[HN Gopher] Latest EmDrive tests at Dresden University shows it ...
___________________________________________________________________
Latest EmDrive tests at Dresden University shows it does not
develop any thrust
Author : sohkamyung
Score : 485 points
Date : 2021-04-01 03:07 UTC (19 hours ago)
(HTM) web link (www.grenzwissenschaft-aktuell.de)
(TXT) w3m dump (www.grenzwissenschaft-aktuell.de)
| walrus01 wrote:
| Considering 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/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 wrote:
| Counterfactual: 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
| zackees wrote:
| This "test" and paper should be seen as possibly political.
| xupybd wrote:
| If 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 wrote:
| Depending 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 wrote:
| Imagine making popcorn in 5 seconds.
| moron4hire wrote:
| Imagine 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 wrote:
| What's the burned popcorn->migraine connection?
| rurban wrote:
| The outcome was known for 4 years already, but then he needed 4
| years to confirm the first results with fool proof
| measurements. Nobody else should need to wait years for test
| results, but the pressure and expected flashback was enourmous.
| cottsak wrote:
| Yeh this effort to confirm seems outrageous
| deepspace wrote:
| Well duh. Nobody who actually studied the original results with a
| critical eye is the least bit surprised. This crap is literally
| Cold Fusion V2.
| prof-dr-ir wrote:
| There 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?
| josu wrote:
| This analogy would have also worked for a quantum computer
| proposal at the beginning of the 20th century.
| moomin wrote:
| Not really, the objection would have been it was completely
| impractical, and it was (and borderline still is).
|
| When the facts change, opinions can change.
|
| The objection to the EmDrive is that is that it makes no
| sense, which is much less likely to change.
| agumonkey wrote:
| reminds me of the hyperloop bubble a bit
|
| also for all the knowledgeable people hurt by naive
| enthusiasm.. I guess a healthy dose of cynicism is to find a
| way to benefit from this and then reuse them for your better
| thought out projects
| gcatalfamo wrote:
| There is a blockchain-applied-to-anything-other-than-finance
| metaphor hidden in this truly sublime analogy.
| the-dude wrote:
| Have 'reverse car races' ever been a thing outside of NL?
|
| https://youtu.be/a59KyXhk74w?t=177
| vanderZwan wrote:
| I don't know, but that video obviously needs a bit of Yakety
| Sax:
|
| https://tubedubber.com/?q=a59KyXhk74w:MK6TXMsvgQg:0:100:174:.
| ..
| pulse7 wrote:
| Indian Man Drives Car Backwards On Busy Highways:
| https://www.youtube.com/watch?v=aox_4-JNed8
|
| => so it may be faster indeed... :-)
| jacquesm wrote:
| For a bit of context: a brand called DAF ("van Doornes
| Automobiel Fabriek") came up with a very clever drive system,
| called variomatic. It is still in use today under CVVT in
| Honda vehicles. DAF had an unfair reputation as a 'womans
| car' because you didn't have to shift gears at all, nor was
| there a finicky automatic gearbox to maintain, just two
| pulleys and a belt for each rear wheel. Which gave it insane
| acceleration as well because the torque convertor gave
| maximum torque at the lowest speeds ramping down the torque
| gradually and continuously as speed increased.
|
| One peculiar aspect of this drive system is that it allows
| your car to go as fast in reverse as it does forward! Of
| course the Dutch could not let this go without setting up a
| race around that theme, which was wildly popular in the past.
|
| Since dafjes have an 'unfair advantage' you also got a
| secondary class, with other car brands, this is a video of
| that race.
|
| Here are the DAFs:
|
| https://www.youtube.com/watch?v=zoh8i0jfpTo
|
| That video really hurts to look at by the way, the casual
| destruction of such a large number of what would be very
| special classics today is grating, especially that pretty 55
| coupe is one that I'd love to keep around.
| the-dude wrote:
| Creative destruction :-)
| jacquesm wrote:
| Fair enough, it is a bit creative, but only really the
| first time. They go for twice the original new price now!
| the-dude wrote:
| If it makes you feel any better : I have very fond
| memories of these shows ( I was very small still ).
| jacquesm wrote:
| My mom had the real thing :)
|
| She'd outpull Porsches just for fun...
| FrojoS wrote:
| Awesome if you like crashes :-D Starts at 35:10 min
| AnimalMuppet wrote:
| Actually, in the US, sometimes demolition derby cars run in
| reverse, because they get to protect the radiators that
| way.
| Seb-C wrote:
| Interesting analogy, but the pessimistic view does not bring
| any progress. The optimistic view may often be wrong, but when
| it is actually right, it makes our civilization progress.
|
| Not so long ago, the experts knew and said it was impossible to
| land and reuse a rocket.
| czzr wrote:
| Doubtful. Who ever said that about rockets?
| simonh wrote:
| There was huge skepticism in the industry that landing and
| re-using first stage boosters was viable. Tony Bruno of ULA
| in 1015, 7 months before SpaceX recoverd their first
| booster, on their plan to recover the engine module of
| Vulcan:
|
| "Our concept for reusability is inside that mathematics and
| realizes that maybe reusability does not start with entire
| stages,"
|
| It's not that they thought it was impossible to do at all,
| but they thought the weight requirement of fuel, landing
| legs, heat protection, etc would be so high that it would
| eat up too much of your payload capacity.
| qayxc wrote:
| Scepticism is way too often confused with negativity,
| pessimism or even outright hostility.
|
| It's also often overlooked that a solution might not be
| the best fit for everyone. Just like it's best for the
| Falcon 9 to discard the second stage.
| simonh wrote:
| Right, the reason ULA can't adapt Vulcan to land the
| first stage propulsively is it can't throttle down low
| enough. It's only barely possible with the F9, and that's
| because it uses a cluster of smaller engines and happens
| to have one in the middle.
|
| That wasn't a design choice driven by reusability,
| originally SpaceX were aiming to recover the stage using
| parachutes. The original plan was a falcon with a cluster
| of 5 engines in a ring. Using a cluster of smaller
| engines was for two reasons. First because they didn't
| have the resources to develop a new larger engine. Second
| they wanted to mass produce the engines to get production
| efficiencies and a bigger run of smaller engines worked
| better for that.
|
| It just worked out serendipitously that this lead to a
| design that was very well suited to adapting for
| propulsive landings. If they'd developed F5 first
| instead, they wouldn't have been able to land it because
| without a single centre engine they would need to use at
| least 2 engines to land, and the thrust would be way too
| high. Even with a design with a centre engine, the Merlin
| would be too powerful for the weight of an F5.
|
| This isn't a criticism, it's just the way things worked
| out.
| marton78 wrote:
| No. The optimistic view incurs opportunity cost: instead of
| attempting the impossible, something useful could have been
| done instead.
| qayxc wrote:
| I see one little caveat with this argument, though: is it
| always known in advance that something really is
| impossible?
|
| As long as there's enough resources to go around to pay 8
| figure meme-value dollar amounts for digital assets without
| intrinsic value, I think there's no harm in spending a
| fraction of that on possibly fruitless research.
| mrguyorama wrote:
| > 8 figure meme-value dollar amounts for digital assets
| without intrinsic value
|
| The problem is the people who do that are hell bent
| against letting the government tax them to fund such
| research, so our research resources are immensely more
| constrained than they could be.
| codeflo wrote:
| What you call the "pessimistic view" might be very
| enthusiastic about projects that are orders of magnitude more
| likely to work. So in my opinion, the relevant axis is not
| optimistic vs. pessimistic, but informed vs. uninformed.
|
| Can an outsider with no knowledge of the field make a chance
| discovery? It's theoretically possible, and we might want to
| support undirected experimentation for the one in a billion
| chance that something might work. But we should take those
| probabilities into account when allocating our collective
| resources.
| ClumsyPilot wrote:
| So tell me, how do we calculate probability for yet unknown
| phenomen? Which is more 'probable' to be correct - string
| theory or loop quantum gravity?
|
| If I want to investigate einstein rosen bridges, whats the
| probability I am wasting my time?
| Dylan16807 wrote:
| We had rockets that landed with Apollo. We had rockets that
| were reused with the shuttle.
|
| Who said it was impossible to combine them? And
| "impractically expensive and counterproductive" doesn't
| count.
| DarmokJalad1701 wrote:
| > We had rockets that landed with Apollo
|
| Correction: We had rockets that could land on the moon.
| There was no orbital-class rocket that could launch from
| Earth and land back at launch site (or further downrange).
| The difference in gravity + lack of atmosphere is a big
| factor.
|
| It is like saying that the Apollo ascent module could get
| to orbit and therefore we can clearly make practical SSTO
| vehicles.
|
| > We had rockets that were reused with the shuttle.
|
| If you consider throwing away the massive external tank and
| external SRBs (without which it couldn't fly) and
| completely re-building the three engines after every
| flight.
| Dylan16807 wrote:
| > It is like saying that the Apollo ascent module could
| get to orbit and therefore we can clearly make practical
| SSTO vehicles.
