23 ms·
Latest EmDrive tests at Dresden University shows it does not develop any thrust
- fnord77 6y agoquel choc
- tmathmeyer 6y agohttps://i.kym-cdn.com/entries/icons/original/000/027/475/Screen_Shot_2018-10-25_at_11.02.15_AM.png https://i.kym-cdn.com/entries/icons/original/000/027/475/Scr...
- wanderfowl 6y agoI’m disappointed to hear that, just because it’d be very useful for this to be a thing. But I love the science behind it, and this is the way it should be.
- xupybd 6y agoYes the strange thing about this drive is it appeared to work with no solid theory behind it. Yes, there was some but my layman's understanding was that it was flawed. It would have been so cool for something like that to have worked. We don't get many discoveries like that.
- deepspace 6y ago> appeared to work with no solid theory behind it. That, my friend is the very definition of Snake Oil. > We don't get many discoveries like that On the contrary, we get far more than our fair share of charlatans claiming physically impossible results. See also: Theranos, Energous, Fontus and a million other scam companies.
- bpodgursky 6y agoIt's really unhealthy to call anything that doesn't fit into the known laws of physics or science "snake oil" If the EmDrive team was trying to sell NFTs and sucker people into investing in their radical invention it would be snake oil. But instead they approached this very responsibly, saying "we don't understand why this works. help us figure it out." That's science done right, and a lot of new science has moved forward by questioning and changing the known rules. Whether or not it happens here.
- deepspace 6y agoI disagree. Something new that challenges areas of physics where our understanding is vague, like neutrino mass or dark matter - sure: feel free to explore new theories Something that challenges something as solidly established as conservation of momentum: Snake oil.
- bpodgursky 6y agoI don't get why you are fixated on that term. They're literally not selling anything. The whole point of the term "snake oil salesman" is that someone is getting defrauded, and a dishonest person is making a quick buck.
- ckozlowski 6y agoNewtonian motion was pretty well established for hundreds of years until general relativity transformed our understanding of gravity. Things seem "established" until evidence comes along indicating it may not be. It doesn't always result in a reevaluation, but there's times it does. This feels like one of those times where there's those in the establishment are yelling at others that their studies are a waste of time and that they shouldn't bother....and if that advice was followed, we'd be missing many of the breakthroughs in knowledge we have today. Of course there will be many times they're unsuccessful. That's why accepting a negative result is a lauded part of the scientific process. Without the bravery required in challenging convention, we would never make progress.
- jasonwatkinspdx 6y agoYou're apparently missing the origins of this whole thing. Shawyer has been soliciting investment for it since 2001, making very hyperbolic claims. This was indeed snake oil from very the start. A couple of people at NASA EagleWorks got permission to use some of their time and facilities to investigate it as a personal project. They did an extremely lazy attempt to control for errors, published their result without review, and the hype exploded. The whole saga is rather frustrating tbh. We knew what the definitive result was going to be 4 years ago. Getting some improved measurement technology is cool and all, but I don't think we had to go about it this way.
- andi999 6y agoI disagree. This is the definition of progress in fundamental science. The difference between science and snake oil is what you do after your first signal. Do you try to find every possible way why it could be wrong and most importantly do you let other people try, then it is science, like the faster than light neutrinos come in mind as another example. Or do you start selling and let other people not test it. Well then its snake oil
- ALittleLight 6y agoNobody was selling emdrives (to my knowledge). It was more of a "Hey, this is a weird effect" and an effort to explain it. That's less snake oil and more science. Most of the time there is some explanation that doesn't break your framework. Sometimes there's a breakthrough as you figure out the new thing. Sometimes you can't figure it out.
- jasonwatkinspdx 6y agoShawyer absolutely was soliciting investment. Anyone with a basic physics education could see his proposed mechanism was utter nonsense, so it's hard to be charitable towards his rather hyperbolic marketing.
- dleslie 6y ago> That, my friend is the very definition of Snake Oil. Is it? How does a bicycle work? https://www.nature.com/news/the-bicycle-problem-that-nearly-broke-mathematics-1.20281 https://www.nature.com/news/the-bicycle-problem-that-nearly-...
