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Old 16th November 2016, 08:49 PM   #81
BenBurch
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Originally Posted by Horatius View Post
Wow, this alone makes me think they really don't know what they're doing. I had more data than that for my Master's thesis, and that was on something that wasn't even physically impossible

Anyone who thinks that this would be enough data to overturn so many different laws of physics should just be ignored.
Thing is, the thrust expected is so small that it could also be generated by interaction with the Earth's magnetic field, so launching into Earth orbit isn't really going to settle the matter.
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Old 17th November 2016, 04:10 AM   #82
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Originally Posted by acementhead View Post
The EM drive is just as real as Rossi's "ecat" Neither works because they can't work. The world has FAR to many "scientists" of low ability. No chance for them to do anything worthwhile so they "work" on crap like EM drive and LENR.

The ecat is a knowing fraud and so is EM drive.
The ecat is not the topic of the thread.

I, for one, hope the EM does in fact work, though mostly just to prove people wrong that say "x cannot work, because, laws of physics!!!!"

The laws of physics are not immutable. Given enough evidence for an observation then they can be rewritten and refusing to look at things or denigrating people that try out whacky or unconventional ideas is more than a little presumptuous.
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Old 17th November 2016, 04:53 AM   #83
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Originally Posted by Ambrosia View Post
The ecat is not the topic of the thread.

I, for one, hope the EM does in fact work, though mostly just to prove people wrong that say "x cannot work, because, laws of physics!!!!"

The laws of physics are not immutable. Given enough evidence for an observation then they can be rewritten and refusing to look at things or denigrating people that try out whacky or unconventional ideas is more than a little presumptuous.


I really, really want it to work. Even if it produces tiny thrust.

Unfortunately I think that all the anomalous data that has been collected can be more easily explained by error rather than physics being wrong.
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Old 17th November 2016, 05:39 AM   #84
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Originally Posted by Ambrosia View Post
Given enough evidence for an observation then they can be rewritten[...]
They can. There is as yet, however, no credible evidence that this is the case in this instance.
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Old 17th November 2016, 05:46 AM   #85
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Originally Posted by Ambrosia View Post
Given enough evidence for an observation then they can be rewritten and refusing to look at things or denigrating people that try out whacky or unconventional ideas is more than a little presumptuous.


You know, it's not "Trying out" wacky stuff that gets people denigration; it's the insisting that the stuff isn't wacky in face face of a complete lack of evidence, in the face of evidence that it doesn't actually work, all while carrying out poorly designed experiments while ignoring every piece of advice given as to how to improve those experiments.

Back when Cold Fusion first came out, there were hundreds of regular scientists who looked into it, and even tried to replicate it. I worked with a few of them that summer. No one "denigrated" them for these attempts at reproducing the reported results. Of course, they all came up empty, and so moved on with other research.

It's the people who are still doing the same crappy experiments year after year, for decades now, producing the same crappy data that doesn't actually prove anything, that get laughed at.
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Old 17th November 2016, 06:00 AM   #86
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Originally Posted by Ambrosia View Post
I, for one, hope the EM does in fact work, though mostly just to prove people wrong that say "x cannot work, because, laws of physics!!!!"

The laws of physics are not immutable. Given enough evidence for an observation then they can be rewritten and refusing to look at things or denigrating people that try out whacky or unconventional ideas is more than a little presumptuous.
The "laws of physics" aren't things in and of themselves, they are descriptions of how nature works based upon observations. For them to be rewritten would require some very obvious evidence nature does not work the way we see it working. So far they appear to describe nature's working very well.

As for being immutable which is a separate question, it appears to the best we can determine to date that they are immutable.

What Horatius wrote in post 85 is an honest remark.

Last edited by Steve001; 17th November 2016 at 06:03 AM.
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Old 19th November 2016, 04:19 AM   #87
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Eagleworks peer-reviewed paper now published.

http://arc.aiaa.org/doi/10.2514/1.B36120
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Old 19th November 2016, 03:49 PM   #88
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Seems to be basically the same as the leaked version, so the critiques I posted earlier are still applicable. I wonder when we'll get critiques published somewhere more official than reddit?
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Old 21st November 2016, 06:42 AM   #89
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Originally Posted by dlorde View Post
Did anyone notice this yesterday: German scientists confirm NASA results of propellantless 'impossible' EM drive.

