14 ms·

I think what I most enjoy about the possibility of the EmDrive is that it's similar to how things were often discovered during the "golden age" of science. Oft

• rimunroe 10y ago
  I don't think really any scientists in the relevant fields actually think it's an interesting mystery. Lots of people make extraordinary claims about new theories or perpetual motion machines, but those claims frequently get reported on a disproportionately large amount. This is from the perspective of a former physicist who is grumpy about the endless torrent of "Einstein was wrong!"-type articles. I personally feel like it's risky to allow people to pin their hopes on something that's pretty obviously bunk, but I imagine it does have some benefits. I just don't think it's worth it.
  • maaku 10y ago
    > Lots of people make extraordinary claims about new theories or perpetual motion machines. Such claims don't often get replicated by multiple, independent labs, as is the case here.
    • moron4hire 10y ago
      And they seem to be basing their work on "Einstein was right, we just didn't fully understand what it meant."
    • crusso 10y ago
      I'm not up on every instance of "replication" -- but so far, the ones I've read about have been really shoddily performed. http://io9.gizmodo.com/no-german-scientists-have-not-confirmed-the-impossibl-1720573809/1720737686 http://io9.gizmodo.com/no-german-scientists-have-not-confirm... I'd love for this phenomenon to be real, but the Technology Review article did not present a realistic picture of the verification attempted to date.
      • austinz 10y ago
        I am skeptical about the EmDrive (although I would very much like it to be real), and my opinion on the drive or its theoretical underpinnings is not really relevant, given my lack of knowledge about the field. But I don't think that writeup is very good either: From the IO9 article: > The experimental setup is so flawed that it’s continuing to produce measurable “thrust” while in null mode when it should do nothing. From the Wikipedia page on RF resonant cavity thrusters (and corroborated by the citations): > the 'null test article', was designed without the internal slotting that the Cannae Drive's creator theorised was necessary to produce thrust > The null test device was not intended to be the experimental control. The article's author seems to fundamentally misunderstand the purpose of the null test setup. Setting everything else aside, if the null articles did produce thrust, this would disprove the Cannae theory (which requires the slotted configuration), but would say nothing about the efficacy of RF thrusters in general. Their quotes from various physicists about why the drive is probably nonsense are a lot more compelling.
        • DavidSJ 10y ago
          Pardon my ignorance, but I don't think anyone seriously doubts that the null article produces no thrust. So it's not a question of whether the null article's production of thrust disproves the efficacy of anything. It's a question of whether the experimental setup which measured that thrust is trustworthy.
          • taneq 10y ago
            Holy triple negative batman! Do you mean that nobody thinks the null article produces thrust? Or did I parse that wrong?
    • mcnamaratw 10y ago
      If you read the papers, the claims are not very well backed by independent experiment. (The claims are 'replicated' meaning lots of people repeat them!) There's little data and what there is is right at the limit of measurement error. Results from different groups conflict wildly. Tech Review is a PR rag, not a scientific publication.
  • 51Cards 10y ago
    Considering that the 2 rounds of NASA testing are now undergoing peer review it seems that some "...scientists in the relevant fields actually think it's an interesting mystery." That doesn't state that they think it works or doesn't... but they are investing time to clarify which is which. And that to me qualifies as it being an "interesting mystery". http://www.popularmechanics.com/space/news/a20076/the-emdrive-will-undergo-peer-review-that-it-wont-pass/ http://www.popularmechanics.com/space/news/a20076/the-emdriv...
  • gaur 10y ago
    > "Einstein was wrong!"-type articles I like popular articles about dark energy. About the only thing you learn from them is "Einstein called the cosmological constant his greatest blunder!".
