Cannae/EmDrive

[Sean Mirrsen]

Fortunately, it's also a reason to be absolutely certain that nothing will come out of it, beyond, maybe, new applications in ion propulsion. We just can't be that wrong about foundations and only be finding out about it now.

I think you're underestimating the capacity of a system as complex as the Universe for having distinct recognizable patterns. If the exact same things couldn't be explained in several different ways, we would never have competing theories. And no matter what goes on with the EMDrive, you're a bad scientist if you exclude even the slightest chance of any of the things you know being wrong.

[ZetaX]

Well, for starters, FTL neutrinos wouldn't really be nearly as big of a deal. Neither from theoretical nor practical standpoint. It seemed likely that there was an experimental error, but it wouldn't have uprooted anything fundamentally if it wasn't. Enough things appear to propagate FTL on both Quantum and Cosmological scales to merit merely a "huh" on the freaky physics scale. And there were no direct applications. If they could propagate slightly FTL through vacuum, maybe there would be some use. And even that's a stretch. If you have to send them through a rock, well, that's just a theoretical curiosity, then, with no practical use.

I think this FTL would break causality (as neutrinoes carry information, energy, ...). And it would probably be a type of FTL that does not come from general relativity nor quantum effects. Essentially a kind of "special relativity FTL" (more formally: local), which should not exist. I think disproving Einstein and inventing time travel is a big deal

Edited May 9, 2015 by ZetaX

[Scotius]

Whoa, whoa! Hold your horses. How did we arrived to time travel and risk to causality from a metal box turning electricity into thrust?

[K^2]

I think this FTL would break causality

What of it?

local

Well, yes, breaking local causality would be kind of bad. But QM already shows us that notion of locality gets a bit slippery on a small scale. And if our space happens to have a more complicated underlying geometry, say, similar to Holographic QM, you could actually end up with macroscopic light barrier violations via QM without ever truly violating locality. And it wouldn't be inconsistent with anything we've measured so far by any statistically significant margin.

It's ugly, and Occam's Razor suggests that it shouldn't work that way, but that'd be in category of tweaks to the theory, rather than "start from scratch".

How did we arrived to time travel and risk to causality from a metal box turning electricity into thrust?

Any momentum conservation violations in one frame are energy conservation violations in another. Ergo, no local time symmetry. Ergo, no causality. It's actually very straight forward.

Fortunately, it doesn't go the other way for (global) causality. Local causality we'd still like to keep, with the above caveats in mind.

Edit: Just to clarify, it did arise from a different discussion, but these things are quite related. ZetaX seems to suggest that both causality and symmetry violations are equally bad, and I disagree. Causality violations, even if they appear local at a glance, could simply mean that the rabbit hole goes deeper. Symmetry violations means that there is no rabbit hole, and we've been in the padded room all along.

Edited May 9, 2015 by K^2

[ZetaX]

What of it?

The usual stuff (which you already hinted to later on): depending on your frame of reference, sending the neutrinoes might happen after they are received.

Edit: Just to clarify, it did arise from a different discussion, but these things are quite related. ZetaX seems to suggest that both causality and symmetry violations are equally bad, and I disagree. Causality violations, even if they appear local at a glance, could simply mean that the rabbit hole goes deeper. Symmetry violations means that there is no rabbit hole, and we've been in the padded room all along.

No, not equally bad. I am aware that FTL is not really contradicting most theories, while EM drive is. I am saying that both would be comparably shocking (for me at least, but probably for many, physicists and others alike) to find out. FTL/time travel might not be bad for our current understanding of physics, but it actually being possible is quite a game changer.

But I did not consider

Any momentum conservation violations in one frame are energy conservation violations in another. Ergo, no local time symmetry. Ergo, no causality. It's actually very straight forward.

by which indeed makes the EM drive strictly worse than FTL/no causality.

Whoa, whoa! Hold your horses. How did we arrived to time travel and risk to causality from a metal box turning electricity into thrust?

How about reading the last ten posts¿ Or at least the part I quoted¿ Seriously, ...

[CptRichardson]

No, because conserved currents. The momentum has to be carried away by stable particles, or it can't work in vacuum. That means mass poles. That means you have to have propellant.

At best, Dr. White's hypothesis buys it a greater length scale, which could allow the craft to use low vacuum, such as that found in low orbit, as propellant. It would prevent the craft from operating in interplanetary space, but could still be useful for LEO operations. Of course, even this is a huge if.

