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The 'Impossible' EM Drive Being Tested By NASA May Finally Be Explained (technologyreview.com)
MarkWhittington writes: The EmDrive, the so-called "impossible" space drive that uses no propellant, has roiled the aerospace world for the past several years ever since it was proposed by British aerospace engineer Robert Shawyer. In essence, the claim advanced by Shawyer and others is that if you bounced microwaves in a truncated cone, thrust would be produced out the open end. Most scientists have snorted at the idea, noting correctly that such a thing would violate physical laws. However, organizations as prestigious as NASA have replicated the same results, that prototypes of the EmDrive produces thrust. How does one reconcile the experimental results with the apparent scientific impossibility? MIT Technology Review suggested a reason why.
We'll eventually find out we really live in a simulation...
Great job lets not even try to attempt to summarize the article, instead lets post this like its a trailer for the 11 o'clock news!
Really appreciate the complete lack of even a whiff of the explanation in the summary.
Don't disappoint your bird dog. Go to the range.
https://en.wikipedia.org/wiki/...
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I was honestly expecting to find an explanation of some subtle source of experimental error that covered it, not a possible theory explaining why it (maybe) works. I'm really looking forward to experimental testing of the improvements predicted by the theory. Who knows? With a decent explanatory theory, it might even be possible to turn it into a practical thruster. That would be awesome.
If you have multiple emitters into the chamber, angled toward a reflector, each emitter has a vector of momentum parallel to the axis of the motor, and another perpendicular to it. If the emitters are spaced properly, the perpendicular vectors will cancel, and the parallel components, summed, will be less than the momentum of the photons leaving the chamber through the "nozzle", giving a net forward thrust.
If they miniaturize it and connect it to a battery and a computer it could behave as the back to the future hoverboard. It could also mean drones without without a wind propeller.
Have they tried analyzing this thing with an E-meter?
Most scientists have snorted at the idea, noting correctly that such a thing would violate observed physical laws.
The EM drive was discussed at length on other sites, and few posts were able to shine any light on the issue. Some items of note:
First, if your understanding of physics does *not* predict the Casimir effect, then you probably shouldn't be blithely dismissing the theory. The EM drive is based on a theory of physics that's more sophisticated than simple "momentum is conserved". It supposes an hypothesis that's different than what is currently accepted, but in a subtle way that is difficult to detect.
It's similar to relativity: most of our tests validate Newtonian physics, but you find relativity when you go looking for it.
Second, if you want to appeal to Noether's theorem, note that the theorem refers to smooth manifolds. If space is quantized, then Noether's theorem doesn't apply (despite being true). It's possible that Noether's theorem will break down at small scales. (If space is smooth, ie *not* quantized, then the true location of any particle is a [mathematical] real number with infinite entropy and it's action is non-computable. Not that having a non-computable universe is a problem, but...)
All in all, I get the impression that everyone commenting on the EM drive should probably keep quiet and let the experts sort it out.
I don't have any comment on either the theory or the experiment, but it's an interesting proposal.
From the Wikipedia page:
This is analyzed by Rothman and Boughn[32] who point out that the standard theory of radiation pressure is more complicated than the simplified analysis suggests.
NASA tested it in vacuum chamber to prevent this issue.
Architectural plans are like computer source code with a couple of differences: You only compile once.
Yeah that whole air-pushing thing explains the results they got in a vacuum.
Don't disappoint your bird dog. Go to the range.
I'm of the firm belief that if humans can think of it, we can eventually find a way to do it, even if it's by proxy.
Go back 100 years and the differences in thinking about what is "impossible" would be marked.
The ship stays where it is and the engines move the universe around it
The engine appears to work by utilizing a Maxwell's demon.
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And yet they admit there are some thermal issues in your cited article. "He also admits that there are still traces of contamination caused by thermal expansion in the system". It still worth noting that these are tiny forces being measured and it's on the order of experimental error rather than useful thrust.
