11 ms·
The warp drive will have to wait
- dmichulke 10y agohttps://translate.google.com/translate?hl=en&ie=UTF8&prev=_t&sl=de&tl=en&u=http://www.golem.de/news/em-drive-der-warp-antrieb-muss-noch-warten-1606-121641.html https://translate.google.com/translate?hl=en&ie=UTF8&prev=_t... The critical passages - translated by myself Page 2: The hint: "Again it showed the same behavior - until the drive was directed towards the top for testing purposes. Usually, the drive is put on a torsion balance in a way that it can best turn the scale left or right. With the drive directed towards the top nothing should be measurable. [...] However, the drive directed toward the top in this experiment still showed the same force as when directed to the left." The test result at TU Dresden, Germany: "Tjalmar said: 'I can't say I proved or refuted the EM drive'" (because they didn't have the means to test it with a battery instead of an external power supply) Reference to a follow-up from a Chinese university: "But a research group from China did the necessary to refute it. As soon as the EM drive doesn't get its power from a cable outside [i.e., it get's its power from a battery], there is no measurable force anymore." The link to the Chinese paper http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=20160220&flag=1&journal_id=tjjs&year_id=2016 http://www.tjjs.casic.cn/ch/reader/create_pdf.aspx?file_no=2... The final sentence of the abstract: "Within the measuring range of three-wire torsion pendulum thrust measurement system，the independent microwave thruster propulsion device did not detect significant thrust. Measurement results fluctuate within ± 0.7mN range under the conditions 230W microwave power output，and the relative uncertainty is greater than 80%"
- aargh_aargh 10y agoSo... you're saying all we need to do is pull an extension cord behind our spacecraft? Unlimited powahhh!
- chris_wot 10y agoSort of like an electric mower with a power cord?
- jerf 10y agoThat's basically the thinking behind the laser-propulsion plan. The rocket equation gets a lot less hostile when the engine is not mounted on the rocket, but that has its own practical issues. Less than trying to drag a literal cord, of course.
- neutronicus 10y agoJust building a kilometer-wide lens to keep it focused and a several-Terawatt power source. Space travel. Shit's hard.
- jerf 10y ago(Six hours later correction: I should have said when the fuel is not in the vehicle.)
- jsprogrammer 10y agohttps://en.m.wikipedia.org/wiki/Electrodynamic_tether https://en.m.wikipedia.org/wiki/Electrodynamic_tether
- zyxzevn 10y agoThanks. Looks like the wires create the push with magnetic fields.
- rurban 10y agoCannot you write at least name right? The Austrian experimental physicist https://en.wikipedia.org/wiki/Martin_Tajmar https://en.wikipedia.org/wiki/Martin_Tajmar is a legend already, since he measured in 2002 a gravitomagnetic effect in spinning superconductors at Seibersdorf, but this sensational effect is also probably just bad experimental setup and not a new gravitational theory. He is the author of the classic book "Advanced Space Propulsion Systems".
- bleuarff 10y agoI guess a cheap and efficient propulsion that doesn't fit our understanding of physics was too good to be true. Still, it's a bit sad, that would have been beautiful if it were true.
- bayesian_horse 10y agoAs far as I understand it, it's not quite over yet. Maybe the refusal itself can't be replicated by the other groups. Now that will keep these physicists busy for a while...
- Obi_Juan_Kenobi 10y agoIt's not really over until we understand where these readings are coming from, whether error or new physics.
- marvin 10y agoThat was my thought as well. I'm glad someone spends the time required to refute a claim like this, because it did seem more long-lived and potentially within the realm of possibility than your run-of-the-mill claim that violates known physics. If we never take the time to explore claims that violate our current understanding, our understanding will stop advancing. Too many scientists are overly dogmatic.
- Tomte 10y agoI think the best sentence is this: "The theoretical expectation is that you don't measure anything. Now you're measuring something, and you can learn extremely much on this hunt for the error."
- ucaetano 10y agoSounds a bit like Fermi's quote: "If the result confirms the hypothesis, then you've made a measurement. If the result is contrary to the hypothesis, then you've made a discovery."
- api 10y agoI remember that quote too, and the key take aways always seemed like: in science you always learn something. Taking the EMDrive as an example -- we have measurements that contradict current theory, so we are either going to discover new physics or we are going to learn something about the art of making very precise measurements of force in complex mechanical systems. In no case do we learn nothing.
- aminorex 10y agoA third option, of equal merit: We may learn to apply existing theory more correctly and more adequately in a novel configuration.
