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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.
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/...
Only the State obtains its revenue by coercion. - Murray Rothbard
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.
The problem was that even with all you just said the thrust was higher than they expected. Hence the big issue with the drive and why people said it couldn't work. Yet it kept working in real world tests.
we are all invisible unless we choose otherwise
It's true that a lot of comets are made of ice, but still I don't see the connection...
To be fair, assuming no race conditions, we'd never know if they took us offline. We could be running then stopping and running then stopping, and as long as the state was preserved, we'd never know (being part of that state).
"stop the world, I want to get off" just became a real thing...
Physicists get Hadrons!
The summary of the article is very wrong, there is no nozzle. If it had a nozzle it would be easy to explain, anything with a nozzle will operate as a rocket regardless of the wavelength you produce (Newton's law about action/reaction) and laser/microwave drives with nozzles have been built, we already use ion drives after all.
This 'engine' is completely closed. It's basically a closed cone in which you send microwaves and somehow you get acceleration. In Newtonian physics this would make no sense because it's a closed system, there is no "action" on the outside (basically the sum of all vectors of force generated come out to 0). However there seems to be something happening at the quantum level (the sum of all vectors is not 0 perhaps because at some quantized level there are hypothetically 'rounding errors').
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> We'll eventually find out we really live in a simulation...
And only the soul programs that have been save()d will be uploaded to the next life.
If both time and space are quantised to the extent that we're the simulation, there's some interesting corollaries to do with numerical instability - basically that the computational steps in time have to be below a certain limit or spatial anomalies will occur, and vice versa.
And vice versa. :)
Physicists get Hadrons!
Thank Douglas Adams for that quote, not the AC...
We'll eventually find out we really live in a simulation...
If you ever find yourself experiencing an uncontrollable urge to do something you wouldn't normally do, it's probably because you're being clicked-and-dragged.
I don't care if it's 90,000 hectares. That lake was not my doing.
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"?
A theoretical physicist should go around all the time and say: According to Theory T, this should be impossible!
I'm pretty sure I've been replaced with a simple shell script.
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.
Sometimes I feel like I'm a dancing paper clip offering unwanted advice to people.
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.
But of course we are living in a simulation. How else would you explain the apparently inborn feeling that there is a higher being or beings that controls the rules of the Universe, and observes us constantly even when we are alone or in the dark?
To quote Douglas Adams: "that's just perfectly normal paranoia. Everyone in the Universe has that.”