    • raattgift 10y ago
      Removing the CC from the normal form of the Einstein Field Equations was what he considered his blunder. It was there originally, but he realized that he could not have a static universe with a nonzero CC, so he removed it, as Hubble, Lemaitre and Friedmann had not yet demonstrated the universe is non-static. When there was overwhelming evidence of what we now call the Hubble flow, he realized that a small positive cosmological constant produces exactly that, and thus he put it back in. What you don't usually learn in those articles about dark energy is that in the Friedman-Lemaitre-Robertson-Walker model of the standard cosmology, you have an assortment of matter fields which are characterized by density and pressure. Matter (in the most general sense of non-gravitational field content) has positive pressure, and some matter can clump (leading to non-uniform densities, and where density is higher, so is pressure; super-dense massive objects have enormous positive internal pressure). Dark energy is in its simplest form a field with slightly negative pressure, and with constant density (i.e., it does not clump and it does not dilute away with the expansion like the matter fields do). This constant density is the "cosmological constant". Its absolute value is very small compared to the pressure even in slight overdensities of ordinary matter (like in sparse gas and dust clouds), so it's drowned out entirely by the positive pressures in structures like galaxies or stars. Pressure and density are terms which are in the (Robertson-Walker) metric, and the metric describes the 4-lengths of spacetime intervals. Positive pressure contracts these lengths; negative pressure increases them. So when fields with nonzero pressure are treated as the principal generators of the metric (i.e., matter and dark energy tell spacetime how to curve), you can call the result the metric expansion (or contraction) of space.
  • keeperofdakeys 10y ago
    A famous example of this was polywater, https://en.wikipedia.org/wiki/Polywater https://en.wikipedia.org/wiki/Polywater.
    • ridgeguy 10y ago
      Ironically, it was Boris Derjaguin's participation in the polywater debacle that caused many to dismiss him when he claimed to have synthesized diamond by chemical vapor deposition, at pressures far below the thermodynamic stability region for diamond. In fact, he was right and diamond synthesis by CVD is routine today. We probably lost about a decade of progress in diamond CVD because of Derjaguin's having been tarred with polywater, as it were.
  • Aelinsaar 10y ago
    "Einstein Was Wrong- Click here to find out why!". That's the real, ugly truth. This is the endpoint of clickbait, a kind of Brandolini Black Hole.
• gaur 10y ago
  > the EmDrive has created a very interesting mystery. Microwave cavities have been a workhorse technology in many fields for many decades, and everyone has found that existing physics (classical electrodynamics, superconductivity, and a few other things) is entirely sufficient to explain how they work. There's a very simple explanation for why a small group of people would report an unphysical, novel effect in a well-studied physical system: sloppy experimentation.
  • luhn 10y ago
    That was the initial response, but the results have since been replicated several times by several organizations, including NASA. "Sloppy experimentation" seems unlikely at this point.
    • gaur 10y ago
      > the results have since been replicated several times by several organizations The results are random. Sometimes nonzero thrust is observed in a direction opposite to what was expected [0]. Know what that sounds like? A null measurement dominated by statistical and systematic uncertainties. > including NASA I'll repeat what I said elsewhere: NASA is so big that that doesn't mean anything. Not everyone affiliated with NASA is a top-notch researcher. The word "NASA" is not automatic proof of good research. [0] https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#Testing_and_replication_claims https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#Te...
      • gjulianm 10y ago
        The theory seems to predicts reversed thrust in certain conditions, it's at the end of the abstract. I don't know for certain whether they're random or not, but at least this looks interesting.
        • ajuc 10y ago
          A theory that allows for different signs of the effect sure is convenient ;)
• gus_massa 10y ago
  > I think what I most enjoy about the possibility of the EmDrive is that it's similar to how things were often discovered during the "golden age" of science. There were also a lot of false discoveries. Someone made a machine that does something, and after a few iterations it was discovered that it was only a bad measurement (or a scam). It happens also with theoretical ideas, the most famous are aether and flogisto. They were good ideas, they explained a lot of experiments, but after a time it became obvious that they were wrong. > The EmDrive is one of the rare modern situations where someone has engineered a device that shouldn't work according to what we know and the scientists are having to come up with the explanation. The obvious explanation is that they have an error in the measurement. Probably something get very hot and the thermal effect produce a tiny force, some experiments show that it need some time to build up and it continue a little after the current is off, like a thermal effect. Another possible explanation is that the high currents produce a magnetic field that produce a tiny force. They are putting a lot of electricity and energy in a small device, and they only measure a tiny force, it's very difficult to rule out experimental errors. A similar case are the faster than light neutrinos, that were the product of a bad measurement.
