NASA confirms that the ‘impossible’ EmDrive thruster really works | Hacker News Reader

NASA confirms that the ‘impossible’ EmDrive thruster really works

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198 pointsfahimulhaq179 comments

Remember the faster-than-light neutrinos? Where they repeated the experiment multiple times with the same result? And nobody could find a plausible explanation for an error? And then, some months later, they found it was just a bad cable.

The sane rule of thumb on these kinds of experiments that seem to contradict basic physics is to assume it's just an error in the experiment or the data calculations. Even if they did it multiple times. If this gets replicated by multiple independent teams worldwide with different experiments - then we can talk about new physics. But it's important to understand how extremely unlikely that is.

The best you can learn from these kind of stories is how hard it is to get science right and how subtle errors can be.

Don't get me wrong: I'd love to see some star-trek-like science becoming real. But it certainly doesn't help to replace critical thinking with wishful thinking.

Difference here is that the experiment has been done by two different teams from different countries using different protocols.

If I recall correctly, the two teams got different results. Although they both found very small amounts of thrust that they couldn't explain, the actual amount of unexplained thrust was different by something like an order of magnitude.

And no team had a conclusive result.

I'll agree that experimental error is the most likely explanation by far but I think there's still a noticeable chance that the explanation is some novel effect that doesn't actually violate conservation of momentum. If I were to give a break down on my expectations they'd probably be something like

  90% Experimental error
  9%  Unexpected and novel consequence of current physics
  1%  New physics that doesn't actually violate momentum conservation
  ~0% Violation of conservation of momentum.

But this has gone the point where even if it's experimental error I expect the mechanism will be at least somewhat interesting, as with the Italian speed of light experiment.

> ~0% Violation of conservation of momentum.

I don't think the chance of violation of the conservation of momentum would be 0%. Unlikely? Yes. Highly unlikely? Most definitely, but not zero. Why? Because we don't yet have a "theory of everything". For all we know, (not saying this is the case, just a thought experiment/hypothetical) the string theorists have it right, and there are extra dimensions, or brane universes (a multiverse) and maybe this effect is in some way related to that (pulling/utilizing an energy from a higher 4th dimension). Granted, it goes against everything we currently know about physics, but so did a lot of things at one point. And that usually happens when we don't know enough about the area we're researching.

And when it comes to quantum mechanics, we're only scratching the surface of what we know. There are plenty of things in quantum mechanics that are completely inexplicable. Things like the double slit experiment, quantum entanglement, quantum tunneling, etc.. We know those things occur, but very little or nothing at all as to the "how" and "why". They seem to defy known physics but there they are...

That squiggly line in front of the zero means "approximately," so really you're in agreement. The chances are not exactly 0, but more like 0.0000001%.

It's certainly not impossible, which is why I put the "approximately" symbol in front of the zero. I would be very, very surprised if the TOE broke conservation of momentum but then again I found it very surprising that there's basically just one experiment that breaks reflective symmetry (I forget what it's Noether[1] equivalent conservation law is).

[1]https://en.wikipedia.org/wiki/Noether%27s_theorem

> which is why I put the "approximately" symbol in front of the zero.

Ah, I missed that somehow... Haven't had my coffee.

No problem, I'm sure I've responded after similar misreadings many times.

There isn't a Noether conservation law corresponding to reflective symmetry, is there? The situation where Noether's theorem applies is where you have a smooth family of symmetries, with one of them being the identity (i.e., the trivial symmetry where you don't change anything at all), but reflections don't fit that pattern.

On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law. But (so far as anyone knows, I think) the laws of physics really are rotation-invariant and conservation of angular momentum really does hold.

> On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law.

This is an interesting idea, but, I think, too weak. It is true that every rotation is a composition of two reflections, but there's such an important difference between rotations (orientation-preserving) and reflections (orientation-reversing) that I think one shouldn't say that invariance under the former implies anything about invariance under the latter.

And some clarifications at http://math.ucr.edu/home/baez/noether.html . And I think Noether's theorem covers regular conservation of momentum - that is, equivalence of laws in every point of space - which is actually at question here.

I think violation of conservation of momentum is more likely than new physics. Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry. (GR Energy Momentum conservation would still be in effect in that case, but classical momentum conservation would not.)

Apart from that, I am unhappy about your percentages, I think the non experimental error explanations are an order of magnitude less likely.

My physics education topped out at special relativity and statistical mechanics so I'll take your word for it.

> Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry.

Given the setup, it seems highly unlikely that this thing produces something that requires a GR explanation. The energies aren't high enough; there's no high gravitational field or high acceleration.

> I think violation of conservation of momentum is more likely than new physics.

But if GR is out, then violation of conservation of momentum is new physics.

I agree, or actually I assume that the disagreement is only about words. I would not call it new physics, if, for example, we have to couple quantum fields to GR in a not straightforward way, so in the case were we already know all the parts but not the specific combination of the parts. I would only call it new physics if we have to rewrite basic textbooks.

If this showed us how to couple quantum fields to GR, that would be pretty good. Personally, I would consider that "new physics", given how unclear it is how to do so at the moment. If doing so doesn't significantly change either GR or quantum, however (and so the basic texts are still valid), I could go with your view.

Doesn't GR conserve local momentum by construction? Since Spacetime is a Lorentzian manifold, the metric is always locally translation invariant.

Yes, up to first order. ( So it seems implausible that a rather small EM thruster would provide trust, but the thing is already implausible in the first place.)

Not a bad cable - wasn't it failing to account for relativistic effects in the GPS satellites used for time/location reference?

It was an improperly attached cable, and a bad clock. Relativistic effects on the GPS satellites was proposed as a potential explanation, but was not the final accepted cause.

No, it was one connector on one cable that had a fault that introduced latency in a rather unexpected way. The people doing this are much more sophisticated than "oops, forgot GR when doing GPS calcs."

Headline is wrong. Correct topic sentence from article :

    "In essence, by utilizing an improved experimental procedure,
     the team managed to mitigate some of the errors from
     prior tests — yet still found signals of unexplained
     thrust."

No, the EmDrive does not work, they just haven't yet figured out yet why they see the spurious acceleration in their measurements.

How do we know it doesn't work? Because it violates conservation of momentum, without involving any of the extreme conditions where our current understanding of physics might break down. Basic physics is REALLY REALLY well tested. The chances that some new experimental configuration will expose new physics, without involving extreme energy concentrations or extremely large or tiny spatial dimensions, is so near to zero as to be negligible.

True, but how many clicks would the headline "NASA has not yet eliminated enough errors in its EM Drive experiment to conclusively prove that it doesn't work" have got.

But yeah, no one with any understanding of physics is betting money on this thing working.

I wouldn't bet more than a nickel that it works. But I wouldn't bet more than $1000 that it doesn't, either.

(Disclaimer: I actually wouldn't bet anything either way, but I think the sentiment is right.)

'know it doesn't work' - seems a bit strong here.

1) While a violation of a widely accepted law of nature is indeed unlikely - it's not like it hasn't happened before.

2) There may yet still be some way to model the experimental data that at once makes the em-drive viable, while still preserving conservation of momentum. Still unlikely, but arguably more likely than 1).

3) And while these both remain unlikely - it is yet rational to have an increased credence for them while the experimental data remains unaccounted for. In fact, it's arguable that this increase of credence is significant - for if it were not, performing the necessary experiments to find out either way would be a waste of time. There are of course some very smart domain experts performing these experiments. Your tone and use of the word 'know' implies their irrationality. I would advise greater humility.

Can I 'know' that if I drop my phone it will fall to the floor? We 'know' the EmDrive doesn't work in exactly the same sense and nearly the same certainty.

If you believe we do indeed have that degree of certainty - then you believe the experiments are indeed a waste of time, and that the experimenters are behaving irrationally - contra 3).

I think they are rational - and certainly it's rational for me to defer to their judgement on the matter.

That's fine if you don't agree. But if you're replying in order to help me update my beliefs, then you'll need to provide a rebuttal to 3) - which you haven't. :)

The rationality of performing the tests is social and societal reasons. The lab doing this has funding to test out-of-the mainstream ideas that could lead to new propulsion systems. By testing this kind of thing, even if they also 'know' it won't work, they get publicity and attention for themselves. It helps to keep the funding rolling, and builds operational experience testing small effects, and gives the scientists a chance to play "what if" thinking about possible new physics.

That's quite a reasonable, if cynical, reply.

To be honest I don't know how to evaluate the which of these two explanations of the scientist's behaviour are more likely.

I'd like to see some data on how much one can obtain funding by performing what is, given your beliefs, literally garbage science.

If we can establish at least precedent that scientists can attract funding on the basis of their projects that were (at the time, not in hindsight) - un-controversially junk research. Then your explanation would have the upper hand.

If we can establish a clear pattern of such rewards, then you win a slam dunk.

There is a large difference between well thought out research ideas that break the mould (which absolutely deserve a fair chance and funding opportunities) versus those that are diametrically opposed to our current understanding of well tested science. The EmDrive is not the former.

> The rationality of performing the tests is social and societal reasons.

The rationality of performing the tests is that it's the basis of science. If someone claims something is possible, the role of science is not to respond with contempt and condescension, it is to prove the matter one way or the other. If the claimant is a crackpot then the experiment will prove it, which is what will happen most of the time. But not all of the time.