One begins to wonder what is the error they are all making, or, if it's not an experimental error, how to account for this effect within the current framework...
No, the em drive has not been confirmed; only the experimental method proposed has been peer reviewed and accepted.
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Old 21st November 2016, 08:11 AM   #90
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FWIW, here is a summary of some earlier criticisms posted, with quite a bit of discussion of specifics in the comments.
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Old 21st November 2016, 08:15 AM   #91
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Originally Posted by Steve001 View Post

As for being immutable which is a separate question, it appears to the best we can determine to date that they are immutable.
What do you mean by that? Things as basic as conservation of mass, energy, and our understanding of how velocities add changed in just the last century.
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Old 21st November 2016, 02:12 PM   #92
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Quote:
So far they appear to describe nature's working very well.
ummm you might want to ask a few cosmologists about that. They don't seem to be working well at all regarding galaxies and gravity.
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Old 21st November 2016, 02:41 PM   #93
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Originally Posted by macdoc View Post
ummm you might want to ask a few cosmologists about that. They don't seem to be working well at all regarding galaxies and gravity.
That seems to be more of a problem with us not being able to see everything than it is a problem with gravity.
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Old 21st November 2016, 02:58 PM   #94
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Originally Posted by Ambrosia View Post
The ecat is not the topic of the thread.

I, for one, hope the EM does in fact work, though mostly just to prove people wrong that say "x cannot work, because, laws of physics!!!!"

The laws of physics are not immutable. Given enough evidence for an observation then they can be rewritten and refusing to look at things or denigrating people that try out whacky or unconventional ideas is more than a little presumptuous.
Conservation of momenta and conservation of energy goes a very long way deep into physic that a rewrite would need an extra layer of demonstration and evidence, an extraordinary claim if you prefer. So far I haven't seen anything corresponding to extraordinary evidence from EM. In fact COE derive from mathematical conclusion if one see the universe as isotropic , this mathematically lead to the differentiation. See Noether theorem.

A rewrite would be a boon for researcher and believe me, when one say that some law seem fundamental, it is almost always with deep regret it is said by somebody researching in fundamental physic domains. One would gain far more fame by rewriting laws or showing old law invalid, than one gain by verifying for the umptenth time that the laws still hold within the looked at approximations and experimental errors.

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Old 21st November 2016, 03:15 PM   #95
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Originally Posted by BenBurch View Post
Thing is, the thrust expected is so small that it could also be generated by interaction with the Earth's magnetic field, so launching into Earth orbit isn't really going to settle the matter.
There must be some caveat you're leaving out. Otherwise we'd have a drive that works like the EM drive claims but doesn't violate any currently accepted laws.
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Old 21st November 2016, 03:16 PM   #96
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Originally Posted by Tolls View Post
Why do they think it's easier to see this effect up there than down here in a lab under significantly better controlled conditions?
Because you can't create free fall in vacuum conditions for years in a lab?
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Old 21st November 2016, 03:43 PM   #97
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Originally Posted by RecoveringYuppy View Post
Because you can't create free fall in vacuum conditions for years in a lab?
Why are free fall conditions necessary to measure a force?
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Old 21st November 2016, 03:57 PM   #98
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Originally Posted by macdoc View Post
ummm you might want to ask a few cosmologists about that. They don't seem to be working well at all regarding galaxies and gravity.
Really? There are many models that explain most, what are you referencing?
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Old 21st November 2016, 03:58 PM   #99
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Originally Posted by RussDill View Post
Why are free fall conditions necessary to measure a force?
The force under discussion is extremely small. Letting it persist for years will make it easier to measure it's effect and also allow it to be distinguished from other random forces that wouldn't add up over time.
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Old 21st November 2016, 04:05 PM   #100
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Originally Posted by Aepervius View Post
A rewrite would be a boon for researcher .... One would gain far more fame by rewriting laws or showing old law invalid, than one gain by verifying for the umptenth time that the laws still hold within the looked at approximations and experimental errors.

This is something a lot of the purveyors of the fringe topics just don't seem to get. Like Ambrosia said, they seem far too often to be motivated but some sort of "You'll all see!" petty motivation, where discovering new physics isn't their main motivation, but mere a means to an end of pulling some sort of "gotcha" on their critics. But what they don't get is, real scientists don't think that way.

We're not saying the EM drive is unlikely to work just to be mean to the people promoting it; we're saying it because that's our best understanding of the claimed phenomenon, and its place in our overall understanding of how the universe works. We've only got so much time and money to spend on research topics, and so we try to direct our efforts where they're most likely to bear fruit, and this isn't it.

But if someone does do this work, and proves we're wrong? We'd be ecstatic! This would bring all sorts of new physics to research, it would be like the first discovery of radiation and radioactive decay, that suggested our notions of conservation of mass and energy were incomplete. If there's really that big a gap in our understanding of conservation of momentum, we've got all sorts of cool **** to figure out. Decades worth of exciting work, probably.

