, the same for super-conductors. Yet we are using machines based on semiconductors using the field effect to do Boolean logic to read this very website!

Re:Get it right, IBTimes!

[Megol]

Ümläüts? Wë dön't nëëd ümläüts!

Re:Good

[Gilgaron]

Now that I think about it, other than internet pedants, I've never heard anyone of any nationality use "American" to mean anything but a citizen of the United States. (along similar lines, when traveling and asking where people are from, Americans usually reply with what state they are from, whereas others usually reply with which country). At what point does a correction of your sort move from 'technically correct' to merely 'antiquated and wrong', I wonder, with languages changing as they do?

Re:two words

[BlueStrat]

This allows them to pass through the wall of the cavity like it wasnt even there.

Transparent Aluminum

Pfft!

Where have *you* been, Mr. Late-To-The-Party?

http://phys.org/news/2009-07-t...

Heck, it was even on Slashdot!

https://science.slashdot.org/s...

Strat

Re:Good

[Salgak1]

And now, I'm picturing Linus Torvalds as the Swedish Chef. . .

"Hin-de-foo, dee leenux in dee ker-null. . . ."

Re:what's that word

[Anonymous Coward]

"You become a scientist when obtaining a PhD"

Is that seriously how deluded we have become?

Re:Good

[jittles]

That was a bit flippant, so let me explain. "American" is a nationality

There are 35 American countries. So which country, pray tell, is an American from? And yes, I was born in the US and, unless you're Native American, my family has probably been here longer than yours.

Re: Must be a first for slashdot RTFA skimmed summ

[Gr8Apes]

Most physicists would define a photon as having no mass, yet it would carry momentum proportional to its energy. Mass is seen as a property of a particle that makes it resist changes in speed, but photons always travel at the speed of light (in a vacuum) -- never speeding up, or slowing down... and never at rest.

Apparently you can slow or stop photons. The speed of light c in a vacuum is constant as far as we know.

Re: Must be a first for slashdot RTFA skimmed summ

[angel'o'sphere]

The only way the EM drive can work is if there is entirely new physics.
All articles I have read explain it with standard physics. Perhaps I missed something, care to point it out?

It is as certain as anything is in science that the EM drive cannot work.
So far you failed to explain, why it can't work.

Why don't you simply read the theories about it and debunk it for us, so we can share your wisdom?

Re:But what if we fed it more power?

[Anonymous Coward]

I can claim I made an ICE powered automobile that gets 3000 MPG. The fact that my claim is bunk does not make all internal combustion engines stop working.

Ummm, that's actually true. It used to be a popular thing for engineering students to compete in.

Of course, the "automobile" weighs about 100 pounds. Here's a real example, 3587 MPG:

http://www.wired.com/2013/04/3...

Re:Good

[flopsquad]

And now, I'm picturing Linus Torvalds as the Swedish Chef. . .

"Hin-de-foo, dee leenux in dee ker-null. . . ."

Bork bork bork!

Re:what's that word

[angel'o'sphere]

You are a scientist when you perform science.
It dos not matter if you have a Ba, Ma, Phd or are a professor.

Most of the titles above require you to do science before you even can acquire such a title, as in a diploma thesis, or for more "natural" sciences: field studies outside in the woods.

Don't know in what world you live, but in Germany a student physics is called: Physicist.

Q: "What are you doing?"
A: "I'm a Physicist"

A completely valid answer for a student of physics.

Re:Good

[angel'o'sphere]

As a side note: Schengen States != EU.

There are EU states that did not join the Schengen Treaty. E.g. UK.
ONTO there are non EU states that did join it: e.g. Switzerland and Norway.

It is actually only really important when you acquire a visa to visit an EU country, as the visa usually states if it valid in all of Schengen or only in the country. (All of Schengen, haha ... perhaps I should write that different, rofl)

Re:But what if we fed it more power?

[angel'o'sphere]

An experimenter found an effect that did not fit in the current paradigm.
Actually that is not what happened regarding the EM drive.

One guy thought it out and published his thoughts.

Now plenty of research labs are building prototypes: and all found unexplainable thrust

Right now the race is to either find flaws in the experiments and also to find simpler explanations than the ones the original guy(s) had to present (Roger Shawyer, Guido Fetta).

Re:Good

[Troyusrex]

They have no herritage [SIC] with Sweden and the only thing they have in common with the Swedes is that they speak a dialogue of the language.