|
| If we didn't have to worry about fuel, we could. "put in
| enough fuel so it can land" is not a _hard_ problem to
| solve with earth rockets, it just costs payload.
|
| > completely re-building the three engines after every
| flight
|
| It's complicated but the level of rebuilding was driven
| more by very high standards than it actually being
| necessary to make it launchable.
| dmos62 wrote:
| That's an elaborate "I told you so"!
| nimbius wrote:
| hello, speaking as a diesel engine mechanic, this is exactly
| what modern emissions controls have sadly become.
|
| professional drivers (truckers) want to cut out all the
| emissions control systems because "older trucks get better
| mileage!" On the face of the issue this seeems to be true, but
| even after cutting everything out and switching back to low-
| grade diesel all you've done is create a smoke and soot
| belching mess from the 1960's. Why is this?
|
| Two reasons: older trucks got great mileage because there was
| less traffic congestion and fewer weigh station stops, and the
| national maximum speed limit law in 1973 made sure trucks drove
| a speed that got great mileage.
| marvin wrote:
| On the other hand, this is the sort of attitude that would make
| an informed skeptic reject the theoretical possibility for
| nuclear power, two weeks before the first nuclear bombs were
| used in war.
|
| It took a team of physicists four years to disprove this
| result. Did they do it just to prove a point, or because they
| didn't understand the car analogy? No, professional scientists
| are rarely that callous with their time.
|
| There was a slim possibility that our understanding of physics
| was wrong, and now we know for sure that _this_ was not an
| instance of that.
|
| But everything that's really interesting happens at the edges.
| No groundbreaking scientific result, ever, has happened by
| rejecting out of hand unlikely observations that violate
| established theory.
| lostcolony wrote:
| These weren't rejected out of hand - from the very first
| results there were ripe questions being asked (i.e., why did
| it take so long to measure thrust, and how were they
| controlling for thermal expansion, see even here on HN,
| quoted elsewhere in this thread -
| https://news.ycombinator.com/item?id=12962579 )
|
| You're absolutely correct that building better testing to
| disprove it completely is a good thing to do, just to remove
| the extreme unlikelihood that one of the most fundamental
| laws in thermodynamics are incorrect, but extreme skepticism
| is definitely warranted when the claim is so huge, and people
| are able to find realistic flaws (sufficiently realistic as
| to be proven to be correct) that would explain it entirely.
| marvin wrote:
| I'm not arguing against the points you are making, but they
| are subtly different from what OP implied. It's hard to
| make specific claims against a vague analogy that just
| seems to embody a mindset, but that's what I'm trying to
| do. And it's not a strawman even if it would happen to miss
| OP's intent; you see this mindset everywhere.
|
| My point was that OP _appears_ to would have rejected this
| hypothesis out of hand, and that this approach that would
| be wrong if everyone that matters did it. Obviously there
| were people who mattered who did _not_ , as the experiment
| demonstrates.
|
| A posteriori it's difficult to put numbers on it, but I'd
| say this experiment was worth doing even if your heuristics
| put it at a 0.1% chance of succeeding. Obviously that's not
| the case for Mad Morty's 1000th garage-built perpetual
| motion machine, but multiple physicists obviously evaluated
| this hypothesis as less shitty than that.
|
| All in all we would probably agree if we could just zero in
| on our key points, so I probably shouldn't have spent four
| paragraphs on this.
| saboot wrote:
| ? A nuclear power plant was built _before_ the bombs. It 's
| main purpose was to generate bomb material, but they
| definitely showed the principle worked and powered a
| lightbulb with it.
| kevinwang wrote:
| Not 2 weeks before, but the parent comment applies if you
| switch out "two weeks" with "a couple years", right?
|
| https://www.atomicarchive.com/history/manhattan-
| project/p1s2...
| marvin wrote:
| I was making a rhetorical point, but it works if you switch
| out 'theoretically' with 'actually', and 'two weeks before'
| with 'while the first nuclear reactor was supercritical in
| Chicago'.
|
| I'm pretty certain that the practicality of a nuclear chain
| reaction wasn't widely accepted in December of 1942, even
| though fission was first demonstrated by Meitner and Hahn
| three years before.
| RyEgswuCsn wrote:
| There is a difference here: cars are built by car mechanics;
| they know cars inside out --- cars are never designed to drive
| in reverse. Physicists, on the other hand, didn't invent
| physics, so they know their current understanding of physics
| could be wrong.
| gameswithgo wrote:
| This whole thing has been obviously dumb for a number of
| reasons not even related to physics. You could almost use it
| as a good litmus test for who should be running a company, or
| working at important positions in government.
| plutonorm wrote:
| This idea that we are so sure of everything is pervasive. The
| kind of people who like science are often the kind of people
| who crave certainty. And so for them science becomes like a
| religion, it provides them with a sense of certainty.
| Consistency. So when they rally against stories like this
| what they are really doing is reaffirming their own faith in
| an orderly universe, reaffirming their own faith in their
| scientific religion. It serves an emotional need. Which is
| why, paradoxically, their arguments are not alterable through
| logic.
|
| If you go read what the real experts in a field have to say
| about the state of knowledge, they are often incredibly
| humble. They state that there is so much that they do not
| know. That are so many things that could be wrong. That there
| are even bigger pictures just beyond their grasp.
|
| Now these reactionless thruster concepts don't look to be
| doing too well. But I for one am not particularly convinced
| that mach 's principle is so stupid.
| ska wrote:
| > This idea that we are so sure of everything is pervasive
|
| I think this is a common misconception made mostly by
| people who distrust science as a whole, but not really
| broadly held. I don't know anyone who understands an area
| of science at any depth who holds such a view.
|
| The really broad problem is that in science there are
| things we have very high confidence in, and there are
| things we have very little confidence in but are the best
| working models currently - and everything in between.
| However, communication about where the confidence lies is
| often poorly done. Many observers who mostly hear about
| things through the lay press have no good tools to
| differentiate between "some person with a Ph.D said Y once"
| and "the vast majority of experts in this field are
| confident that X".
|
| You are quite right that real experts have a healthy feel
| for what they don't know - and often humility - but those
| are often very different things from those that worry
| people outside the field. All of those same experts could
| happily give you a list of things they and their colleagues
| have very good confidence in. It's almost always the right
| thing to do to accept these and move on.
|
| On the flip side any scientist will tell you there is small
| but real value at the margins for someone plugging away at
| a "crazy" theory. They are almost always wrong, but
| occasionally it turns up something really interesting. The
| trick is not to involve more people or too much resources,
| as these are long bets that will mostly fail.
| supernovae wrote:
| The framing of "science becomes like a religion" is just
| projection, nothing else...
|
| For many of us, we just accept that science is, what it is,
| and its the facts we know at this time. That doesn't mean
| unwavering absolute faith as implied by saying it's
| religious, it's just we don't feel the need to have
| knowledge be anything else other than knowledge that we
| continuously build upon.
|
| Of course in general, lots of scientists know much more
| than other scientists and there is always bickering, people
| who have their identities married to it and so much more -
| but often times those very same people are often religious
| too so i question if the religiosity argument really exists
| or if its merely weaponized by people who fear the comfort
| of others who are ok with science without faith.
| plutonorm wrote:
| I'm an atheist. I also have a degree in comp sci a degree
| in Mathematics and a master's degree in mathematics. I
| read arxiv daily. I love science, I read constantly.
| Watching the cutting edge of science from afar is a
| passion of mine. I like to try to hold a holistic vision
| of it all in my head - an impossible task, but it keeps
| me busy.
|
| So, I'm not an enemy of science, I just dislike people
| harping on about 'impossible' from behind their keyboards
| when they have little more than a rudimentary knowledge
| of the subject at hand and too high an opinion of
| authority.
| knodi wrote:
| well everything is a people thing because we're people.
| What science offers is proof and data that can be
| reproduced. So no two scientists bickering is not the
| same as two theologian.
| twodave wrote:
| I appreciate the nuance here. As a person of faith one of
| the things I love most about both science and religion is
| the sheer amount of mystery there is in all of it. If
| there were no mystery in either, science would be dead
| and faith would be unnecessary. Yet science and religion
| pretend to be opposed.
|
| Throughout history the greatest clashes between faith and
| science have occurred when scientific understanding
| threatens the faith-based assumptions of the age. Imagine
| Abraham arguing with God over his request to sacrifice
| Isaac. Instead, he reasoned that God would find another
| way.
|
| Sometimes our understanding of religion limits our
| thinking with regard to not just science, but our faith
| as well.
| karmelapple wrote:
| > The kind of people who like science are often the kind of
| people who crave certainty.
|
| Just to clarify - are you implying scientists crave
| certainty, or non-scientists who enjoy reading about
| science crave certainty?
|
| The life scientists I know are the people in my life who
| are the most comfortable with uncertainty, or at least can
| recognize how uncertain the world can be. Perhaps they
| crave quantifying the uncertainty? But they certainly
| understand, respect, and live with uncertainty.