Actually, the particles shouldn't have to STAY stable. They only have to be stable for long enough to carry reaction out of the chamber, at which point they're free to turn into itty-bitty bursts of radiation. The space/time warp signal actually provides a pretty neat explanation as to how the virtual particles were being stabilized, as experimental math has proven in the past that warped regions of space tend to separate virtual particle pairs. Which granted raises a dozen other questions but those questions were already raised.

[K^2]

Actually, the particles shouldn't have to STAY stable. They only have to be stable for long enough to carry reaction out of the chamber, at which point they're free to turn into itty-bitty bursts of radiation.

I don't know how many times I need to reply to this nonsense. If massless radiation is carrying momentum p, it has energy E = pc. That means, you need 300MW per 1N of thrust. I'm fine with that. If that's the power-to-thrust ratio they claimed, they would have had a photon drive, and nobody would care. But they claim a much lower energy use. So you can't have momentum carried out by massless radiation. If the mass was generated by the drive, add mc² onto the above. It becomes even less energy-efficient. The only way you can break 300MW/N is by using a reaction mass. That's the only way this math works out.

[StrandedonEarth]

I don't know how many times I need to reply to this nonsense. If massless radiation is carrying momentum p, it has energy E = pc. That means, you need 300MW per 1N of thrust. I'm fine with that. If that's the power-to-thrust ratio they claimed, they would have had a photon drive, and nobody would care. But they claim a much lower energy use. So you can't have momentum carried out by massless radiation. If the mass was generated by the drive, add mc² onto the above. It becomes even less energy-efficient. The only way you can break 300MW/N is by using a reaction mass. That's the only way this math works out.

I'm just addressing this one part: virtual particles pop into existence, requiring mc² worth of energy. Virtual particles pop out of existence, releasing the same amount of energy. (I don't know what happens to added momentum when the particles vanish.) So a constant energy input is not needed to create mass, rather it is recycled.

I do hope this develops into a working, propellant-less "space drive." That would be a huge game-changer for space exploration.

[Rakaydos]

My view is, at minimum we've invented a super ion drive. If they made a "low vaccum MHD propeller" (if Dr White's theory is correct) all the better. If it's truely symmitry breaking... then i admit we've got a problem.

Edited May 9, 2015 by Rakaydos

[K^2]

I'm just addressing this one part: virtual particles pop into existence, requiring mc² worth of energy. Virtual particles pop out of existence, releasing the same amount of energy. (I don't know what happens to added momentum when the particles vanish.) So a constant energy input is not needed to create mass, rather it is recycled.

a) Virtual particles do not require that energy. They are off-the-shell. Their energy could be "anything". Of course, the further the particle is off the shell, the less it's going to be around.

Momentum has to be, eventually, transferred into real, on-the-shell particles. Energy for that has to come from somewhere.

Virtual particles do not solve any problems here. They simply allow you to transfer energy/momentum to something else.

[Rakaydos]

Virtual particles do not solve any problems here. They simply allow you to transfer energy/momentum to something else.

Even if it only works in a low vacuum it will still be a remarkable find.

[Sean Mirrsen]

[humorouscomment] I wonder if K^2 will explode if it's found that the EMDrive achieves above-photon-drive-power propellantless thrust via generating FTL neutrinos. [/humorouscomment]

[Aanker]

On the topic of negative tests - this discussion happened a few pages back so I won't quote - wouldn't using different types of EM waves (radio, X-ray, etc...) be possible (if not negative) controls? Can they apply different microwave wavelengths and see different results? What happens if they have the resonance chamber, and just leave it on the rig without anything beaming at it? etc

[Nuke]

if i were to guess, the dimensions of the cavity have to be proportional to the wavelength. xray might make the drive ~10x smaller. and of course everything would have to be made to more exacting tolerances. you might also have issues with cooling too.

[Aanker]

if i were to guess, the dimensions of the cavity have to be proportional to the wavelength. xray might make the drive ~10x smaller. and of course everything would have to be made to more exacting tolerances. you might also have issues with cooling too.

So to my understanding, if the hypothesis behind the physics of the drive is correct, using a mismatched wavelength and cavity dimension would produce less or (preferably) no thrust? If so, I believe we have a negative control.

Of course, assuming that cooling, materials etc. would not be an issue for those types of tests.

[Leszek]

So to my understanding, if the hypothesis behind the physics of the drive is correct, using a mismatched wavelength and cavity dimension would produce less or (preferably) no thrust? If so, I believe we have a negative control.