This is not true. The Finnish is NOT related to Swedish but is related to Hungarian.

High temperature superconductors

[Weaselmancer]

We don't have a current accepted theory for high temperature semiconductors either, but they exist and we're working with them.

Sometimes theory leads experiment, sometimes not.

Re: If this is correct it should be easy to chec

[Lije Baley]

A nuclear rocket uses fuel, such as hydrogen which is expended long before the nuclear reactor quits. Doing away with that fuel is the goal.

Re: Must be a first for slashdot RTFA skimmed summ

[joe_frisch]

In the article they say "These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator" This doesn't make sense. If the electromagnetic fields from the photons cancel, then the energy density and probability of finding a photon vanishes. There is nothing in that location to escape.

The more general argument is that all known physics (including quantum, gravity and relativity) conserves momentum (4-momentum if you are using relativistic terms). Since momentum is conserved in every interaction, it has to be conserved in the overall system. It is almost exactly the same reason that you can't make a perpetual motion machine out of gears and pulleys.

Experimentally there is lots of evidence that this doesn't work. I'm an accelerator physicist, I work with high (and low) power microwave systems which cavities with much higher fields than in this experiment. Some of the superconducting cavities are extremely sensitive to loss (1e-10/cycle) and no unexpected loss is seen. No unexpected forces are seen.

Electromagnetism (with electro-weak as an extension) is understood and measured from the scale of planetary magnetic fields (maybe even galactic), to 100 GeV interactions in lepton colliders. There really is no room for new physics to be hiding

The descriptions use words that sound like science but they don't actually make scientific sense. The most charitable explanation is that the writers are confused, but of course in general they are looking for funding......

Re: Must be a first for slashdot RTFA skimmed summ

[chihowa]

Photons are their own antiparticle, so when they interact strongly with each other, the force drops to zero, so the pair doesnt interact with anything else.

Particle-antiparticle interactions imply annihilation, which doesn't occur in typical photon-photon interactions (which are wave-like). Instead, you get a time- or space-localized interference and a change in the probability of finding a photon. There are situations where it makes sense to think of photons as their own antiparticle (largely in the context of matter-antimatter annihilation), but that's not a helpful way of looking at interference. Interference and tunneling are wave-like behaviors.

Perhaps pedantic.

Interesting historical comparison with Tesla.

[tarpitcod]

The explanation for the photons escaping the cavity sound similar to the comments by Tesla about longitudinal waves versus regular transverse waves being attenuated.

Re: Must be a first for slashdot RTFA skimmed summ

[angel'o'sphere]

Your argumentation makes no sense.

If the photons vanish as you claim in your first part, then obviously the momentum is conserved, contrary to your claim in the second part.

You can not start arguments with claims and then turning them around to explain why something is not working.

I suggest to start with the conversation of momentum, and then work backward. Explain us why momentum is not conserved when every physicist involved in this drive is explaining us: it is. If it was not conserved: the drive would not work! Apparently the drive is woking: so it is plain obvious that the momentum is conserved.

The question is: why? Or more precisely: how?

So, now as you probably might have been able to explain us that the momentum is indeed not conserved, then you can go back to step one and debunk the reason for it.

Electromagnetism (with electro-weak as an extension) is understood and measured from the scale of planetary magnetic fields (maybe even galactic), to 100 GeV interactions in lepton colliders. There really is no room for new physics to be hiding
And what exactly has this EM drive to do with:
a) Electromagnetism and magnetic fields?
b) new physics?
c) GeV interactions in colliders?

All explanations use standard physics, only the guys trying to debunk it need new physics, very strange I would say :D

No more gas stations

[ememisya]

So does this mean we can make a new Voyager with infinite fuel, less cancer, and have it loop back around?

Re: Must be a first for slashdot RTFA skimmed summ

[joe_frisch]

To be clear I was quoting the article's INCORRECT description.

In locations where the photons fields vanish, the energy density vanishes. The probability of finding photons IN THOSE LOCATIONS goes to zero. Think of it as waves - if I drop two rocks in the water, there will be places where the waves interfere and there is not wave amplitude. That means that there are no waves in that location, but it doesn't mean that all the waves have vanished everywhere.