The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka" but "That's funny..." —Isaac Asimov

The history of science is littered with prestigious people who "knew" that an idea was not worth experimenting with, so they did not while justifying it with their definitive statements. It is also littered with not so prestigious people that didn't "know" that the idea was not worth experimenting with and they found something interesting, whether it relates to the initial subject of the experiment or not. Those people were crackpots until they were not, it's been the way of science for a long time.

Incorrect. The original phenomenon was discovered by observing sattelites around the earth. If their antenna was facing the same direction as they were moving, their orbit would decay at a faster rate. Whereas sattelites with rear facing antennas would decay slow than models predict.

That's where this research started. Is it reaction less? Possibly. Possibly not. It could be something like ablative losses from the metal. Or it could be other sources of experimental error. But right now, the understanding of the experiment is showing some unknown mass effect much greater than equalivalent ion thrust drive.

___________________________

EDIT: This story is false. Read further down for source video by creator. Reasoning: Missile guidance systems during Cold War.

Interesting, I've never head of this phenomenon , do you have any sources? Quick googling reveals nothing.

My source is a comment from a user on reddit who has cited their sources before, along with accurately correcting errors when found.

I'll look for the user, and ask of their source.

________________________________________

EDIT: Ok. It looks like the Satellite pushing story was just that: a story. That narrative came from the NASAspaceflight forums where Shawyer was misquoted and the "telephone game" ensued.

The correct way this phenomenon was founded was during missile guidance and testing during the cold war.

Proof: https://www.youtube.com/watch?v=GGTjy6atKMs

One time I dropped my phone and searched the floor for several minutes looking for it, only to eventually figure out that it had fallen behind my leg into the cuff of my pants. Sometimes unlikely things happen.

Every time these EM Drive people release another unconvincing result, oodles of people enthusiastically jump onto their bandwagon. Those of us who are experts in the subject matter (tenured physics professor with PhD from UChicago, here) try to make it clear why there's nothing worth getting excited about (e.g. https://news.ycombinator.com/item?id=9473209), and the crowd evidently doesn't care.

Let me be emphatically clear: if your mental model of the scientific community doesn't include "There exist a whole lot of crackpots out there", your mental model of science is wrong. The odds of bold new ideas being crackpottery are far greater than the odds that some unappreciated genius has upended the well-tested laws of physics. (Believe me. I get their emails.)

Crackpots get jobs at NASA apparently. See point 3).

Yes, and I really don't understand it. Every dollar spent on these folks is a dollar that could more usefully be spent supporting, say, searches for life on Europa, or laying groundwork for asteroid mining, or improving exoplanet searches, or heck, mapping Earth's surface composition to find Mayan ruins.

I've seen theories about why NASA continues to fund such a patently baseless project. (As I noted in my earlier linked comment, the project's own FAQ answer that tries to explain why their drive doesn't violate conservation of momentum essentially says that it does violate conservation of momentum.) I don't know which ones are right, or whether it's a good idea, but I'm frustrated about the credibility that NASA continues to lend to them.

I wasn't going to give your reply further consideration than what I gave... It doesn't deserve more. But I really feel something needs to be said here - given that you are in a position of power, and imo - setting an appalling example.

Since we're citing experience - let me give you some of mine. I have been in academia for many years as both a PhD student and an administrator. I have worked in many different departments - with many different types of academics. I have studied under them, I have sat in their committee meetings, I have gotten drunk with them.

The majority of them are just decent folk. Sure, there were some weirdos, some lazy... and plenty whose research is questionable.

But I would say with supreme confidence that exactly 0 of these people deserved to be called a "crackpot"... i.e. deserving of the implication of being totally divorced from reality.

But there was a significant minority (20% approx) that I would quite happily describe as arrogant, status obsessed assholes, who would sooner shove their own colleagues under a bus than acknowledge the SLIGHTEST value in what they were doing.

So no - my mental model of science does not include large numbers of crackpots. And I will rejoinder if your mental model doesn't include large numbers of arrogant, status obsessed assholes, then YOUR mental model of science is wrong.

I will further retort, that if you are going around calling significant numbers of your peers "crackpots", then you need to seriously consider that you might be one of those assholes I just described. And if this is something you really can't bring yourself to do - I would advise a more general maxim as a matter of simple pragmatic, self preservation:

Stop whining about what's in your neighbour's bowl. It just doesn't play well.

I believe Steuard means people not a part of academia. These "crackpots" are typically people who do not have formal training in physics or related fields. Yet, they are convinced that "Einstein is wrong", and they will contacts academic physicists, such as Steuard, explaining their theories.

Steuard was directly talking about "the scientific community" and employees of NASA.

I've been a lot more impatient this go-around than I've generally tried to be in previous incarnations of this topic. It just gets frustrating. It feels like I've tried patient education, over and over, and it falls on deaf ears. Clearly the blunt approach goes over even more poorly, and I've known that, too, but I'm running out of ideas for things to try.

I do not consider any significant number of people who are actively engaged with mainstream science to be crackpots, so you needn't worry on that score. (Goodness knows that with my specialty, I'm living in a glass house on that one.) So (as was my point earlier) I have no idea why NASA is continuing to lend their funding and their credibility to what is to my eye a clear crackpot project. My whole point is that this case is an exception to my usual expectation that (at least) scientific work that receives mainstream support deserves at least the benefit of the doubt. (The crackpots I'm talking about are usually very much on the fringe of mainstream conversation, with only tenuous connections to any sort of active, mainstream lab or university or research group. But their ideas still occasionally go a bit viral among non-expert physics enthusiasts. I'd much rather see that wonderful enthusiasm directed in support of halfway viable ideas, even if it means acknowledging that our sci-fi dreams are farther away than we wish they were.)

So maybe I'll ask you for advice. Set aside this specific case, if you'd like, and consider a hypothetical situation where a fundamentally flawed idea for some reason gets a lot of press and generates a lot of public excitement. You're an expert in the subject, and you recognize fundamental flaws in the idea. You see other experts whom you respect reaching the same conclusion (and none on the other side, expressing support). How would you recommend communicating that to non-experts?

(As previously linked, here's what I tried last time: https://news.ycombinator.com/item?id=9473209 You can see today all the good it did. I'd really love to know how to communicate this sort of thing successfully.)

I think the explanation is pretty simple.

There is a (very likely) crackpot idea floating around that has gotten a lot of press. This crackpot idea, if it is what is claimed, would have immense value in NASA's primary field of operations and expertise. And this idea has gone through a couple rounds of experimentation where thrust has been measured, but is likely experimental error.

Here is the important part: NASA is investigating this because they are being pressured to investigate this. And they have succeeded in proving the existence of a few sources of experimental error. But not all of them, because there is still some measurement of thrust. And as long as the testing is relatively cheap and the pressure to validate is relatively strong, they will continue to test it. It is entirely likely that not a single physicist at NASA believes this thing works, but they are still getting paid to prove their intuitions as correct.

And I don't buy that testing this is a waste of money. It has already done some good: they've been able to identify and control for sources of measurement error of thrust at the near zero bounded end of thrust magnitude. That experience and capability is still valuable in designing and testing new ion thrusters.

> It is entirely likely that not a single physicist at NASA believes this thing works, but they are still getting paid to prove their intuitions as correct.

This, to me, is a key point. I'd rather some of my tax money go toward proving scientific stuff than a lot of the rest of what it goes toward. Maybe there are other scientific pursuits that are more worthy, but an imperfect prioritization of the importance of funding science doesn't seem like it should rate very high on the outrage-o-meter.

Surely in testing this device, NASA will develop techniques in how to test the efficacy of similar extremely low power propulsion devices?

Or put another way, in testing this device, NASA are refining their ability to conduct a "control" experiment, whilst at the same time debunking some crackpot science that seems to be the subject of discussion every time they talk to senior politicians??

Well - I'm struggling to understand what your beliefs about the scientific community actually are. You very clearly stated - in no uncertain terms - that the scientific community had significant numbers of crackpots... You're now backing away from this claim... and are now stating that this em-drive situation is just an isolated anomaly from an institutional point of view and that your real frustration is with the untrained public that won't listen to what you say.

Okay - I'm happy to roll whatever direction you're rolling - so long as we signpost the forks in the road clearly along the way. We're no longer talking about professional, institutional crack-pottery - we are talking about the untrained public. Signposted.

I won't abstract away from this particular example just yet - as there is a clear point of dis-analogy between your hypothetical and this em-drive case... in this case there is a prestigious institution backing this research. It is impossible for non-trained people to make an independent assessment of the cost vs benefits of this research. So it's entirely reasonable for them to be interested and excited when they see such an institution running experiments on what otherwise seems like a moonshot.

Even if other institutional voices like yours are arguing against it - in such cases - it's still quite reasonable for a layperson to shrug and say - well, I see the institutional powers that be disagreeing, but the outcome would be so cool if it turns out to be correct. So meh - let's give it a shot.

And I contend that this is an entirely reasonable response of the layperson in this SPECIFIC case. If it turns out to be the case that this was an egregious waste of money, then the public shouldn't be blamed. And if it is also true that this is an isolated case of institutional failure (as you now seem to believe) - i.e. something which was not a result of systemic flaws in the institution of science - then it's just one of those things... a fuck-up that couldn't be helped because you can't control everything in complex science, and giant institutions.