- pilsetnieks 6y agoAccording to science, a bumblebee shouldn't be able to fly. /s A bicycle isn't some unknown mystery of the universe, the very article you linked lays it out pretty clearly. A bicycle's stability is a function of its mass distribution, geometry and the gyroscopic effect. Their exact relation depends on the bicycle and since there is no one standard SI unit of a bicycle in the Bureau international des poids et mesures, there is no apparent equation. The "nearly broke mathematics" in the title is just pure clickbait.
- ncmncm 6y agoI have found I can teach kids to ride a bike in (literally) seconds, just by not lying to them about how it works. "Use the handlebars to stay up. Lean to turn." Just like that, and they're off. (I am absolutely not exaggerating.) (And, no, gyroscope effect has nothing to do with it.) They get the idea to twitch the handlebars the opposite way, to lean, all by themselves. Most never notice they are doing it.
- wruza 6y agoThat’s because leaning is such a bad term to describe what happens! Even when I learned to ride bikes, it felt so strange that “you have to lean left/right”, cause I understood somehow that I’m a much more massive object and the center of masses is around my butt at best. So leaning doesn’t change much in mass/geometry/momentum configuration. You may shift a bike under you with your arms, but this is limited to their lengths. What really happens is that you always fall either to the left or to the right. If you fall in a desired turn direction, you turn a little. If not, you turn even more than is required to support a normal turn, so that your bike moves below you to the point that now your mass part is to the other side of it, and now you fall in the other, initially desired direction. Then you quickly turn at where you need. With practice all this movement reduces to centimeters and very smooth curves at all joints. You move and (importantly) rotate your bike under yourself. It has nothing to do with leaning, because it’s the road/front tire that make a difference in a balance, not your flanks. Leaning helps to not fall off the seat when you cycle, but not in turns. It’s clearly a trainer’s delusion to me (that thing when your trainer explains things that do not actually work/exist but you translate or ignore these terms showing respect to a good man).
- Igelau 6y agoand yet, SSRIs
- andbberger 6y agoyou because there's no systemic understanding of SSRIs work? But you could say the same for most drugs. Most of the pharma industry is just targeting a specific protein without regard for how it fits into the system as a whole
- walrus01 6y agoIt's not snake oil if you have a weird unexplained effect, and: A) you're not trying to sell anything to anyone B) you fully open source the design, specifications, schematics and your notes, and invite any interested third party to try to duplicate or debunk the effect. C) you intentionally refrain from making hyperbolic claims about how revolutionary your thing is, before it's been duplicated. Maybe some clueless third parties engaged in hyperbole but not the original creators of the concept. Science is working as intended.
- pfdietz 6y agoIt's snake oil if you, as an experimenter, has not absolutely ruled out what's the most likely (and mundane) explanation. What's the saying? If a theoretician is right just once, he's a hero; if an experimentalist is wrong just once, he's a goat.
- kenneth 6y agoOn Energeous, the science is sound in theory. In practice I don't believe the company will be able to execute; but transmitting power over RF is something we've understood for a long time (since Edison first demonstrated the technology). I'm an investor in a competitor: Reach Labs which has systems in production powering swarms of low power devices wirelessly. I've seen the technology work in person.
- walrus01 6y agoWhat size and wattage load of devices?
- ncmncm 6y agoIf there is anything thoroughly Snake Oil in modern currency, it's Tokamak Fusion. "Give us enough billions, we'll have one working in 2050. Or 2060, or someday. It won't produce any power, oh no, of course not. But give us ten times more money after 2050 (or 2060) and by 2100, or 2140, or anyway someday maybe, we will have a prototype power station for you. "Sure, it will cost a hundred times as much for each kW-hr as whatever you will be using by then—and the plant will destroy itself after only two years—but it will be fusion power. And that will be so cool!" Tokamak fusion is mainly a jobs program for hot-neutron physicists, to maintain a population ready to draw on for weapons work, but is also a massive boondoggle providing a steady flow of corruption money to well-connected pockets. (Hot-neutron physicists are not getting the $billions.) Every cent spent on Tokamak fusion is stolen from actually practical work. So don't talk to me about snake-oil until after you kill Tokamak.
- xupybd 6y agoOut of interest is there another more promising controlled fusion option?
- ncmncm 6y agoI am interested in Field-Reversed Configuration, although it seems more practical for driving spacecraft. Anything aneutronic that works will be infinitely better than Tokamak. If it doesn't have to work, you are back in Tokamak territory.