I believe that the drive is not in fact working. The forces that they are talking about are tiny and very difficult to measure. These are ~100 micro newton forces on a ~10Kg object. There are a lot of boring things that could mimic thrust:

Small tilts of the experimental apparatus: this could be as simple as experimenters standing on different parts of the lab floor when they turn on and off the RF power. Cable and RF waveguide expansion - there will be some heat dissipated in the RF cable, that might make it flex.
  Gas desorption - the system was tested in vacuum, but when RF power is put it, it presumably gets hot and the hot parts can release gas trapped on the surface of the metal. Magnetic fields that change when the power supply is turned on. They have tried to correct for effects like this but Its a really difficult experiment to do correctly. This really is the key issue. There is no theoretical reason to think the drive should work and the experimental evidence is from an experiment that is very easy to get wrong.

The EM drive claims to produce thrust from electromagnetic fields, so electromagnetism should be able to predict the effect and it does not. GeV interactions are an example of a test of electromagnetics (+weak force) at very high energies. Planetary magnetic fields are an example of a test of electromagnetism in very weak fields. Basically electromagnetism has been tested over a very wide range of conditions, there is no reason to think it should not work for this particular experiment.

The explanations for the effect do not use standard physics - photons do not go through metal walls when the fields cancel - that doesn't make physics sense.

The best I can do is to say to remember this. You can't know which "expert" to trust, so instead wait 20 years and see whether or not this is ever turned into something real, or like cold fusion remains in the background, never actually becoming real because it doesn't work.

Why all the double-talk!?

[SkyLeach]

I read it. Then I read it again. I can't help but laugh.
The paper doesn't address the main problem: that of conservation of energy. Why? because it doesn't explain where the photons are gaining directional mass-to-thrust equivalence. 180-degree separation along a probability curve should, even given their equations, result in a net thrust of 0 or close relative to the atom that emits the photons.[1]

In essence, they are suggesting the same kind of 'free energy borrowing' from the vacuum as is suggested for the explanation of CP-symmetry violation in the low-order probability variant of Kaon decay. Zero point energy. Also quantum gravity.

1 Taken from the 'What is Gravity' section of the publication. Paper 'glosses over' the fact that gravity is being conflated with the surface of EM drive without explaining how or why. See the explanation of the equation (labeled (3) )

This paper needs a LOT of additional theoretic explanation before it's going to be even close to explanatory.

Re:But what if we fed it more power?

[ceoyoyo]

There were too proposals for EM drives, one by an Englishman and one by an American. The English one is (reported to be) quite a bit more efficient. NASA tested the American one first (surprise) and the Chinese evidently elected to test the English one. The Chinese also cranked the power up.

Re:Good

[quenda]

There are a number of British Isles, as well as mainland Brittany, but we know that the country of "Britain" is shorthand for the otherwise long-winded "United Kingdom of Great Britain and Northern Ireland". Irish Republicans are not offended, even though they are geographically British.

Re:Good

[quenda]

Have you been to the Southern border? I'm guessing not.

Yes, seen fenced sections, and even swum across the unguarded creek that is the Rio Grande. Don't worry: Drumpf will build the giant ice wall.

Re: Must be a first for slashdot RTFA skimmed summ

[joe_frisch]

Its difficult to explain to a layman because you don't have the background. Imagine explaining why 2048 bit RSA is difficult to crack to someone who doesn't have the math background.

They claim to produce thrust without any exhaust. That is a violation of conservation of momentum. If they claim that the exhaust in just photons, then that is a standard photon drive which works but has a well known power / thurst ratio that is too high for practical applications. If you generate microwaves and send them out the back of a spacecraft you will get thrust, but the power requirements are too large to be useful.

Electromagnetism is the theory of photons, microwaves, electric fields, magnetic fields. So it does cover this experiment. Electro-weak theory is an extension of electromagnetism to high energies - but the changes are not significant for this experiment..

Tunneling is understood. If the photons tunnel then some of the photons are being used as exhaust. That works but it is a standard photon drive. No point having them tunnel though, might as well just point the microwave source out the back of the spacecraft. (but see above for energy requirements). Tunneling is insignificant for think materials of the sort that they used here, so there will be essentially no emission of tunneled photons in this experiment.

My understanding is that the EM drive claims to produce thrust with no exhaust, and / or claims to produce more thrust / power than can be produce by photons. Neither of those is possible because both violate conservation of energy / momentum. (the energy/ momentum ratio of a photon is known).

What do you see as their claim?

Re:Good

[quenda]

in Belgium. We have three official languages.