So in THIS case - just chill. It's not a big deal.

Turning to your hypothetical case - which seems to assume that there is no institutional disagreement whatsoever... well that's a different story. Here your frustration with the public is understandable... although I would tend to diagnose that you have a bad habit of taking it out of your colleagues and the public in cases like the em-drive one where they probably don't deserve it. I probably shouldn't have been so hard on you for that - I'm certainly guilty in the past of having been less than generous to my opponents.

So in the interest of all round good mental health - since this is likely the TRUE source of the frustration... perhaps it's worthwhile thinking it over a little bit for both if respective sanities.

Here is what I believe to be the UR-FACT of public/scientific(academic) interaction.

UR-FACT: It is IMPOSSIBLE to communicate modern science to lay people - unless they go through a significant number of the same hoops required to become a scientist.

Let me qualify this. You can communicate its results, models and data in various high level, poetic and metaphorical language. But you cannot communicate it in such a way so as to enable a layperson to examine a particular result and make an independent and accurate judgement as to whether or not that result is true or not... unless you start from scratch and properly induct that person into the institution of science.

I'm not going to argue at length for the UR-FACT unless you challenge me on it. It's prima-facie true.

Let's now evaluate your frustration in light of the UR-FACT. You mention that you are getting frustrated because you have tried "patient explanation", but people still don't agree with you. Well - given the UR-FACT, it's clear that patient explanation was never going to get you anywhere.

So here's a question you need to be asking yourself VERY SERIOUSLY. I'm going to call this question the UR-QUESTION of public/scientific(academic) interaction.

UR-QUESTION: If the public is in general incapable of any genuine understanding of scientific practice as per the UR-FACT, why do scientists (like yourself) take the time out to give ANY sort of explanation at all?

I can't overstate the importance of this question... because if it turns out that there is NO value to this process of engagement between science and the general public, then this has very broad and extreme implications for human progress and its political organisation. If the progress that science makes possible must be protected and if we can't protect this progress through engagement with a democratic polity - then the democratic nature of that polity will have to be eradicated, and the institution of science defended through force.

This would be a nightmarish scenario - so until we are really SURE that engagement has NO value, we had better start coming up with some good models of what the value of that engagement might be, and start applying those models in practice so that we can realise whatever value is there.

But what possible value is there in engagement with the public if it's not to produce understanding?

Here's one possible hypothesis I think is worth considering. Public engagement derives its value not from any understanding it produces, but in the signalling act between scientist and layman.

What do I mean by "signalling act" - well it's a long story. It derives from the concept of signalling in evolutionary biology - which has since been applied to behavioural economics and other domains. The gist is - people employ signals to covertly convey information to other humans about things like status, tribal loyalty, mate fitness and reliability - stuff that was basic to survival back in the day. So we drive fast cars to signal status... we buy expensive rings to signal mate reliability.. etc.

So what is going on then between scientist and layman when they get into arguments about funding priorities in science? If it isn't about actually exchanging understanding, then what explains the behaviour? Why would humans have evolved to waste THAT much time on such a waste of time? The signalling hypothesis suggests that what is going on is a status game between scientist the layperson. The scientist demands to be agreed with - i.e. requests a signal of his/her status, and when the layperson refuses to give that agreement, it is taken by the scientist that their status is being challenged.

Status was important back in the day. Those at the bottom of the tribe status-wise faired poorly. So we evolved psychological mechanisms to motivate us to seek status. That frustration you feel when you "patient explanations" didn't work? That's negative affect that your brain evolved to make you feel miserable at your perceived loss of status.

So if this hypothesis is true - and it is just a hypothesis (google "costly signalling theory" and go nuts). What advice would it suggest in terms of managing relations between scientific institutions and the public?

Well - I think it would suggest that you as Scientist should do better to control your own signalling behaviours driving you to seek recognition of your status and start thinking about what the public's own signalling behaviours imply they need and want - what will placate them?

And what they want - is the same thing you want. Status. So just give it to them. It's the EASIEST thing in the world. Rather than hitting them over the head with your technical, long winded "patient" explanations - that ring in their brains as nothing more as another status play by the know-it-all scientist... instead, praise their passion, tell them that you scientists are indeed working on every conceivable angle - really show that you are engaging with their suggestions - no matter how crack-potty they may actually be. And maybe at the end of your comment just throw in something like: "but of course we need to be really cautious, because of concerns x,y,z..." - so that your comment has a little educational value as well.

And if this means blowing a few million here or there on some dumb projects so the public feels like the things it cares about are being looked at - then it's probably worth the cost - insofar as we interpret that as a signalling act that conveys the idea that they do have status, they are part of the process... etc.. I'm sure that with practice - we could get the costs of these faux labs/experiments down to a minimum, while getting maximum signalling yield out of them.

But doing what your doing - self-deceptively going about on forums with your so called "patient explanations" as if you don't actually care about your status being ignored, when you clearly do, given how you erupted to accuse not just the public, but the whole institution of science of being guilty of crack-pottery - this behaviour is incredibly harmful when you view it from the point of view of the status signalling that is in play.

This is my advice to you OH PROFESSOR OF PHYSICS! Take it or leave it. :)

Thanks for writing this. There's a lot to think about here, but just for starters, your very first paragraph finally helped me to understand what failure of clarity on my part led to the hostility that we've been going back and forth with this whole time. So in the interest of improving that clarity, let me try to rephrase my original comment about crackpots to do a better job of conveying what I intended:

----- If your mental model of "the set of people who publicly discuss science" doesn't include "There exist a whole lot of crackpots out there", your mental model of scientific discourse in our society is wrong. The odds of radical new ideas being crackpottery are far greater than the odds that some unappreciated genius has upended the well-tested laws of physics. -----

I'm not sure whether it was carelessness or generosity that led me to use the term "the scientific community" in a way that included those working at (or beyond) the far fringe of respectability. On reflection, I think that I've done them that courtesy before; I'm often careful to specify a label like "mainstream" when I intend a more narrow definition of "the mainstream scientific community". My comment "Believe me. I get their emails." was very much meant to refer to the non-mainstream theories that folks out there seem to regularly send to active physicists in any related field (not as a backhanded slap at the handful of professional peers and colleagues who occasionally write to me). So from my perspective, I haven't made any shifts in intended meaning over the course of this conversation that would merit your signposts, but I can definitely see how my words could have given the other impression. (And now you get to judge whether I'm piling lies upon lies in a scramble to retract a broad insult to my peers, or whether I've been expressing a consistent belief system this whole time. Darned if I know any way to make that judgement easy for you.)

As for your broader points: One of the things that troubles me in the discourse between professional scientists and the public is that it's painfully common for us to wind up disappointing the very people who are the most fervent supporters of what we do. This is no doubt a reflection of your UR-FACT. A scientist who gets gleefully excited about an unexpected discovery or a strikingly elegant theoretical model is still constantly aware of the tentative nature of science: her enthusiasm is a measure of how rare even the possibility of transformative progress can be. But when that enthusiasm spills over to the public at large (by whatever channels), most listeners don't have the training and experience to recognize just how tentative the underlying idea inevitably still is. So when, nine times out of ten, the early promise of the discovery either fizzles or gets mired in technical details with no clear end in sight, the science enthusiasts in the public wind up feeling betrayed. (Even mundane things like the seemingly constant flip-flopping of nutrition warnings is a part of this.)

I don't know how to fix this. As you say, it may be truly impossible, though I'd like to think that better early and ongoing education about the process and nature of science could help a little. But I think that's what is behind my attempts to dial back the enthusiasm I see for this EM Drive work. What they're claiming is something that so many of us long to be true! (I certainly wish it were, both for the thrill of the new physics to explore and for its impact on the future of humanity.) But this isn't even a case where justified scientific enthusiasm has wound up being oversold to the public: the science here is just wrong, and the people directly involved in the work (or at least in publicizing it: http://emdrive.com/faq.html) seem to not even know the science well enough to recognize that it's wrong (or if you were inclined toward conspiracies, they could be knowingly obfuscating its flaws with technobabble). It's a case where it's all but certain that a big chunk of the enthusiastic public is getting set up for a fall. This goes beyond the challenges of your UR-FACT: something is clearly wrong in how this piece of science is being communicated to the public.

And at that point, if I as an expert see someone selling snake oil (regardless of whether they believe in it themselves), don't I have some sort of obligation to warn people not to buy into their so-appealing patter? The human cost here is clearly far less than the "vaccines cause autism" scam turned out to be, but they feel fundamentally similar to me. (As do the "bomb detectors" purchased at great cost by various government agencies in Iraq, as do the "magnetized water" devices that get sold to insufficiently skeptical farmers, as do...) Again, maybe you're right and the cost in this case is a drop in the bucket of legitimate research, but isn't one big purpose for society in training and supporting experts to ensure that there's someone around who can police this sort of thing? (And, more philosophically, isn't a big part of society's purpose in supporting experts the hope that we'll help to uncover and disseminate fragments of Truth, whatever that may mean?)

Clearly, we (and especially I, it seems) do a pretty poor job of it, if so, as illustrated today by the perennial popularity of this story. I really don't know how I or we can do better (clearly today's angle hasn't gone over as well as the last one did). Maybe it's all some sort of status-driven signalling, as you suggest, and my chatter about the public good is just so much self-deception. There may be value to the recommendation that you've made on that basis. But I'm not sure that I could live my life (or any life) with that framework as my premise.