| jk7tarYZAQNpTQa wrote:
| > Just to clarify - are you implying scientists crave
| certainty, or non-scientists who enjoy reading about
| science crave certainty?
|
| Mostly the latter, but also the former to some degree.
| The scientists holding the status quo are often the most
| resistant to a paradigm shift.
| snowwrestler wrote:
| I took it to mean the fans of science who pile into
| forums like HN with expressive enthusiastic skepticism,
| the kind of people who think experimental physics is like
| working on a car.
| jacquesm wrote:
| This sort of argument is routinely used to dismiss the laws
| of thermodynamics as merely 'theories' and to then move on
| to the most outrageous violations of known physical law.
|
| We are pretty sure of what we are sure of and we are pretty
| sure of what we aren't sure of, impressions
| notwithstanding. Science is a method, not a set of facts,
| and it has a built in mechanism to allow greater insights
| to replace lesser ones. As long as we stick to science
| we'll one day find the limits of what is knowable.
| jchrisa wrote:
| There is a strong argument to be made that there is no
| scientific method:
| https://en.wikipedia.org/wiki/Epistemological_anarchism
| sixstringtheory wrote:
| Can't say I agree with the idea, but it's certainly
| interesting to consider and at the least should help
| strengthen or discard a few assumptions!
|
| I think he's conflating the process with all the other
| human factors involved. Sure, Galileo maybe did some
| shady stuff to convince people of his arguments. But that
| in no way makes a telescope stop working the way it does.
| marvin wrote:
| I don't think you and GP are in disagreement. The
| scientific method to let greater insights replace lesser
| ones is precisely to try and fail at falsifying
| observations that violate known physical laws.
|
| No physical law is holy for this purpose, although
| scientists will necessarily have heuristics for what
| presumed observations they consider good enough to
| examine closer. Evidently, the EmDrive observations made
| the threshold! And now we know for sure. Well, close
| enough, anyway.
| raverbashing wrote:
| > it has a built in mechanism to allow greater insights
| to replace lesser ones. As long as we stick to science
|
| Well you're not sticking to science when you assume any
| non-explained phenomenon is "impossible" and dismiss it
| outright.
|
| Science has a long list of "impossibles" that have been
| proven to be possible. Though of course that list was
| mostly of phenomenon we couldn't ignore.
|
| Saying "EMdrive is impossible given our current knowledge
| therefore it is not worth measuring" is tautological!
|
| Electricity and magnetism were seen as separate
| phenomenon as well and it seems a lot of people would be
| opposed to even try to put a compass next to a wire!
|
| The only thing I know is that the skeptics don't get the
| Nobel Prizes.
|
| Good, they measured, and as expected, no thrust. Cool.
| roywiggins wrote:
| Part of the problem is that it's much easier to come up
| with a new perpetual motion machine or reactionless drive
| concept than to prove that it doesn't work. After seeing
| them all fail, at a certain point people are going to
| stop paying them any attention. Oh, this time it uses _X_
| force in _Y_ configuration? Go away until you have data,
| we could be more profitably spending time on just about
| anything else.
| JackFr wrote:
| What makes this article so refreshing and so compelling
| is that they replicated the NASA results, and then
| explained and eliminated them. Another "We don't see
| anything and it's impossible anyway so you guys are
| idiots or charlatans" would not be helpful. This is.
| Brian_K_White wrote:
| Just because nothing is 100% knowable ultimately, doesn't
| mean all unknowns are equal.
|
| Everyone who doesn't want to invest 10000 human lives and
| a small countries total resources trying to find out if
| maybe oxidization isn't _really_ exothermic but just
| somehow always looks that way (is fire hot?), isn 't
| guilty of being incurious or religious.
|
| Come on now.
| Aeolun wrote:
| > As long as we stick to science we'll one day find the
| limits of what is knowable.
|
| I'm rather inclined to believe the opposite. That if we
| stick to science, we never will.
| jacquesm wrote:
| Feel free to go to aromatherapy, crystals, alchemy,
| astrology, free energy, ley lines, quackery and so on.
| I'll be on the other side of this debate and I'll stick
| to science. It has worked better than any other mechanism
| that we've thought of to-date to give us actionable
| insights as well as a ton of abstract knowledge.
| Aeolun wrote:
| Huh? I was more trying to imply that there are probably
| no limits to what is knowable. Or at least, if we stay
| scientific, we should never believe we've reached the
| limits.
| techdragon wrote:
| Thank you for more eloquently expressing a sentiment that I
| have harboured for some time. After quoting the relevant
| Cave Johnson quote from PORTAL 2 so many times... it
| clicked and I came to the realisation that there is only
| one way to "do science" you "throw it at the wall and see
| if it sticks".
|
| At a fundamental level, you must throw your results at the
| wall of publication and see if they stick, the only way
| science sticks is when it can be replicated by others. It
| remain on the wall!
|
| When people's refutation of things like the em-drive is
| simply "this can't work" my response is "prove it" not
| because I believe, but because "can't work" just isn't
| science, science is done by proving that something "does
| not work". That means for something like the em-Drive you
| prove it doesn't do what it claims, you prove it by
| replication and better measurement... and you learn how to
| build things better, learn how to measure better and that's
| the value of these efforts! Or you prove it by detailed non
| destructive analysis of the experiment apparatus and prove
| your work by detailed physical simulation, publishing your
| code to prove you didn't make any mistakes yourself! You
| cannot just give the answer you must show your work if you
| expect to go around calling what you do "science".
| Providing such proof is not a waste, or bad science, it is
| the very essence of science itself.
| jacquesm wrote:
| You are missing a very important part of how science is
| done: science starts with a hypothesis, the refutation or
| confirmation of that hypothesis is done by experiment.
| Plenty of science has been locked into the theoretical
| phase for decades before experimental verification could
| be obtained.
|
| If all we did was experiments we'd surely find some
| interesting stuff but without theory to guide where to do
| the next set of experiments science would be very
| inefficient. It's the closing of the loop that powers
| this tremendous progress you see from the renaissance to
| today.
|
| Without that we'd be stuck in alchemy, astrology and
| other pseudo sciences.
| adwn wrote:
| > _science starts with a hypothesis_
|
| No, science starts with an observation which is not
| explained by the prevailing theory. _Then_ you form a
| hypothesis, etc.
|
| At least in principle. The reality of science is a lot
| messier.
| MereInterest wrote:
| I think there's one more step that goes a bit earlier in
| the process. Before an observation is made, there needs
| to be a choice on what experiments are done. Typically,
| those measurements will be done with one of two goals.
| The first is to measure a free parameter in the theory
| that isn't well-constrained by existing experiments.
| (e.g. "According to Maxwell's equations, the speed of
| light should be constant. Let's measure that constant
| value." [0]) The second is to find an unintuitive
| prediction from current models, then measure what happens
| in those circumstances. (e.g. "According to special
| relativity, passage of time should vary based on
| velocity. That's weird. Let's measure and see if it is
| the case." [1])
|
| The purpose of these is to narrow down which experiments
| are being performed, trying to choose experiments that
| will try their hardest to break an existing theory.
|
| [0] https://en.wikipedia.org/wiki/Speed_of_light#Time_of_
| flight_...
|
| [1] https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_
| experim... (This article currently has an incorrect edit
| made yesterday. It seems to be based on a mistaken
| assumption that the rotating earth is a stationary
| reference frame. The opening paragraph should read "were
| consistent" rather than "were not consistent".)
| jacquesm wrote:
| So much for theoretical physics then. Or Einstein's
| 'gedanken experimenten'.
| electrograv wrote:
| Science must find a balance between extremes in how
| experimental resources are invested:
|
| Extreme "Exploitation" Bias: _"For maximally economical
| progress, experimental physics must strictly stay within
| the hard boundaries established by theoretical
| frameworks."_
|
| Extreme "Exploration" Bias: _"For maximally fundamental
| progress, experimental physics must question all
| theoretical assumptions and boundaries with extreme
| suspicion."_
|
| It makes sense to diversify the kind of experimental
| investments we make along this risk/reward or
| exploration/exploitation spectrum. There are unique
| dangers if we weight too heavily on either extreme.
| Certhas wrote:
| > If you go read what the real experts in a field have to
| say...
|
| If you go to read what the real experts in the field have
| to say then you would learn that not a single one of them
| thought that the EM Drive had even the slightest chance of
| being true.
|
| In fact all the publications and work on EM Drive strictly
| avoided the real experts (physicists). They were all
| engineering journals. A paper that claims experimental
| evidence that overturns all physical theories from Newton
| onwards that's very telling isn't it?
| kosievdmerwe wrote:
| Scientism. The deification of scientists and our current
| models.
|
| Which is ironic as we know our models are wrong somehow as
| we can't mesh Quantum mechanics and general relativity.
| There is clearly some undiscovered idea or principal.