But we just don't judge that as being at all likely, even as we realize how cool it would be if we were wrong.
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Old 21st November 2016, 04:09 PM   #101
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Originally Posted by RecoveringYuppy View Post
The force under discussion is extremely small. Letting it persist for years will make it easier to measure it's effect and also allow it to be distinguished from other random forces that wouldn't add up over time.
How would it be distinguished from other random forces that do add up over time?
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Old 21st November 2016, 04:14 PM   #102
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Originally Posted by RussDill View Post
How would it be distinguished from other random forces that do add up over time?
Such as?

But, generally, it would be distinguished by the satellite being in a higher orbit than it ought to be.
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Old 21st November 2016, 04:22 PM   #103
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Aside from systematic errors which could produce a false positive if not properly accounted for, accumulating over time some random noise with a mean of zero almost certainly yields a non-zero total (see random walk).
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Old 21st November 2016, 04:38 PM   #104
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Originally Posted by RecoveringYuppy View Post
Such as?

But, generally, it would be distinguished by the satellite being in a higher orbit than it ought to be.
Well, given that about half of all satellites are in higher orbits than they "ought to be", pretty much any force that acts on objects in LEO. If your only indicator to success is if the test results differs from expected in the right direction, you really need to go back and learn quite a bit about statistics and the scientific method.
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Old 21st November 2016, 04:45 PM   #105
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Originally Posted by ctamblyn View Post
Aside from systematic errors which could produce a false positive if not properly accounted for, accumulating over time some random noise with a mean of zero almost certainly yields a non-zero total (see random walk).
Your link doesn't work, but I'm familiar with what you are saying. Still, how often (serious question) do we see satellites consistently spiraling out of orbit even by a small amount?

The question to me doesn't seem to me how an experiment in orbit could help settle this question, but, rather, at what altitude would the thrust exceed other confounding factors?

If the answer is "no altitude is high enough" then I'd change the question to "where did the original claims that this drive could get us to Mars quickly come from"?
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Old 21st November 2016, 04:48 PM   #106
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Originally Posted by RussDill View Post
Well, given that about half of all satellites are in higher orbits than they "ought to be", ...
For what reasons? And do they show a consistent trend?

Originally Posted by RussDill View Post
... pretty much any force that acts on objects in LEO.
Again, such as?

Originally Posted by RussDill View Post
If your only indicator to success is if the test results differs from expected in the right direction, you really need to go back and learn quite a bit about statistics and the scientific method.
No, I'm looking for consistency over years.

ETA: You said LEO. OK, forget LEO, what orbit is required?
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Old 21st November 2016, 05:11 PM   #107
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Originally Posted by RecoveringYuppy View Post
Your link doesn't work, but I'm familiar with what you are saying. Still, how often (serious question) do we see satellites consistently spiraling out of orbit even by a small amount?

The question to me doesn't seem to me how an experiment in orbit could help settle this question, but, rather, at what altitude would the thrust exceed other confounding factors?

If the answer is "no altitude is high enough" then I'd change the question to "where did the original claims that this drive could get us to Mars quickly come from"?
(Hopefully the link is now fixed.)

The general problem, for me, is that without any sort of theoretical understanding of how large this tiny, tiny thrust should be*, and exactly what all the sources of errors are, how do you even begin to take the results seriously? When do you (or rather, the supporters of the EmDrive) accept that there is probably nothing there?

As for what altitude would be sufficient, it's hard to answer for the same reasons. There are effects other than those due to the Earth - e.g. solar winds, solar radiation - and how do we know whether they're negligible?

* - aside, of course, from the very robust theoretical prediction that the thrust is zero.
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Old 21st November 2016, 05:14 PM   #108
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Originally Posted by RecoveringYuppy View Post
For what reasons? And do they show a consistent trend?


Again, such as?
http://www.mariecurie.org/annals/volume4/mat2.pdf

Quote:
No, I'm looking for consistency over years.
LEO orbits are very consistent over years. They all decay and crash into the Earth

Quote:
ETA: You said LEO. OK, forget LEO, what orbit is required?
Anywhere you put it, it will be subject to multiple sources of radiation pressure as well as resulting thermal emission. It'd be much easier to control for this sort of thing on the Earth.
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Old 21st November 2016, 05:17 PM   #109
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In fact, let's turn this around.

We have a very sound theoretical prediction that the thrust is zero. We do the experiment in space, try to take into account all the external forces, and measure a tiny residual acceleration (detected by seeing that the end point of the satellite's path is very slightly displaced from where we expected it to be).