- pfdietz 6y agoNot really. Fusion has inherent generic engineering problems, particularly DT fusion, that are independent of the details of plasma confinement.
- rcxdude 6y agoGiven sufficient evidence, there's no need to have a solid theory of operation for a given claim. That said, if it contradicts known laws of physics that evidence had better be damn good.
- kjrose 6y agoWhile I will accept these results if valid. I sincerely hope that other labs are able to reproduce these results and the concept isn't dismissed out of hand. While it's good to have multiple labs trying to reproduce results, that needs to apply in both directions to ensure that no unintended bias caused issues.
- BelenusMordred 6y agoFeel free to cheer it on, but extraordinary claims require extraordinary evidence. All the evidence here has never been verifiable and comes across as experimental sleights of hand. Always reminded me of Eugene Podkletnov and his gravity shielding, an interesting research avenue with physical experiments sure, but no one can ever replicate what he has said is happening. I sometimes enjoy to tin-foil that things like the emdrive and all those whacky navy patents are actually superpowers intentionally wasting the time of rivals. One space faring nation recently spent a lot research effort getting an emdrive into space to test it.
- kjrose 6y agoI'm not cheering anything on. I'm saying that there are many reputable groups that tried and got results. Including NASA themselves. It's important to disprove this solidly by having more than one group test and have a negative result. I think it's total bs. That doesn't mean the proof it is bs doesn't deserve to be repeated.
- Waterluvian 6y agoI was looking at the image on the page and my brain was oscillating between "that looks like a science machine" and "that looks spot on like a quack perpetual motion machine." I guess context really does drive perception.
- infofarmer 6y agoHmmm… those oscillations in your brain, did they feel perpetual? We need some more data to see if we can harvest their energy for motion.
- dsq 6y agoA TANSTAAFL-defying machine...
- OliverJones 6y agoThere's a reason the US Patent Office requires a working model from inventors who would patent a perpetual motion machine. Every other kind of invention may be described on paper.
- walrus01 6y agoConsidering how much waste heat can be thrown off by high powered microwave stuff (as in the original resonating cavity waveguide horn setup of the emdrive, which people thought to be producing thrust), I am not surprised at all that the apparent thrust was thermal expansion and contractions. Klystrons and TWTAs are not exactly known for being low wattage pieces of equipment, in terms of their TDP (thermal dissipated power). Ask anyone that's ever worked on a 1000W+ uplink power amplifier for two way geostationary satellite stuff... It's a lot of heat to get rid of. So these guys are trying to duplicate results of like 1 millinewton per kilowatt, meaning you'll need a microwave source of at least 3-4kW, of course it's going to throw off a lot of heat. I do wonder if any of the scientists trying to duplicate this effect have thought to bring in some commercial industry manufacturers of big C, X, Ku band TWTAs and get their advice on building a test rig. Or to try modern small but high power GaaN SSPAa vs TWTAs... https://www.cpii.com/docs/datasheets/17/t22ci_mkt326.pdf https://www.cpii.com/docs/datasheets/17/t22ci_mkt326.pdf https://www.cpii.com/products.cfm/153 https://www.cpii.com/products.cfm/153 Even very low powered terrestrial microwave radios are a lot of waste heat compared to what they output in rf. The radio head on a ptp microwave dish setup that is a 35W load on -48vdc might be outputting around +18 into the waveguide, equivalent to around 200 milliwatts. The rest is all radiated into the atmosphere and what it's mounted on. This why you'll see ridges of heatsink fins on the body of a full outdoor modern 18 or 23GHz radio. This is considered to be totally normal (a 35W 1024qam dual linear polarity radio with a capacity close to gigabit Ethernet line rate is sure a big improvement over a full 42RU rack size Harris Megastar 64QAM radio consuming 1800W from 25 years ago)
- Gravityloss 6y agoCounterfactual: Assume it worked, let's say it's producing a millinewton per kilowatt. That would mean one could put it on a spinning arm with a generator in the center and make overunity power. If you ran it at 1 m/s, it would only produce 1 milliwatt (1 mN * 1 m/s). Underunity. If you ran it at a million metres per second, it would produce its own power, 1 kilowatt. And if you ran it at 2 million metres per second, it would produce twice the energy that it consumed. 2 million metres per second is 2000 km/s and less than 1% of light speed. Relativity can be ignored. Would it be possible to build such a system? In vacuum with UHMWPE wire, one could build a spinning system 2000 kilometers in diameter that would spin 3 times per second. The centripetal acceleration would be 200,000 gees. Wikipedia tells me this is in current ultracentrifuge acceleration range. https://en.wikipedia.org/wiki/Ultracentrifuge https://en.wikipedia.org/wiki/Ultracentrifuge
- zackees 6y agoThis "test" and paper should be seen as possibly political.