|
| Science is about the process not about the body of
| knowledge we amassed. Science is about doing experiments to
| poke at the gaps of our knowledge. Not to like the Ancient
| Greeks debate our way to truth or worse declare something
| false based clearly on our flawed understanding.
| supernovae wrote:
| Do you really believe this?
|
| Celebrity scientists aren't deified... in fact, they have
| a tough life because people assume they're all knowing.
| Look at our man Neil DeGrasse who called a Bull a Cow
| because where he lives in NYC everything is a cow and he
| got ripped by other scientists for being stupid.
|
| There is no universality to people period... i'm not sure
| why you feel its important to label some as "scientism"
| when there is no such thing as "scientism" with any
| universality.
| kosievdmerwe wrote:
| Scientists aren't deified because people assume they're
| all knowing?
|
| As for scientism, there's a lot of people in this thread
| who essentially said "We could have known it wouldn't
| work by basic application of conservation of momentum".
| Or some other principal held to the standard of absolute
| truth.
|
| Our knowledge of the world is faulty and incomplete. All
| scientific knowledge is subject to tweaking or
| replacement based on experimental evidence. Not the other
| way around.
|
| We have models and guesses of how the world works, we
| don't have its source code.
| andi999 wrote:
| Actually the whole point why this EM drive is interesting
| actually is that the measurements contradicted
| conservation of momentum. Otherwise having a small effect
| not contradicting any established physics is basically
| worthless.
| kosievdmerwe wrote:
| Sure, but if the contradiction bore out, then what's
| false (at least in some edge cases) is established
| physics not the experiment result.
|
| The strength of the established physics just means that
| there is an extremely high chance that the EM drive is
| experimental error, especially with the small effect
| size, rather than something novel.
| arbitrage wrote:
| > cars are never designed to drive in reverse.
|
| that's just plain wrong, friend.
| pif wrote:
| > they know their current understanding of physics could be
| wrong.
|
| Sure, we do know!
|
| And we know how to recognise when someone masters current
| literature (a.k.a. factual knowledge) and proposes a
| breaktrough in a yet uncovered field, and when someone is
| speaking out of his ... nothing!
|
| If you prefer a non-car analogy: we all do _know_ that a
| hundred consecutive heads is possible, still you are not
| going to bet your week pay on it, even if you were promised
| 2^100 weeks of pay in return.
| galangalalgol wrote:
| There are plenty of cases where someone who doesn't
| understand the underlying theory has contributed due to the
| outsider effect or just pure luck. The hype, and the
| swindling are not ok, but when an organization like NASA
| thinks they maybe successfully reproduced an experiment
| that invalidates a law of nature you have to keep trying.
| Sure I'm hoping for new science, always, because that is
| more fun, but mostly you need to know for sure what the
| experimental error was so that you don't repeat it in an
| experiment whose result you aren't as skeptical of.
| arbitrage wrote:
| > There are plenty of cases where someone who doesn't
| understand the underlying theory has contributed due to
| the outsider effect or just pure luck
|
| Are you talking about anyone who was born in the last 100
| years?
| dotancohen wrote:
| Lemaitre?
| tobmlt wrote:
| A low number of dollars spent to put to bed an idea that
| would have upended physics is a fairly cost effective
| play in the risk to reward game. That's what it comes
| down too.
|
| Negative results are good. Utter quackery is not good.
| But hard data from experiment is usually not quackery.
| Even if the whole thing stands outside the established
| paradigm. I'd argue we could stand a bit more of it, in
| this age of funding bandwagons and careerism.
| thenewwazoo wrote:
| > Utter quackery is not good.
|
| That's the OP's point. The EmDrive is utter quackery. It
| _cannot_ exist because it _necessarily_ violates the laws
| of thermodynamics. Anything that disproves those will
| literally undermine the _entire_ foundation of what we
| understand about the universe. It would be directly
| comparable to discovering that the earth is flat.
| tobmlt wrote:
| What an exciting time we live in, where links between
| quantum mechanics, thermodynamics, and GR May finally be
| emerging in physics! What will the final ramifications
| be? Hopefully something new comes of it. If there are
| cases where conservation laws break down, or physical
| principles constrain one another in unforeseen ways, and
| they can be accessed at human scale, what an exciting
| thing! I'd guess you mostly feel this way too if I have
| not yet imposed any quackery on you, and suppose where we
| diverge is I do not see the harm in exploration as far
| out as the experimenter can dream to go. --Even if there
| is no theory for it. I know, the horror! Do I think it
| will work? Well heck no. But that does not mean I wish
| the attempt to be quashed like I'm the inquisition. On
| the contrary, I bid them good luck. And if they do have
| good luck, they better have some results that are easily
| duplicated. I hope they do overthrow the foundations of
| physics. Why not? The earth will still possess curvature,
| and all the extant physics will still be as approximately
| right, and beautiful, as it was yesterday.
| nwallin wrote:
| We already know the laws of thermodynamics has
| exceptions. In very small systems, the entropy of a
| system fluctuates randomly - up _and_ down. A light ray
| traveling over extremely long distances will have its
| energy reduced through red shifting, and that energy
| doesn 't "go" anywhere, it is destroyed. In both of these
| regimes, over extremely small scales and extremely large
| scales, there are exceptions carved out of the laws of
| thermodynamics.
|
| We know for certain that our understanding of physics is
| incomplete. General relativity (as formulated) is
| certainly wrong, because it precludes the possibility of
| small things existing; and yet they do. Quantum mechanics
| (as formulated) is certainly wrong, because it precludes
| the possibility of curved spacetime, and yet we know
| spacetime is curved.
|
| There is, of course, a minuscule possibility that the
| emdrive actually works. It almost certainly doesn't.
| Ballpark one in a thousand. But we can't exclude the
| possibility that it works, based on the principle that
| the the laws of thermodynamics, which already has two
| exceptions, cannot have a third exception.
|
| There's big talk about humanity traveling to other stars,
| colonizing other star systems, colonizing the galaxy and
| so forth. For this to happen, we would have to be wrong
| about physics. There's simply not any way to do it by
| building on the foundation of what we understand about
| the universe. So investing in low probability speculative
| ideas like emdrive is still necessary, even though for
| any given idea, there are lots of nines that say it won't
| work.
| ChrisLomont wrote:
| >the laws of thermodynamics has exceptions
|
| No, they don't. The "laws" you learn in high school are
| large scale approximations to the actual rules, which is
| codified in stat mech.
|
| It's like claiming solids are not solid because atoms...
| Of course physicists know all this.
|
| >General relativity (as formulated) is certainly wrong,
| because it precludes the possibility of small things
| existing
|
| Having worked on GR stuff for a long time, this is news.
| GR most certainly allows any size thing to exist - it's a
| continuous theory.
|
| >Quantum mechanics (as formulated) is certainly wrong,
| because it precludes the possibility of curved spacetime
|
| No, it does not. QM in curved spacetime is so old and
| well understood it has a Wikipedia page [1] - from which
| you can start digging back into the literature.
|
| You should really google such claims when making them to
| be sure you understand what you're claiming.
|
| [1] https://en.wikipedia.org/wiki/Quantum_field_theory_in
| _curved...
| galangalalgol wrote:
| The guy had an experiment, his explanation for the
| results were utter quackery. I don't think the people at
| NASA expected his explanation was the right one, but they
| didn't have one so they replicated. MIT had an
| explanation of the results that was not due to thermal
| effects, and wasn't the originator's explanation. It
| didn't upend thermodynamics. The problem wasn't people
| exploring a tricky experiment, it was people buying in to
| a specific explanation of the experiment prematurely.
| [deleted]
| sidlls wrote:
| Can you name some of those cases?
| ChrisLomont wrote:
| >There are plenty of cases where someone who doesn't
| understand the underlying theory has contributed due to
| the outsider effect or just pure luck.
|
| There are far more such cases where the outsider was
| wrong, so many more of these, that using the extremely
| rare event to claim this may be one is simply terrible
| reasoning. It is far more likely that this is yet another
| crackpot pushing nonsense.
|
| No outside has found a breakthrough that for decades (the
| length the EmDrive people have been making noise) was
| discarded. In fact, when an outsider finds something
| useful or novel, for a long time now the science
| community nearly immediately understands and embraces it.
|
| This is the opposite of that.
| RyEgswuCsn wrote:
| > we all do know that a hundred consecutive heads is
| possible, still you are not going to bet your week pay on
| it, even if you were promised 2^100 weeks of pay in return
|
| The expected reward is just one-week's pay --- you have to
| offer better than that with all the uncertainty ;)
|
| What if the reward is potentially infinite amount of money?
| If the investigation proved our current understanding of
| physics wrong, that could lead to historic breakthroughs in
| natural science.
|
| Better yet, we don't know what the odd is. It might only
| need 32 consecutive heads.
| rini17 wrote:
| I'd be very curious how it's possible to have 2^100 of
| anything :)
| pif wrote:
| Oh, it's just 1024^10, a bit more than 10^30, or 10
| million moles.