>And now you get to judge whether I'm piling lies upon lies in a scramble to retract a broad insult to my peers, or whether I've been expressing a consistent belief system this whole time. Darned if I know any way to make that judgement easy for you)

Well kudos for updating your self-presentation on this matter. It's the example I thought that set which was the most concerning thing. As for your soul... well - establishing authenticity of an individual is hard enough in real life let alone on the internet. But I'm not all that interested in your soul anyway. You and god can sort that out later. :)

>It's a case where it's all but certain that a big chunk of the enthusiastic public is getting set up for a fall. This goes beyond the challenges of your UR-FACT: something is clearly wrong in how this piece of science is being communicated to the public.

It doesn't go beyond the UR-FACT though. The UR-FACT is what prevents your patient explanations from being successful in changing people's minds, and helping them realise the nature of this mis-representation.

>And at that point, if I as an expert see someone selling snake oil (regardless of whether they believe in it themselves), don't I have some sort of obligation to warn people not to buy into their so-appealing patter?

Well - I don't envy you the responsibility of having to overcome a fundamental constraint in human communicative ability. There is no solution to the UR-FACT... period. Even if we embark on a massive education campaign... institutional science is too big. There is simply too much to know. And therefore, on most scientific questions, EVERY individual is in the position of not being able to know for themselves if a given result is true or not. It just takes too much time.

Of course - you don't believe the UR-FACT, or you wouldn't express this responsibility, nor have any hope that you could ever meet it.

There is only one way you can to any degree meet this responsibility - and that is by expending the time in inducting new people into the institution of science. You can't bridge the gap to lay people - but you can convert a small number of them into professionals. As a professor you are in a privileged position to do that. If you are research only, and have no PhD students - get one. Pay for that time by staying off hacker news.

>but isn't one big purpose for society in training and supporting experts to ensure that there's someone around who can police this sort of thing?

Well - this goes back to the UR-QUESTION. If engaging with the public has no chance to change their opinions because of the UR-FACT, and if the public ultimately determines scientific funding via democracy - how can we protect the authority of scientific institutions? The problem is that lots of you guys are taxpayer funded - so these lay people are your boss. And imagine showing up for work every day at a job where your boss barked commands at you that were literally impossible to fulfill? Yeah - that's your nightmare...

That's a problem universities are increasingly facing. Right now scientific institutions are reasonably insulated - but they are already starting to shut down liberal arts degrees like philosophy... but science won't stay insulated forever. Politics is getting increasingly polarised - and more and more extreme nutters from both the left and the right are getting closer to real power. When science outputs things they don't want to believe - you better believe they'll try to shut you down.

As a bulwark against barbarism, if you have any responsibility whatsoever - it is to protect yourself. And as you have admitted, naive attempts at engagement aren't getting you anywhere. So - why aren't you being more scientific about it? Find a better model of human communicative interaction and apply it.

>Maybe it's all some sort of status-driven signalling, as you suggest, and my chatter about the public good is just so much self-deception. There may be value to the recommendation that you've made on that basis. But I'm not sure that I could live my life (or any life) with that framework as my premise.

Oh dear lord... now it's my turn to be frustrated. If the signalling hypothesis I suggested is correct - but implies a reality that is so abhorrent that you couldn't bear to live in it... then why would you be so upset about folks wanting to believe in the fantasy of em-drives? That's like being disappointed in a child for believing in Santa when you are unwilling to accept that unicorns might not exist.

Look - I'm not saying I know my hypothesis is correct. I don't. But you're hitting a brick wall by your own admission. So your model is likely wrong. Holy crap - your a scientist... run some damn science!

I really wonder why outside their specific domain of expertise - it's so common to see scientists throw all their training out the window. And trust me - I've met a LOT of scientists. This is common.

When I worked in university admin, I used to watch scientists come down to our office to send faxes... and many would just stand and stare at it doing nothing... and eventually - without trying anything - they would come and interrupt one of us admin folk and ask us for help. We didn't mind helping of course - but it always astonished me that all their training as scientists just flew out the window when faced with the simple task of sending a fax. Here is a bunch of people trained to run experiments, isolate variables and determine causality... the very bedrock of existence - and they can't find the self-confidence to just press a button on a machine to see what happens.

I kinda feel that way with you right now. You know your approach is not working. So do some research! Find an alternative. You don't have to accept mine - but if you take your responsibility seriously, then you DO have to find your own - and it has to get results...

Note - it has to serve as a better model for your own behaviour as well... you need an answer to the UR-QUESTION... why are you expending all this time speaking to lay people? You know that it doesn't achieve anything. But then you express this hope that somehow you're making a little bit of a difference - all the while feeling this frustration.

And as for the signalling idea, it aint so bad once you get used to it. I know - it'sis not particularly appealing. It's not what we want to believe about ourselves. But if that's what's stopping you from considering it - you're not so different from the people wanting to believe in em-drives afterall. (There are plenty of good scientific reasons to challenge it - mind you).

Anyway - I'm quite happy to admit that I'm at least partly expending all this energy in the hope that a Professor of Physics out there somewhere thinks I'm bright chap. But I'm cool with this... who doesn't want to be regarded well by bright people?

Read Rhetoric by Aristotle. You're using what he calls Dialectic (facts and figures) to convince people. Most people either don't care about facts and figures or can't understand them. You need to make appeals to emotion, or rhetoric. As for how to effectively communicate in Rhetoric, if I knew that I'd be far more popular than I currently am. :) Maybe ask tptacek for some pointers?

Something else to keep in mind: speaking from a place of authority might help as well. On this matter, you have a serious disadvantage. An anonymous person on the internet will never be able to convince most people that NASA is wrong about space. Unless you're literally a rocket science and can prove you're an expert in the field, most people will believe NASA because they trust NASA.

Amen. Steuard's arrogant tone is incredibly insufferable.

You read arrogance. I read exasperation at trying to explain the fundamentals of his field to lay-people.

I wonder how many professors who are exasperated about trying to explain fundamentals of their field to lay-people have considered that maybe "professor" isn't the best line of work for them to be in.

There's a difference between lay-people who listen, and try to learn, and ask questions to try to learn, and lay-people who say "No, you're wrong, your whole field is wrong, I'm the one with the truth, let me explain it to you."

A professor who doesn't welcome the former is in the wrong line of work. A professor who doesn't welcome the latter is a reasonable human being who gets tired of wasting time.

And every dollar spent looking for life on Europa could be spent on preserving endangered life on this planet.

The device has intrigued many of your more curious colleagues. You never know what can be learned by solving this particular puzzle. The solution might be in the field of physics, science journalism, or maybe psychology. Either way, knowing more is better.

Or we can stop wasting money on military and using on preserving endangered life on this planet or simply to produce enough food so no body would be hungry again.

I prefer cut money to military...

I was trying to make the point that it's silly to argue "the money could be better spent on..." because there's no end or correct answer. You're response demonstrates that.

I certainly don't think we should cut funding to basic research. I'm happy that some very smart people are looking closely at this device because I do think there's something to be learned here even if it isn't in the field of physics.

> The device has intrigued many of your more curious colleagues.

It really hasn't. Every single time that I've seen a colleague (or a colleague of a colleague) comment on this research, they've been talking about either specific flaws in the experimental setup, specific flaws in its theoretical basis, or general concerns about unfounded ideas getting broad attention.

Spending dollars looking for life on Europa and spending dollars on preserving endangered life on Earth are both fantastic goals, with some reasonable hope of a positive impact on humanity in one way or another. I have not yet thought of a way in which spending dollars on this EM Drive idea has any upside like that. (Surely we can learn about science journalism and humans' psychological reactions to science news just as well by studying how people react to exciting stories about actual, mainstream science!)

Check this : http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2004017...

The "Institute for Scientific Research" that did that study is a big pork-barrel project with exactly zero reputation for quality. I would bet that if you dig, the only reason NASA was associated to the research you link was congresional earmark requiring it.

See http://www.nytimes.com/2006/04/08/washington/08earmarks.html

[Edit: dug a little more]

"Examples of such earmarking, which have prevented NASA from allocating funding to programs that it considered to be most critical, include $15.5 million for the Institute for Scientific Research, in Fairmont, West Virginia"

Source: http://caib1.nasa.gov/events/public_hearings/20030514/transc...

Because taking a small fraction of the total budget and throwing it at a bunch of wacky longshot research projects is how you find the occasional important thing you would otherwise have missed.

I'm not saying I think they've really got a reactionless drive here. They probably haven't. I'm saying if you fund a hundred of these things, ninety-nine of them will fizzle but the other one might find something interesting you didn't expect, that could far more than pay for the other ninety-nine.

But why spend that money on a project that we already know is almost certainly wrong? Surely there are bold, crazy ideas out there worth exploring that aren't in violation of well-tested physical principles! Fund a hundred of those.

Because science is built on evidence. All the chalk on blackboards didn't prove Einstein was right, experiment after experiment over the decades did.

We built the LHC, we're building ITER, we built the Kaminokade neutrino detector, we build things because we're human and desire to "know" things. For some of us, the chalk on blackboard version isn't enough for us to feel we know it yet.