- xupybd 6y agoIf the investigating this drive did nothing else this is a good outcome. "We were able to greatly improve our measurement technology as a result"
- walrus01 6y agoDepending how far down the rabbit hole they go in weird microwave resonating cavities and power amplifiers, maybe something of practical use for radar systems or other uses of multi-kilowatt microwave band power amplifiers will come out of it.
- p1mrx 6y agoImagine making popcorn in 5 seconds.
- moron4hire 6y agoImagine giving half your building a migraine in 5.1 seconds because you didn't catch it in time and have now burnt the popcorn.
- smcl 6y agoWhat's the burned popcorn->migraine connection?
- saagarjha 6y agoPresumably, it triggers the fire alarm.
- moron4hire 6y agoThe smell of burnt popcorn can induce migraine in some people (such as myself).
- rurban 6y ago
- deepspace 6y agoWell duh. Nobody who actually studied the original results with a critical eye is the least bit surprised. This crap is literally Cold Fusion V2.
- tunesmith 6y agoThis is like rationalism vs empiricism. It's nice when the empirical results align with the rational conclusion again.
- dleslie 6y agoI am both unsurprised and disappointed. This is one of those things where it'd be _really cool_ if it worked, but also hugely unexpected.
- Edman274 6y agoI also might feel disappointment, but I think that the greater disappointment would come from learning that foundational principles in physics had been overturned, because what it would mean is that we've all done a really, unacceptably bad job of getting a true version of reality. The difference between Newtonian physics and Special Relativity is not so much as to shake basic scientific principles to their core. But overturning conservation of momentum is like saying that we're making up physical laws as we go along.
- Andrew_nenakhov 6y ago> but I think that the greater disappointment would come from learning that foundational principles in physics had been overturned, That would have been exciting, actually. More stuff to learn, more natural laws to discover, more possibilities!
- wruza 6y agoI’m not a physicist, but it seemed unlikely that one can overturn a century of physics research by microwaving a bucket. Unlikely that something so obvious yet groundbreaking wasn’t encountered in any other experiment ever made, in one form or another.
- yetihehe 6y ago> But overturning conservation of momentum is like saying that we're making up physical laws as we go along. We ARE making up physical laws as we go along. We see something unexpected, we try to find why it could be, we invent new possible laws of nature and we check if those laws are sticking to wall with experiments. What sticks to wall, is then called "law of nature", but it might nit be exact or true. We only know it fits what we've seen up to now.
- tomrod 6y agoTo the dustbin! I had hope for the promise of the drive, but such as it is.science proceeded and now we know more.
- Taniwha 6y agooooh, scientists doing science!
- olliej 6y agowasn't it already established that the force measured was related to current in the power cables or something?
- xt00 6y agoYea I definitely remember that being discussed previously. Basically the amount of current in the wires was large enough to cause deflections that that particular group did not have a good way to account for so my recollection was they mentioned it as a likely source of the displacement. I was sort of hoping somebody would hook this thing up on top of an air table and power it with a huge battery so it’s a fully closed / stand alone system and see if the setup starts drifting one direction when it turns on.
- KMag 6y agoIt's an important step to fix the observed flaw and then experimentally verify results are now as expected.
- deleted 6y ago[deleted]
- junon 6y agoKudos to the team working on this, it's not often we get definitive findings and an update about something that was "futurology hype" like this. Not a failure. It's just science. Cool stuff either way.
- Andrew_nenakhov 6y agoAh, those April 1 jokes. Don't fall for them. Of course it did develop trust. It is the future of space propulsion.