|
| A water molecule contains 18 nucleons, thus a mole of
| water weighs 18 grams. 10 million moles of water are 180
| cubic metres: an Olympic pools contains an order of
| magnitude more moles than that! ;-)
|
| Sure, I hope nobody is paid so poorly that 2^100 times
| its week salary exists!
| mannerheim wrote:
| There are certainly people who aren't paid anything.
| shawnz wrote:
| The design of a car is obviously limited by fundamental
| aspects of physics which are outside of the control of car
| manufacturers. For example, car manufacturers didn't invent
| combustion, aerodynamics, etc.
| Certhas wrote:
| I agree that on this point the analogy is weak. But it
| describes the ignorance of all those hyping it up well.
|
| People are generally aware that if someone is presenting a
| perpetuum mobile they are wrong. Free energy doesn't exist.
| The fact that you can't have free momentum is just as strong
| (and has been known longer), yet less widely intuited.
|
| Let me give you an analogy though:
|
| Let's say someone proposes a water base perpetuum mobile like
| this:
|
| https://en.wikipedia.org/wiki/Perpetual_motion#/media/File:W.
| ..
|
| It only works if you place the machine under a massive
| waterfall though. Now this would be very difficult to refute
| experimentally, because you have to account for all possible
| interactions in the waterfall.
|
| That's what the EM Drive is. A perpetuual motion machine
| built in such a way that there's a lot of energy going around
| and it's hard to eliminate all spurious interactions.
| zackees wrote:
| "The Taylor drive is not in a cavity so of course it has zero
| thrust!"
|
| From one of the scientists working in the field. Who doesn't
| want to be named because that's the state of the world today.
| ChrisLomont wrote:
| > Physicists, on the other hand, didn't invent physics, so
| they know their current understanding of physics could be
| wrong.
|
| They also know they have experimented _extensively_ over the
| region this effect claims to exist, and have found nothing of
| the kind for well over a century, and that if the EmDrive did
| what some claimed, it would violate literally thousands to
| millions of experiments already conducted.
|
| Claiming physicists don't know everything about possible
| physics does not imply they don't know a tremendous amount
| about the places they have extensive experimental and
| theoretical agreement. Those places are not likely to ever
| change.
| ModernMech wrote:
| It's tough to know absolutely everything about a complex
| dynamic system, even if it's built by humans. Take the
| economy, for instance. Invented by humans, made up of humans
| and human technologies and concepts, and yet people only have
| vague ideas about how to control it.
|
| Or take computers for that matter. People designed and built
| them from scratch. Someone had to design and lay out the
| transistors on the CPU, and presumably they know everything
| about how to do that. And yet we are currently trying to
| figure whether there's an ordering to switching the
| transistors on and off that would imbue the CPU with human-
| level intelligence. There are plenty of people who know
| computers inside and out, yet there are still questions that
| need answers. We have a whole discipline called Computer
| Science that performs experiments on computers for the
| purpose of answering these questions.
| arethuza wrote:
| I really don't think cars are designed by the same people who
| end up fixing them - ease of repair really doesn't seem to be
| a big factor in lots of designs.
| bluGill wrote:
| Ease of repair is a factor, but there are other factors.
| Safety and Fuel Economy (Aerodynamics and mass) are more
| important than ease of repair so many things to make it
| easy to repair just get tossed out.
| sandworm101 wrote:
| Ease of repair has largely been replaced by lack of need of
| repair. Cars, especially IC engines, are so much more
| reliable today that repair is relatively rare. Engine
| rebuilds are almost unheard of on small cars. Transmissions
| regularly outlast the chasis. Even tires rarely get flats.
| People now expect to drive many tens or even a hundred
| thousand miles without engine failure, on no more
| maintenance than an occasional oil change.
| kungito wrote:
| But 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 wrote:
| It only happens in periodic dramas made for 15-year olds
| Chris2048 wrote:
| > Now suppose you are a car mechanic in all this .. the
| disadvantages in air flow
|
| Not sure a mechanic is better than anyone with understanding of
| car dynamics, but the "air flow" argument is the key to this.
|
| Who are the experts on emDrive tech, and what principle does
| the emDrive violate? If you can't say, then you _are_ indeed a
| pessimist.
| prof-dr-ir wrote:
| > the "air flow" argument is the key to this.
|
| I would point out that cars have gears, but then someone
| would say that in the US they do not, and I would have to
| explain that that is not the case, actually, and it would all
| get very tiring very quickly.
|
| > Who are the experts on emDrive tech, and what principle
| does the emDrive violate?
|
| A physicist would point out that momentum is conserved, so
| nothing can start moving without something else moving in the
| opposite direction, but then someone would point out that
| cars seem to be able to do just that, and then I would point
| out this big round thing underneath a car, and it would all
| get very tiring very quickly.
| Chris2048 wrote:
| > I would point out that cars have gears
|
| How does that relate to airflow?
| j4yav wrote:
| It doesn't have anything to do with airflow but does with
| whether or not cars are faster in reverse.
| Chris2048 wrote:
| But it's a response to me pointing out air-flow is
| relevant (key).
| j4yav wrote:
| He is saying that air flow is not more important than
| gearing, but if he were to raise it he'd end up in a
| never ending series of replies debating the details but
| missing the point.
| Chris2048 wrote:
| Sure, but I don't agree gearing is in the same category
| of the specific thing I mentioned. Would he also end up
| in a never-ending series of replies wrt airflow too? If
| not, it has nothing to do with my point, if so why change
| the topic..
| pif wrote:
| Literally in the first paragraph on Wikipedia:
|
| It is purported to generate thrust by reflecting microwaves
| internally in the device, in violation of the law of
| conservation of momentum and other laws of physics.
|
| https://en.wikipedia.org/wiki/EmDrive
|
| Extraordinary evidence is required for extraordinary claims.
| Any hint of evidence at all is required for idiot claims
| before waisting people's time.
| Certhas wrote:
| This seems a lost battle. Every EM Drive discussion I have seen
| has been dominated by non-scientists pontificating about how we
| don't know anything, and our theories might be wrong, and we
| should keep an open mind ...
| foreigner wrote:
| What you do is short them on the stock market. Put your money
| where your mouth is!
| bjoernbu wrote:
| How exactly could this be done reliably? With shorts you have
| to commit to a timeframe for not only finding evidence to
| reject the claim but also for the news to break and convince
| other investors.
|
| Meanwhile you can be targetted by financial actors that play
| your positions on the stock market, at times even
| disregarding the atual company behind it. Further you have to
| mind monetary policy. If faith in the stock suffers compared
| to other stock but the overall market just goes up and up,
| your shorts have a problem again.
|
| Personally, I have no informed opinion on EmDrive, but I have
| been very pesimistic about companies in the past and I am
| about some right now. Still, I do not think that shorts are
| anything appropirate for me. I'd much rather buy
| competitior's stock than burn myself with shorts or waste
| hundreds of hours getting into the financial market that I
| could also use to create value in my actual job/profession
| moonbug wrote:
| ala, he'd rather put is mouth where our eyeballs are.
| sideshowb wrote:
| An irrational market can stay irrational for longer than you
| can stay solvent
| Radim wrote:
| How would that work, in the analogy?
|
| Short the individual researchers? Research projects? Short
| private funding?
|
| Scams like EmDrive (but there are countless others - "save
| the planet with X") may be amusing, as long as it's on
| someone else's dime. Live and let live.
|
| But the minute they manage to convince enough people, whether
| by virtue or shady marketing, it becomes a political problem.
| And then it's your problem too, through taxation and "too big
| to fail", no matter your position. _Shorting on the stock
| market_ gets you only so far, and only for entities that
| actually exist on the stock market.
| pjc50 wrote:
| The stock market currently thinks Gamestop is the most
| revolutionary company in the world.
| andlier wrote:
| This reminded me of the extended range with reversed ski box
| for tesla. https://electrek.co/2020/03/24/tesla-model-3-roof-
| rack-box-r...
| electrograv wrote:
| Ironically, this serves as an excellent refutation of the
| above analogy's goal (to scoff at EMDrive experiments):
|
| * Imagine telling a mechanic that mounting a ski box on your
| car with the fat/blunt end pointed forward seems to improve
| fuel economy vs being mounted the other way.
|
| * The mechanic believes it's absurd to claim you can improve
| fuel economy from a change that _increases wind drag_ , so
| therefore your experiment is wrong since it seems to
| contradict established theory -- case closed.
|
| * Imagine that you more carefully measure, and find that it
| still seems to work surprisingly well (though also
| mysteriously reducing braking and cornering performance)!
|
| * The mechanic still denies the result (which is unfair), and
| questions your test methodology and demands replications of
| the experiment (which is fair).
|
| * Imagine someone else tries to replicate the experiment with
| a differently shaped ski box (i.e. not an airfoil, or with
| the airfoil shape vertically inverted), and fails to
| reproduce your results.
|
| * The mechanic community concludes that the original result
| was obviously just experimental error, since the latter
| failure to replicate aligns with current theoretical
| consensus of what _should_ happen.