But the universe won't notice the maintenance downtime to support development of universe 2.0.
Me.
We apologize for the inconvenience.
God.
Send one of these suckers into space and see if it works? AFAICT, if it does you have a spaceship with no fuel requirement, if it doesn't you just have some space debris. As it has no fuel, it doesn't have to be a big craft, so it could go up with something else.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
You might find this interesting.
The amount of thrust they're seeing, even at microNewtons, is far higher than could be produced by the radiation pressure of simply emitting photons at those energy levels. If it wasn't, there wouldn't be all this fuss.
NASA measured an average of 91 microN with 17 W, or 5.3 microN/W. The Chinese measured 720 milliN at 2500 W - about 300 microN/W. By contrast, expected radiation pressure would be closer to 0.003 microN/W.
Why would anyone engrave "Elbereth"?
If this was just about photons having mass, well then simple flash lights would be showing similar thrust. But they don't as such measurements show flashlights demonstrate much much much less thrust by directly emitting photons.
This thing is warping space slightly within the cavity, and whatever net inertia due to the microwave photons slinging back and forth inside the cavity is not balanced - resulting in a much larger thrust than emitted photons from a flash light.
Somewhere somebody suggest attaching some these thrusters to the ISS to keeps its altitude trimmed without needing to refuel - couldn't hurt to try?
"If Photons have mass (i.e. not relativistic mass, actual mass) the world becomes a damn site simpler"
No it doesn't.
General relativity would be fundamentally changed.
What does this statement mean?
Reading the reference http://arxivblog.com/?p=207 didn't help me understand.
It looks like nonsense because it treats photons as if they were Newtonian particles and with ignorance of Maxwell's equations and relativity.
Start with section 2. It treats photons as particles with some momentum m*v. I mean, what? That's just wrong. Photons are relativistic p = E/c and quantum mechanical, E = 2\pi hbar f.
I mean take a look at this:
"Normally, of course, photons are not supposed to have inertial mass in this way,
but here this is assumed. It is not clear what the size of this mass is, but it is
clear for example that light inside a mirrored box produces a kind of inertial mass
for the box. "
So in orthodox physics, photons are not supposed to have inertial mass, but also in orthodox physics light makes inertial mass and it's clear that it's so.
The second statement, about light inside a mirrored box, is so because of relativity and the assertion of the equivalence principle. Electromagnetic fields are part of the stress energy tensor (following Maxwell) which feeds into the source term of general relativity. So yes, there is some sort of inertial contribution, but in fact it can be computed pretty exactly, and it's extraordinarily tiny, and really mostly related to the energy density of the EM field.
So relativity sometimes, but not other times? WTF?
And if the non-standard theory that inertia comes from matter interacting with Unruh radiation, how exactly does that work with photons? Photons don't interact with photons. Zero cross section until the point that they are so energetic they can pop out electron/positron pairs from the vacuum, which is so far not an experimentally accessible regime.
Presumably the idea is that the Unruh radiation inside the cavity is quantized in a particular way different from free space, but wouldn't that mean that inertia of (presumably charged) particles inside that cavity would be altered? But he was talking about the non-sensical 'inertial mass' of the photons themselves. WTF?
I don't mind non-standard theories and their exploration at all, but it's necessary to be clear which standard axioms are being rejected and which others are preserved, and follow that consistently. I just saw very unclear physics.
Why would you be able to detect the thrust when applied to the ISS but not on a bench test in the lab?
Why would it be a problem?
Maybe "the speed of light" is a misnomer, c is just a maximum speed defined by the universe, and photons travel at speeds that are extremely close to this cosmic speed limit. It would then be perfectly possible for them to have a tiny amount of mass. No laws break down (at least not in GR), you just have to replace Einstein's flashlights by hypothetical devices that transmit information slightly faster than light, with precisely the speed c.
Turns out "faster than light" is possible after all (but not faster than c).