- ucaetano 10y agoI always understood it as: science is far more interesting when thing don't go as expected. Kinda like how discovering the Higgs Boson was boring. It would have been far more exciting if they hadn't found it!
- aminorex 10y agoA third and equally useful possibility is that we might learn to correctly and productively apply the current theory in a situation and configuration where previously we did not know how to do so.
- Odenwaelder 10y agoIf something sounds too good to be true, it usually isn't true.
- seanosaur 10y agoOr, it's a scientific breakthrough. That won't happen often, but it also can't be ruled out completely.
- ocdtrekkie 10y agoAt the very least, if we can't figure out why it doesn't really work, we're likely to learn something new proving it doesn't.
- Certhas 10y agoIf it's free energy or free momentum, using only physics that has been perfectly described in hundreds of millions of contexts and experiments, for one and a half centuries, using mathematics that don't allow for either, you can rule out this alternative. The likelihood that free momentum and free energy are possible is indistinguishable from 0. They are empirically impossible in the strongest reasonable sense the word can have.
- HCIdivision17 10y agoThe critical detail here is that this is neither free energy nor free momentum in this setup. Energy is pumped in, and some momentum is generated - that's incredibly boring and not at all something that should raise any skepticism. The question of what in the hell was being pushed against to convert that energy to momentum, on the other hand, is a really interesting question, but not one to deeply pursue until we're actually sure it's happening. Which seems like the cavity wasn't the interesting bit in the end. A shame and a bit boring after so much careful testing, but nothing to get worked up over. And the experiments didn't make it obvious that the setup didn't work. I mean, I don't think anyone took the inventor's theoretical claims seriously, but the device did generate some small thrust in a difficult to explain way. Besides, we know that space isn't nothing, so being able to tractor against whatever is there would be a rather intersting engineering find; physicists would then likely take the experiment and go "oh, there's a neat edge case in this system of equations that explains it". There are a lot of interesting edge cases left to find and engineer.
- aminorex 10y agoEM drive is not an argument such that it might be refuted. It is a device. As such it has fitness for purpose, which depends entirely on the purpose at hand. Snarkiness << skepticism.
- ceejayoz 10y ago"It doesn't work" is a fairly critical issue when talking about the device's fitness for purpose.
- aminorex 10y agoIf a device doesn't work for the purpose for which you built it, then you built it wrong. I can't help with that. What I can potentially help with is finding the purposes for which the EM drive mechanism can be useful, but I'm not there yet: The phenomenon is not yet understood well enough to determine those purposes.
- peterbonney 10y agoThe OP may not be a native English speaker (located in Europe), so any perceived snarkiness is likely based on an overly literal reading of his word choice. How about this alternative (which, btw, is how I interpreted the headline): "Principle behind EM Drive refuted" or "Experimental results of EM Drive refuted".
- tp1024 10y agoI'm the author of the article. The quote wasn't meant to be snarky. It was meant as an explanation why it is worthwhile to occasionally do experiments, even if you believe the device can't work the way it is supposed to. He also said it was excellent experiment for the purpose of teaching his students.
- zackbloom 10y agoSure, if you need a paperweight, it very well may be the device for you. But the question is it's fitness as a propulsion device.
- FreeFull 10y agoI wonder what was causing the measurement, then. Magnetic repulsion due to the current flowing through the cable?
- peterbonney 10y agoYes, that is what is suggested by one of the experimenters at the end of the article.
- SubiculumCode 10y agoI dont see any other article on the internets discussing these results
- welterde 10y agoJudging from the date in the URL of the linked paper [1] and the corresponding section in the Wikipedia article on the EMdrive suggests that you might have better luck looking at somewhat older news articles. Publication date (and PDF metadata) seems to be 2015 though [2]. [1] https://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_maschinenwesen/ilr/rfs/forschung/folder.2007-08-21.5231434330/ag_raumfahrtantriebe/JPC%20-%20Direct%20Thrust%20Measurements%20of%20an%20EM%20Drive%20and%20Evaluation%20of%20Possible%20Side-Effects.pdf https://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_m... [2] http://arc.aiaa.org/doi/10.2514/6.2015-4083 http://arc.aiaa.org/doi/10.2514/6.2015-4083
- IgorPartola 10y agoSo was it a hoax or a mistake by its inventors?