|
| In a similar way, early pioneers experimenting with winged
| aircraft design were laughed/scoffed at endlessly by
| established scientists/engineers of the era, ridiculed and
| crackpots wasting valuable time and resources.
|
| The aerodynamics of the airfoil (which also explains the
| above ski box phenomenon) is an extremely non-obvious
| emergent effect, and even to this day is not as fully
| understood as most people probably assume.
| bena wrote:
| It was an aerodynamics engineer who suggested flipping the
| box around.
| Aeolun wrote:
| I have zero doubt that this whole thing could have been applied
| to the first airplane, or to a thousand other firsts.
| HPsquared wrote:
| Re the airflow point, many cars are indeed MORE aerodynamic
| than normal in reverse, particularly hatchbacks.
|
| It's best to have a smooth, progressive tail to minimise flow
| separation at the rear of the car (think of an airfoil shape -
| quite blunt at the front, thin at the back).
|
| Hatchbacks often have very flat rear ends compared to the front
| which usually has a more progressive slope. A famous example is
| the Austin Allegro, but it's actually quite common.
| staticassertion wrote:
| All the time on HN I read posts saying how we should celebrate
| negative results. Here we have a negative result.
|
| Why not celebrate it?
| prof-dr-ir wrote:
| Claim: banging your head against the wall makes you smarter.
|
| Experimenters: that sounds amazing! So we tried. We can
| report that all test subjects reported a massive headache.
| Unfortunately none seemed to get significantly smarter.
|
| You: a negative result, well done! Time to celebrate!
|
| And now I hope you will accept my apologies for exaggerating
| to the point of being rude, all in reply to your entirely
| reasonable question.
|
| I guess my point is this. There has to be a cutoff where a
| claim is too obviously incorrect and testing is simply not
| useful any more. But the natural cutoff point depends
| enormously on perspective. Are you a car mechanic, a rally
| driver, or a complete layman? And as the latter, who do you
| trust?
|
| My original comment was written to highlight the frustrating
| perspective of the car mechanic. But an interested layperson
| (or a non-expert handing out grant money) might have the more
| difficult time.
| dotancohen wrote:
| > I guess my point is this. There has to be a cutoff
| > where a claim is too obviously incorrect and testing
| > is simply not useful any more.
|
| Such as claims of giant lizards ruling the Earth, or claims
| that all matter (and time!) was once a singularity, or
| claims that man had descended from - get this - apes?
| prof-dr-ir wrote:
| Emphatically not. There is an important difference
| between 'outlandish' and 'in flagrant contradiction with
| billions of experimental results [0]'.
|
| I am not saying that the difference is always easy to
| spot, but I think that you cannot deny that it exists.
|
| [0] For a crude estimate, see 'number of collisions per
| second' at https://home.cern/resources/faqs/facts-and-
| figures-about-lhc . And those people are looking _really
| hard_ for possible violations of the law of conservation
| of momentum: in this context it is called 'missing
| transverse energy' and it is a key method in the search
| for new physics.
| microtherion wrote:
| But it seems to me that in the earlier EmDrive experiments,
| there were forces found that were not explained
| satisfactorily. Now, through better experimental controls,
| all of these have been accounted for. That sounds like
| valuable research to me.
| mLuby wrote:
| Good point. It should both make future experiments more
| accurate and also debunk similar claims more easily.
|
| Science isn't a bunch of scientists saying "we doubt
| it'll work"--science is a bunch of scientists
| experimentally _proving_ it doesn 't work.
|
| The people funding the scientists decide what's worth
| testing. In this case, the possible benefit _vastly_
| outweighed the cost of testing.
|
| To fix the head-to-wall metaphor: in some experiments,
| subjects who banged their heads against the wall reported
| being cured of all mental illness. However more rigorous
| tests showed this remarkable effect was actually a
| placebo caused by the subjects believing they were
| involved in making history.
| [deleted]
| junon wrote:
| Kudos 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.
| binarycoffee wrote:
| Just 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
|
| But then, nobody had Tajmar's perseverance; kudos to his team!
| unityByFreedom wrote:
| Lol 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 wrote:
| Day made. Good chuckle that.
| IshKebab wrote:
| I 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...".
| Sebb767 wrote:
| Sorry if this is a stupid question, but what is thermal drift
| in this context?
| binarycoffee wrote:
| Not a stupid question -- sorry for the jargon.
|
| It is what is mentioned in this fragment of the article:
|
| "When power flows into the EmDrive, the engine warms up. This
| also causes the fastening elements on the scale to warp,
| causing the scale to move to a new zero point"
|
| Basically, thermal expansion of the thruster and the
| measurement device causes the rest position of the thrust
| balance to drift with time, which is hard to differentiate
| from the actual thrust generated. This is most critical when
| the thrust-to-weight ratio is low, as is the case here.
| fnord77 wrote:
| what are the inventor's credentials? I searched and searched and
| could only find vague descriptions like "scientist"
| bitcharmer wrote:
| Why 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 wrote:
| I 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.
| Andrew_nenakhov wrote:
| Ah, those April 1 jokes. Don't fall for them. Of course it did
| develop trust. It is the future of space propulsion.
| qayxc wrote:
| Too bad the article dates two weeks back :D
| rurban wrote:
| Oh, 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 wrote:
| Shhh, stop ruining _my_ joke!
| Chris2048 wrote:
| What is the likelihood that these drives _do_ work and the team
| just want a head start on development?
| 127 wrote:
| What is the likelihood that I win the lottery every week for
| a year straight?
| Chris2048 wrote:
| How is that relevant?
| krageon wrote:
| Both of those hypotheticals don't really make sense.
| Chris2048 wrote:
| Why? Are incentives not a thing?
| majewsky wrote:
| University professors are almost never the ones making the
| big money from a new discovery, so it wouldn't make sense for
| this guy to put his reputation on the line for a few bucks.
| vlovich123 wrote:
| For 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.
| spaetzleesser wrote:
| So far I think it has been handled well. Let's just hope this
| doesn't end up like cold fusion where no amount of proof that
| it doesn't work can't make it go away and conspiracy theories
| keep growing.
| plutonorm wrote:
| Yeah 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 wrote:
| These 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 wrote:
| Or 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!
| tlibert wrote:
| Yeah, those morons at NASA'S Advanced Propulsion Physics
| Laboratory sure have no idea what is a good use of their
| time.
| selimthegrim wrote:
| This fellow (Eagleworks guy) was told in no uncertain
| terms by his PhD thesis committee at Rice that this was a
| bad idea and forced to rewrite his thesis. He clearly
| doesn't know when to take a hint.
| anthony_r wrote:
| Yes there are commonly clever people that know how to
| play organizational ladders with minimum amount of work
| in every sufficiently large organization. Also a fair
| amount of "morons".
| tlibert wrote:
| Arthur C Clark has addressed this general point in his
| first law:
|
| " When a distinguished but elderly scientist states that
| something is possible, he is almost certainly right. When
| he states that something is impossible, he is very
| probably wrong."
| shoefindortz wrote:
| This 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.
| anthony_r wrote:
| This is like with being a teenager - you simply don't
| realize just how dumb you sound.
|
| https://en.wikipedia.org/wiki/Newton%27s_laws_of_motion#I
| mpo...
|
| It is fascinating how such "fake news" grabs people
| attention, for extended periods of time. Fake news can
| last forever :)
| plutonorm wrote:
| I have MSc in mathematics, I can follow the idea of
| conservation of momentum. I just know a little more than
| you and understand that things are not so simple.
| c1ccccc1 wrote:
| "Velocities add" is also mechanics 101, and turned out to
| be incorrect at sufficiently large speeds. I think we have
| to go to Noether's theorem to show why we should be so sure
| the EM drive doesn't work: EM drive proponents must either
| tell us where the momentum goes, or explain why space isn't
| symmetric under translation.
|
| (Actually, fun side note, in a gravitational field, space
| isn't symmetric under translation. IIRC, this was the
| original problem that caused Noether to prove her famous
| theorem. She found that while there was still a conserved
| quantity of a sort due to "translations" in space and time,
| it wasn't just the energy-momentum tensor, but also
| depended on the gravitational field. In any case, the EM
| drive is supposed to work in flat space, so that shouldn't
| become an issue.)
| [deleted]
| tunesmith wrote:
| This is like rationalism vs empiricism. It's nice when the
| empirical results align with the rational conclusion again.
| dleslie wrote:
| I 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 wrote:
| I 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 wrote:
| > 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 wrote:
| I'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 wrote:
| > 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.
| garmaine wrote:
| > 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
|
| Physicist here: that's not how physics works, at all. We
| don't even pretend to have a "true" (complete?) model of
| reality at all. There are many gaps in our knowledge.
| Unfortunately they are either so small, so large, or so high
| energy that we can't easily expand across those limits to our
| knowledge using data gathered from labs here on Earth. But
| every now and then you get a really simple test that
| demonstrates a gap in our knowledge that reveals new physics,
| and that's how we make advances.