What I don't understand is what the size of the observable universe has to do with anything. As far as we know, the universe itself is unbounded. The size of the observable universe is just the distance light has been able to travel since the big bang. Why would the wavelength of Unruh radiation be bounded by that? I don't see any physical reason for that.
It seems it was conceived by a single man, who obviously could not test it alone (it takes expensive Nasa facilities, it seems). And yet it seems to work, with much surprise from all the world's most expert scientists. One might wonder if he's an alien, or a man from the future... It 's a perfect science-fiction plot, does anyone know this movie: https://en.wikipedia.org/wiki/...
So you've recreated this experiment and proved this? Have you published your results to spare everyone the waste of time of further environments?
I'm no physicist, but this new explanation sounds just as wacky as the inventor's original explanation of why it (allegedly) works.
Table-ized A.I.
The main trouble with all this talk is it doesn't mention amounts. One may be able to have all kinds of funny effects like Casimir and radiation behind the horizon and what not and it's interesting to figure out how momentum is conserved but to go from a measurable effect to 'let's use it for propulsion' is outright silly. The effect will be in the wrong ballpark and you'll be much better off by just using removing the back and using the actual microwaves for propulsion.
Every test performed on GR has shown it to be correct.
Including the description of velocity addition at velocities close to c.
Basically particles with mass are unable to reach c.
I don't mind the "what if" questions, but they do need to be grounded on some established knowledge to some extent.
Why would there be one and only one universe?
By the definition of universe. Multiverse theories do exist, but are not germane to the discussion of how many wavelengths fit into the universe.
What is you definition of universe?
Any event that could create one could create two or 3 or N universes.
...this assumes the universe was "created" in an "event", and that the concept of multiple universes is even sensible. Even assuming that, it's an unsupported assertion. It could very much be like saying "anybody who can discover the Theory of General Relativity can discover two or 3 or N Theories of General Relativity."
Indeed it would have to have something very special to make one and then stop. Something that does not exist in other branches of physics.
What?
If there's more than one, then space is continuous and there's no limit on the wavelength of Unruh radiation.
What? The number of universes has nothing to do with whether space is continuous, and as best I can tell, nothing to do with Unruh radiation.
Laws of physics.... Laws of physics are created by men to explain certain things, they aren't set in stone and aren't absolute..
"Space Travel Causes Kitty Porn, News at 11!"
Table-ized A.I.
I strongly believe that this drive does not work but still needs to be investigated. First we find new things that we must consider when testing physical phenomenom. Second we might actually find some new mechanishm that translate force to earth, air or somewhere else.
Did you even read my post? I'm not questioning the validity of GR, in fact I was arguing that there needs to be no contradiction between GR and the possibility that photons could have a tiny amount of mass and travel slightly slower than c.
The speed "c", commonly but perhaps erroneously called the "speed of light", remains the ultimate speed limit. Velocity addition remains valid, particles with mass still cannot reach c, etcetera.
I'm just saying that maybe photons travel at speeds slightly slower than c, and that would be OK.
Short version: photons seem to have inertial mass after all.
You cannot just rewrite fundamental physics to fix one issue without also looking at the implications of your theory for other predictions which is it likely to change. Worse it seems that nobody has tested these drives for the emission of charged particles. A far, far simpler explanation is that this drive works by electron emission. There are a variety of way this can work which all work in a vacuum but whic would unfortunately not work in space where you are electrically isolated and would eventually build up a counter charge and cause the thrust to reduce to zero over time. This all uses established fundamental physics so it would be nice to see this ruled out BEFORE coming up with crazy new physics. It might be less exciting but it is better science.
The amount of concentrated stupid some people are spewing in response to this is really staggering. And they do it again and again. They will probably claim because it was "in a vacuum" that there can be no air effects, completely missing that no vacuum on earth is perfect and the one used here not even nearly so.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
P. T. Barnum's "law" of the con: "There's a sucker born every minute"
Guess which one is more relevant here.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
The lopsided nature of the cone causes the Ether Turtle's shell to become warmer than its belly. This difference is uncomfortable to reptiles and makes it shift around a bit, causing the turtle underneath to adjust to compensate, in turn triggering a similar re-shuffling of the turtle below it, and so on all the way down, causing the universe to shift position relative to the probe.
