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Given that reactionless thrust is even less plausible on a theoretical basis than superluminal neutrinos, I really hope this doesn't come as much of a surprise
by roywiggins 8y ago
Given that reactionless thrust is even less plausible on a theoretical basis than superluminal neutrinos, I really hope this doesn't come as much of a surprise to anyone.
- delecti 8y agoNot a surprise, but certainly a disappointment. It would have violated our understanding of physics, but it's not like that's never happened before.
- drspacemonkey 8y agoAgreed. There's nothing more exciting in science than finding out that our widely-held beliefs about something are wrong.
- beevai142 8y agoNot a surprise and not a disappointment either, when it was clear from the start that all results are within measurement error bars, so that there was neither experimental nor theoretical reason to expect to see something.
- delecti 8y agoIt wasn't clear from the start or there never would have been follow-ups. There seemed to be a measurable effect going on, so they tested it.
- monochromatic 8y agoStill, would have been nice to find a real effect. And by nice, I mean it would have changed the future of space travel.
- mrkstu 8y agoIt also would have literally meant the end of the world in a short period of time. Reactionless rockets with little to no cost or requiring high technical capability would lead to a terrorist shortly speeding up a hunk of lead to near lightspeed and slamming it into a earthside target, and that would be that.
- Lucent 8y agoWe've had a few thousand nukes, many secured with the password 0000, lying around for a few decades now in a dozen countries, and that hasn't materialized. For some reason, we seem to be much better at imagining ridiculous scenarios for terrorists than they are at implementing them.
- A2017U1 8y agoWe could witness the great filter firsthand
- flukus 8y agoWell first that need to get it into orbit and outside of the suns gravity well. Then they'd have to get it far enough away that the lead could get up to light speed before hitting it's target, you can't do this in solar system because you can't change trajectory that fast. Finally they have to aim it correctly at earth from that distance. A big ask for a group of people who's best technical achievement so far is to fly a plane into a building.
- hn_throwaway_99 8y ago> It would have violated our understanding of physics, but it's not like that's never happened before. I've heard this sentiment a lot when it comes to the EMDrive, but honestly I think it really misunderstands how science progresses in general. For EMDrive to be real, virtually everything we know to be true about physics would have to be false: if you're saying conservation of momentum can be violated, or conservation of energy can be violated, then basically all of modern physics would have to be wrong. When science, and especially physics, advances, it is very rarely, if ever since Newton's time, that the settled physics is 100% wrong. Instead, the "old" physics tends to be an approximation under most conditions, or there is a new phenomenon that can be explained without really violating the old rules. For example, conservation of momentum still holds under special relativity, it's just that we discovered things without mass can have momentum. Thus, the only explanation that would really be plausible is if there is "something else" going on with the EMDrive where momentum and energy are still conserved, just that there is something happening beyond our current understanding of "energy" or "momentum". I haven't seen any explanations that even try to postulate what that could be. All I ever have seen is "but the old physics could be wrong!" without an explanation of how it could be wrong.
- mdorazio 8y agoI could be wrong, but I believe the postulation was along the lines of a quantum effect utilizing virtual particles from quantum vacuum fluctuations to generate microthrust. If that were true, it wouldn't really be a violation of the standard model - more of an addendum like a lot of things involving quantum mechanics.
- whatshisface 8y agoIf virtual particles are the ones I know from Feynman diagrams, then momentum is still conserved at every vertex (interaction element). Unless the person who speculated that meant something else by "virtual particles," I don't see in the slightest how they could be used to obtain momentum or squirrel it away. Besides, virtual particles have to go away at the end of every diagram... They can act as conduits between other particle fields but if a new particle remains after the interaction it will be just another reaction product (nothing virtual or spooky). Some go so far as to say that virtual particles don't particularly exist, but that's a philosophical statement I guess (they do indeed lack many properties of other things that exist). However I can't say much about that as the arguments for this-or-that nonintuitive ontology usually emerge from advanced theoretical research that is beyond my knowledge. (I.e. in momentum space virtual particles don't even remotely seem to exist, but maybe the picture seems more reasonable when you write it all down some other way.)
- lawlessone 8y agoAt least we learn from the mistake and what kind of strange things can cause this errors like this. A lot of these things are often scams, but in this case i think everyone involved was genuine and believed they had found something great.
- chris_va 8y agoWith some exceptions, depending on how you define reaction-less: https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly
- gilbetron 8y agoThat's not a reactionless situation, there is an asymmetry of photons causing the acceleration.
- chris_va 8y agoYes, of course, but there is no finite propellant being consumed.
- danbruc 8y agoThe photons come from the decay heat of the plutonium in the radioisotope thermoelectric generator, so that is a finite propellant being consumed.
- chris_va 8y agoA theoretical EM-drive would run on electricity, as well, so thus wouldn't be propellant-less? Well, assuming one can violate only one law of physics at a time, this is just semantics.
- gilbetron 8y agoThere is nothing coming out of the EM-drive, it just creates a force, which is why it would be awesome.
- roywiggins 8y agoNo, it is different. Photon drives are like a reactionless drive in that you are not expelling matter, but photon drives are emitting mass/energy in one direction and moving in the other and conserve momentum. Reactionless drives just produce force, pushing off "nothing." They violate conservation of momentum and break physics as we know it pretty conclusively.