|
| If the Em drive were real, it would be just like the
| photoelectric effect or quantum-slit interference patterns:
| things which defy classical explanations but which are
| evidently quite real. And I assure you, those were NOT
| disappointments. Far from it--every physicist dreams of
| discovering such an experiment, and it would certainly win
| the Nobel prize.
| arethuza wrote:
| _" The most exciting phrase to hear in science, the one
| that heralds new discoveries, is not 'Eureka' but 'That's
| funny...'"_
|
| Isaac Asimov
| moring wrote:
| > The difference between Newtonian physics and Special
| Relativity is not so much as to shake basic scientific
| principles to their core.
|
| Special relativity says that the temporal order in which
| events happen can ( _) depend on the frame of reference of
| the viewer, and thus, such events do not have any objective
| order in which they occur.
|
| (_) that is, if their relative "time-position" is spacelike,
| or in other words, if light is "too slow" to travel from one
| event occurring to the other event occuring.
|
| To add on top of this, it says that if faster-than-light
| particles exist, a chain of FoRs can be constructed such that
| an event happens before itself.
|
| If that isn't shaking basic principles, I don't know what is.
| ganafagol wrote:
| > [...] is like saying that we're making up physical laws as
| we go along.
|
| Um .. what's your alternative description on how scientific
| knowledge comes about?
| [deleted]
| adwn wrote:
| > _The difference between Newtonian physics and Special
| Relativity is not so much as to shake basic scientific
| principles to their core._
|
| But it is! Before special relativity, _conservation of mass_
| was thought to be a law of physics; SR refined this law to
| _conservation of mass-energy_.
| at_a_remove wrote:
| But "refinement" is the correct word to use.
|
| In the vast majority of scenarios, you can keep your
| conservation of mass separate from your conservation of
| energy. You only have to pay attention in very specific
| cases: fusion, fission, and relative velocities that are
| quite intense.
|
| This refinement, which we see again and again in physics,
| is "oh, sure, if you do THIS, here's a correction you can
| apply ... should start showing up three or four sigfigs
| in."
| kelnos wrote:
| I think the difference here is that conservation of mass
| was an _incomplete_ understanding of what was going on, and
| conservation of mass-energy was an evolution of the law.
|
| If the EmDrive worked, it would mean that several
| foundational things are just wrong. Not incomplete, just
| completely wrong.
| AnimalMuppet wrote:
| Newtonian momentum is not conserved in Special Relativity.
| That is, momentum is conserved, but momentum is redefined -
| it's not just mass times velocity any longer. The new
| definition is more correct than the previous one.
|
| Had this worked, it probably wouldn't have overturned
| conservation of momentum either. It might have redefined
| momentum again, though.
| tomrod wrote:
| To the dustbin!
|
| I had hope for the promise of the drive, but such as it
| is.science proceeded and now we know more.
| dudeinjapan wrote:
| That's what she said
| codethief wrote:
| I 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)
|
| > Lorincz, 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/f...
| snarfy wrote:
| He'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 wrote:
| > 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 wrote:
| My 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 wrote:
| If 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-qu...
| dkbrk wrote:
| This 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
|
| [1]:
| https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_...
|
| [2]: https://medium.com/predict/james-woodward-on-machs-
| principle...
| codethief wrote:
| I 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...
| codethief wrote:
| Addendum: I just noticed that the EmDrive article has
| something to say about the Woodward effect:
|
| > In a third paper, the Dresden physicists then describe
| their research on the "Mach-Effect Thruster":
|
| > "Here we have proven that the Mach-Effect-Thruster (an idea
| by J. Woodward) is unfortunately a vibration artifact and
| also not a real thrust."
| Taniwha wrote:
| oooh, scientists doing science!
| the__alchemist wrote:
| Relevant XKCD: https://xkcd.com/1404/
| darepublic wrote:
| I wanted to believe
| ChrisMarshallNY wrote:
| I am sad, but not surprised.
|
| I really want something like this to work, and it may, one day.
|
| Just not yet, I guess.
| hermitcrab wrote:
| I'm sure this is no surprise to any professional physicists
| anywhere.
| fnord77 wrote:
| quel choc
| tmathmeyer wrote:
| https://i.kym-cdn.com/entries/icons/original/000/027/475/Scr...
| Ma8ee wrote:
| Kudos 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 wrote:
| > 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-
| paulist...
|
| [2]
| https://www.sport1.de/fussball/bundesliga/2021/02/bundesliga...
| yaya69 wrote:
| We're trapped like beavers
| walrus01 wrote:
| For 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/Nuclear_photonic_rocket
|
| https://en.wikipedia.org/wiki/Laser_propulsion
| brazzy wrote:
| I 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.
| cygx wrote:
| Note that in contemporary usage, the term 'mass' without
| qualifier is normally understood as a reference to invariant
| mass (aka rest mass). Photons have energy, but no mass. They
| can be used for propulsion due to having nonzero momentum.
| rssoconnor wrote:
| While the 'working mass' in this case is massless,
| nevertheless the spacecraft still loses its own actual mass
| as it accelerates, which is something you might not expect
| from something labeled as "thrust without reaction mass".
| cygx wrote:
| True. After sending out a photon of energy E, a spaceraft
| of mass m will have its (invariant!) mass reduced by a
| factor of sqrt(1 - 2E/mc2).
|
| In terms of energies, this is all rather trivial
| conceptionally: Rest energy (aka 'mass') gets converted
| into the kinetic energies of the spacecraft and the
| photon.
| fsloth wrote:
| You 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 wrote:
| Neat 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.
| TeMPOraL wrote:
| Your main losses will be just from inverse-square law.
| Even if your ship is reflecting a laser off its rear end,
| you can only focus the beam so much; at some point the
| spot size will be bigger than the ship, and you'll be in
| the inverse-square regime (same surface area, 1/r^2
| energy within it).
| sfink wrote:
| That doesn't seem fundamental, though. You could have a
| series of relays that catch the beam, convert it to
| energy, and re-beam it out.
|
| But I'm sure the efficiency would be awful, and if you
| have a chain of N of these things, now you're dropping
| off exponentially with N. And N is linear in distance.
| Hm... this isn't sounding like such a great workaround
| anymore.
|
| Not to mention that the incoming beam would be shoving
| your relay forward. Does the outgoing beam push it
| backwards? I don't know how that works. (Even if it does,
| you'd be shoved forward proportionally to the energy
| loss.)
|
| Bleagh. You'd be better off sending out a series of
| energy pellets well in advance that a traveling ship
| would scoop up along the way. _That_ must be what Pac-Man
| was all about...!
| fsloth wrote:
| There are different configurations to transfer energy to
| the space-craft that is converted to it's momentum
| https://en.wikipedia.org/wiki/Beam-powered_propulsion
| waheoo wrote:
| You push the "ship" with a laser from a satellite.
| tylerhou wrote:
| You don't even need a dish to catch the energy; just use
| a mirror that reflects the laser. You will lose energy to
| particles in the laser beam, and possibly also due to
| redshift.
| sbierwagen wrote:
| >How much energy do you lose?
|
| Not entirely the right question. Usually in spaceflight
| you are overwhelmingly concerned with efficiency, since
| you have to carry your fuel with you. But with laser-
| boosted light sails, you leave your engines at home. At
| reasonable distances, (100+ AU) most of the beam is
| wasted, but the spacecraft doesn't care about that.
|
| https://en.wikipedia.org/wiki/Solar_sail#Interstellar_fli
| ght
| nomercy400 wrote:
| Wouldn't you push your satellite in the opposite direction?
| Not saying that it isn't a good idea. The satellite might
| be in orbit, so it could use gravity to negate that.
| yccs27 wrote:
| The difference is quantitative, but multiple magnitudes big:
| The ratio of impulse to mass is given by the exhaust
| velocity, and velocities for massive propellants barely reach
| 0.01% of the speed of light. Thus the thrust can be more than
| 10 000 times higher for the same propellant mass.
|
| On the flip side, the exhaust velocity also determines the
| ratio of (kinetic) energy to impulse, so energy beam
| propulsion needs over 10 000 times more stored energy.
|
| Energy beam propulsion is only viable if you have compact
| high-capacity energy storage available (antimatter?).
| Iv wrote:
| The thing is we know how to harvest solar energy while in
| space. Harvesting matter has been proposed with ram scoops
| but contrary to solar cells, these are just theoretical
| propositions.
|
| Being able to use energy directly instead of propulsion mass
| would make a lot of travels more sustainable and with
| potentially lighter vehicles.
| brazzy wrote:
| I'm pretty sure the amount of energy you can harvest that
| way is a couple of orders of magnitude too small to be
| useful.
| ReptileMan wrote:
| I mean I would just load couple of metric tons of antimatter
| in the ship and then just use up picked up interstellar space
| mass (1 atom per cubic meter is not much, but you will be
| moving trough shitload of them) along the way to annihilate.