Table-ized A.I.
Its a puzzle to me why its a puzzle to them.
When an object gains speed it gains kinetic energy. If there was no inertia - ie objects would instantaniously changed speed from X to Y given a force with no measured speed inbetween then this would mean the energy transfer between the pusher and the object would, for an instant, be of infinite power (power = energy / secs where secs = 0). Which clearly isn't allowed under any known physics.
I agree that in principle the speed of light does not have to be the same as the limit speed and that they tend to be confused. Only even the tiniest mass of light particles would easily be measured and experiments have been made that are extremely sensitive to this 'nonzeroness' , mainly because they would strongly affect how electrostatic forces depend on distance. So the mass would have to be ridiculously small. ('ridiculous' differs orders of magnitude from 'extreme' ).
Ah yes, the good of "Reversal of Proof" logic fallacy strikes again.
All you need is a simple flux capacitor, a conductor to capture a lightning that can deliver 88 Gigawatts of electricity. That is all.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
But it is well known that the momentum of a photon depends on its frequency. If the device spits out microwaves in two directions, the same number of photons per second, but the microwaves come out in one direction are of a higher frequency than the other, then more momentum will be emitted in photons in one direction than the other. I would expect the quantities involved to be miniscule, but that's the first guess I had in mind when I read about this.
John_Chalisque
The supposed thrust is many orders of magnitude too small to be of any use to keeping the ISS in orbit. If it were that strong of a thrust, everyone would believe it's real.
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Now to find a planet with giant worms.
The guy who said the election was rigged won the presidency with the second-most votes.
Quoting a sci-fi novelist as an authority in a scientific debate doesn't exactly hold any weight, it simply confirms for your opponent that you're engaging in the wishful thinking he's accusing you of. At any rate, the young scientists are as skeptical of the em drive as the old scientists.
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The theories are different (?), but this reminds me of seeing a light mill for the first time and immediately thinking a light engine should be possible one day.
You were right the first time. The people testing the EmDrive were clowns, and Mike McCulloch should never have received a PhD. This reddit thread, which he participated in, should be sufficient to destroy his credibility.
I am incensed this made it to the front page. This is worse science than most climate deniers manage; they are usually a little less blatantly unphysical. The firehose needs a way to tag things as complete bullshit, preferably with the ability to submit a rebuttal link. There is no need for Slashdot to run hoax stories, terrible science, or anything else blatantly untrue.
Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
http://www.wired.com/2015/05/n... Here's a snippet: So who are these guys? Despite the fact that the group works out of Johnson, under the auspices of NASA, Eagleworks still only runs on $50,000 a year in funding. “That’s not enough to conduct a high-quality experimental research program,” says Davis. “They’d need $1.5 million, $2 million for five, six, seven years.” Research into breakthrough propulsion physics—even when it had its own lab at Glenn, under Millis—has never been particularly well-funded. So “the way that this really happens is people dabble in addition to their day job,” says Millis. According to him, Eagleworks started with White working on concepts in his free time, not officially supported or sanctioned by NASA, and then eventually got a little money to run his lab out of Johnson. But the NASA banner doesn’t legitimize the work—if anything, NASA seems to want to keep the project under the radar.
In tomorrow's news, it will be unveiled that Robert Shawyer is a fake name.
> If you bounced microwaves in a truncated cone, thrust would be produced out the open end. Most scientists have snorted at the idea
I can see why porcine scientists would snort with approval. After all, if you bounce refrigerators around in a truncated cone (nozzle), they'll produce thrust as they exit the narrow end. If you bounce toasters around, they'll produce thrust out the nozzle. Same with coffee makers. Therefore, if you bounce microwaves around a nozzle ...