Of course, assuming that cooling, materials etc. would not be an issue for those types of tests.

We can use that to rule out some possibilities...

But assuming for a moment the device works, we don't know how or why. That would mean that a proper negative control is almost impossible. We could play with various variables and try to figure more things out, but the device in its current is unfalsifiable.

There are plans to scale up the device so that it has output that isn't near the limits of what is detectable. That is when tests will be definitive.

[Aanker]

So until then, our best guess is magic?

[Leszek]

Okay. But what of the next step? Eagleworks would have went "huh", and tried to determine what creates the thrust, since thrust is a thing you can measure, and they had been measuring it. If the tampered-with, beyond-a-shadow-of-doubt nonfunctional test article still produces measurable thrust, something is going on. That is, as I said, the one area where Eagleworks is at an advantage. They were not aiming to prove the existence of thrust as a concept. They already know that thrust is a thing that exists, so when their results show that there is thrust, they know that something is happening. Blondlot had to prove that he wasn't, as it were, "seeing things" first.

Like I said, I don't know if anyone tried to do any follow-up experiments to determine what, if anything, the experiments were actually detecting before. But unless the creator of the concept of N-Rays admitted that he made the whole thing up, I think it was a thing that could have been looked into - at the very least so that whatever that factor was does not interfere with any future experiments.

Sorry about taking some time to reply to this.

I had just spent several posts explaining why all this is dead wrong and useless.

They haven't really measured anything. Nothing. Zilch. (Nothing that can be trusted anyway.)

Understand that as long as you are near the limits of detection, all sorts of errors creep into the data and that makes it really hard to validate anything.

For example. The Hubble mirror is famously out of whack. When they were making the mirror they had to account for the traffic in the parking lot. What finally got them is that some paint on the sensor was worn and not the proper thickness.

With the EmDrive, it could be that turning the device on causes it to expand slightly due to normal thermal heating. This causes the device balance to change. This causes thrust to be measured when there in fact isn't any.

It is not the scenarios that we can imagine that will get us, it is the scenarios we can't.

You may have pictured in your minds eye a flat line measuring thrust that moves up when the device is turned on. That itself would be suspicious. Being near the limits of detection means that the line is going to be jittery and jumpy and the thrust of the device is going to have to be detectable in that noise.

The electricity going to the device could be making an electric field that is acting on the walls.

When you are near the limits of detection, there is NO WAY to know that you ruled all the sources of error out. You might think you have, but you can't know for sure.

That is WHY it is dangerous to work with data near the limits of detection. That is why pseudoscience likes to stay there. It is easy to imagine data in the noise whether there is data or not.

When they scale up the device so that it produces results of a larger magnitude, then and only then will they have something definitive.

Edited May 9, 2015 by Leszek
Fixed wording error.

[Rakaydos]

With the EmDrive, it could be that turning the device on causes it to expand slightly due to normal thermal heating. This causes the device balance to change. This causes thrust to be measured when there in fact isn't any.

They've identified that effect and compensated- the key attribute being that thermal effects arnt instantanius. When they turn the device on, there is an instant responce, followed by a thermal effect rampup, then when they turn it off, there is an instant drop, followed by a fade in thermal effect.

[Leszek]

They've identified that effect and compensated- the key attribute being that thermal effects arnt instantanius. When they turn the device on, there is an instant responce, followed by a thermal effect rampup, then when they turn it off, there is an instant drop, followed by a fade in thermal effect.

Yes I am aware that they probably thought of everything I will and then some. Doesn't change the point.

[Sean Mirrsen]

Yes I am aware that they probably thought of everything I will and then some. Doesn't change the point.

Likewise, they probably thought of the limits of detection as well. While I agree that it's impossible to account for everything without knowing everything - that's even the point I'm making to K^2 in regards to how the drive might operate in violation of known physics, however well-established - you should still probably give the Eagleworks team some credit. Even if they're NASA, they probably ruled out the obvious suspects by now at least.

The comment about the power supply acting on the walls of the chamber made me want to comment that they already tested an "RF load" with the same power supply and nothing happened, but at the same time it made me remember that the drive is a weird electromagnetic device that uses a vaguely thruster-shaped chamber. While the walls of the testing chamber are probably insulating the device from outside interference, could it be creating a "shaped" magnetic field that extends primarily in one direction, pushing off one side of the chamber but not the other? Is that theoretically possible (cue K^2 answering "sure is more possible that reactionless thrust"), and how would one test for/against it?