Dutch, French, and ? ... Arabic?

Re:Good

[PCM2]

So you call yourself a "United Statesian"? Piss off.

Re: Must be a first for slashdot RTFA skimmed summ

[angel'o'sphere]

Its difficult to explain to a layman because you don't have the background.
Actually I have the background. Hence my complaint :D

Electromagnetism is the theory of photons, microwaves, electric fields, magnetic fields.
In the grand picture of things, yes.

But not in this case, or a wind turbine creating power with a generator based on electrons moved inside of a cable through a static magnetic field would be the same as a microwave creating photons.

Which is clearly not the same thing :D

Reducing everything down to Maxwell does not help if you don't grasp those differences.

So far you made no single argument that made any sense to a Physicist.

My understanding is that the EM drive claims to produce thrust with no exhaust, and / or claims to produce more thrust / power than can be produce by photons. Neither of those is possible because both violate conservation of energy / momentum.
Here it is again.

WHY PLEASE PLEASE PLEASE: Neither of those is possible because both violate conservation of energy / momentum. Why do you jump to this sentence? There is no logical relation between those statements, and none based on laws of physics. You just say that.

First of all, the inventors of the EM drive don't claim that there is no "exhaust". There are plenty of things that happen in the universe that have "no exhaust", conserve the momentum and accelerate something. E.g. a stone dropping to earth in a gravity field.

Instead of throwing random "it violates the law of conservation of momentum" into the room you should e.g. read this: http://emdrive.com/principle.h... and point out the flaw.

The principles "the inventors" think, make the thing working are based on the law of conservation of momentum!

Perhaps they made a mistake? Point it out and you will be famed. But your arguments sound like: at night it is darker than outside. A grammatically completely correct sentence. However I would likely not start my PhD thesis with it.

The claim is that due to particles/waves moving at the speed of light you can not use classical "mechanics" but have to use relativist calculations. Coming from those calculations the "inventors" built the first prototypes. And a few international research labs did the same. All claim to have found "unexplainable" thrust (That includes NASA, btw).

Others think that "very low amounts" of acceleration have some strange side effects (on the other hand, that would be new physics and I don't believe that): https://www.technologyreview.c...

Interesting are e.g. those passages:

"Crucially, McCullochâ(TM)s theory makes two testable predictions. The first is that placing a dielectric inside the cavity should enhance the effectiveness of the thruster.
The second is that changing the dimensions of the cavity can reverse the direction of the thrust. That would happen when the Unruh radiation better matches the size of the narrow end than the large end. Changing the frequency of the photons inside the cavity could achieve a similar effect."

So, bottom line I have no idea if the drive works or not. I simply find the self proclaimed debunkers extremely unscientific because none of them was able to write a bunch of sentences that follow a line of logic, math and laws of physics.

For starters: there is no law of physic that can be simply pulled out of a book that states: "this is impossible". But that exactly is what they do (and you did).

The only ways to debunk this device is to explain why we see thrust (NASA is reporting thrust in a hard vacuum) in those experiments and why e.g. that finish paper is wrong, in other words, where it is wrong..

As a wishful thinker I hope we put one in space and watch what happens :D Probably we can use a 100g nano satellite ...

Re: Must be a first for slashdot RTFA skimmed summ

[joe_frisch]

Are you a physicist?

Looking at your link: Its true that in a waveguide electromagnetic radiation propagates at different speeds than in a vacuum. The group velocity is lower than C, and the phase velocity is higher. There is some force on each end plate, and some net longitudinal force on the tapered side walls. You could do a complicated simulation / calculation to sum up the forces (difficult to get correct due to the complex boundary conditions), or you can fall back on basic principals. Imagine that the walls are prefect conductors. Break up the volume into tiny cells. Maxwell's equations are obeyed in each volume. Those equations conserve momentum. Since momentum is conserved in each tiny volume element, it is conserved in the entire system.

The think is, they ARE claiming violation of momentum conservation. Depending on what paper you read they claim that either:

A closed system generates force without any exhaust. That is by definition violation of conservation of momentum.

OR

A system generates thrust without consuming any fuel, AND that thrust is larger for the amount of power applied than can be explained by emission of photons. To produce momentum in the rocket, you need to produce the same (opposite direction) momentum in the exhaust. If you are not consuming fuel, the mass of the exhaust must be created from the energy consumed. This is a photon drive - you create mass (photons) that are emitted at the speed of light. If you emit the mass at a lower speed it will have less momentum for the same total energy (including the energy required to create the mass).