What's that you say, an actual News for Nerds story? Bravo, Slashdot!
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I try, but as a non-physicist/non-mathematician, all I can really get out of this saga is:
1. Some guy builds and runs a funky apparatus in his lab/garage, and gets some strange results. He reports these excitedly to the world at large.
2. He's obviously smart but possibly deranged, since he claims that the apparatus violates the conservation of momentum, which is a classic crackpot move.
3. Any reputable scientists who have these results brought to their attention uniformly and immediately dismiss them as obvious crackpottery.
4. One night, while drunk, a small group of reputable scientists build the apparatus in their own lab, as a joke, and observe the same strange results.
5. Repeat steps 3-4 a bunch of times.
6. ???
7. Space probe to Alpha Centauri in my lifetime?
So the complaint with this drive is that no matter is sent out the back(law of conservation of mass). but since we know that mass and energy are transferable states and that we can in fact split an atom eg. destroy matter in the classical meaning of the law and remove energy from the action, the notion that this drive is not going to produce force is obsolete.
What should be most telling was that this "engine" produced more "thrust" when it was turned off than when it was turned on. That should tell you how stupid this thing is but everyone is so caught up in the "I want to believe" moment that they ignore all the warning signs.
I think you have demonstrated how stupid you are with that statement. They found thrust in the NULL experiment, not when it was off. The null experiment used a different shaped reflector that they felt would cancel out the acceleration. If they don't understand the theory of how the acceleration is created, then they could very well have failed to create a null experiment and instead created another shape that works as an EM drive. Once they understand how the trust in generated correctly then they can successfully create a null experiment that works correctly and produces no thrust.
The "thrust" measured by every study is so tiny that it's equivalent to the gravitational attraction of the contraption to your body. There are thermal effects that could explain this tiny thrust. So when the contraption was cooling off, the thermal effects were enough to push the air in a non-symmetric way that it produced a tiny push on the sensors. You could have measured more thrust just blowing on the stupid thing.
They also tested it in a vacuum so there is no air to push off of.
-- ssoorrrryy,, dduupplleexx sswwiittcchh oonn.. -Quote found on actual fortune cookie.
The idea that there is something wrong with the current "laws", more accurately, theories, warrants study. What we have with data on electromagnetism and gravity are theories which have been tested in particular and limited experimental conditions. It has never been proven that the EM and gravity behaves in the way which has been tested in all contexts because there are such a large number of other contexts which have not been investigated. That is, it is not out of the question that EM And Gravity may be more complex than current theory and may behave in a different way than now understood under certain field arrangements and conditions which have not been tested. The assumptions of EM and gravity behave the same way even in settings on which there is no data is an unfounded extrapolation that since these forces act one way under certain settings the behave in the same way under all other settings, without any data on those other settings.
The idea that you haev these laws called EM and Gravity which are just absolute perfection and we cannot question and cannot have any flaws with them, and we assume without data that they behave in the same way always and in all situations even ones where there is no data, and that when an anomaly is detected it is automatically assumed it cannot be due to a problem with the theory of EM and gravity, is just plain arrogance.
If Maxwell's equations are correct then the speed of light must be a constant for all observers.
It would be extremely hard to come up with a model for the universe that could have two speeds that are constant for all observers (I would say impossible except that someone will post a 4000 page paper proving that it can be done by warping of space time :-) )
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
I've been following Professor McCullouch's works for a couple of years now. His theories make more sense than the alternatives. I suggest checking out is web-log at http://physicsfromtheedge.blogspot.com/ and getting his book.
"Uh oh–you've read all five of your free articles for this month."
Uh, no, I've yet to read a single one (and have fixed IP).
"Become an Insider for unlimited access to online stories for as low as $29.95/year."
Do you really think I'll pay $30 to folks who can't count to one!?
This "thing" shows the interesting interaction between the engineering community and the scientific community. This is why you should take scientist statements with a grain of salt.