- rurban 6y agoOh, bad timing. Tajmar worked 4 years to verify the results. But now quacks can blame April 1. Look at the dates: the conference papers were published march 17-19. The interview was march 21. Ion drives are the future, but hopefully gravitational drives. Otherwise we will not get far
- Andrew_nenakhov 6y agoShhh, stop ruining my joke!
- Chris2048 6y agoWhat is the likelihood that these drives do work and the team just want a head start on development?
- walrus01 6y agoFor everyone that's disappointed, remember that thrust without reaction mass is still possible with enough electrical power and lasers, and doesn't appear to violate any known laws of physics. https://en.wikipedia.org/wiki/Photon_rocket https://en.wikipedia.org/wiki/Photon_rocket https://en.wikipedia.org/wiki/Nuclear_photonic_rocket https://en.wikipedia.org/wiki/Nuclear_photonic_rocket https://en.wikipedia.org/wiki/Laser_propulsion https://en.wikipedia.org/wiki/Laser_propulsion
- brazzy 6y agoI mean, sure, ultimately mass==energy. It broadens your options but doesn't change the problem that you have to take it with you, it gets used up, and the more you take the more you have to use.
- fsloth 6y agoYou can beam the energy to the spaceship from a planet or satellite for the first leg of the voyage in many physically plausible configurations.
- sillysaurusx 6y agoNeat idea. How much energy do you lose (assuming a vacuum)? You could imagine some kind of dish that catches the energy, but that's the extent of my knowledge -- I don't know how you'd convert it back to propulsion.
- prof-dr-ir 6y agoThere were days on the internet when a car analogy was appreciated -- let me try here. Suppose there was a rally driver who would claim that rally cars could go much faster if they were always driven in reverse. He did some rudimentary experiments and might have found a significant improvement. The general public and other racing drivers, who in my analogy can all be wonderful people but happen to know little about the mechanics of cars, are naturally enthusiastic: a potential breakthrough in driving! But clearly we need more experiments. So other rally drivers get to work: they set up an elaborate system with ropes and pulleys so they can reverse the driver's position in the car and run a car as fast as they can, but in reverse, on a test track. What do they find? Sadly, their answer is somewhat inconclusive, probably negative, but perhaps the test track had many bends. So they would like to repeat the experiment on a track with a few more straight segments: they write grant proposals, build a track, and plan other test runs... and all the time their progress is eagerly followed by the general public. Now suppose you are a car mechanic in all this. What are you to do? This cannot work! It flies completely in the face of the way cars are set up, not to speak of the disadvantages in air flow. So you can loudly dismiss the claim as preposterous early on, but then you will be called a pessimist and the public point out that at least the rally drivers are trying something new - what the bleep have you been doing all this time? So you just wait the whole thing out, see it come... and go. I guess I should at least be happy that I did not buy any shares in EnDrive Inc?
- kungito 6y agoBut what if it turns out that the experiment showed that cars really are faster in reverse? It turns out that by driving in reverse you create anti-drag in front of the car which pulls it forward. It's so simple yet powerful. How did you not think of this? Now everyone must think you are stupid because you were being so negative while everyone believed in it. Time to open the internet to see the reaction... Wow, no one cares. It turns out unless Apple releases this in their new car as iEM Drive with exclusive iEM Aqua car paint finish no one would know or care about this.
- heavenlyblue 6y agoIt only happens in periodic dramas made for 15-year olds
- binarycoffee 6y agoJust to be clear, for most anyone with low-thrust measurement experience, thermal drift had been suspect nr 1 from the moment Eagleworks published their work. Here is a comment I made back at that time: https://news.ycombinator.com/item?id=12962579 https://news.ycombinator.com/item?id=12962579 But then, nobody had Tajmar's perseverance; kudos to his team!
- unityByFreedom 6y agoLol at the lone reply you received. You called it and that's what you got. I hope we can learn to look at all points from more perspectives in the future.
- waheoo 6y agoDay made. Good chuckle that.
- IshKebab 6y agoI mean, most people didn't believe that this was real. It's not like he was the lone voice saying "nah this is surely bollocks...".
- unityByFreedom 6y agoThat wasn't clear at the time. This post shows how hard it was for scientists to prove it's bollocks. And the above comment shows how the general population doesn't want their hopes dashed.