Which is more likely:

(1) The EmDrive violates conservation of momentum, and produces a thrust.
(2) There was an external force coming from somewhere which we missed.
(3) We made a measurement error.
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Old 21st November 2016, 05:32 PM   #110
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Really like the way this guy is thinking: http://www.metafilter.com/141548/NAS...-works#5667111
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Old 22nd November 2016, 06:07 AM   #111
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Originally Posted by RussDill View Post
Really like the way this guy is thinking: http://www.metafilter.com/141548/NAS...-works#5667111
Is that actually true, though? Wouldn't the same thing hold for an ion drive or photon thruster?
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Old 22nd November 2016, 06:29 AM   #112
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Originally Posted by RecoveringYuppy View Post
Still, how often (serious question) do we see satellites consistently spiraling out of orbit even by a small amount?
The typical lifespan of a LEO satellite, without adjustment, is around five years.
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Old 22nd November 2016, 07:45 AM   #113
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Originally Posted by catsmate View Post
The typical lifespan of a LEO satellite, without adjustment, is around five years.
But is that ever an >escape< from Earth? I meant "out" literally.
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Old 22nd November 2016, 07:53 AM   #114
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Originally Posted by Squeegee Beckenheim View Post
Is that actually true, though? Wouldn't the same thing hold for an ion drive or photon thruster?
An ion drive would require reaction mass be moved continually to the outside of the wheel and spun up to the speed of the wheel. Similarly for the photon thruster.
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Old 22nd November 2016, 08:04 AM   #115
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Originally Posted by RussDill View Post
An ion drive would require reaction mass be moved continually to the outside of the wheel and spun up to the speed of the wheel. Similarly for the photon thruster.
That post doesn't talk about reaction mass, but about the fact that you can get constant acceleration from a constant input of power. Is that not also what ion drives and photon thrusters promise in a vacuum?
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Old 22nd November 2016, 08:08 AM   #116
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Originally Posted by RecoveringYuppy View Post
But is that ever an >escape< from Earth? I meant "out" literally.
If you had enough force to do that, then there probably wouldn't be a need to be a space based experiment.
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Old 22nd November 2016, 08:21 AM   #117
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Originally Posted by Squeegee Beckenheim View Post
That post doesn't talk about reaction mass, but about the fact that you can get constant acceleration from a constant input of power. Is that not also what ion drives and photon thrusters promise in a vacuum?
The important aspect here is that the constant force vector is attached to a rotating wheel. Conservation of momentum, angular momentum, and energy are actually really closely linked and the rotating wheel thing is just a simple mental exercise.

If you are into low level physics, just imagine an EmDrive in empty space. Energy is applied and it accelerates. Presumably some energy is lost to heat, but some energy is being converted into kinetic energy. Now, imagine some related situations. An EmDrive ship is slowly approaching, it brakes using it's drive to come to a halt. It spent energy in bringing it's kinetic energy to zero. Where did both it's kinetic energy and the energy consumed by the EmDrive go?

At the particle level, physics operates the same forwards or backwards once you flip a few signs. Play both tapes in reverse. In the first tape, you have an EmDrive that slows to a stop and converts it's kinetic energy into electrical energy. In the second tape, you have a drive that accelerates away while producing electrical energy.

A common problem to these is that whether the kinetic energy of the system is increasing or decreasing depends on the inertial reference frame of the observer. Don't forget that KE = ½mv². So the amount of kinetic energy that's being added (or removed) depends on the relative velocity of your inertial reference frame.

The problem gets much worse when you start considering non-inertial reference frames.
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Old 22nd November 2016, 08:45 AM   #118
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Here's a linear version of the wheel. We commonly produce energy by heating things up and then using that heat to drive an engine. Lets make an engine by taking EmDrive ships and crashing them into something really big. When they crash, their kinetic energy is converted into heat. Each ship converts ½mv² of kinetic energy into heat which powers our heat engine.

Let's say that by accelerating each ship for a year, we get to a break even point. The amount of energy used to accelerate the ship is equal to the amount of kinetic energy of the impact. What happens if we run the ship for two years? The kinetic energy quadruples while the energy we spent only doubled. Yay, free energy for all.

This same free energy lunch does not occur with a traditional momentum engine.

If someone tells you they have a reactionless thruster, what they are really telling you is that they have a free energy device.
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Old 22nd November 2016, 09:02 AM   #119
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Originally Posted by RecoveringYuppy View Post
There must be some caveat you're leaving out. Otherwise we'd have a drive that works like the EM drive claims but doesn't violate any currently accepted laws.
It's possible to generate thrust off the Earth's magnetic field.

https://en.wikipedia.org/wiki/Electrodynamic_tether
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Old 22nd November 2016, 09:20 AM   #120
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Originally Posted by phunk View Post
It's possible to generate thrust off the Earth's magnetic field.

https://en.wikipedia.org/wiki/Electrodynamic_tether
Sure, but I don't see how that relates to BenBurch's statement.
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