Engineers: look, this works!
Scientists: that violates the laws of science and is impossible.
Engineers: who gives a sh*t what you think? Here's the data
Scientists: the data must be wrong
Engineers: you try it
Scientists: we have no f*cking idea what's happening, but it's happening
Engineers: f*cking pinheads
Scientists: oh, maybe this is what's happening
If you take scientists too seriously, you never get past step #1.
I suspect it has to do with the fact that the causally linked universe *is* bounded. Due to the expansion of the universe, nothing propagating through normal spacetime can ever interact with anything outside the Hubble Sphere, the boundary beyond which space itself is moving away from us faster than the speed of light. This is incidentally much smaller than the visible universes, since most of the visible universe has already traveled beyond that boundary in the eons since the light currently reaching us was emitted. Or to put it another way, that light has travelled considerably further than the Hubble boundary radius, since the space it was traveling through has been expanding the entire time.
As to why that should matter, this is pure speculation, but I imagine a "photon" of Unruh radiation must be causally connected with itself - and if its wavelength would be larger than the cosmic event horizon, that's probably not possible.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
The Maxwell equations use "c", which is not necessarily equal to the speed of light. It is entirely possible that Maxwell's equations are correct, c is constant, but the speed of light is very slightly less than that (but close enough to have gone undetected in all experiments so far). That would mean that the speed of actual photons is not constant, although you would have to accelerate to enormous speeds to notice the difference.
Now I'm not saying that I definitely believe that this is all true, just that maybe it could be a possibility. Photons with a very tiny mass and a speed very, very close to c. There need be no contradiction if we stop calling c the speed of light.
I've wondered, how does the constantness of the speed of light work with the known differences between speed of light in different media (vacuum, water, air)? The only concession to that I've seen has been use of "the speed of light in a vacuum" as the _true_ c but then we get into "well, if atoms being in the vacuum can make a difference, what about other types of mass/energy" and I've never seen that addressed. Can you point me to anything on this?
The speed of light in a vacuum is a consequence of Maxwell's equations, the fact that it is a constant value also follows from Maxwell's equations. Einstein's insight that spacetime is variable came directly from the confirmation of Maxwell's predictions.
EM radiation is nothing like a billiard ball, it is an electric and a magnetic field "falling over" each other. It's "mass" is proportional to it's wavelength. If a photon actually came to rest it wouldn't have a wavelength and therefore no mass, it would cease to exists - which is exactly what happens when it is absorbed by (say) an electron. The photon's energy doesn't disappear it is transferred to the electron.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Lots of things can be wrong. Tests can be badly designed. measurement devices can be badly calibrated, people can lie.
but if the result really is thrust, then there is thrust. actual test results are true, period.
now, it could be that the effect is coming from other source of energy or some other way, and that may in fact be consistent with the laws of nature as we know them. Or, very unlikely, we could just be wrong about some detail of the laws of nature. (but thats probably one of the last cases to consider)
but, the result is the result. it can't be "wrong"
Ah yes the good old "avoiding the question" fallacy strikes again. You're clearly the greatest expert in the field so let's see your proof.
I've wondered, how does the constantness of the speed of light work with the known differences between speed of light in different media (vacuum, water, air)?
The photons travel at the same speed regardless of the medium. However, whereas in a vacuum the photons would be traveling continuously from A to B by the shortest path, in water or air they're interacting with matter along the way. This means that the energy spends part of its time traveling at light speed in the form of photons and part of the time at rest as potential energy absorbed by the particles that make up the medium before being re-emitted as photons. Combining the time spent traveling and the time at rest yields the average speed of light in the medium. Mediums which interact less with light will have less of a slow-down compared to a vacuum (at a particular frequency).
"The state is that great fiction by which everyone tries to live at the expense of everyone else." - Bastiat
Perhaps a better understanding of c is the 'speed of information'.
