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Headline is wrong. Correct topic sentence from article : "In essence, by utilizing an improved experimental procedure, the team managed to mitigate s

by dzdt 11y ago

Headline is wrong. Correct topic sentence from article : "In essence, by utilizing an improved experimental procedure, the team managed to mitigate some of the errors from prior tests — yet still found signals of unexplained thrust." No, the EmDrive does not work, they just haven't yet figured out yet why they see the spurious acceleration in their measurements. How do we know it doesn't work? Because it violates conservation of momentum, without involving any of the extreme conditions where our current understanding of physics might break down. Basic physics is REALLY REALLY well tested. The chances that some new experimental configuration will expose new physics, without involving extreme energy concentrations or extremely large or tiny spatial dimensions, is so near to zero as to be negligible.

mangecoeur 11y ago
True, but how many clicks would the headline "NASA has not yet eliminated enough errors in its EM Drive experiment to conclusively prove that it doesn't work" have got. But yeah, no one with any understanding of physics is betting money on this thing working.
- AnimalMuppet 11y ago
  I wouldn't bet more than a nickel that it works. But I wouldn't bet more than $1000 that it doesn't, either. (Disclaimer: I actually wouldn't bet anything either way, but I think the sentiment is right.)
grovulent 11y ago
'know it doesn't work' - seems a bit strong here. 1) While a violation of a widely accepted law of nature is indeed unlikely - it's not like it hasn't happened before. 2) There may yet still be some way to model the experimental data that at once makes the em-drive viable, while still preserving conservation of momentum. Still unlikely, but arguably more likely than 1). 3) And while these both remain unlikely - it is yet rational to have an increased credence for them while the experimental data remains unaccounted for. In fact, it's arguable that this increase of credence is significant - for if it were not, performing the necessary experiments to find out either way would be a waste of time. There are of course some very smart domain experts performing these experiments. Your tone and use of the word 'know' implies their irrationality. I would advise greater humility.
- dzdt 11y ago
  Can I 'know' that if I drop my phone it will fall to the floor? We 'know' the EmDrive doesn't work in exactly the same sense and nearly the same certainty.
  - grovulent 11y ago
    If you believe we do indeed have that degree of certainty - then you believe the experiments are indeed a waste of time, and that the experimenters are behaving irrationally - contra 3). I think they are rational - and certainly it's rational for me to defer to their judgement on the matter. That's fine if you don't agree. But if you're replying in order to help me update my beliefs, then you'll need to provide a rebuttal to 3) - which you haven't. :)
    - dzdt 11y ago
      The rationality of performing the tests is social and societal reasons. The lab doing this has funding to test out-of-the mainstream ideas that could lead to new propulsion systems. By testing this kind of thing, even if they also 'know' it won't work, they get publicity and attention for themselves. It helps to keep the funding rolling, and builds operational experience testing small effects, and gives the scientists a chance to play "what if" thinking about possible new physics.
      - grovulent 11y ago
        That's quite a reasonable, if cynical, reply. To be honest I don't know how to evaluate the which of these two explanations of the scientist's behaviour are more likely. I'd like to see some data on how much one can obtain funding by performing what is, given your beliefs, literally garbage science. If we can establish at least precedent that scientists can attract funding on the basis of their projects that were (at the time, not in hindsight) - un-controversially junk research. Then your explanation would have the upper hand. If we can establish a clear pattern of such rewards, then you win a slam dunk.
devit 11y ago
As long as the device doesn't move enough that the original center of mass is no longer inside the device, then externally reactionless motion can be obtained by simply shifting mass inside. Other behavior thought impossible like creation of positive/negative mass pairs or teleportation of internal mass would allow to extend the same mechanism to arbitrary movement.
DevX101 11y ago
Until the theory can account for ALL the evidence, then there are either errors in the experiment or the theory is incomplete . You are dismissing the latter possibility prematurely. The history of science is full of unexplained experimental errors that were later confirmed by an improved theory (see Einstein's General Theory of Relativity vs Newton's 'Law' of gravitation). IF scientists universally adopted your position, then there wouldn't have been any point in further investigating experimental contradictions (time dilation, gravitation lensing) to Newton's Laws since they were clearly impossible based on the REALLY REALLY well tested laws of physics.