But this isn't some new, untested regime: this is an ordinary metal cavity with some sort of resonant electromagnetic wave inside. There's nothing about it that I can see that would lead me to expect results here that would so fundamentally contradict the countless experiments that have been performed on similar systems over many decades. If the folks doing this work had some compelling (or even just plausible) mechanism to suggest why this system ought to be radically different, that would be one thing, but I've seen no indication that they do: it's just a metal tube and some EM waves.

This isn't some grand battle pitting hidebound theorists unwilling to imagine flaws in their sacred equations against bold experimentalists seeking to test those models against the real world for the first time. This is a fundamental incompatibility between the best-tested mathematical models in human history (QED agrees with experimental tests to 11 digits of precision, and both sides of that agreement represent stunningly careful work) and a marginal signal from a fairly complicated system with a whole range of possible sources of systematic error.

So why do so many people seem so willing to throw out those decades of heroic experimental work in this case? (I honestly don't understand it. You're clearly passionate about the value of experimental evidence: why does the hard-won evidence that we already have carry so little weight?)

I completely concur with your point that people shouldn't throw out the existing experimental evidence. I think there is far to much "wishing for new physics" going on.

At the end of the day I want experimental research done, and more importantly I want science to embrace greater value in "reproduction" of existing research. The bias the current "publish or perish" system has developed towards the novelty of each item of research, hurts the foundations of knowledge. Painstaking hard work on the reproduction of an experiment is valuable. Yes there's a reduction in value for each successive reproduction, but the bulk of modern science sadly never gets any reproduction at all.

The EagleWorks team may only succeed in reproducing the past work on resonant cavities, but I see no shame or reason why they can't as scientists decide "we want to measure this $foo, because these exact permutations have not yet been tested". So we gain one more data point, we rule out one more thing, this is the essence of science and I just can't in good conscience be negative about it.

If we focus on only the waste of money and resources... Congress literally forces NASA to be much more wasteful as an entire organisation, in this environment, singling out EW feels like mandating smaller font sizes in order to save on paper costs. The biggest examples I can immediately think of are the entire SLS boondoggle, and the Constellation program complete with the crown jewel of NASA's waste in the last two decades, the A-3 test stand. I'm pretty happy with how I see EagleWorks operating budget wise compared to the rest of all of NASA.

I wish to buy the magnificently high horse you have arrived on good sir, so that I may place it in a museum of equine curiosity.

Seriously though. The level of time and funding these guys get to work on this is, to use a colloquial saying "pissing into the wind". Think of it like NASA giving them 20% time or something like that.

More importantly these experiment have seriously important implications to at least one 'modern' physics theory worked on by serious scientists. Experimentally proving this device definitely doesn't work at all, ever in any way, is evidence useful to the continued work people are doing in quantum field theory.

Your intense derision is unwarranted and saddened me. These are serious scientists and their work is as valid as any as long as they continue to conduct themselves by the scientific method. NASA isn't all about robot space probes and sending astronauts up to ineffectually float in low earth orbit. This is the NASA that works on advances in aeronautics through X plane projects, on propulsion through ion drive research. I'm honestly surprised they aren't researching it more vigorously, which I take as an indication of how cautious they are being that this work does not waste the valuable resources of NASA on something that could still just be ruling out yet another crackpot and writing a few extra quantum field theory papers.

While that's all certainly true, NASA physicists are not all crackpots, and at least some of them are careful experimenters.

Newtonian mechanics was also extremely well-tested. Unexplained error is always interesting and sometimes exciting.

Newtonian mechanics still holds for `normal' levels of energy. Relativity and Quantum mechanics only show up on the edges.

dzdt says that this device does NOT probe the edges---no high energies for example.

The photoelectric effect which led to the discovery of Quantum mechanics is not at all high energy physics and could barely be called an edge case...

> dzdt says that this device does NOT probe the edges

A Cesium clock on board a 747 will slow down even though the 747 will not be flying at relativistic speeds. It's just that it's a clock good enough to show a very small difference.

They are measuring a very small, barely detectable, force.

I think this is a case where the physicists and engineers working on these experiments say one thing, but what gets delivered in the headlines and articles, including NASA's own marketing/journalism department, is completely off. It's just PR. People have been talking about successful experiments with perpetual motion for how long...

> if your mental model of the scientific community doesn't include "There exist a whole lot of crackpots out there", your mental model of science is wrong.

Do you think this is a failure of your industry? E.g. there don't seem to be a lot of crackpots that go into plumbing or whatever. What is it about physics where it's apparently failing to provide most of the people in the field with adequate training?

Have you talked to a lot of plumbers?

Most crackpots aren't in the field. The problem is that woking in physics requires an enormous amount of training, but some people are convinced they can contribute without that training.

What about magnetic water cleaners?

Anything crackpot is an attempt to usurp the way things are with the way people want them to be. Free energy, electric thrusters, magnetic health bracelets, one weird trick for clean teeth... these all apply to other professions but since they obviously don't work it is up to the physicist to ignore? explain?

Physics is the belief in sanity in our confusing mess of a work. It is often an appeal to something simpler. What's the difference between a crackpot and a physicist? Physicists do science and get repeatable results.

There is some effects of a strong magnetic field on a current of water over aragonite and other calcium minerals, on a way that make less probable to a pipe get obstructed. However, this requires :

- a strong magnetic field in some special configuration. - a water current flow, like you can find on a pipe.

These "magnetic water cleaners" that are only a mug with a magnet, don't match these two requisites. Ie, are a fraud.

The crackpots that go into plumbing exist... it's just that they're not crackpots about plumbing. They still email the other guy about discovering zero point energy and space aliens and whatnot.

The crackpots about plumbing, call the plumber crackpots to fix their plumbing obviously.

I've been trying to find a good barber for years now, last one I went to was a borderline schizophrenic. Off his meds, not on them, don't know. Didn't stop him from cutting hair. Being a crackpot doesn't stop someone from being able to snake a drain or fix pipes.

> What is it about physics where it's apparently failing to provide most of the people in the field with adequate training?

The same thing that's wrong with all fields... the people who go into that field do so because of enthusiasm for it. Not because they're competent at it.

Enthusiasm for physics probably starts when some kid grows up watching Star Trek and whatnot.

> E.g. there don't seem to be a lot of crackpots that go into plumbing or whatever.

There are plenty of reality TV shows about crackpot plumbers - either idiot DIYers who don't know what they're doing and who ruin a home or cowboy rogue builders who con their customers and provide substandard work.

> either idiot DIYers who don't know what they're doing and who ruin a home or cowboy rogue builders who con their customers and provide substandard work.

The idiot DIYer may be a crackpot, but the rogue builder isn't. A crackpot is someone who has no expertise, but (crucially) believes that he or she does (or at least that he or she has made a discovery in a domain believed to belong to experts); a con man is not a crackpot.

My thesis advisor had a saying about crackpot physicists: The easiest way to get noticed is to say that Newton is wrong, Einstein is wrong.

Also every other biography - Jefferson was human, Washington was just a man, MLK was a regular guy...

Even assuming we knew with perfect certainty (which may be a reasonable approximation but isn't actually the case) that the effect was due to experimental error, given that we yet cannot point to the error we may very well have useful things to learn about experimentation. Any tiny chance of upending well-established laws of physics is just a bonus.

Even this seems unlikely... while it would be great if we could learn to conduct better experiments or learn to recognize the flaws of bad experiments earlier, what's missing are instruments precise enough to determine the exact cause of the results here.

Am I wrong?

"[T]hings to learn about experimentation" probably sounded more fundamental than I'd meant it. Improvement of precision of instruments should probably fall in the category, as far as my reasoning above goes. It could certainly still be useful.

Can't we learn a lot of wonderfully useful things about experimental technique while studying phenomena that are more likely to be of interest in their own right?

Because in this case, the subject matter of the experiments is explicitly in contradiction with some very well confirmed physical principles, and well within the range of conditions where those prior tests have been done. (This isn't like quantum mechanics supplanting Newtonian physics at molecular scales, this is like someone designing a funny-shaped inclined plane and claiming that Newtonian physics might not apply because nobody has measured accelerations on that shape of ramp before.)

"this is like someone designing a funny-shaped inclined plane and claiming that Newtonian physics might not apply because nobody has measured accelerations on that shape of ramp before"

My understanding has it (and admittedly I've not been paying that close attention, precisely because it's not likely there's anything super exciting here) that the difference between that case and this is that it's not just a claim that understood laws "might not apply", but that we actually have experimental results that look funny. That is precisely the case when we're most likely to learn something. (Probably not something tremendously surprising - that's what "tremendously surprising" means :-P)

As an ex-doctoral student in astrophysics, I can confirm that there are a lot of crackpots out there. The most common claim was that heliocentricity was correct, if you can believe it.

They believe heliocentricity is correct as in they believe the orbital mechanics work out only if you pick Sol as your inertial reference? They don't believe you can pick an arbitrary inertial reference and get the physics to work out, a la general relativity?

Released by NASA. I still as a non-scientist see this as something big. If NASA is saying there is thrust than there is thrust correct? Or is it just "impossible" so it means an error in testing instantly? Did you look at the results?

(Fishing for more details)

It's not NASA, the organization, that has released a vetted, reviewed technical paper about this. This article is based on the casual communications of a NASA scientist, who works for EagleWorks, and has been communicating with a community of interested persons via the NasaSpaceFlights.com forums.