- zamalek 8y agoReactionless thrust is less plausible, yes, but it is strictly impossible. Not all explanations for it involved reactionless thrust. NASA indicated that pilot wave theory might be involved (where the vacuum acts as the propellant). This research is pretty conclusive: it doesn't work. That being said, just because you don't have any reasonable explanation for an effect does not mean that it does not exist. Flight would have been considered reactionless thrust before it was understood that air had substance.
- beevai142 8y agoIt was not "NASA" who indicated something, but a couple of guys working for NASA. Also, the "pilot wave theory" stuff is just idle speculation on topics of which the authors did not appear to understand much.
- nabla9 8y ago> NASA indicated Last time I looked it, this EM Drive research was not NASA project. They just gave a NASA engineer a warehouse to pursue his ideas on his own time like good research organization does. The "Eagleworks Laboratories" or "Advanced Propulsion Physics Laboratory" is just what Harold G. White calls the warehouse. It has no website or staff from NASA.
- zamalek 8y agoThanks for the correction, I had completely misinterpreted what Eagleworks was.
- nonbel 8y agoI really do not understand how people could say something like this (and also things like "GR is one of the most confirmed theories ever"). "Theoretically" 95% of the universe is made of invisible, unexplained stuff...
- db48x 8y agoDark matter and energy are irrelevant, no matter what percentage of the "stuff" in the universe are made of them. Greater than 99% of the things you or I experience from day to day are the result of the electromagnetic force. We experience gravity pulling us down all the time, but that's like one continuous note contained within a symphony. Some of our electricity is produced by nuclear power, but that's hard to pick out from anything else. A few people have lived through a nuclear explosion, which probably had a profound emotional impact on them. Perhaps you've seen the glowing, radioactive paint that they used to use on watch-hands to make them glow in the dark (probably from behind glass in a museum, if you have). But everything else, all of the things you can detect with your senses, comes from the interactions between electrons and photons. Dark matter doesn't interact with either electrons or photons, and neither does dark energy. So they're irrelevant; they can't be used to explain the behavior of the EMDrive, because the EMDrive is made of matter.
- gmueckl 8y agoThen you do not know and/or understand the huge body of work around these theories that support them. These are hard to understand for people not familiar with physics. But especially for GR there are experimental confirmations that are absolutely spectacular (Mercury's apsidal precession computed precisely, time delation by gravity measured by placing atomic clocks on mountaintops and airplanes, etc., observed gravitational waves, gravitational lensing...). And noone was so far able to create an experiment that managed to falsify that theory (it is a perfectly falsifiable theory), but not for lack of trying.
- nonbel 8y ago>"And noone was so far able to create an experiment that managed to falsify that theory (it is a perfectly falsifiable theory), but not for lack of trying." It was falsified by the aberrant rotation curves way back in the 1930s, the "dark matter" save was allowed for awhile but still no other evidence has been found for that. The only evidence is that GR predicts the wrong thing. It doesn't matter how many successes your theory has when we are talking about taking it as fact, only whether there is a single fail. Regarding your individual examples: >"Mercury's apsidal precession computed precisely" - GR was designed to fit this, which is great.. but doesn't count as a confirmation. >"time delation by gravity measured by placing atomic clocks on mountaintops and airplanes" - Looks like they had to modify the original predictions to fit the data, ie Einstein didn't anticipate accounting for the rotation of the earth: http://www.conspiracyoflight.com/Hafele/HafeleKeating.html http://www.conspiracyoflight.com/Hafele/HafeleKeating.html So, like the case of mercury's precession it is more a post-diction. > "observed gravitational waves" - There still hasn't been one independently verified, they need to detect a GW, calculate the coordinates, then tell other people where to find a GRB, kilonova, etc. So far this has not happened. >"gravitational lensing" - This idea predates GR: https://arxiv.org/abs/1206.1165 https://arxiv.org/abs/1206.1165. Also, don't the quantitative predictions here rely on the dark matter fudge factor?
- naasking 8y ago> Given that reactionless thrust is even less plausible on a theoretical basis than superluminal neutrinos, I really hope this doesn't come as much of a surprise to anyone. You can achieve what looks like reactionless thrust by swimming in spacetime, according to GR: http://science.sciencemag.org/content/299/5614/1865.full http://science.sciencemag.org/content/299/5614/1865.full So I think your statement is only true in the strictest sense using the words literally, but the spirit of the claim is actually false: theory actually predicts the existence of reactionless motion.
- smaddox 8y agoDon't have full text access right now, but do they assume a source of "negative mass"?
- naasking 8y agoCached version: http://webcache.googleusercontent.com/search?q=cache:vxJs6kCjpjcJ:web.mit.edu/wisdom/www/swimming.pdf+&cd=5&hl=en&ct=clnk&gl=ca http://webcache.googleusercontent.com/search?q=cache:vxJs6kC... No negative mass, translations can occur purely by mechanical deformations in a curved spacetime.
- smaddox 8y agoAhh. Looks like the affect is proportional to the spacetime curvature. So not particularly effective for interstellar travel. Also, you wouldn't be able to measure a thrust, because there would be none; there would only be translation. Very interesting, though.
- garmaine 8y agoNo one involved seriously thought it was reactionless. There were plenty of theories, such as a focused catalyst for dark matter decay, that would have made it perfectly compliant with Newton’s third law.