If there was some background to push against, then the drive could work. But many many experiments (starting with Michelson Morley) have shown that there is no background ether you can push against. If there was such a background that had somehow escaped all experiments, there is no reason to think it would show up in this particular experiment.

Unruh radiation is a complete red hearing. Its only significant at extreme accelerations and it will conserve momentum

Now, to be clear: if they are only claiming the same thrust as a photon drive, then it can work through some mechanism, but its also boring - its easy to build a photon drive, just no practical way to power one.

If they are claiming that some of the mass oft he rocket is used as exhaust, then that is just a different type of rocket and that is OK.

What is not possible is for it to both not consume fuel AND produce more thrust power than does a photon drive.

Clueless journalists

[SoftwareArtist]

However, a number of tests conducted in Great Britain, Germany, China, and at NASA's Eagleworks at the Johnson Spaceflight Center have resulted in thrust that cannot, as yet, be explained by experimental error.

That's a distortion at best. In fact, experimental error is the only plausible explanation for the results, because they detected thrust whether or not the drive was turned on. Unfortunately, details like that are too subtle for many people who pass as science reporters. In the most recent experiments, they basically published a paper saying, "We've learned these experiments are really hard to do. We clearly still have some stray forces that we haven't managed to eliminate yet, since we register force even when the drive is turned off. Here's a description of our progress so far." But lots of clueless reporters just saw, "We detected a force," then wrote articles about how the experiments confirmed the drive actually worked.

Re: Must be a first for slashdot RTFA skimmed summ

[Gr8Apes]

Apparently you can slow or stop photons. The speed of light c in a vacuum is constant as far as we know.

AFAIK, although you can slow the net propagation of photons (aka the electromagnetic wave dual of a photon) through a material, you cannot slow a photon.

Read the linked article, that was exactly the point of that experiment, not only to slow it, but to stop and then make it go again.

Re:what's that word

[gweihir]

That is actually the formal academic definition.

Re: Must be a first for slashdot RTFA skimmed summ

[david_thornley]

The device is claimed to exert thrust without reaction mass, thereby violating the Law of Conservation of Momentum and invalidating most of physics. It does this without doing anything really odd. The odd things about relativity and quantum mechanics don't show up at normal speeds (with exceptions like the orbit of Mercury, which was previously a mystery).

It isn't a matter of throwing photons off the back end to get acceleration. We know all about photon drives, including how much force one can get out of a given energy input, and the reported thrusts are orders of magnitude greater than a photon drive could do with that energy.

Therefore, either physics is inexplicably wrong or the device is pushing against something in a non-obvious manner or there's a lot of egregious experimental error going on.

Re: If this is correct it should be easy to chec

[Lije Baley]

Such a high class of pedantry today!

Re: Good

[quenda]

USA and American Samoa.

Motivated Reasoning

[Tenebrousedge]

McCulloch's paper has been repeatedly torn to pieces on r/EmDrive and this current theory fares no better. No one has measured thrust beyond the error bars, none of the experimental results have passed peer review, and all theories trying to explain the supposed phenomenon have basic physical errors, and just happen to overturn one of the most fundamental and well-tested concepts in science.

I don't know what combination of ignorance, credulity, and motivated reasoning is required to believe in this. I'd suggest you should reexamine your beliefs about this phenomenon, but at the least you should not be promoting a paper which has been so thoroughly discredited.

Nope

[Tenebrousedge]

You're usually less credulous than this. No labs have shown "unexplainable thrust", and no explanations have passed peer review. In point of fact, no explanations have been without serious physics errors. No experiment has shown thrust outside of their own error bars, and in most cases those error bars have not even been determined. There is no evidence for this phenomenon just as there is no evidence for over-unity energy devices, despite much sound and fury on the Internet.

What you're saying is completely untrue. Please correct yourself.

Re:Nope

[angel'o'sphere]

No labs have shown "unexplainable thrust",
Every /. article about a lab trying this experiments has reported "thrust", and I thought we all agree that this thrust is "unexplainable".
Science magazines are full with such reports. I posted some links, e.g. from technologyreview a few posts back.

No experiment has shown thrust outside of their own error bars, and in most cases those error bars have not even been determined.
Why are you americans always so obsessed with errorbars?
How can something be outside of an errorbar when the errorbar is not determined?