| the faster you move the faster you will go up to a couple of
| limits. BUT deceleration may be a bit of a problem.
| dvdkhlng wrote:
| It's also possible without any energy transmission using lasers
| etc. as long as you are in some non-flat spacetime (i.e. there
| is some mass in your vincinity). It's called "swimming in
| spacetime" [1]
|
| [edit] You can find a less scientific / more illustrative
| introduction to the concept here [2].
|
| [1] http://groups.csail.mit.edu/mac/users/wisdom/swimming.pdf
|
| [2]
| http://www.brophy.net/Downloads/AIL%20Class%20on%20Reality%2...
| conistonwater wrote:
| This is a perfectly realistic technique that has already been
| seen in use: https://www.youtube.com/watch?v=Lnvh08GBOII
| delecti wrote:
| > as long as you are in some non-flat spacetime (i.e. there
| is some mass in your vincinity)
|
| I'm not an expert, but isn't that definitionally everywhere?
| Or is it that it works _better_ when your vicinity is _more_
| curved? The paper is a bit beyond my ability to get anything
| from, and the summary on Wikipedia isn 't much better, and
| also doesn't seem to match what you're implying it is.
|
| > "Swimming in spacetime" is a geometrical motive principle
| that exploits the curved spacetime metric of the
| gravitational field to permit an extended body undergoing
| specific deformations in shape, to change position. In weak
| gravitational fields, like that of Earth, the change in
| position per deformation cycle would be far too small to
| detect, but the concept remains of interest as the only
| unambiguous example of reactionless motion in mainstream
| physics.
| conistonwater wrote:
| I also found the paper hard to read, but check page 6 of
| the pdf at http://www.brophy.net/Downloads/AIL%20Class%20on
| %20Reality%2... ( _Adventures in Curved Spacetime_ ,
| Eduardo Gueron, Scientific American Vol.301)
| JPLeRouzic wrote:
| In 2003 a scientist published a paper about cyclic changes in
| the shape of a quasi-rigid body on a curved manifold. He shown
| that it can lead to net translation and/or rotation of the body
| in the manifold, so in simple words "swimming in space". I
| guess this is only possible on very large structures.
|
| https://dspace.mit.edu/handle/1721.1/6706
| jillesvangurp wrote:
| Scott Manly did an overview of potential ways of propulsion in
| space including some very wacky setups. The most promising ones
| seem to be using nuclear or fusion reactions to accelerate tiny
| amounts of mass to very high speeds. The engineering issues are
| substantial of course. But definitely goes a bit beyond the
| limitations of chemical processes (i.e. burning fuels).
| https://www.youtube.com/watch?v=QEZv_OXA_NI
| pfdietz wrote:
| I'd say beamed energy propulsion is more promising for high
| speeds. That's because the main problem becomes keeping the
| vehicle from destroying itself with waste heat, and beamed
| propulsion keeps the waste heat back at the beam souce. You
| can even actively cool an object with laser light (via anti-
| Stokes scattering and the like.)
| qayxc wrote:
| In the end it's all about a very simple equation: E(kin) =
| 1/2mv2 so it's all about exhaust velocity. The closer you can
| get that to its theoretical maximum (e.g. c), the less
| reaction mass is required.
|
| But the question still remains: is there a practical non-
| Newtonian way? We already know of rather impractical ones,
| such has deforming spacetime.
| jandrese wrote:
| I've wondered if it would be possible to build an efficient
| rocket engine that accelerates its reaction mass so hard
| that it gains an appreciable amount of relativistic mass?
| The fundamental problem with interstellar travel is the
| amount of reaction mass you need to make the trip in a
| reasonable amount of time. The rocket equation is a harsh
| mistress. If you were accelerating each gram of propellant
| so hard that it gained a metric ton of relativistic mass
| you could bypass it, assuming you had some sort of
| lightweight yet near limitless power source.
| admax88q wrote:
| Isnt that basically a high powered ion drive?
| jandrese wrote:
| As far as I know none of our current Ion drives
| accelerate the particles hard enough for them to gain a
| noticeable amount of relativistic mass.
| benlivengood wrote:
| You could use a synchrotron or linear accelerator to
| shoot charged particles out the back.
|
| The LHC gets protons to 99.999999% of c.
| varispeed wrote:
| There is a nice experiment that shows light can move:
| https://www.youtube.com/watch?v=Ng1X8mPJziA
| Mikhail_K wrote:
| Photon drive is not "thrust without reaction mass", because
| photons do have mass (they have zero rest mass, but are never
| at rest). Mass of a photon is, unsurprisingly, E/c^2, where
| E=h\omega. If photons had zero mass, they would not have been
| influenced by gravity, and bending of light by the solar mass
| has been measured in the beginning of 20th century.
| jessriedel wrote:
| You're using outdated terminology. Modern physicists use
| "mass" to refer to what was called "rest mass" shortly after
| relativity was developed in order to distinguish it from the
| new concepts they at the time called "relativistic mass" and
| "inertial mass". The term "relativistic mass" was motivated
| in part by the desire to still think of all gravitation as
| being sourced by some sort of mass, but the modern
| terminology is to say that gravity is sourced by the stress-
| energy tensor, of which (rest) mass is just one component.
|
| Modern physicists unequivocally say "a photon has zero mass,
| but has non-zero momentum and energy".
| at_a_remove wrote:
| I have a physics degree and _still_ say that photons have
| zero rest mass, and then parenthetically mention that they
| never rest, precisely because of the issues of
| communication that tend to arise when we talk about things
| like thrust.
|
| I'm always tailoring it to the audience because sometimes
| physics metaphors _need_ to be unpacked when communicating.
| I have run into people who think that the "hole" that can
| move around in a lattice is an actual particle, not a
| quasiparticle, like it was a swimmy little positron just
| sitting in there, simply because the metaphoric shorthand
| had overtaken reality.
|
| If I were talking physics grad to physics grad, I wouldn't
| do that. Anyone else? Yeah, brushing the complexities under
| the rug with shorthand leads to, well ... the idea that you
| can get thrust without kicking something in the other
| direction.
| jessriedel wrote:
| I wasn't advising him to not explain things, I was
| pointing out that he's saying something that's false when
| interpreted with standard terminology.
| cygx wrote:
| That terminology is outdated. Today, mass generally means
| invariant mass, corresponding to rest mass in case of
| 'massive' particles. The invariant mass of photons is 0,
| hence it's 'massless'.
|
| The gamma factors hidden by the relativistic mass definition
| of course still occur, but they get folded into the 4-vector
| quantities instead, which happens naturally if you use proper
| time for your derivatives.
|
| This way, we avoid having to introduce things like transverse
| and longitudinal mass, which was the explanation within the
| variable-mass picture as to why the spatial part of
| 4-acceleration generally isn't parallel to 3-acceleration.
|
| _edit:_ s /velocity/acceleration/ where appropriate
| unlaxedneurotic wrote:
| The photon paths bend due to the curvature of space-time
| caused by gravity. This does not mean that they have non-zero
| mass. iirc, it has been proved that photons have non-zero
| _momentum_ but I am not sure about mass.
| wanderfowl wrote:
| I'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 wrote:
| Yes 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 wrote:
| > 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.
| kenneth wrote:
| On 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 wrote:
| What size and wattage load of devices?
| bpodgursky wrote:
| It'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 wrote:
| I 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 wrote:
| I 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 wrote:
| Newtonian 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 wrote:
| You'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 wrote:
| I 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
| ncmncm wrote:
| If 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 wrote:
| Out of interest is there another more promising
| controlled fusion option?
| ncmncm wrote:
| I 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 wrote:
| Not really. Fusion has inherent generic engineering
| problems, particularly DT fusion, that are independent of
| the details of plasma confinement.
| ALittleLight wrote:
| Nobody 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 wrote:
| Shawyer 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 wrote:
| > 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-...
| ncmncm wrote:
| I 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 wrote:
| That'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).
| pilsetnieks wrote:
| According 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.
| rcxdude wrote:
| Given 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.
| Igelau wrote:
| and yet, SSRIs
| andbberger wrote:
| you 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 wrote:
| It'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 wrote:
| It'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.
| kjrose wrote:
| While 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 wrote:
| Feel 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.
| olliej wrote:
| wasn't it already established that the force measured was related
| to current in the power cables or something?
| KMag wrote:
| It's an important step to fix the observed flaw and then
| experimentally verify results are now as expected.
| xt00 wrote:
| Yea 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.
| whiw wrote:
| The 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 wrote:
| The 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
|
| Proponents tried to hand-wave these arguments away and claim
| that the EmDrive's empirical results were explained by new,
| unknown physics.
| Waterluvian wrote:
| I 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.
| dsq wrote:
| A TANSTAAFL-defying machine...
| OliverJones wrote:
| There'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.
| infofarmer wrote:
| Hmmm... those oscillations in your brain, did they feel
| _perpetual_? We need some more data to see if we can harvest
| their energy for motion.
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