  • ccvannorman 10y ago
    Not a good comparison, considering six independent research bodies including NASA have experimentally verified that this does work (citing the OP article)
    • simonh 10y ago
      They have verified that there is an effect that needs explaining. Claiming that 'it works' is just as premature as claiming that it definitely doesn't.
    • Joof 10y ago
      The article isn't necessarily truthful. It's still well within the realm of measurement error.
      • JackFr 10y ago
• david-given 10y ago
  See also the Woodward Effect, which was the previous generation of reactionless thrust device. https://en.wikipedia.org/wiki/Woodward_effect https://en.wikipedia.org/wiki/Woodward_effect The tl;dr for this is that Woodward proposed (based, AFAICT, on actual science) that rapid internal energy changes cause transient mass fluctuations. His device used a capacitor on a piezoelectric effector so that the effector would only push while the capacitor was charging or discharging, and only pull while the capacitor was _not_ charging or discharging, so producing an assymetric effect and, therefore, thrust. There have been a number of attempts to verify this experimentally, all of which have been inconclusive; turns out the measuring very small forces when your test equipment is vibrating is very, very hard (see the Dean Drive). My feeble understanding is that the underlying theory is at least plausible; it doesn't seem to violate anything we know about the universe. The last report I've seen of work on this is this (rather good) BoingBoing article from 2014: http://boingboing.net/2014/11/24/the-quest-for-a-reactionless-s.html http://boingboing.net/2014/11/24/the-quest-for-a-reactionles...
  • api 10y ago
    One of the things that keeps me intrigued about this is that this is not the first time someone has claimed anomalous thrust from an asymmetrical EM device of some kind. It could be measurement error combined with a little wishful thinking, or it could be that there's some undiscovered physics there and we're tip-toeing around the edge of the parameter space where it manifests. If that's the case, all these "X effect" systems could be working according to the same principle. There are other cases in science (e.g. early transistor efforts and superconductors) where tinkerers and engineers hit on effects that were not understood and were ignored for a long time until we had some kind of theory that explained them and much more importantly told us how we might optimize for the effect. The McCullough prediction that a dielectric should increase the effect seems easy to test.
    • andygates 10y ago
      There seems to be something that catches the imagination, but I suspect it's closer to that whole class of perpetual motion machines which consist of moveable weights on a wheel, than to a revolution in physics. There's lots of unbalancing wheels, and none of them work.
• nsns 10y ago
  From the Reddit comment linked by rybosome below: >Some have questioned why no companies such as Boeing, Lockheed Martin, or SpaceX have attempted to investigate the device, but regardless of how likely these companies find the results so far, the largest reason is almost surely that the devices are both patented by their inventors.
  • TheSpiceIsLife 10y ago
    That shouldn't stop you from building and testing the device though, right? Only that if you wanted to commercialise it you'd have to come to an agreement with the patent holder, or maybe buy the patent. If it worked, being first to market with an exclusive agreement with the patent holder would be lucrative.
• Aelinsaar 10y ago
  Remembering the hits, and forgetting the misses does make the past seem golden. Meanwhile, Z-Rays...
  • api 10y ago
    True enough, but can you have hits without misses? Most new stuff will not work, but there is no way to avoid trying without also eliminating progress. I'm of the opinion that science today is too conservative and gun-shy. Science needs to be more willing to fail, and scientists who pursue cold leads should not have their careers destroyed.
    • Aelinsaar 10y ago
      The fact that a lot of screwups occur on the way to discovery in no way ennobles screwups, except in hindsight.
• deleted 10y ago
  [deleted]
• upofadown 10y ago
  > ... "golden age" of science. An interesting and relevant example was the Dean Drive: * https://en.wikipedia.org/wiki/Dean_drive https://en.wikipedia.org/wiki/Dean_drive