- Retra 11y ago
  I very strongly disagree that dismissing the possibility of an incomplete theory is premature. The amount of evidence supporting our current theories is absolutely staggering. Some small acceleration on a technology nobody understands isn't going to overturn that evidence. It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity. "IF scientists universally adopted your position [...]" Scientists don't universally adopt positions, so that's not something we have to worry about. We have to worry about non-scientists adopting dreams over facts. But really, there's no point in declaring victory or defeat while the battle is still going.
  - AnimalMuppet 11y ago
    > It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity. But, see, if we follow the approach of the doubters here, we'll never get to almost absolutely undeniable evidence, because we won't bother to investigate it because of how improbable it is. Look, people here are saying that an incomplete theory is possible - not certain, not even probable, just possible. It's happened twice in just over a century, so, yeah, not probable. But saying that it can't happen because the science is settled is, ironically, not a very scientific approach. > But really, there's no point in declaring victory or defeat while the battle is still going. Absolutely.
    - 11y ago
threeseed 11y ago
> No, the EmDrive does not work No. Nobody knows if the EmDrive works or not. That is the point of these tests. And there are theories that don't violate the conservation of momentum. Unless you know something that NASA and countless others don't.
- corporatesss 11y ago
  >And there are theories that don't violate the conservation of momentum. Which theories are those?
  - _0ffh 11y ago
    Take momentum from virtual particles was one, IIRC.
  - threeseed 11y ago
    https://en.wikipedia.org/wiki/Woodward_effect https://en.wikipedia.org/wiki/Woodward_effect
    - corporatesss 11y ago
      That is a hypothesis.
      - threeseed 11y ago
        IANA scientist so I meant theory in layman's term i.e. an explanation. The point is that there are explanations for what this could be that don't involve violating the CoM concept. Nobody knows what it is going on here. Hence why it is premature to say whether it works or not.
        corporatesss 11y ago
        If you were using the non-scientific definition, then your previous two arguments aren't valid.
madaxe_again 11y ago
Look, we KNOW that the sun revolves the earth and is affixed to a crystal sphere, like the planets. It's clear from all observations that this is the case. I mean, we understand epicycles perfectly, and they're due to the motion of the spheres. The chance that some crackpot would expose new physics and prove that the Earth orbits the Sun is so near to zero as to be negligible. Your argument is the same as those made around relativity, as it disagreed with Newton, and what could some fucking patent clerk possibly know that the Greatest Scientist Ever didn't?
- raverbashing 11y ago
  > Your argument is the same as those made around relativity Of that we can be sure The good thing is that "Of course it doesn't work" has not gotten anyone a Nobel price And it may even not violate conservation of momentum
- jschwartzi 11y ago
  The people discounting Kepler and Einstein had actually read their work. They discounted it based on the lack of physical evidence(experimental results). People in Einstein's time were still confused and trying to understand the outcome of the Michaelson-Morley experiment. As for Kepler, he didn't provide any new evidence either. The only advantage to changing the center of the system was to eliminate the need to calculate epicycles when creating an ephemeris. I could certainly see how both theories would have attracted some disbelief in their time. In Einstein's case, people started to accept SR when new experimental results came that only made sense if the speed of light were constant and the laws of physics were invariant in all inertial reference frames. Why do we have to accept that something novel is happening in this case? Can you find any way to explain this effect with existing theory? More importantly, what would have to be changed to accommodate this phenomenon? Is it possible that the engineers are just measuring noise? These are important questions that have to be answered.
- scott_s 11y ago
  No, it is not the same. Einstein proposed a theory which was largely consistent with our experimental evidence in support of Newtonian mechanics. It also agreed with recent experiments which would not find an aether. Relativity made predictions about the orbit of Mercury that were more consistent with the data than orbits predicted by Newtonian mechanics. In this instance, we have a device which is proposed to work by means that violate basic laws of conservation. There is no accompanying theory for why that is. It has been tested by several groups, and as these groups improve their testing methodology, the resultant "thrust" decreases. That is not promising. If the effect under test decreases as experimental rigor goes up, then the default assumption should be there is probably nothing there.
SeanDav 11y ago