What you're saying is completely untrue. Please correct yourself.
As far as I see no creditable debunk, I consider science reports true, perhaps you should correct your attitude towards them?

Re:Nope

[Tenebrousedge]

Every /. article about a lab trying this experiments has reported "thrust", and I thought we all agree that this thrust is "unexplainable".

You can't claim to have shown thrust until you rule out other explanations. The experiments have not been able to rule out other explanations. Specifically, they have not been able to show that this was not measurement error. Few of the studies have even attempted to do so.

How can something be outside of an errorbar when the errorbar is not determined?

I think we agree that not attempting to quantify your measurement error is foolish. Perhaps someone can inform the "researchers" about this.

As far as I see no creditable debunk, I consider science reports true, perhaps you should correct your attitude towards them?

There have been no published studies, because none of the "researchers" can pass peer review, because they can't show that their results are not measurement error. All theories attempting to prove the non-impossibility of this device have been thoroughly debunked. Your "creditable debunk" is the normal laws of physics, which do not permit violation of the conservation of energy/momentum. With no empirical evidence, no theory, and a mountain of both theory and evidence pointing the other direction, you are not describing science.

I can only assume that your desire for this to be true has prevented you from actually trying to evaluate whether it is true.

Re:Nope

[angel'o'sphere]

You can't claim to have shown thrust until you rule out other explanations.
Then lets call it a force, man are you nitpicking.

I think we agree that not attempting to quantify your measurement error is foolish. Perhaps someone can inform the "researchers" about this.
Actually we don't agree :D I'm kind of scientist. At least I had a very scientific school and university education. Error bars were once mentioned in a side note and we certainly understand something different than most on /. do. I'm meanwhile convinced that americans learn something different in school about "error bars" hence the strange posts regarding AGW etc.
Usually we simply take the numbers the measuring device is showing. What else should we do?
To know about an error bar you need to know something about the possible errors. If you don't know such stuff, you don't know anything about the error bars. And: I never saw a scientific publication that had a side note about error bars, sorry.

Your "creditable debunk" is the normal laws of physics, which do not permit violation of the conservation of energy/momentum.
In my eyes it does not violate that law. You throw something out one way and get a reaction the other way. We only need to figure what the "something" is. Or realize: it indeed is a bunch of measuring errors.

Re:Nope

[Tenebrousedge]

Then lets call it a force, man are you nitpicking.

We are not nitpicking. There has not been any force or thrust detected.

Actually we don't agree :D I'm kind of scientist. At least I had a very scientific school and university education. Error bars were once mentioned in a side note and we certainly understand something different than most on /. do. I'm meanwhile convinced that americans learn something different in school about "error bars" hence the strange posts regarding AGW etc.

Your education was incomplete. Quantification of error is fundamental to science, it's why physicists talk about "five sigma" or "six sigma" results -- there is always the chance that an observation is a measurement error, and unless you take steps to minimize that error, and determine how much error is in your measurement, you do not know whether you have measured anything at all. You may not have read any scientific publication which talked about error bars, but I'm willing to bet you've never read a scientific publication that did not discuss p-values, which is the same subject.

In my eyes it does not violate that law. You throw something out one way and get a reaction the other way. We only need to figure what the "something" is.

In this case it's slightly more subtle in that the claim is more energy (momentum) out than energy in, and no fuel expended. There really isn't any way this could be true without throwing most of physics out the window. I would be just as happy as you I'm sure if there was a halfway plausible theoretical explanation as well as the (very dubious) experimental results. Suffice to say that is not the case. At this point, not only is the evidence pointing the other way, but also if it works, it would be pretty trivial to construct an infinite energy device using the same principles. That unfortunately would cause more problems than it would solve, and not just theoretically. Honestly, it's fairly conclusive, at least until either there's a workable theory or credible experiments.

Re:Nope

[david_thornley]

If there's a difference between power turned off and power turned on, that's very strong evidence that something is happening. Currently, I'm assuming that there is unexplained thrust. I could be wrong.

The claim is actually that energy in produces a force, not energy, and a given force over a given time produces a given change in momentum, without any observed change in reverse somewhere to conform to the Law of Conservation of Momentum. It's more force than a straight photon drive could create, by orders of magnitude. In very limited review of the results, I've seen completely inadequate attempts to find what it could be pushing against. I'm not going to take it too seriously unless and until I see that done in more than one lab. (Cold fusion had some inadequately controlled independent confirmations, IIRC.) One suggestion has been to orbit a satellite with the alleged space drive and see if it has thrust in vacuum with nothing around it.

