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I do know quite a bit about physics. But if I just said the EmDrive is nonsense due to conservation of momentum (which is the 100% correct answer with no caveat

I do know quite a bit about physics. But if I just said the EmDrive is nonsense due to conservation of momentum (which is the 100% correct answer with no caveats), people would shut me down because "NASA scientists know what they're doing". That would be an appeal to authority. So I mention Baez preemptively, but it seems like that's not a winning tactic either. What would convince you, pray tell?

vardump 10y ago
> you'd shut me down because "NASA scientists know what they're doing" I've said nothing like that. A working experiment that provides irrefutable data is needed to convince me in any way. Refutation I'd need to leave for others to do, not my competence. I really like EmDrive as an idea and hope it will work out. It's very inspiring when someone has the guts to push it despite the dominant (scientific) opinion. If it does work out, these people will be some of our greatest heroes. After all, sometimes people like these have been right in the past in adverse scientific atmosphere. I'm just content to follow it from the sidelines. If I had to bet on EmDrive, I'd have to bet against it.
- cousin_it 10y ago
  I understand your position. The real question is how much you should weigh a single experiment vs. the abstract idea of conservation of momentum. It's tempting to trust the experiment all the way, and imagine that science demands such open-mindedness. But the more physics you study, the more likely you are to trust the abstract idea instead, because you realize just how incredibly well-supported it is. It's a kind of certainty that has almost no analogue in other sciences. Even in a very careful experiment, measurement error is many times more likely than overturning conservation of momentum. (Also measurement error is much more devious than people imagine, but that's another story.) I'm very confident ($100 to $1 at least) that the EmDrive is a story of measurement error, compounded by ignorance and optimism.
  - vardump 10y ago
    We're largely in agreement. On a philosophical point of view, it worries me that physics might be optimizing towards a local maxima. Which might or might not be the global one. That there even might be something big it has missed. How would we know? Even more so because physicists seem to be more and more specialized to a narrow sub-field. Everything is already so advanced it takes more and more years to just to master it. Individual contributions appear to be getting smaller and smaller. Is it possible there's something they don't see because they're too near looking at it? Studying a mountain with a microscope. Is possible we're stuck in a some sort of dead end? I really can't judge it either way. I just can't stop wondering about that.
  - tunesmith 10y ago
    This discussion is like rationality vs empiricism in action.
    - cousin_it 10y ago
      Yes, that's exactly it. In science, rationalism (Descartes, Leibniz) has been much more fruitful than empiricism (Locke, Hobbes, Hume...) It's really strange when you think about it. The guys who trusted in divine order ended up discovering tons of things, while Francis Bacon, the father of empiricism and the modern "scientific method", didn't discover anything. That's a big part of the reason why I identify as a rationalist.
      - vardump 10y ago
        Yet neither would be anywhere without the other.
  - marcosdumay 10y ago
    By one experiment, you mean one actual experiment, made once, by a single group? Or one single experimental setup, replicated by different groups? If it's the former, I don't trust it at all, but if it's well practiced and interesting, it ought to be replicated. If it's the second, well, if its results are against theoretical models, theory is wrong. No questions, no exceptions. Now, theory correction does not automatically mean a fundamental change, "hey, this approximation we used has a problem here" is as valid a theoretical correction as "ops, all of our models are wrong, everything is much more complex than we thought". Specifically about the EmDrive, I'm not aware of anybody that could actually measure an effect yet. So, there's no experiment showing theory is wrong. There's only a lack of experiments confirming it either (or better, now there is one).
tzs 10y ago
> I do know quite a bit about physics. But if I just said the EmDrive is nonsense due to conservation of momentum (which is the 100% correct answer with no caveats), people would shut me down because "NASA scientists know what they're doing". I wouldn't. However, I would ask why you think violation of conservation of momentum is completely dispositive, rather than just a strong reason for great skepticism? From Noether's Theorem [1] we know that conservation of momentum is a consequence of physics being invariant under space translation. As far as I've been able to find, we don't know that a universe that results from a big bang must be isotropic. Observationally, ours appears to be, but there are some hints that it might not be, and scientists are taking those seriously. [1] http://math.ucr.edu/home/baez/noether.html http://math.ucr.edu/home/baez/noether.html