Many major advances in scientific fields have violated previously held theories of what the state of the world is. While the balance of probabilities says that you are likely correct, humankind is very far from a complete understanding of nature and I am sure that before that understanding is reached, there will be quite a few violations of current best scientific theories.
mabbo 11y ago
Experimental evidence shows that it does work, in the sense that force is applied. The question that remains is whether it works as the (crackpot?) inventor claims, or some other effect that we haven't quite figured out yet.
- scott_s 11y ago
  No, experiments show that there is some unexplained thrust. That does not mean it "works". A much more likely explanation is very boring things like experimental error or a side-effect of heating. See http://theness.com/neurologicablog/index.php/despite-headlines-the-em-drive-is-still-bullshit/ http://theness.com/neurologicablog/index.php/despite-headlin...
SigmundA 11y ago
Can someone explain how the EM drive violates conservation of momentum while radiation pressure does not? In fact it would seem the most obvious way the EM drive works is related to radiation pressure. I am sure I am missing something do to my lack of understanding in the field, but radiation pressure is based on photons having momentum. The EM drive seems to work by emitting a whole lot of photons in the form of microwaves and having them bounce around inside a chamber shaped a certain way leading to it exerting a net force.
- AnimalMuppet 11y ago
  IIUC, the problem is that the chamber is closed. Photons having momentum shouldn't create net thrust if they never escape the chamber.
  - SigmundA 11y ago
    I assumed the chamber wasn't perfect just that they reflect enough times to impart the net thrust before escaping.
    - AnimalMuppet 11y ago
      But if they reflect a lot, they reflect from one side, and then from the other side. Still no net momentum change.
mahranch 11y ago
> No, the EmDrive does not work That is simply inaccurate to say. Just because they have not ruled out all of the errors in testing doesn't mean it does not work, that's premature. You're suggesting that you know with absolute certainty that it's an error in testing and not some new physics or undocumented effect (like the casmir effect). I find that presumptuous, close-minded and frankly, ignorant. Is it an error in testing? Maybe, probably. However, I would never say that I know something "for certainty" when I don't. > Because it violates conservation of momentum We don't know it does this yet. And again, it's inaccurate to claim it does because we don't know if it does. As I said in another comment, for all we know, the string theorists have it right and this effect could be pulling/utilizing energy from some higher dimension that we don't even know exists yet. There are any number reasonable (not physics-breaking, albeit far fetched) ways this could work. And one of them is unknown physics. To pretend we know all there is about physics is ignorant and close-minded. We're nowhere near close to understanding physics in its entirety. There are some huge problems we've yet to solve. When we do, they will most certainly give us more insight into our universe than any of the other discoveries that have come before (like reconciling quantum mechanics with relativity).
gjm11 11y ago
Let me suggest the following way of looking at it. What evidence do we have suggesting that the EmDrive works? We certainly don't have a device observed to be generating large thrusts reactionlessly. What we allegedly do have is a bunch of measurements that, on the face of it, suggest that maybe we could make one by refining this technology. But the path from those measurements to that conclusion goes through a load of physics, and nothing on that path is known with any more certainty than conservation of momentum is known under such "ordinary" circumstances. Suppose someone comes to you with a purported mathematical proof that 2+2 doesn't equal 4. You look at their proof and don't find anything wrong with it. Are you justified in believing that 2+2 isn't 4? No, however carefully you check the proof, because the axioms and rules of inference they use in the proof are going to be no more certain than 2+2=4. If you check the proof carefully enough then you're entitled to conclude that something is very wrong in our conventional understanding of mathematics, but you can't tell what and you should be pretty confident it isn't 2+2=4 until someone demonstrates how every time you put 2 things and 2 things together you're really getting 5 things and just not noticing one of them. Similarly, if someone comes to you with a purported demonstration of momentum nonconservation in "ordinary" circumstances, then if you check their work carefully enough you may be entitled to conclude that something's wrong with our understanding of physics. But you shouldn't leap from there to "momentum isn't conserved" until you actually see momentum clearly not being conserved, or find a coherent theoretical framework that explains what you've seen along with all the previous evidence for momentum conservation, and that has momentum not being conserved as claimed.