Indeed, NASA is annoyed with the continued press from this, and has prohibited any press releases from being released without proper NASA vetting.

The clickbaity online media, however, is more than willing to take a forum posting by a "NASA scientist" as NASA proper.

I have nothing but respect for the work being done by EagleWorks and Paul March, but this is not a NASA communication.

Perhaps your mental model of `the regular folks community` is wrong?

Let me try to explain why I, a regular schmoe who knows nothing about physics, reads these articles (and frequently, the comments) every time a new round comes out. This is how this story looks to me in the news as someone who has no association with NASA, etc.

1) Some nutter comes up with a theory of "mystic orgone drive" or something and explains how it works and demonstrates that if he hooks his widget up to the mains, it pulls.

2) A bunch of other people are like "lol idiote" and do the same thing with their own copies of his widget and are like "wtf..it is pushing..."

3) Somehow, NASA decides to investigate the mystic orgone drive. Because they are NASA and not a bunch of morans, they do a couple things differently from everyone else: - They are very very careful to try to eliminate sources of error such as breezes from experimenter tinfoil hats, etc. and they document this experimental rig very carefully. - They run the experiment backwards as well as forewards. Why not see if there's a dose response curve? Why not see if hooking the negative cable to the positive terminal produces backwards mystic orgone drive or whatever? - They build a version of the device very similar to the original mystic orgone spec, except they put different runes on it or something that are incompatible with mystic orgones.

The results of this are (1) still pushing (2) hooking it up backwards makes it push backwards (3) the mystic orgone runes do nothing; that is to say the non-mystic version works just as well, so the mystic orgone priest's explanation of the device is wrong.

I just don't see how this is not interesting to you, as scientist. Science, especially physics, is about building mathematical machines that can predict the future: if you do this and this, this will happen. Classical mechanics is probably the second-most rigorously tested and understood of the mathematical future prediction machines of all time. Here, you have a bunch of very careful, expert men and women hooking up the mystic orgone drive to the mains power, and it pushes! But the prediction says it should NOT push, at least not nearly this much! How is that not interesting?!

I would think this would seem to a physics professor to be the essence of science, and exactly what ordinary people would and should get excited about. It's very difficult for regular people to understand that its surprising that at three giga electron volts the tau lepton did not decay into any of the known lucky charms marshmallows or whatever, DESPITE what Cereal Supersymmetry predicts.

It's very easy to understand that putting a pair of empty jiffypop tins in a vacuum and powering them should not lead to them trying to bend their handles. It's very easy to understand that if anyone would be capable of checking this carefully, it's NASA.

So if NASA does this and they don't know why they are detecting measurable jiffypop handle bend many orders of magnitude higher than predicted, how do you not click on that article? How do you not think that's interesting?

An explanation for why it's not interesting: http://theness.com/neurologicablog/index.php/despite-headlin...

This post, and the many others like it, simply repeat the experimental shortcomings and potential sources of error that the NASA staff themselves point out in their communications.

It's sort of like science blogspam--repeating what someone else already said, but injecting more emotion into it to attract pageviews.

Normal media does not stress these experimental shortcomings, nor note that the measured effect has decreased. I consider it basic scientific skepticism.

This was a wonderful post. If I may be permitted a TL;DR (although it's almost a shame not to read your extended analogy): although no scientist wants to engage with crackpots him- or herself, everyone should want to see what happens when a scientist does engage (scientifically) with crackpots.

What's wrong with enthusiasm?

It's bad when enthusiasm can be abused to defraud investors or customers. But that's not really what's happening here. The NASA guys are not trying to scam anyone, they're spending a bit of time and money to run some good-faith tests, just in case the universe can still surprise us.

I'm not saying the "emdrive" is likely to work--it's almost certainly not going to change physics. I'm just saying I can't see the harm in folks getting excited about the possibility. It's essentially hope--hope that we'll get to experience some of the amazing things we tell stories about, stories like Star Trek and other sci-fi.

Steuard answered a very similar question the last time around: https://news.ycombinator.com/item?id=9473914

As long as the device doesn't move enough that the original center of mass is no longer inside the device, then externally reactionless motion can be obtained by simply shifting mass inside.

Other behavior thought impossible like creation of positive/negative mass pairs or teleportation of internal mass would allow to extend the same mechanism to arbitrary movement.

Until the theory can account for ALL the evidence, then there are either errors in the experiment or the theory is incomplete . You are dismissing the latter possibility prematurely.

The history of science is full of unexplained experimental errors that were later confirmed by an improved theory (see Einstein's General Theory of Relativity vs Newton's 'Law' of gravitation).

IF scientists universally adopted your position, then there wouldn't have been any point in further investigating experimental contradictions (time dilation, gravitation lensing) to Newton's Laws since they were clearly impossible based on the REALLY REALLY well tested laws of physics.

I very strongly disagree that dismissing the possibility of an incomplete theory is premature. The amount of evidence supporting our current theories is absolutely staggering. Some small acceleration on a technology nobody understands isn't going to overturn that evidence.

It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity.

"IF scientists universally adopted your position [...]"

Scientists don't universally adopt positions, so that's not something we have to worry about. We have to worry about non-scientists adopting dreams over facts.

But really, there's no point in declaring victory or defeat while the battle is still going.

> It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity.

But, see, if we follow the approach of the doubters here, we'll never get to almost absolutely undeniable evidence, because we won't bother to investigate it because of how improbable it is.

Look, people here are saying that an incomplete theory is possible - not certain, not even probable, just possible. It's happened twice in just over a century, so, yeah, not probable. But saying that it can't happen because the science is settled is, ironically, not a very scientific approach.

> But really, there's no point in declaring victory or defeat while the battle is still going.

Absolutely.

Anything is possible. You have to make decisions based on what is likely, not what is possible.

A startup succeeding is not likely. People invest in them anyway. Why? Because if it does succeed, the payoff is high enough to make it worth the gamble.

Same thing here. This is not likely to be new physics. But if it is, the payoff is high enough to make it worth looking at seriously.

Note well: This does not mean "start doubting all of physics until we disprove this". It means, yes, it's worth it to have a team at NASA spend some time trying to figure out what's going on. And even if they don't find new physics, they're going to learn something about an error factor to control for, which, among other things, might shed some light on the Pioneer anomaly.

How much are you willing to bet that this investigation leads to new physics or experimental methods? And are you willing to assert that this is the best way to achieve those same results?

I would not bet enough to cover a team of NASA engineers spending their time on it.

It's never scientific to dismiss the possibility of an incomplete theory. In fact we know our theories of physics are incomplete somehow because of yet-unexplained observations (dark matter, dark energy), and because of problems reconciling quantum mechanics with general relativity.

The question is really one of priority: how much effort should we put into chasing down each potential new result?

For some questions we spend staggering amounts of effort--think of the Hubble Deep Field images, proposed gravity wave observatories, neutrino observatories, and the Large Hadron Collider. We predicted the Higgs, but we still spent billions of dollars to go confirm that!

In contrast, we're spending a very small amount--just a couple people with a small budget--to investigate things like the Elcubierre "warp drive" and the "Emdrive." And we spend basically nothing to investigate things that are obviously fake.

It seems proportionate to me.

> No, the EmDrive does not work

No. Nobody knows if the EmDrive works or not. That is the point of these tests.

And there are theories that don't violate the conservation of momentum. Unless you know something that NASA and countless others don't.

>And there are theories that don't violate the conservation of momentum.

Which theories are those?

Take momentum from virtual particles was one, IIRC.

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

That is a hypothesis.

IANA scientist so I meant theory in layman's term i.e. an explanation.

The point is that there are explanations for what this could be that don't involve violating the CoM concept.

Nobody knows what it is going on here. Hence why it is premature to say whether it works or not.

If you were using the non-scientific definition, then your previous two arguments aren't valid.

Isn't it nice that we're now discussing newtonian physics using layman's terms in order to keep you from being wrong?

The point is that's not an explanation. A hypothesis says "We propose this happens". A theory says "We propose this is why that happens". If you don't have the why, you don't have a theory, and you don't have an explanation.

Are you really making a meaningful counter argument to the post you're responding to? or are you just inflating a poor word choice to derail the argument?

Look, we KNOW that the sun revolves the earth and is affixed to a crystal sphere, like the planets. It's clear from all observations that this is the case. I mean, we understand epicycles perfectly, and they're due to the motion of the spheres. The chance that some crackpot would expose new physics and prove that the Earth orbits the Sun is so near to zero as to be negligible.

Your argument is the same as those made around relativity, as it disagreed with Newton, and what could some fucking patent clerk possibly know that the Greatest Scientist Ever didn't?

> Your argument is the same as those made around relativity

Of that we can be sure

The good thing is that "Of course it doesn't work" has not gotten anyone a Nobel price

And it may even not violate conservation of momentum

The people discounting Kepler and Einstein had actually read their work. They discounted it based on the lack of physical evidence(experimental results). People in Einstein's time were still confused and trying to understand the outcome of the Michaelson-Morley experiment. As for Kepler, he didn't provide any new evidence either. The only advantage to changing the center of the system was to eliminate the need to calculate epicycles when creating an ephemeris.

I could certainly see how both theories would have attracted some disbelief in their time. In Einstein's case, people started to accept SR when new experimental results came that only made sense if the speed of light were constant and the laws of physics were invariant in all inertial reference frames.