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
What we have here is a new version of the solar sail! Hear me out.
The device bounces photons back and forth within the cone, effectively either a) "slowing" their speed (the speed of light), or b) at a minimum, altering their direction. Surrounding environmental photons, however, continue to travel in the direction they already were. The cone shape provides a larger area, or "net", at one end to catch more photons moving in that direction, which then push the device in the direction they are traveling as they collide with the slowed/altered photons.
If this is correct, theoretically this device could reach the speed of light!
I might be way off, but I hope someone much smarter than me, with many more resources, looks into this further.
To make it even worse, the microwaves are contained in a sealed chamber, so they're not being emitted in any direction. AND the observed forces are ~1000x larger than you would get from a photon-rocket, which is what you get if you simply blasted them all out the rear in the most efficient manner possible. If it's not experimental error, then something very strange is going on.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Huh. I'd have thought that absorption and re-emission would tend to randomize the direction of travel. Very interesting. Thanks!
My hunch - Same effect as you see in Crookes radiometer.
https://en.wikipedia.org/wiki/...
The problem is producing hard vacuum is - well really hard. Lots of people have fooled themselves here.
Bring one up on the shuttle - fire it up - will work until it is full de-gassed..
You will notice that there is no link to a paper - where one might be able to see their methods and figure if they know how to make a really hard vacuum..
So...
Gravitation is described by Einstein's non-linear field equations with singularities.
Quantum mechanics yields the best experimental predictions of any theory, but unfortunately is not consistent with relativity.
Inertial mass may be related to Unruh radiation.
Mass may come from the Higgs boson
Physicists can't even agree whether a simple metal cone with some radiation in it is actually producing thrust or not in a repeatable experiment.
It's amazing that given this sorry state of physics, so many physicists have the boldness to make definitive statements about anything concerning gravitation, mass, or reactionless drives. Guys, get your house in order and get your theories cleaned up.
The above was a somewhat simplified explanation which glossed over the dual particle/wave nature of light (among other things). Here is a wiki article with some more detail using the wave interpretation of light in case you're interested: Refractive index: Microscopic explanation. The wave explanation makes it a bit clearer why the emitted photon generally proceeds in the same direction. (My non-expert take from a particle point of view is that the photon is re-emitted very quickly relative to how "energetic" the absorbing particle is, so the particle doesn't have time to change its momentum. A longer excited state (e.g. florescence or phosphorescence) would probably make for more randomly-oriented emissions, whereas low-energy forms of matter such as B.E.C.s can retain the original direction longer.)
"The state is that great fiction by which everyone tries to live at the expense of everyone else." - Bastiat
We don't like relying on unexplained phenomena anymore than scientists do.
Their observation was within their error bounds, and massively contradicts well-tested theories. That's called, "back-to-the-blackboard" for the testing lab. It's not necessary for them to invent a new theory to cover their results (and note that McCulloch's theory can be safely discarded), but there's no point in anyone attempting to reproduce a non-result. Similarly, no one should feel compelled to believe in or reproduce over-unity devices, and any such claims should be treated with the greatest skepticism -- ditto for claims about faster-than-light neutrinos.
George_Ou is entirely correct: the burden of proof is on the person claiming a new phenomenon. So far, the evidence is distinctly lacking, and there's no reason to believe this will even pass peer review. It would be nice if this device worked; I want to go to Alpha Centauri too. However, anyone willing to throw out centuries of empirical evidence based on a single admittedly flawed test is entirely too credulous.
Those who advocate genocide deserve every protection afforded by law, and none afforded by common human decency.
...is that the EM drive's thrust has been reproduced by several independent institutions. So now where are all the pedantic Slashdot experts that just recently were absolutely sure that the EM drive was bunk?