by dzdt 11y ago

mangecoeur 11y ago

True, but how many clicks would the headline "NASA has not yet eliminated enough errors in its EM Drive experiment to conclusively prove that it doesn't work" have got. But yeah, no one with any understanding of physics is betting money on this thing working.

AnimalMuppet 11y ago
I wouldn't bet more than a nickel that it works. But I wouldn't bet more than $1000 that it doesn't, either. (Disclaimer: I actually wouldn't bet anything either way, but I think the sentiment is right.)

grovulent 11y ago

'know it doesn't work' - seems a bit strong here. 1) While a violation of a widely accepted law of nature is indeed unlikely - it's not like it hasn't happened before. 2) There may yet still be some way to model the experimental data that at once makes the em-drive viable, while still preserving conservation of momentum. Still unlikely, but arguably more likely than 1). 3) And while these both remain unlikely - it is yet rational to have an increased credence for them while the experimental data remains unaccounted for. In fact, it's arguable that this increase of credence is significant - for if it were not, performing the necessary experiments to find out either way would be a waste of time. There are of course some very smart domain experts performing these experiments. Your tone and use of the word 'know' implies their irrationality. I would advise greater humility.

dzdt 11y ago
Can I 'know' that if I drop my phone it will fall to the floor? We 'know' the EmDrive doesn't work in exactly the same sense and nearly the same certainty.
- grovulent 11y ago
  If you believe we do indeed have that degree of certainty - then you believe the experiments are indeed a waste of time, and that the experimenters are behaving irrationally - contra 3). I think they are rational - and certainly it's rational for me to defer to their judgement on the matter. That's fine if you don't agree. But if you're replying in order to help me update my beliefs, then you'll need to provide a rebuttal to 3) - which you haven't. :)
  - dzdt 11y ago
    The rationality of performing the tests is social and societal reasons. The lab doing this has funding to test out-of-the mainstream ideas that could lead to new propulsion systems. By testing this kind of thing, even if they also 'know' it won't work, they get publicity and attention for themselves. It helps to keep the funding rolling, and builds operational experience testing small effects, and gives the scientists a chance to play "what if" thinking about possible new physics.
    - grovulent 11y ago
      That's quite a reasonable, if cynical, reply. To be honest I don't know how to evaluate the which of these two explanations of the scientist's behaviour are more likely. I'd like to see some data on how much one can obtain funding by performing what is, given your beliefs, literally garbage science. If we can establish at least precedent that scientists can attract funding on the basis of their projects that were (at the time, not in hindsight) - un-controversially junk research. Then your explanation would have the upper hand. If we can establish a clear pattern of such rewards, then you win a slam dunk.

devit 11y ago

As long as the device doesn't move enough that the original center of mass is no longer inside the device, then externally reactionless motion can be obtained by simply shifting mass inside. Other behavior thought impossible like creation of positive/negative mass pairs or teleportation of internal mass would allow to extend the same mechanism to arbitrary movement.

DevX101 11y ago

Until the theory can account for ALL the evidence, then there are either errors in the experiment or the theory is incomplete . You are dismissing the latter possibility prematurely. The history of science is full of unexplained experimental errors that were later confirmed by an improved theory (see Einstein's General Theory of Relativity vs Newton's 'Law' of gravitation). IF scientists universally adopted your position, then there wouldn't have been any point in further investigating experimental contradictions (time dilation, gravitation lensing) to Newton's Laws since they were clearly impossible based on the REALLY REALLY well tested laws of physics.