Why do we have to accept that something novel is happening in this case? Can you find any way to explain this effect with existing theory? More importantly, what would have to be changed to accommodate this phenomenon? Is it possible that the engineers are just measuring noise?

These are important questions that have to be answered.

No, it is not the same. Einstein proposed a theory which was largely consistent with our experimental evidence in support of Newtonian mechanics. It also agreed with recent experiments which would not find an aether. Relativity made predictions about the orbit of Mercury that were more consistent with the data than orbits predicted by Newtonian mechanics.

In this instance, we have a device which is proposed to work by means that violate basic laws of conservation. There is no accompanying theory for why that is. It has been tested by several groups, and as these groups improve their testing methodology, the resultant "thrust" decreases. That is not promising. If the effect under test decreases as experimental rigor goes up, then the default assumption should be there is probably nothing there.

Many major advances in scientific fields have violated previously held theories of what the state of the world is.

While the balance of probabilities says that you are likely correct, humankind is very far from a complete understanding of nature and I am sure that before that understanding is reached, there will be quite a few violations of current best scientific theories.

Experimental evidence shows that it does work, in the sense that force is applied.

The question that remains is whether it works as the (crackpot?) inventor claims, or some other effect that we haven't quite figured out yet.

No, experiments show that there is some unexplained thrust. That does not mean it "works". A much more likely explanation is very boring things like experimental error or a side-effect of heating. See http://theness.com/neurologicablog/index.php/despite-headlin...

Can someone explain how the EM drive violates conservation of momentum while radiation pressure does not? In fact it would seem the most obvious way the EM drive works is related to radiation pressure.

I am sure I am missing something do to my lack of understanding in the field, but radiation pressure is based on photons having momentum. The EM drive seems to work by emitting a whole lot of photons in the form of microwaves and having them bounce around inside a chamber shaped a certain way leading to it exerting a net force.

IIUC, the problem is that the chamber is closed. Photons having momentum shouldn't create net thrust if they never escape the chamber.

I assumed the chamber wasn't perfect just that they reflect enough times to impart the net thrust before escaping.

But if they reflect a lot, they reflect from one side, and then from the other side. Still no net momentum change.

> No, the EmDrive does not work

That is simply inaccurate to say. Just because they have not ruled out all of the errors in testing doesn't mean it does not work, that's premature. You're suggesting that you know with absolute certainty that it's an error in testing and not some new physics or undocumented effect (like the casmir effect). I find that presumptuous, close-minded and frankly, ignorant. Is it an error in testing? Maybe, probably. However, I would never say that I know something "for certainty" when I don't.

> Because it violates conservation of momentum

We don't know it does this yet. And again, it's inaccurate to claim it does because we don't know if it does. As I said in another comment, for all we know, the string theorists have it right and this effect could be pulling/utilizing energy from some higher dimension that we don't even know exists yet. There are any number reasonable (not physics-breaking, albeit far fetched) ways this could work. And one of them is unknown physics. To pretend we know all there is about physics is ignorant and close-minded. We're nowhere near close to understanding physics in its entirety. There are some huge problems we've yet to solve. When we do, they will most certainly give us more insight into our universe than any of the other discoveries that have come before (like reconciling quantum mechanics with relativity).

Let me suggest the following way of looking at it.

What evidence do we have suggesting that the EmDrive works? We certainly don't have a device observed to be generating large thrusts reactionlessly. What we allegedly do have is a bunch of measurements that, on the face of it, suggest that maybe we could make one by refining this technology.

But the path from those measurements to that conclusion goes through a load of physics, and nothing on that path is known with any more certainty than conservation of momentum is known under such "ordinary" circumstances.

Suppose someone comes to you with a purported mathematical proof that 2+2 doesn't equal 4. You look at their proof and don't find anything wrong with it. Are you justified in believing that 2+2 isn't 4? No, however carefully you check the proof, because the axioms and rules of inference they use in the proof are going to be no more certain than 2+2=4. If you check the proof carefully enough then you're entitled to conclude that something is very wrong in our conventional understanding of mathematics, but you can't tell what and you should be pretty confident it isn't 2+2=4 until someone demonstrates how every time you put 2 things and 2 things together you're really getting 5 things and just not noticing one of them.

Similarly, if someone comes to you with a purported demonstration of momentum nonconservation in "ordinary" circumstances, then if you check their work carefully enough you may be entitled to conclude that something's wrong with our understanding of physics. But you shouldn't leap from there to "momentum isn't conserved" until you actually see momentum clearly not being conserved, or find a coherent theoretical framework that explains what you've seen along with all the previous evidence for momentum conservation, and that has momentum not being conserved as claimed.

They didn't confirm anything. It was merely a rerun of tests with more of the potential background causes mitigated. It is going to require a lot more tests before someone like NASA unequivocally states that this works. Especially given that this device relies on physics we don't yet know about.

Worth reading here: http://forum.nasaspaceflight.com/index.php?topic=38577.940

Not much unlike the recent string of Bell tests. Closing one loophole after another until you can feel confident there's no other reasonable explanation left except a single one, the proof or invalidation of the theory you're trying to prove.

Except this is more fun. Like a few other devices before it, the emdrive (claims it) doesn't do what physics predicts it should do, without offering either explanation or theories to replace existing physics.

This certainly seems to make a certain class of people very angry, but it's really quite exiting.

This is very different from the Bell inequalities.

The Bell inequalities is an easy to calculate result of quantum mechanic, the whole calculation is less than 1 page long. (It's not easy to discover, but once Bell discovered it, anyone can check the calculation.)

It follows the same rules of all the other QM experiments that have been thoughtfully tested, so it's totally expected to be true. The problem is that it's unintuitive, or to be more clear it's even more unintuitive that the usual QM results.

The loopholes were very weird, like:

"The PRNG of my computer is conspiring with the PRNG generator of your computer to get the results of the Bell inequality. They can conspire using signals that travel at less than the light speed, so perhaps we have conspiring hidden variables and not QM."

So to close the loophole someone has to use a real RNG instead of a PRNG, and be sure that it random. And do the measurements in a short time so the crystal in one site can't conspire with the crystal in the other site, and do the experiments far away so the light doesn't have enough time to travel from one sensor to the other sensor. The loopholes were totally paranoiac loopholes, but to disprove the hidden variables theories you have to close all the loopholes. (I think it's possible to imagine even more weird loopholes, so expect a few linkbait announcement in the next year with the discovery of an insane loophole in the last Bell experiment.)

The EM drive breaks the current accepted physics theories if the thrust/energy ratio if greater than 1/c = 3.33 nano-Newtons per Watt.

Some of the loopholes are:

The electromagnetic force between the wires in the device (it's like an electromagnet, without the iron core, so it's not as strong as a true electromagnet)

The force due to thermal effects, like expansion or convection, because the device get really hot when in use. Some of the experiments measure a delay that is expected when you need some time to heat the device and some time to cool the device after use.

The problem is that they still are closing the obvious loopholes, not the weird ones.

The usual trick is to have a very strong force that is much more than the expected effects of heating and electromagnetic interactions of the wires, but they have measured only a very tiny force.

The "Chaotic Ball" model,local realism and the Bell test loopholes

http://arxiv.org/abs/quant-ph/0210150

I love this comment on the forum thread:

Any thrust greater than 3.33 nano-Newtons per Watt would require new physics.

It's so ... fantastically clear-cut. If X, then physics is broken. :) It kind of gives me goose bumps just reading that statement.

Of course I hope they really find something, pushing the boundaries of physics is always a good thing in my book.

Why don't they just put one of these things in space, with solar panels, turn it on, and see what happens? I guess the expense? It does seem the most expedient way to verify whether it works or not.

even SpaceX launches cost over 50 million dollars (https://www.google.com/search?q=spacex+launch+cost has a big pullquote to that effect, for example)

A lot of skepticism and negativity here, and I get that. But it's exciting to watch science play out. This could be a huge discovery, or it could be crap. I love seeing the methodology in making each test more and more definitive by reducing variables and outside influences.

I love that the question of this technology's validity is so grand it can be approached with Fermi's Paradox. If such physics indeed exists, allowing interstellar expansion of life, then it increases our chances of detecting a signature of extraterrestrial life out there. Since we haven't detected anything yet, it seems that EmDrive-tech is less likely to be real than if we would have.

This technology doesn't make interstellar travel much easier, even if it works. You only save reaction mass, but you still need huge amounts of energy. Our best bet currently are nuclear pulse engines [1]. Super advanced civilizations might use Hawking radiation instead [2].

[1] https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

[2] https://en.wikipedia.org/wiki/Black_hole_starship

Seems like they need to do the hardware equivalent of a "git bisect" here. Instead of fiddling around with the current version of the device, trying to figure out if the observed effect is actually propulsion or just an artifact, someone should start tearing the thing apart, testing as they go, and find out at what point the observed effect goes away. That would probably be instructive.

Very interesting. I've been following this in the news for some time, hoping to learn the results of the latest research.

In previous tests it seemed like the significance of the effect was diminishing on each iteration, suggesting it might be experimental error. Anyone have a handle on how the latest results have changed? I don't get a good sense from the article.

The purpose was to reduce the Lorentz force interactions:

1) Built and installed a 2nd generation, closed face magnetic damper that reduced the stray magnetic fields in the vacuum chamber by at least an order of magnitude and any Lorentz force interactions it could produce.