The theory of this thing is a mess. We've seen different theories proposed, none of which work. This should have been obvious to the theorists, since the claim violates the Law of Conservation of Momentum, and if it does we're going to need new physics at a very fundamental level.

And here is where I find this as a reactionless drive unbelievable. We've found new physics by going to new extremes, although not as extensive as violating basic conservation laws in any way we can detect (I think of virtual particles as the Universe sticking its tongue out at us behind our backs). This thing is bouncing microwaves around in a particular shape of chamber, and that's something we've been doing since WWII

Re:But what if we fed it more power?

[cwsumner]

These several new theories that claim to disprove the old theories, are even crazier than the old theories. 8-)

The truth is "we don't know". But they can't say that, because the public punishes anyone who says that, even if it is the truth.

And, if it gets several orders of magnitude better output than simple EM thrusters, then it doesn't matter if it is. We still get the added thrust.

Re: If this is correct it should be easy to chec

[Chrontius]

In a nuclear rocket, the fuel and the reaction mass are two different components, and the fuel is likely to outlast the reaction mass by a massive margin, due to the nature of criticality - without enough fuel, the engine won’t work at all, so we tend to massively overfuel nuclear anything compared to the mission’s actual energy needs.

Re: If this is correct it should be easy to chec

[Chrontius]

It’s not like it’s rocket science, or anything.

Oh, wait...

Re: Must be a first for slashdot RTFA skimmed summ

[NotAPK]

"However I would likely not start my PhD thesis with it."

You've never written a thesis then. My own most definitely starts with a very basic and verified observable truth. The idea of a thesis is to build on knowledge and so the best place to start is to lay out what is considered to be accepted knowledge, with appropriate citations and references.

Re:But what if we fed it more power?

[RockDoctor]

Ohhh, you've mangled the history of plate tectonics severely there. Final out come is about right, but there re some severe slews in the intervening path.

You've missed out Alexander Du Toit, though mentioned his work on Gondwana fossil distributions and glaciations. He also added the mantle convection idea, though that was greatly clarified and improved by Holmes.

The 1955 "turn up at a conference" was by a couple of geophysicists who'd been publishing their results for several years by then. Started 1952, I think.

The consensus was still "vigorous argument" well into the 1960s. And details are still being worked on to this day - the terrane / microplate concept is still being argued to this day, though more about "which generates more testable hypotheses" than about which is "true", since both are to some degree true.

Re: Must be a first for slashdot RTFA skimmed summ

[RockDoctor]

More, photons are massless

Having no rest mass (because they are never at rest) is not the same as having no momentum. Photons have momentum.

Re: Must be a first for slashdot RTFA skimmed summ

[RockDoctor]

In locations where the photons fields vanish,

When I hear the word "location" in a discussion where quantum effects are almost certainly present, I always start looking for Heisenberg's location under Schrodinger's cat.

I remember giving myself a headache one month trying to work out what would happen in the last moments of the evaporation of a black hole, by Hawking radiation. At some point, the size of the remaining black hole is going to be so small that the blackhole is smaller than the wavelength of the particle/anti-particle pairs it needs to emit ... which ... makes ... my ... head ... hurt. Will the black hole be able to radiate in that energy range, or will it stop radiating? Beyond my physics. And maths. But I do get very cautious about non-classical concepts of "location".

Re:what's that word

[gweihir]

Actually, a student of physics has the title "Stud. Phys." or "Cand. Phys." while not having graduated. The titles are temporary. They become proper physicists (with a permanent academic title) only after graduation. The actual title names may have changed after Bologna, but a student of Physics is most decidedly not a "physicist" in Gemany. Try calling yourself "physicist" in anything official while still being only a student, and see how "Fuehren eines akademischen Titles ohne Berechtingung" plays out for you.

Re:what's that word

[angel'o'sphere]

A student of Physics is a physicist in Germany (and likely in the rest of the world, too). And that is not a title.