Retra 11y ago
I very strongly disagree that dismissing the possibility of an incomplete theory is premature. The amount of evidence supporting our current theories is absolutely staggering. Some small acceleration on a technology nobody understands isn't going to overturn that evidence. It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity. "IF scientists universally adopted your position [...]" Scientists don't universally adopt positions, so that's not something we have to worry about. We have to worry about non-scientists adopting dreams over facts. But really, there's no point in declaring victory or defeat while the battle is still going.
- AnimalMuppet 11y ago
  > It needs to be almost absolutely undeniable that this drive works, not a mere suspicion or curiosity. But, see, if we follow the approach of the doubters here, we'll never get to almost absolutely undeniable evidence, because we won't bother to investigate it because of how improbable it is. Look, people here are saying that an incomplete theory is possible - not certain, not even probable, just possible. It's happened twice in just over a century, so, yeah, not probable. But saying that it can't happen because the science is settled is, ironically, not a very scientific approach. > But really, there's no point in declaring victory or defeat while the battle is still going. Absolutely.
  - 11y ago

threeseed 11y ago

> No, the EmDrive does not work No. Nobody knows if the EmDrive works or not. That is the point of these tests. And there are theories that don't violate the conservation of momentum. Unless you know something that NASA and countless others don't.

corporatesss 11y ago
>And there are theories that don't violate the conservation of momentum. Which theories are those?
- _0ffh 11y ago
  Take momentum from virtual particles was one, IIRC.
- threeseed 11y ago
  https://en.wikipedia.org/wiki/Woodward_effect https://en.wikipedia.org/wiki/Woodward_effect
  - corporatesss 11y ago
    That is a hypothesis.
    - threeseed 11y ago
      IANA scientist so I meant theory in layman's term i.e. an explanation. The point is that there are explanations for what this could be that don't involve violating the CoM concept. Nobody knows what it is going on here. Hence why it is premature to say whether it works or not.
      - corporatesss 11y ago
        If you were using the non-scientific definition, then your previous two arguments aren't valid.

madaxe_again 11y ago

Look, we KNOW that the sun revolves the earth and is affixed to a crystal sphere, like the planets. It's clear from all observations that this is the case. I mean, we understand epicycles perfectly, and they're due to the motion of the spheres. The chance that some crackpot would expose new physics and prove that the Earth orbits the Sun is so near to zero as to be negligible. Your argument is the same as those made around relativity, as it disagreed with Newton, and what could some fucking patent clerk possibly know that the Greatest Scientist Ever didn't?

raverbashing 11y ago
> Your argument is the same as those made around relativity Of that we can be sure The good thing is that "Of course it doesn't work" has not gotten anyone a Nobel price And it may even not violate conservation of momentum
jschwartzi 11y ago
The people discounting Kepler and Einstein had actually read their work. They discounted it based on the lack of physical evidence(experimental results). People in Einstein's time were still confused and trying to understand the outcome of the Michaelson-Morley experiment. As for Kepler, he didn't provide any new evidence either. The only advantage to changing the center of the system was to eliminate the need to calculate epicycles when creating an ephemeris. I could certainly see how both theories would have attracted some disbelief in their time. In Einstein's case, people started to accept SR when new experimental results came that only made sense if the speed of light were constant and the laws of physics were invariant in all inertial reference frames. Why do we have to accept that something novel is happening in this case? Can you find any way to explain this effect with existing theory? More importantly, what would have to be changed to accommodate this phenomenon? Is it possible that the engineers are just measuring noise? These are important questions that have to be answered.
scott_s 11y ago
No, it is not the same. Einstein proposed a theory which was largely consistent with our experimental evidence in support of Newtonian mechanics. It also agreed with recent experiments which would not find an aether. Relativity made predictions about the orbit of Mercury that were more consistent with the data than orbits predicted by Newtonian mechanics. In this instance, we have a device which is proposed to work by means that violate basic laws of conservation. There is no accompanying theory for why that is. It has been tested by several groups, and as these groups improve their testing methodology, the resultant "thrust" decreases. That is not promising. If the effect under test decreases as experimental rigor goes up, then the default assumption should be there is probably nothing there.