- IshKebab 6y agoIt really was clear at the time. Even then people pointed out that the measurements didn't behave in the way you'd expect if it actually worked (e.g. thrust didn't correlate with power). There were plenty of people saying "But imagine if it did work! We could get to other stars in a few years!" but you always get crazy optimists that ignore all the evidence with stuff like this (c.f. solar roadways).
- Ma8ee 6y agoKudos for spending four hard years to publish a negative result! It will hardly make any of them famous, while it still is a very important result. Hopefully this means that we can leave the whole EmDrive debacle behind us once for all. And to those that says that the outcome was given, and that they wasted their time, I'd say that we do have to sometimes try for the really long shots. In addition, it is important to show that we don't sweep any controversial results under the carpet just because they don't align with current "dogma".
- missurunha 6y ago> Kudos for spending four hard years to publish a negative result! All scientific results are positive, but I have the feeling people end up skewing their research just to show what they want to see. Yesterday I read a study [1] by the most renown Brazilian university claiming that the control of Covid on Brazilian football is bad because 11% of the players got it while in Germany only 0.5% were sick. Then I looked the data up and the Bundesliga has the exact same 11% [2], but the researchers chose a very specific time frame in which they didn't have many cases, just to "prove" their point. This was easy to verify, but I wonder how many long term researches find gibberish results and no one will ever know. [1] https://globoesporte.globo.com/sp/futebol/campeonato-paulista/noticia/estudo-aponta-que-numero-de-infeccoes-por-covid-no-futebol-paulista-se-assemelha-ao-de-profissionais-da-linha-de-frente.ghtml https://globoesporte.globo.com/sp/futebol/campeonato-paulist... [2] https://www.sport1.de/fussball/bundesliga/2021/02/bundesliga-corona-infektion-bei-jedem-zehnten-spieler https://www.sport1.de/fussball/bundesliga/2021/02/bundesliga...
- bitcharmer 6y agoWhy is this subject coming back? A while ago they conducted this experiment in Earth's orbit and found that the drive basically pushes itself away from Earth's electromagnetic field. Sadly it's useless in deep space.
- yellowapple 6y agoI mean, that sounds like something that could be pretty handy for LEO satellites at least, though there are surely more effective and less convoluted ways of achieving that.
- darepublic 6y agoI wanted to believe
- dkbrk 6y agoThis is unsurprising. I doubt there was anyone with a modicum of understanding of the physics (even the teams doing the testing) who expected it to work. That doesn't, however, mean that testing it was a waste of time. There was an anomalous result that has now been resolved. I think it's a vital scientific virtue to follow up anomalous results until they're satisfactorily resolved, no matter how ridiculous or physics-defying they seem. The EmDrive was always a long shot, but it wasn't the only reactionless drive under investigation. Unlike the EmDrive, which never had a plausible physical mechanism for how it could work, the Woodward Effect [0] does have such a mechanism and has yet to be experimentally disproven. It exists in this weird place where it seems to be a straightforward theoretical prediction from general relativity; where, almost by exploiting a loophole in physics, the maths says you can get thrust without propellant, and much more of it than possible with a photon rocket for the same power. This, apparently, doesn't violate conservation of momentum, either, because the momentum would be carried by gravity waves, essentially "pushing" against distant masses throughout the universe. Whether this is actually predicted by general relativity or is a misapplication of the theory, is very subtle and not something I'm capable of evaluating. This is being evaluated by NASA [1] -- not that that says very much, NASA will evaluate some pretty crazy things, see exhibit A: EmDrive -- but they've yet to achieve a negative result. Not that that says very much either -- EmDrive didn't have a negative result until it did. Still, while the chances of the Woodward effect working are small, I would still rate it as much, much higher than the EmDrive ever seemed to be. It's something to keep an eye on, anyway. There's also this interview with James Woodward [2] that might be of interest. [0]: https://en.wikipedia.org/wiki/Woodward_effect https://en.wikipedia.org/wiki/Woodward_effect [1]: https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_I_Phase_II/Mach_Effect_for_In_Space_Propulsion_Interstellar_Mission/ https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_... [2]: https://medium.com/predict/james-woodward-on-machs-principle-for-reactionless-inertial-propulsion-34384863ad50 https://medium.com/predict/james-woodward-on-machs-principle...