I agree with you, that was a key claim of the article. It made me extremely skeptical of anything else they had to say because the experimental results have absolutely not been reproducible. The results varied by orders of magnitude and even by direction! The results were always down near the noise threshold. It is true that many experiments got non-zero results that could not be fully explained by their analysis of all the sources of noise. The fact that the magnitude of the non-zero result scaled with the magnitude of the noise over orders of magnitude should be tip off that these claims are extremely fishy. Getting non-zero results right at the noise floor that vary over orders of magnitude and vary in direction is pretty much the exact opposite of reproducible results.
Whenever a new anomalous result is found it is always possible that it will upend established physics but in 999,999 cases out of a million, the cause is experimental error (incomplete analysis of all potential sources of noise). That is certainly what seems to be happening here. It appears that this is yet another entry in the Nobel Prize lottery -- and it has about as much chance of paying off as a lottery ticket.
But for the sake of argument, let's say that despite all of the experimental results to the contrary, the effect is real and this is the correct explanation for the effect. Two points:
1) It directly contradicts the previous "theoretical explanation".
2) The effect does not scale well and would be useless for any practical applications such as space-flight. The effect only occurs because the size of the acceleration is very small compared to the size of the apparatus (the units of size and acceleration are related through certain natural constants such as the speed of light).
We don't see the world as it is, we see it as we are.
-- Anais Nin
Or the speed of causality, as explained in this episode of pbs spacetime: https://www.youtube.com/watch?...
Install windows on my workstation? You crazy? Got any idea how much I paid for the damn thing?
the experimental results have absolutely not been reproducible.
Actually they are. And space agencies like the Chinese are planning to put space probes up to see them working in real life.
The EM drive works completely upon established physics. Otherwise it would likely not work at all.
But thanks for your concerns.
The effect only occurs because the size of the acceleration is very small compared to the size of the apparatus
Wow, you spent a 20 lines post to explain us why it does not work and then in the final sentence you give us a (very unscientific explanation) under what circumstances it does work?
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
Look. Photons travel at c if Maxwell's equations are correct.
It's some basic algebra. Start with Maxwell (in my sig). Drop the parts that depend on charges and currents. Substitute D=epsilon0 E, B=mu0 H (we're in a vacuum) - the "trick" is to use this vector identity:
https://en.wikipedia.org/wiki/...
and you will derive a wave equation that has a constant speed. We use c but you can use k if you like and use c for something else - but you'll only confuse anybody else trying to understand your work.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Assuming you're prepared to believe this guy had a good enough grasp on all the physics involved, this was debunked ~8 months ago: https://www.reddit.com/r/EmDri...
I think the idea is that there's a mathematical link between Unruh radiation and the cosmic event horizon, which you can sort of understand as the wavelength of the Unruh radiation having to fit inside the universe. Because that event horizon changes when you accelerate and energy is quantized, if Unruh radiation is responsible for inertia then inertia must be quantized too.
The explanation for the em drive appears to be that if you confine the system to a small space then the quantization of inertia becomes much bigger, to the point where it can create a Casimir-like effect that's observable as thrust.
Not that long ago, neutrinos were thought to be massless particles traveling at the speed of light. AFAIK, nobody's ever come up with a good estimate how much slower they are, and for supernovae in distant galaxies the neutrinos arrive about the same interval before the photons as for much closer ones. (The bang starts in the center, so while the neutrinos just leave the photons have to blast their way out of the star.)
We then found that neutrinos could change flavor in flight, and things don't change when they don't experience time, so they had to be very slightly slower than light.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Thing is, the photons emitted are also absorbed, as the system is self-contained. This means that any imbalance in momentum of photons generated will be exactly reversed by photons absorbed. There's also the fact that the thrust claimed and reported is far higher than could be accounted for by photon momentum even if the photons were sent out of the system instead of being absorbed. Photons suck at transferring momentum.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
Extraordinary claims require extraordinary evidence, and this claim is about as extraordinary as they come. Come up with some extraordinary evidence and we'll talk. Finding the effect in orbit would be a start, but I'd still be wondering about interactions with the Earth's magnetic field.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
p = mv