SeanDav 11y ago

Many major advances in scientific fields have violated previously held theories of what the state of the world is. While the balance of probabilities says that you are likely correct, humankind is very far from a complete understanding of nature and I am sure that before that understanding is reached, there will be quite a few violations of current best scientific theories.

mabbo 11y ago

Experimental evidence shows that it does work, in the sense that force is applied. The question that remains is whether it works as the (crackpot?) inventor claims, or some other effect that we haven't quite figured out yet.

scott_s 11y ago
No, experiments show that there is some unexplained thrust. That does not mean it "works". A much more likely explanation is very boring things like experimental error or a side-effect of heating. See http://theness.com/neurologicablog/index.php/despite-headlines-the-em-drive-is-still-bullshit/ http://theness.com/neurologicablog/index.php/despite-headlin...

SigmundA 11y ago

Can someone explain how the EM drive violates conservation of momentum while radiation pressure does not? In fact it would seem the most obvious way the EM drive works is related to radiation pressure. I am sure I am missing something do to my lack of understanding in the field, but radiation pressure is based on photons having momentum. The EM drive seems to work by emitting a whole lot of photons in the form of microwaves and having them bounce around inside a chamber shaped a certain way leading to it exerting a net force.

AnimalMuppet 11y ago
IIUC, the problem is that the chamber is closed. Photons having momentum shouldn't create net thrust if they never escape the chamber.
- SigmundA 11y ago
  I assumed the chamber wasn't perfect just that they reflect enough times to impart the net thrust before escaping.
  - AnimalMuppet 11y ago
    But if they reflect a lot, they reflect from one side, and then from the other side. Still no net momentum change.

mahranch 11y ago

> No, the EmDrive does not work That is simply inaccurate to say. Just because they have not ruled out all of the errors in testing doesn't mean it does not work, that's premature. You're suggesting that you know with absolute certainty that it's an error in testing and not some new physics or undocumented effect (like the casmir effect). I find that presumptuous, close-minded and frankly, ignorant. Is it an error in testing? Maybe, probably. However, I would never say that I know something "for certainty" when I don't. > Because it violates conservation of momentum We don't know it does this yet. And again, it's inaccurate to claim it does because we don't know if it does. As I said in another comment, for all we know, the string theorists have it right and this effect could be pulling/utilizing energy from some higher dimension that we don't even know exists yet. There are any number reasonable (not physics-breaking, albeit far fetched) ways this could work. And one of them is unknown physics. To pretend we know all there is about physics is ignorant and close-minded. We're nowhere near close to understanding physics in its entirety. There are some huge problems we've yet to solve. When we do, they will most certainly give us more insight into our universe than any of the other discoveries that have come before (like reconciling quantum mechanics with relativity).

gjm11 11y ago

Let me suggest the following way of looking at it. What evidence do we have suggesting that the EmDrive works? We certainly don't have a device observed to be generating large thrusts reactionlessly. What we allegedly do have is a bunch of measurements that, on the face of it, suggest that maybe we could make one by refining this technology. But the path from those measurements to that conclusion goes through a load of physics, and nothing on that path is known with any more certainty than conservation of momentum is known under such "ordinary" circumstances. Suppose someone comes to you with a purported mathematical proof that 2+2 doesn't equal 4. You look at their proof and don't find anything wrong with it. Are you justified in believing that 2+2 isn't 4? No, however carefully you check the proof, because the axioms and rules of inference they use in the proof are going to be no more certain than 2+2=4. If you check the proof carefully enough then you're entitled to conclude that something is very wrong in our conventional understanding of mathematics, but you can't tell what and you should be pretty confident it isn't 2+2=4 until someone demonstrates how every time you put 2 things and 2 things together you're really getting 5 things and just not noticing one of them. Similarly, if someone comes to you with a purported demonstration of momentum nonconservation in "ordinary" circumstances, then if you check their work carefully enough you may be entitled to conclude that something's wrong with our understanding of physics. But you shouldn't leap from there to "momentum isn't conserved" until you actually see momentum clearly not being conserved, or find a coherent theoretical framework that explains what you've seen along with all the previous evidence for momentum conservation, and that has momentum not being conserved as claimed.