- HCIdivision17 10y agoThat's sort of an unnecessary dichotomy. Enthusiasm doesn't mean hoax, and the mistake was propagated by more than just the inventors. Everything suggests that it was just science in action. There was an experiment, and it failed to reject the null hypothesis of 'no thrust'. A few groups have repeated the experiment, but not to the experimental power needed to thoroughly reject it. This test seems to be a more definitive rejection of it, but we're still not sure why there was any thrust measured in the first place, though there are some pretty reasonable leads on that.
- IgorPartola 10y agoI can see that to a point, but there was a commercial venture set up around it too.
- api 10y agoSetting up commercial ventures based on speculative hypotheses is what a large chunk of Hacker News does for a living.
- HCIdivision17 10y agoThose sort of things are always a bit grey and (IMHO) a bit sketchy, but it's worth noting that it's a bit costly to even test the ideas. Starting a business is a decent way to raise the capital to run the experiment, since grant money is likely far harder to get. But, yeah, doing it that way also really makes it basically impossible to be unbiased. Let a few more rounds of experimentation and refutation go through, and if it's clear it can't work at all, and they stay in business without pivoting, then we can breeze right past hoax and jump to fraud. Time will tell about it, I guess.
- JoelBennett 10y agoI'd go more with mistake. Properly measuring things can be hard.
- Libermentix 10y agoIn case you are curious about some data. There is a German maker who has been posting about his experiments as well. https://hackaday.io/project/10166-flying-an-emdrive https://hackaday.io/project/10166-flying-an-emdrive
- HCIdivision17 10y agoHoly mackeral, that is cool. I really appreciate the "well, let's just try it" approach. I can't wait to see what happens when he launches his little satellite. If it shows positive results, lots of people will replicate it. This is win-win: if it works awesome happens. If it fails then you're left with the experience of having built a little satellite!
- api 10y ago> I really appreciate the "well, let's just try it" approach. That's called "science." :)
- deleted 10y ago[deleted]
- James001 10y agoDoesn't this show that his version of the EM Drive shows thrust even when supplied with power from batteries? (instead of an external cable?)
- th0br0 10y agoThe more scientific posts seem to be at https://hackaday.io/project/5596-em-drive https://hackaday.io/project/5596-em-drive
- sctb 10y agoWe updated the link to the translated version of the article. If someone can suggest a good English article, we can update it again.
- leecarraher 10y agoWhy not run the setup without the cavity, or replace the magnetron with a big ass resistor, and see if you still get deflection. I suspect this is the beginning of a refutation, but it feels like there's a carrot still dangling.
- James001 10y agoYeah, this is hardly a refutation. This is just one failed attempt at replication using batteries
- raverbashing 10y agoYeah, this seems an easier way to test it
- arijun 10y agoI believed in the EM drive in the same way I occasionally buy lottery tickets: there's no way I could win, but wouldn't it be _so cool_ if I did?
- shrikrishna 10y agoThere's an xkcd for that! http://xkcd.com/955/ http://xkcd.com/955/
- raverbashing 10y agoWell, the probability is non-zero. And people win. Sure, it is extremely small. But even that is different from zero.
- aminorex 10y agoReward is finite. Risk is infinitesimal. No-brainer.
- cousin_it 10y agoCome on folks. John Baez has dismissed it [1]. For those who don't know who John Baez is, it's as if Terry Tao dismissed your math homework. For those who don't know who Terry Tao is... whatever. Just stop. [1] https://plus.google.com/app/basic/stream/z13gzfm4xt2tuxehl04chvywcofjhhzhwbk https://plus.google.com/app/basic/stream/z13gzfm4xt2tuxehl04...
- danharaj 10y agoJohn Baez and Terence Tao are as nice as they are smart and i think you're doing them a disservice by using them to be condescending.
- cousin_it 10y agoHave you read Baez's post that I linked? It's way more harsh than my comment. "Mumbo jumbo", "Failed a course in quantum field theory and then smoked too much weed"... Also I'm getting seriously creeped out by the amount of EmDrive non-skeptics on HN. Maybe we should make a poll whether 0.999... = 1, and then say that anyone who insists on the correct answer is "condescending".
- vardump 10y agoAd hominems and appeals to authority are such letdowns. Almost as those who might even admit they know nothing about it, but feel they're qualified to judge validity of some scientific claim. And provide <insert subculture> mantra as "evidence".
- cousin_it 10y agoI do know quite a bit about physics. But if I just said the EmDrive is nonsense due to conservation of momentum (which is the 100% correct answer with no caveats), people would shut me down because "NASA scientists know what they're doing". That would be an appeal to authority. So I mention Baez preemptively, but it seems like that's not a winning tactic either. What would convince you, pray tell?