- codethief 6y agoI came here to mention the Woodward Effect. I had never heard of it until last week when someone here on HN mentioned the blog of Tom Mahood (a former master's student of Woodward) in an entirely different context (namely: UFOs). It ended up sending me on a deep dive into the subject and, ultimately, led me to an article by Mahood[0] about the Woodward effect. The upshot is: > But Tom, is this stuff ……real? > I….don’t…. know. And I say that after being involved in chasing it down for 10+ years. At this point, I see arguements on both sides. > Fundamentally, the mathematics are extremely compelling. I have yet to come across anyone credible in General Relativity who can say why the derivation is incorrect. About as damning as I’ve heard is something along the lines of, “Wait,…This can’t be right….But I don’t know why it’s not right”. The math is straightforward. > The effect (or something like it) has been demonstrated in a wide variety of different types of devices and experimental setups. Something has been observed if it’s merely capacitors being shuttled back and forth, but also with later generation devices composed of all PZT discs. > […] > As time progressed and the experimental apparatus more refined, the “effect” seemed to get smaller, and that’s a REAL bad sign. It was already well below what the theory predicted. That sets off alarm bells. After all this time, if something isn’t in hand to float around a table top, its should still at least be producing unequivocal results. [0]: https://www.otherhand.org/home-page/physics/graduate-studies-in-physics-at-cal-state-university-fullerton/ https://www.otherhand.org/home-page/physics/graduate-studies...
- whiw 6y agoThe knowledge that we have gained from this experiment is that the experimental data disagrees with the theoretical justificiation for the idea. That isn't the same as proving that the theory is wrong, even if that seems the more likely explanation. To be sure that the theory is wrong we would need an analysis of why that is the case and what were the false assumptions and faulty reasoning behind it. Any volounteers?
- teraflop 6y agoThe original theoretical justification for why the EmDrive was supposed to work was also wrong. The idea was to use a cavity shaped like a truncated cone, such that the forces on the big end and the small end don't precisely cancel. But this neglects the force on the sloping sides, which (of course) balances everything out. Here's a detailed analysis by Greg Egan showing why the EmDrive would not be theoretically expected to generate any thrust: https://www.gregegan.net/SCIENCE/Cavity/Cavity.html https://www.gregegan.net/SCIENCE/Cavity/Cavity.html Proponents tried to hand-wave these arguments away and claim that the EmDrive's empirical results were explained by new, unknown physics.
- vlovich123 6y agoFor everyone that’s expressing a view like “what a waste of time”, consider this. This hypothesis was by a respected scientist. The experiments have been done by lots of labs. There has been a reasonable position the skeptics have taken throughout. It still has taken a very long time of a bunch of smart people on how to build an experiment to rule these kinds of things out. That means theories have tighter bounds. Technology has been improved in the area which can have knock on beneficial educational and technological effects, etc. Being able to quickly and efficiently rule out hypotheses is a hallmark of the area that science shines in. Being able to say “no, definitely not” with very good certainty is a useful thing to this disciplines toolbelt. From that perspective it’s a pure win and worth any distraction on the scale of all human investment globally.
- plutonorm 6y agoYeah this is great - they have made an advance in how they can make measurements. There will be many more reaction-less thruster concepts to analyse in the future. Now we have a much better idea how to test them effectively.
- qayxc 6y agoThese measurement techniques are useful in other areas, too. Less error means more confidence in results for experimental physicists and potentially one less source of error to care about.
- anthony_r 6y agoOr maybe finally learn mechanics 101 - what the conservation of momentum is. The kind of stuff we expect to understand from smart 16 year olds. This is the physics equivalent of someone writing a brute-force recursive SAT solver and wondering why it takes so long. Perhaps we don't measure time correctly? What if mirrors are an illusion? We mustn't stop advancing the field!
- shoefindortz 6y agoThis argument reminds me of the historical arguments made against heliocentrism vs geocentrism. Just because we have widespread belief of one thing to be true does not mean we should blindly accept it and not test things that appear to oppose it. In my opinion, the tests that have happened with the EmDrive are exactly what _should_ happen to make sure that our knowledge is strong and that we do keep advancing the field.
- hermitcrab 6y agoI'm sure this is no surprise to any professional physicists anywhere.