vardump 10y ago

> you'd shut me down because "NASA scientists know what they're doing" I've said nothing like that. A working experiment that provides irrefutable data is needed to convince me in any way. Refutation I'd need to leave for others to do, not my competence. I really like EmDrive as an idea and hope it will work out. It's very inspiring when someone has the guts to push it despite the dominant (scientific) opinion. If it does work out, these people will be some of our greatest heroes. After all, sometimes people like these have been right in the past in adverse scientific atmosphere. I'm just content to follow it from the sidelines. If I had to bet on EmDrive, I'd have to bet against it.

cousin_it 10y ago
I understand your position. The real question is how much you should weigh a single experiment vs. the abstract idea of conservation of momentum. It's tempting to trust the experiment all the way, and imagine that science demands such open-mindedness. But the more physics you study, the more likely you are to trust the abstract idea instead, because you realize just how incredibly well-supported it is. It's a kind of certainty that has almost no analogue in other sciences. Even in a very careful experiment, measurement error is many times more likely than overturning conservation of momentum. (Also measurement error is much more devious than people imagine, but that's another story.) I'm very confident ($100 to $1 at least) that the EmDrive is a story of measurement error, compounded by ignorance and optimism.
- vardump 10y ago
  We're largely in agreement. On a philosophical point of view, it worries me that physics might be optimizing towards a local maxima. Which might or might not be the global one. That there even might be something big it has missed. How would we know? Even more so because physicists seem to be more and more specialized to a narrow sub-field. Everything is already so advanced it takes more and more years to just to master it. Individual contributions appear to be getting smaller and smaller. Is it possible there's something they don't see because they're too near looking at it? Studying a mountain with a microscope. Is possible we're stuck in a some sort of dead end? I really can't judge it either way. I just can't stop wondering about that.
- tunesmith 10y ago
  This discussion is like rationality vs empiricism in action.
  - cousin_it 10y ago
    Yes, that's exactly it. In science, rationalism (Descartes, Leibniz) has been much more fruitful than empiricism (Locke, Hobbes, Hume...) It's really strange when you think about it. The guys who trusted in divine order ended up discovering tons of things, while Francis Bacon, the father of empiricism and the modern "scientific method", didn't discover anything. That's a big part of the reason why I identify as a rationalist.
    - vardump 10y ago
      Yet neither would be anywhere without the other.
- marcosdumay 10y ago
  By one experiment, you mean one actual experiment, made once, by a single group? Or one single experimental setup, replicated by different groups? If it's the former, I don't trust it at all, but if it's well practiced and interesting, it ought to be replicated. If it's the second, well, if its results are against theoretical models, theory is wrong. No questions, no exceptions. Now, theory correction does not automatically mean a fundamental change, "hey, this approximation we used has a problem here" is as valid a theoretical correction as "ops, all of our models are wrong, everything is much more complex than we thought". Specifically about the EmDrive, I'm not aware of anybody that could actually measure an effect yet. So, there's no experiment showing theory is wrong. There's only a lack of experiments confirming it either (or better, now there is one).

tzs 10y ago

> I do know quite a bit about physics. But if I just said the EmDrive is nonsense due to conservation of momentum (which is the 100% correct answer with no caveats), people would shut me down because "NASA scientists know what they're doing". I wouldn't. However, I would ask why you think violation of conservation of momentum is completely dispositive, rather than just a strong reason for great skepticism? From Noether's Theorem [1] we know that conservation of momentum is a consequence of physics being invariant under space translation. As far as I've been able to find, we don't know that a universe that results from a big bang must be isotropic. Observationally, ours appears to be, but there are some hints that it might not be, and scientists are taking those seriously. [1] http://math.ucr.edu/home/baez/noether.html http://math.ucr.edu/home/baez/noether.html