2) Changed up the torque pendulum's grounding wire scheme and single point ground location to minimize ground loop current interactions with the remaining stray magnetic fields and unbalanced dc currents from the RF amplifier when its turned on. This reduced the Lorentz force interaction to less than 2 micro-Newton (uN) for the dummy load test.

3) Rebuilt the copper frustum test article so that it is now fully integrated with the RF VCO, PLL, 100W RF amp, dual directional coupler, 3-stub tuner and connecting coax cables, then mounted this integrated test article at the opposite end of the torque pendulum, as far away as possible from the 2nd generation magnetic damper where only the required counterbalance weights now reside.

Now since they were still seeing 100uN of force that means they have 98uN of force unaccounted for. And the next iteration of the test is trying to mitigate the effect of any thermal forces.

At which point it would be actually cheaper to put this whole thing in space, turn it on and see if it produces any trust? If it does, then it definitely works. As long as it's on Earth, they will spend forever trying to account for extra variables.

Yeah. The general rule of thumb is that it costs $10,000/pound to put something into orbit. The cost would increase by orders of magnitude once you include all of the other resources needed to track the experiment, but this does seem like a relatively cheap experiment to run in space.

http://www.nasa.gov/centers/marshall/news/background/facts/a...

I think what's preventing this is:

1.) NASA can only run a certain amount of experiments at once and I'm sure there's a long waiting list. If they run this one, something else doesn't run.

2.) Space may not be the extra variable-free environment we're hoping for here: tons of intense electromagnetic activity and so forth.

Can someone please explain to me how does one creates new technology without having alt least one of the following? a) working prototype, b) consistent theory why the new technology will work.

In other words, what made Roger Shawyer believe his engine will work if he does not know how should it work nor have a prototype?

So if an EmDrive worked, what would it give us? A star trek impulse drive type thing? Or is it so low level an effect it would be useless?

Impossible to know without knowing _why_ it works. It's in contradiction with what we currently know of physics (so it's still far, far more likely that NASA eliminates a few more possible outside causes of the tiny measured thrust and the effect disappears), but if it does work then who knows what else could also work.

The impulse engine in Star Trek was just a fancy fusion-powered plasma rocket.

http://memory-alpha.wikia.com/wiki/Impulse_drive

Actually, there are several in-universe articles saying otherwise:

The interaction between the shields and a conventional propulsive system would be horrible (you’d get fried in your own plasma).

Therefore the Interacting Magnetic Pulse system (sorry, I’m translating back here, so I dunno if that’s the correct term in the correct in-universe article in english) actually uses some weird interaction of microwaves to create "gravitational waves on which the ship then rides", as one engineer said poetically.

It would give us one more point of serious divergence between our physics theories and the real world. What would that give us ? Good question.

Something between what the discovery of the bandgap in semiconductors got us and what finding out that the speed of sound in cheddar cheese is much more temperature dependent than in brie.

I would like a source on that cheese article please.

They won the 2006 Ig Nobel in chemistry!

CHEMISTRY: Antonio Mulet, José Javier Benedito and José Bon of the University of Valencia, Spain, and Carmen Rosselló of the University of Illes Balears, in Palma de Mallorca, Spain, for their study "Ultrasonic Velocity in Cheddar Cheese as Affected by Temperature."

REFERENCE: "Ultrasonic Velocity in Cheddar Cheese as Affected by Temperature," Antonio Mulet, José Javier Benedito, José Bon, and Carmen Rosselló, Journal of Food Science, vol. 64, no. 6, 1999, pp. 1038-41.

WHO ATTENDED THE IG NOBEL PRIZE CEREMONY: The winners delivered their acceptance speech via video recording.

Source:http://www.improbable.com/ig/winners/

If it works, it would mean that you could go into space without reaction mass. It would open up the possibility of relativistic travel. You could build a rocket the mass of a VW camper and push it into space by remotely powering it with lasers, as all the EMDrive apparently needs is electrical energy.

In an unpublished NASA report they are seeing over 100uN when feeding 80W power to the drive. Assuming a spacecraft to weigh a ton, that would accelerate it by ~3 m/s per year. So it's not only a question of EmDrive working, but also a question of whether it's possible to scale up the technology.

Isn't that an incredibly tempting figure? Almost like the result was picked because it almost has to be commercialized?

You'll get various war stories about what it really took in practice for satellite XYZ, but geosynch satellites burn along the lines of fifty or so m/s of delta-v per year for station keeping. To a first order simplification its true that you launch a geosynch comsat into space and it stays over the same general point on the earth for infinite time, blah blah but in practice there is always slow drift and impact of solar winds and lunar gravitation and whatever, so its not actually motionless and requires continuous, eternal, fine tuning.

Anyway using a couple hundred watts to completely eliminate the stationkeeping thruster fuel completely seems a fair enough trade...

And yes I know stationkeeping isn't a perfect continuous demand for thrust all year long, etc. Still, its interesting, and of the right magnitude, more or less.

I don't think it would be terribly useful for human transport, true. But its suspiciously right at the mass, power, and thrust values required to be commercially viable for comsat station keeping. That's either incredibly lucky, sometimes the universe does smile on us, or ...

Economical crisis are recognizable by the fact people tends to announce "infinite energy source", "cheap energy", or "perpetual movement" finally made true.

It is very interesting that while NASA that has been a clear "cache nez" during cold war to mask the use of nazis scientists and technologies for the USA they are now having a problem: space programs are considered to costly for their return other investment. Especially when you know the budget of ESA for rosetta/philae mission compared to NASA's budget.

Being on the grill, NASA is lobbying for even more costly mission to mars and support their own propaganda (intestallar, alone on mars...).

And now, miracle, they have an opportunistic new technology that could help achieve "cheap easy journey" to far away distance.

I can't help to be a little suspicious. The timing is so perfect.

And as numerous comments are spotting there is no new technology until we can explain the causation. Because that is how science work: experiments should be consistent with theory, and vice-versa. Else this is religion or philosophy.

Maybe emDriver could be the proof God exists, but it is not likely. Well, if it existed, and since we would have a physical place where to search I would kill it anyway. I hate Gods, I prefer to drive my own destiny without a "père/mère fouettard(e)" looking upon my shoulder like a stalker.

Woo hoo! The reactionless thruster! Next: Outsider hyperdrive!

http://news.larryniven.net/concordance/main.asp?alpha=T#thru...

I almost want to flag this link for playing loud sound advertisements on page load, but I'm not sure that's proper in this community. Is there not a better link to this content?

Previous discussion: https://news.ycombinator.com/item?id=10496638

I'd really like to see @dang et all at HN add digitaltrends.com to the penalised-by-default domains on HN. This is simply irresponsible hackery.

Rick Stella as well.

Momentum has velocity, but the velocity of light is the same in all reference frames. It seems like there is a conflict between conservation of momentum and special relativity. From the point of view of the light beam, nothing is moving.

The speed of light in a vacuum is constant in all reference frames, but a photon's frequency is not constant in all reference frames, so it's momentum (hf/c) is not constant.

This is bog-standard special relativity.

Ah, this makes sense.

Momentum and Special Relativity don't conflict. Momentum is modified with a Lorentz Factor which for a particle with mass runs to infinity as the speed approaches the speed of light.

For electromagnetic radiation like light the momentum is a function of the energy, not the velocity.

Cold fusion is the power source too.

Caution is called for. After all, blowing past warp 5 can damage the space-time continuum.

I can't name sources, but I have it in good confidence that this man ("Sonny" White) was forced to rewrite his dissertation by his PhD committee (mind you not his advisor, who was old and about to retire and had to be cajoled into line by the rest of them) because his first try was apparently all about this EMDrive stuff. This is a pathology.

Won't they look pretty stupid if this turns out to be real :)

I know, I know, it's not real, it's not how science should be done, blah blah. I'm sure you're right.

So, I'm being down voted for stating a relevant fact? I was asked not to reveal this by my source.

For disagreement, probably with the final line.

For stating irrelevant hearsay, perhaps.

What, and if I break confidence and name names from the Rice faculty that would somehow be better?

Being forced to rewrite entirely at a defense by the rest of one's committee is a BFD, it absolutely impacts his credibility.

Without knowing the details of what happened, we have no idea how it affects this person's credibility.

You have no credibility, so your unverifiable story conveys zero information. All it does is stir things up. Substantiating the story would be good, and failing that, saying nothing would be better than essentially spreading a rumor.

I'm a physics grad student at a university not too far from Rice. How am I supposed to substantiate this short of producing the first draft of his PhD thesis? Do you think academia keeps these things around?

I was sworn to secrecy on how I found this out, but a very reliable source that I can't name told me that selimthegrim murdered 17 homeless people over the last few years.

Note: this is satire, just for anyone who missed it.

It doesn't sound like you can substantiate it. But that has no influence on your credibility, or on the believability or relevance of what you're saying. From the outside, a true story that inherently can't be substantiated is indistinguishable from a made-up story that can't be substantiated. And it doesn't even have to be you who made it up, it could be the person you got it from, or wherever they got it, or all the way up the chain. Or maybe it's true! I have no idea, which is why I called it "hearsay" instead of "lies."

It's not the first time with this user:

https://news.ycombinator.com/item?id=10176671

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