- codethief 6y agoI just had a look at Tajmar's other publications[0]. They read like science fiction (well, that's of course because in a way they are): > Tajmar, M., and Assis, A.K.T., "Particles with Negative Mass: Production, Properties and Applications for Nuclear Fusion and Self-Acceleration", Journal of Advanced Physics 4, 77-82 (2015) > Tajmar, M., and Bertolami, O., "Hypothetical Gravity Control and Possible Influence on Space Propulsion", Journal of Propulsion and Power 21(4), 692-696 (2005) > Lörincz, I. and Tajmar, M., "Null-Results of a Superconducting Gravity-Impulse-Generator", 52nd AIAA Joint Propulsion Conference, AIAA-2016-4988, Salt Lake City, July 25-27 (2016) I think his job ranks among the coolest positions in physics that I've come across: He does fundamental physics (something almost every physics undergrad dreams of doing), both theory and experiment and both quantum mechanics and General Relativity, and he literally does rocket science. Unreal. I didn't think such a position could exist. [0]: https://tu-dresden.de/ing/maschinenwesen/ilr/rfs/forschung/forschungsfelder/raumfahrtantriebe-und-neue-konzepte/breakthrough-propulsion-physics https://tu-dresden.de/ing/maschinenwesen/ilr/rfs/forschung/f...
- snarfy 6y agoHe's had some controversy in the past and had a bit of a quack reputation. It's nice to see this research done. When I saw the name associated with this I assumed the opposite result.
- codethief 6y ago> He's had some controversy in the past and had a bit of a quack reputation. Can you provide more details or, possibly, sources? Was it just because he dared considering (and testing) "crazy claims" like the EmDrive in the first place?
- snarfy 6y agoMy impression was that yes, the majority of controversy was around his areas of research. I first heard of Tajmar when researching Heim theory which was itself pretty controversial.
- UncleSlacky 6y agoIf anyone's interested, Roger Shawyer (the inventor of the EMDrive) is speaking at the online APEC conference on April 3rd: https://www.altpropulsion.com/events/apec-4-3-the-emdrive-quantum-gravity-control/ https://www.altpropulsion.com/events/apec-4-3-the-emdrive-qu...
- ChrisMarshallNY 6y agoI am sad, but not surprised. I really want something like this to work, and it may, one day. Just not yet, I guess.
- dudeinjapan 6y agoThat's what she said
- yaya69 6y agoWe're trapped like beavers
- fnord77 6y agowhat are the inventor's credentials? I searched and searched and could only find vague descriptions like "scientist"
- the__alchemist 6y agoRelevant XKCD: https://xkcd.com/1404/ https://xkcd.com/1404/
- ZephirAWT 6y agoThese experiments were apparently well designed and thoroughly done - they just don't apply to actual EM-Drive but speculative [infrared laser version](https://www.reddit.com/r/Physics_AWT/comments/iz2d4x/darpa_laser_version_of_emdrive_has_a_test_result/ https://www.reddit.com/r/Physics_AWT/comments/iz2d4x/darpa_l...) of it. There are [good theoretical reasons](https://aetherwavetheory.blogspot.com/2010/11/do-galaxies-shrink-with-time.html https://aetherwavetheory.blogspot.com/2010/11/do-galaxies-sh...) for why EMDrive should work better with radiation longer than wavelenght of CMBR, i.e. vacuum fluctuations. Also the geometry of resonators tested is [very distant](https://i.imgur.com/zTrRFum.gif https://i.imgur.com/zTrRFum.gif) from conical shape of EMDrive, mildly speaking - and actually nonsensical with respect to EMDrive theory, which is based on polarization during reflection under Brewster angle. I'd even suspect, that Tajmar published negative results for misleading designs intentionally for to slow-down Chinese competition in this research. Most probably they already tested conical resonators - because there is no good reason why not to simply do it - but they hide their data before public for to get more time for further research of it. The pathoskeptical Popular Mechanics journal repeatedly attempted to [dismiss if not discredit EMDrive technology](https://www.popularmechanics.com/science/a15323/temdrive-controversy/ https://www.popularmechanics.com/science/a15323/temdrive-con...) and now it just jumped at new opportunity with all vehemence. The path to replication of original [R. Shawyer's EMDrive drive design](https://i.imgur.com/inLGS5G.jpg https://i.imgur.com/inLGS5G.jpg) is thus still fully opened.