Cand. Phys. is a kind of title that you legally could use but no one does at it was kinda meaningless before bachelors got introduced. (A Cand. "Something" is somewhere in between a bachelor and a master, closer to the master in most universities).
A true title is "Dipl. Physiker" or "Dipl. Physicist" (or "Dr. Res.Nat." / a PhD) which would be "MA in Physics", albeit a Diploma is a bit higher ... traditionally ... than a Master.

Try calling yourself "physicist" in anything official while still being only a student, and see how "Fuehren eines akademischen Titles ohne Berechtingung" plays out for you.

The academic titles are hence "Cand. Phys." and "Dipl. Phys." Calling your self a Physicist or a Mathematician or a Scientist is not claiming an academic title. It is pointing out your profession or your "line of work", or even hobby.

If a little child is watching the stars every clear night and is making notes about its discoveries: it is an Astronomer. No title, studies or other stuff involved. It is not a Cand. Astro, Dipl. Astro, or BA Astro or MA Astro, but if it is smart it will say: I'm a physicist, focusing on Astronomy.

If someone is painting he is a painter, probably he is an artist, too. No where did he imply he studied Art in Bologna :D

As I said before, if two students sit in a pub and one asks: "what are you doing?" the answer: "I'm a physicist" is completely legal and everyone around will understand: he is studying physics. Same for any other profession/course of studies (and again: I'm pretty sure this terminology is valid and legal for English or French countries, too).

Re: Must be a first for slashdot RTFA skimmed summ

[angel'o'sphere]

You've never written a thesis then.
Can you show the logical path that let to that conclusion?

Your claim makes no sense, even if it was true.

Re:Good

[jittles]

There are a number of British Isles, as well as mainland Brittany, but we know that the country of "Britain" is shorthand for the otherwise long-winded "United Kingdom of Great Britain and Northern Ireland". Irish Republicans are not offended, even though they are geographically British.

So what is your argument, that it goes by the largest landmass or the largest population of that heritage? Because the Americas are named after an Italian who was sailing on behalf of the Portuguese crown. It's not named after a specific region or heritage. And since the American continents are much larger in land mass than the United States of America, that argument makes no sense either.

Re:Good

[jittles]

So you call yourself a "United Statesian"? Piss off.

No, when one someone asks me, I tell them I am from the United States. It is certainly more specific than saying American and I don't look like an arrogant asshole. Since your only argument for or against this seems to be 'piss off,' one can certainly make assumptions on the impression you would give people in a foreign country.

Re:what's that word

[gweihir]

That is bullshit, and you know it. Calling yourself a physicist or mathematician unqualified is a claim that you have permanent academic title of that nature. (If the person is clearly a student from the context, that is not unqualified anymore. The language is relaxed at Universities in this regard, but not in general.) The only thing that saves you in a formal context is that "Fuehren eines akademischen Titels ohne Berechtigung" is usually only prosecuted on PhD-level.

Similarly, doing mathematics does not make you a mathematician. (Same for physics.) Otherwise a 1st grader could call himself "mathematician" for having done simple sums.

Re:But what if we fed it more power?

[david_thornley]

Actually, there were reported cold fusion replications. A quote from the Wikipedia article: "Many scientists tried to replicate the experiment with the few details available. Hopes faded due to the large number of negative replications, the withdrawal of many reported positive replications,"

Re:But what if we fed it more power?

[vivarin]

In the Einstein case, he said "The theory predicts gravitational waves, but they'd be nearly impossible to detect."
In the EM dive case, what's going on is "Here's a theory for radical behavior that we cannot yet reliably detect."

If you're going to blow off Newton, it's more important that you get pretty airtight experimental results that are significantly better than "might not be noise" than you have a theory to explain them.

Enough. This is a peer reviewed paper.

[Catbeller]

I can only add to this back-and-forth that the paper in question has been peer reviewed. You all are not dealing with Shawyer's self-published non-reviewed paper here. This is physics, an actual hypothesis. Those of you who disagree have to consider that your comprehension of photon-photon "annihilation" and momentum conservation might be flawed. In any case, we have a way forward; all the previous negative responses had in common (endlessly) was the fact that physics had to be completely wrong for a resonant cavity drive to provide propellantless propulsion. Now we have a way in which EM drives do not violate physics. And - it's emminently testable. Even if Shawyer is completely valueless here, he might have triggered a new way of thinking about momentum transfer, a hack in the universe we can use for propulsion. We need one badly.

Re:Good

[shutdown -p now]

Swiss also speak a language that's more German than what the Germans speak.