[Rakaydos]

Likewise, they probably thought of the limits of detection as well. While I agree that it's impossible to account for everything without knowing everything - that's even the point I'm making to K^2 in regards to how the drive might operate in violation of known physics, however well-established - you should still probably give the Eagleworks team some credit. Even if they're NASA, they probably ruled out the obvious suspects by now at least.

K2 is a lot happier with "low vaccuum QMHD" than "breaks conservation of momentum" and the first is almost as good for our purposes.

[Leszek]

Likewise, they probably thought of the limits of detection as well. While I agree that it's impossible to account for everything without knowing everything - that's even the point I'm making to K^2 in regards to how the drive might operate in violation of known physics, however well-established - you should still probably give the Eagleworks team some credit. Even if they're NASA, they probably ruled out the obvious suspects by now at least.

The comment about the power supply acting on the walls of the chamber made me want to comment that they already tested an "RF load" with the same power supply and nothing happened, but at the same time it made me remember that the drive is a weird electromagnetic device that uses a vaguely thruster-shaped chamber. While the walls of the testing chamber are probably insulating the device from outside interference, could it be creating a "shaped" magnetic field that extends primarily in one direction, pushing off one side of the chamber but not the other? Is that theoretically possible (cue K^2 answering "sure is more possible that reactionless thrust"), and how would one test for/against it?

How much credit EagleWorks gets is irrelevant. It is a hazard in working in that regime.

Now, if the device is scaled up to put out say a pound of force, then almost all those objections disappear, and what is left is easily accounted for. (And actually it could be a whole lot less than that.) That is why they are trying to scale up the device. And be sure that if they do and the device thrust doesn't disappear, about a 100 labs would have their own EmDrive being tested the next day. (Figuratively of course.)

[DaMichel]

Didn't the Chinese build a similar device already which produced a much larger anomalous thrust?

By upscaling, the right steps are being taken, that we can all agree on. The NASA people are certainly among the most knowledgeable experts one can find. So if they are puzzled by this thing there is probably something interesting to learn. Will it turn out to be just a broken wire? Who knows ... but it is a low risk, high profit endeavour .. so no problem if it does.

[PB666]

With the EmDrive, it could be that turning the device on causes it to expand slightly due to normal thermal heating. This causes the device balance to change. This causes thrust to be measured when there in fact isn't any.

It is not the scenarios that we can imagine that will get us, it is the scenarios we can't.

You may have pictured in your minds eye a flat line measuring thrust that moves up when the device is turned on. That itself would be suspicious. Being near the limits of detection means that the line is going to be jittery and jumpy and the thrust of the device is going to have to be detectable in that noise.

The electricity going to the device could be making an electric field that is acting on the walls.

So you reply to what you think is whack with equal dose of whack?

The basic and fundamental problem in all of human discovery can be summarized to the layman with the following.......

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

Examples: Coelecanth, http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14447.html, the 2008 financial system collapse, relativistic physics.

All of these things are examples in which past trends predicted could not occur that occur. There are two essential phases to future predictions human conception follows

that past trends will in the future will almost always be true, therefor we tend to discount or denigrate that which does not follow the past trend. However, true innovation follows the discovery of new trends.

As a consequence, even in the beloved world of quantum mechanics, there are still unknowns and still things that can be discovered.

The question is are you one who calls the black swan a unicorn out of profound insight, or are you painting black swans white out of a lack of imagination.

- - - Updated - - -

Likewise, they probably thought of the limits of detection as well. While I agree that it's impossible to account for everything without knowing everything - that's even the point I'm making to K^2 in regards to how the drive might operate in violation of known physics, however well-established - you should still probably give the Eagleworks team some credit. Even if they're NASA, they probably ruled out the obvious suspects by now at least.

The comment about the power supply acting on the walls of the chamber made me want to comment that they already tested an "RF load" with the same power supply and nothing happened, but at the same time it made me remember that the drive is a weird electromagnetic device that uses a vaguely thruster-shaped chamber. While the walls of the testing chamber are probably insulating the device from outside interference, could it be creating a "shaped" magnetic field that extends primarily in one direction, pushing off one side of the chamber but not the other? Is that theoretically possible (cue K^2 answering "sure is more possible that reactionless thrust"), and how would one test for/against it?

As has been stated oh so many times, you test the device by putting a couple of panels on it and place it into an orbit, if it can gain altitude then it works.

MY suspicion is that it will work, but it will not produce as much force as it does in the laboratory.