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Of course it is. Nearly every physicist knew this was quackery from day one. It should of course be tested properly, but nobody should be surprised.
by gaze 8y ago
Of course it is. Nearly every physicist knew this was quackery from day one. It should of course be tested properly, but nobody should be surprised.
- tabtab 8y agoJust because one cannot explain a phenomenon using known physics doesn't mean they should outright dismiss it. A good many discoveries started with, "Hmmm, that's odd...". And, science mistakes are good lessons, such as "why didn't we think to check that?"
- scott_s 8y agoI think you are not doing credit to the many physicists and science communicators who thoroughly explained why this was quackery. And in a world with quacks - people who have deceived themselves or are deliberately deceiving others - I think it is defensible for most of us to ignore people who claim to have violated the conservation of momentum with scant evidence.
- dwringer 8y agoIf it had been thoroughly explained then there wouldn't have been anomalous experimental results. I agree that it's rather likely that we're seeing experimental artefacts rather than new unexplored areas of physical law, but we must scientifically explain the results or else be very cautious, in general, when declaring something to be impossible. As the joke goes, that is well known to be the surest way in science to eventually be proven wrong. Even if it turns out these pseudoscientific dismissals were reaching the correct conclusion; well, as they say, even a stopped clock is right twice a day.
- pixelcloud 8y agoIt find it super funny how it was a cable related issue just like this famous one https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...
- scott_s 8y agoI'm not claiming impossible. I'm claiming so unlikely that it's not worth our attention. The problem is that we live in a world of people trying to fool us. People trying to actively undermine the scientific process. There is a long history of charlatans claiming free energy; it's not feasible for us to entertain all of their claims.
- 2bitencryption 8y agowell, I should either trust you, and your idea that we shouldn't give a second thought to crazy ideas like this... or I should trust NASA, who believed there was enough interesting things to learn there that they experimented with it on their own. It's close, but NASA wins this round.
- aetherson 8y agoFor the 100,000,000th time, the Eagleworks thing isn't a NASA operation, except in as much as NASA owns the property it's on.
- nebulous1 8y agoIs that correct? Brief research indicates that it is not.
- scott_s 8y agoDon't confuse "NASA" and its agenda with small groups inside of NASA with open mandates and the ability to spend time on side projects.
- tabtab 8y agoRe: you are not doing credit to the many physicists and science communicators who thoroughly explained why this was quackery To my knowledge, general intent to deceive was NEVER proven. Or are you using a different definition of "quackery"? Yes, it appeared to violate known physical laws, but it was still possible that A) physicists missed a curious aspect of current models, or B) the existing models of physics are wrong or need tuning. It happens. Not common, but it happens.
- deleted 8y ago[deleted]
- 2muchcoffeeman 8y ago> Just because one cannot explain a phenomenon using known physics doesn't mean they should outright dismiss it. I don’t think most people appreciate how solid our models of well-trodden physics is. Any new engine is going to be more exotic than microwaves in a chamber.
- dnautics 8y agoyou have to be careful, many experimentally verified observations could have been called quackery, too (an electric current has an effect on a magnet only if it's out of the plane of the magnet? QUACKERY!) If you go to biology and biochemistry, there's plenty of things that still have zero (or very tenuous) basis in underlying theory that are observationally verified (lots of sweet-tasting compounds, basically all anaesthetics, tylenol, e.g.)
- varjag 8y agoActually no you don't have to, if the claim breaks some fundamental property like conservation of energy or momentum. Tremendous skepticism is most warranted.
- dnautics 8y agoAtomic fission breaks the 'fundamental property' of 'conservation of energy', hence https://en.wikipedia.org/wiki/Nuclear_binding_energy#Mass_defect https://en.wikipedia.org/wiki/Nuclear_binding_energy#Mass_de... and E = mc^2
- magicalhippo 8y agoThe energy released was put into the atom when it was created through fusion.
- Turing_Machine 8y agoOf course, but acknowledging that required that the supposedly immutable "laws of physics" be rewritten.
- magicalhippo 8y agoThat makes no sense to me. Which laws rewritten how?
- selimthegrim 8y agoThe last time I tried to tell the story behind the academic community's attempts to stop this in its tracks I was downvoted. Rest assured, academia tried its best.
- Pyxl101 8y agoWhy is it impossible? Is it the amount of thrust that's generated that's impossible, or the mere concept of generating thrust from electromagnetic waves? The reason that I'm asking is because light has momentum. If I shine a beam of light out the back of my spacecraft, then I will accelerate in the opposite direction. Not a lot, just a little. Was EmDrive impossible because it was claimed to generate way more thrust than could be explained from the energy levels involved? (Edit: It looks like an additional reason it's impossible is because the EmDrive was claimed not to emit radiation, and rather keep it bouncing around in the cavity. Thanks for the replies and explanations!) Imagine that I attach a 1 megawatt laser in the 630 nm spectrum to my spacecraft. From some rough calculations based on (1), it looks like the laser will generate about 0.003 newtons of thrust (equal to the weight of 0.2 pounds on Earth), which is very little thrust, and impractical for accelerating a spacecraft over regular time scales. (1) Momentum of a laser beam: http://umdberg.pbworks.com/w/page/50455623/Momentum%20of%20a%20laser%20beam http://umdberg.pbworks.com/w/page/50455623/Momentum%20of%20a...
- twinkletwinkle 8y agoThe EmDrive claimed to violate conservation of momentum. To extend your analogy, instead of shining the light out the back of your spacecraft, you shined it inside the spacecraft at the back wall. It bounced around and came out as net positive thrust. Hence the extreme skepticism.
- gascan 8y agoOk, if you shine it on the back wall one might expect the radiation pressure balances out and there is zero net force. What happens if you used a waveguide to turn it around 180 degrees to the front wall? Photons have no mass, so turning it in a waveguide would result in zero force on the waveguide right?
- GW150914 8y agoPhotons have momentum and energy.
- roywiggins 8y agoSuch a drive would necessarily be a perpetual motion machine. Perpetual motion machines are a dime a dozen and we don't test all of them rigorously because approximately none of them will ever work. https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494
- mojomark 8y agoNo, it wouldn't.
- roywiggins 8y agoI thought the arxiv paper was fairly convincing. What's wrong with it?
- mojomark 8y agoPer the arxiv paper "...Thus, at some point, the kinetic energy of the device-driven mass exceeds the energy input, and if this energy is collected via decelerating the mass (via regenerative electromagnetic braking, for example), then there would be a net gain in energy." So, first of all, the author of the paper certainly acknowledges the simple priniciples that make EM drive propulsion function. The author is simply arguing how feasible the technology would be for achieving any significant acceleration. He doesn't claim that EM drive is in principle a perpetual motion machine, rather that 'ar some point' [during acceleration] the energy input to achieve any signiificant acceleration to make the technology feasible would require output energy greater than the possible energy input aboard an engine of a given mass (a statement which is certainly dependant on the efficiency of the 'power conversion' of the system, which can be improved with, for example, more efficient conductors/resonator cavities, etc.). The paper is fine IMO; it's the comment that cited the paper that is inacurrate.
- roywiggins 8y agoTo quote from the abstract: "any device with a thrust-to-power ratio greater than the photon rocket would be able to operate as a perpetual motion machine of the first kind, and thus should be excluded by the First Law of Thermodynamics" seems pretty categorical to me. The problem is, when you look at an object with a given velocity v, it has a kinetic energy proportional to v^2. To accelerate it from 0 to v, you must have put in all that kinetic energy (ie, v^2 energy). But reactionless drives give you velocity directly in proportion to energy. At some point, the v^2 and v lines will cross, and your object will have more kinetic energy then you put into it in the first place. For every unit of energy you pump into the drive, the velocity goes up by a unit, but since the kinetic energy of the object is proportional to v^2, at some point the kinetic energy you get out will be more than the electric energy you put in. The problem goes away with photon drives because that crossing point turns out to be at the speed of light. This is the argument the paper is making: If you can generate velocity directly from energy, you will eventually end up generating more energy than you started with.
- mojomark 8y ago> Of course it is. Nearly every physicist knew this was quackery from day one. Source of disproof? From two years of atomic physics study at my university, I don't see any reason you can't generate thrust using EM emission from an anetenna attached to the object being propelled. No laws are violated. First of all, before getting to conservation laws, the author's statement that an EM drive requires no fuel, right after stating the engine is powered by microwaves (generated by some stored energy source, a.k.a. fuel) is nonsensical. So, about those conservation laws. EM drives absolutely fully conserve energy and momentum in the system. Anyone who studied physics at the university level should have a firm understanding that photons do not "launch" themselves off of the surface from which they are emitted, like a rocket from a platform. Instead, the energy and momentum change forms as they transfer from the source (e.g. an atom) to the photom (e.g. a microwave). In atomic orbital decay (say spontaneous emission from an exciton), emitted photons recieve their energy and momentum from the atom's decaying orbital energy and angular momentum. That's it. See here (1) for a deeper breakdown of what's going on, but if you're generally trying to figure out where the energy and momentum are coming from, at the high level that's all there is to it - no quackery here. If you need a mental image, just try to imagine throwing (imparting a force on) a photon emitted from a light bulb in your hand. You can't do it. A photon travels at the speed of light in a vacuum the instant it is created at the bulb's filament. Because you're hand and the lightbulb (both made of matter and traveling in the same direction as the photon) cannot travel at the speed of light, the photon will always be forward of your hand/light bulb and no energy can be transferred from your hand/light bulb to the photon, and vice versa. There is no "recoil" felt by your hand. That's exactly the same for the EM drive's antenna (or any antenna or emitter for that matter). However, that same photon can certainly interact with matter and transfer it's energy and 'linear' (angular) momentum to an incident piece of matter, for a kinetic reaction. So, again, I don't see the problem. 1. http://www.eng.fsu.edu/~dommelen/quantum/style_a/consem.html http://www.eng.fsu.edu/~dommelen/quantum/style_a/consem.html
- roywiggins 8y agoI found this paper pretty convincing. Any "reactionless" drive more efficient than a photon drive is probably a perpetual motion machine: https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494 The claimed thrust of the EMDrive was incompatible with photon thrust- it was much too powerful.