I set up this blog to practice writing, and look what happens. Oh well. In the meantime I post things on Quora and Facebook that would be perfect candidates for reposting here. Maybe I should cross-post? Let's do this thing.
A few days ago, some news of some new space thruster (the Cannae drive) that seemed to drive itself without shooting out some sort of reaction mass (apparently violating the conservation of momentum). A conference proceeding was posted and at the very end, it details being able to make some quite impressive trips around the solar system.
So, it was asked (on Quora): Does this new device disprove conservation of momentum?
Short guess: The drive doesn't work, and this is merely an experimental error. Conservation of momentum is not in question.
Pithy quote: "Extraordinary claims require extraordinary evidence." - Carl Sagan.
Another pithy quote: "Science is hard" - The most trusted name in news.
Longer answer:
Conservation of momentum is a fairly robust idea, and it would take a lot of evidence to show that it's been broken. The basic idea is a consequence of Noether's theorem--any symmetry of the universe leads to some conserved quantity. If we assume things are the same from one moment to the next, then energy is conserved. If things are the same if you move a few inches to the side, momentum is conserved. If things look the same when you rotate yourself, then angular momentum is conserved.
Doing accounting of these conserved quantities is a fundamental task of many working physicists, and very small discrepencies in the ledgers either means (generally most likely) that you made some experimental error/are dealing with too much noise or there is some new physics there. Momentum would not appear to be conserved with two magnets moving past each other--UNTIL you account for the momentum inherent in electromagnetic fields (or photons) themselves. Missing momentum and energy in particle tracks helped point the way towards things like neutrons and neutrinos, which generally otherwise would appear invisible but we've managed to find ways to detect and sometimes even use them.
And when we realized that parity (basically, left/right-handedness of things) is NOT conserved in certain particle interactions--after much methodical testing by Chien-Shiung Wu and others--that told us some very important things about the Weak interaction and the fundamental symmetries of the universe. Import enough to lead to the 1957 Nobel prize in physics. Rest assured there are physicists looking carefully for very tiny deviations in other conserved quantities, trying to tease out if there are any other interesting subtle effects to the universe.
Now, on to the Cannae drive--could it be generating thrust through some novel means, sticking the momentum into some unknown form? Yes. But I am EXTREMELY skeptical that they've measured anything real. And their comments about interaction with some quantum vacuum virtual plasma is pretty much just word salad. Nobody outside of NASA Eagleworks (who did the testing) uses that term, which should raise some red flags right away.
First, they are trying to do a torsion balance test, which are known for being extremely tricky and finicky (see Impossible Thruster Probably Impossible for some details on that front). This was tested over only a few days and only a few times, which is not much time for trying to iron out all of the issues. I would want to see months of testing to confirm any sort of results. Did I mention that Science is Hard?
Second, there are a number of real effects that could play a role. The tests were carried out at ambient pressure (confusingly, the original paper, which is mirrored here, talks about having a vacuum system to pump down the system--but then in their "Future Work" section they mention needing to change their RF circuitry to properly work under vacuum. Their official NASA abstract says the testing was done at ambient pressure), which means that there was plenty of air to interact with. If one side got warmer than the other, this would easily provide some thrust in a manner similar to a Crookes radiometer.
The report speaks of the difficulty of providing full shielding of the microwaves, and so any leaky waves (which would go about the distance of 1 wavelength, which for ~ 1GHz is about 1 foot) could interact with water vapor or other parts of the aparatus. They also mention several sources of error (they talk about waves from the Gulf Coast affecting measurements) but don't quantify how big they are. Major, major alarms here.
Third, their null test gave about as much thrust as their proper test. While one could argue that the null test was not "really" a null test as, since they don't really know how it works, maybe how they made it null (removing the slots) wasn't affecting it much, but it definitely kills their explanation of how it works (since their theory relied on the slots).
Fourth, this is a conference proceeding, not a paper. This means that nobody in the greater scientific community has formally vetted it (though now many are making comments in response to the news) and let me tell you, many many proceedings turn out to be wrong (I've caught mistakes in my own proceedings). These are more "interim" reports than anything final. So I'd give it fairly little scientific weight.
And, while this may sound a bit petty, the report looks sloppy, which does not inspire me with confidence. The fact that for their own proceedings they did things like take photos of graphs on their computer screens instead of downloading the data and putting it in nice graphs (which takes 20 minutes of effort, mostly to make the graph look nice): sloppy*. They talk about irrelevant things in the experimental set-up (like what sort of solder they used) and ignore important things like what the Cannae cavities are made out of (Copper? Or some kind of superconductor?). They have some inconclusive results and then end the report with some grand scheme of all the things that could happen if they scaled this up.
Just no.
This is the kind of thing I put out if I'm rushing to write a lab report for a class and am not putting too much thought into it. I will later accept the C grade and then never look at the report again. While you could have a shoddy paper for interesting results, this really does not instill any confidence in me that this test was undertaken with enough care and precaution to counteract all the sources of experimental error.
So I cannae vouch for the Cannae drive. Like the neutrinos we thought were faster than light (a measurement that was later found to be due to a loose wire) it's all too easy for these sorts of things to be some experimental hitch.
Science is Hard.
For more reading, I recommend John Baez's post: https://plus.google.com/1
*Alternately, you could just press "Print Screen" on your keyboard, open up MS Paint, and crop the image to get something that looks nicer. That takes 30 seconds. IT TOOK MORE WORK TO TAKE THE IMAGES OFF OF A CAMERA LIKE THEY DID.
A few days ago, some news of some new space thruster (the Cannae drive) that seemed to drive itself without shooting out some sort of reaction mass (apparently violating the conservation of momentum). A conference proceeding was posted and at the very end, it details being able to make some quite impressive trips around the solar system.
So, it was asked (on Quora): Does this new device disprove conservation of momentum?
Short guess: The drive doesn't work, and this is merely an experimental error. Conservation of momentum is not in question.
Pithy quote: "Extraordinary claims require extraordinary evidence." - Carl Sagan.
Another pithy quote: "Science is hard" - The most trusted name in news.
Longer answer:
Conservation of momentum is a fairly robust idea, and it would take a lot of evidence to show that it's been broken. The basic idea is a consequence of Noether's theorem--any symmetry of the universe leads to some conserved quantity. If we assume things are the same from one moment to the next, then energy is conserved. If things are the same if you move a few inches to the side, momentum is conserved. If things look the same when you rotate yourself, then angular momentum is conserved.
Doing accounting of these conserved quantities is a fundamental task of many working physicists, and very small discrepencies in the ledgers either means (generally most likely) that you made some experimental error/are dealing with too much noise or there is some new physics there. Momentum would not appear to be conserved with two magnets moving past each other--UNTIL you account for the momentum inherent in electromagnetic fields (or photons) themselves. Missing momentum and energy in particle tracks helped point the way towards things like neutrons and neutrinos, which generally otherwise would appear invisible but we've managed to find ways to detect and sometimes even use them.
And when we realized that parity (basically, left/right-handedness of things) is NOT conserved in certain particle interactions--after much methodical testing by Chien-Shiung Wu and others--that told us some very important things about the Weak interaction and the fundamental symmetries of the universe. Import enough to lead to the 1957 Nobel prize in physics. Rest assured there are physicists looking carefully for very tiny deviations in other conserved quantities, trying to tease out if there are any other interesting subtle effects to the universe.
Now, on to the Cannae drive--could it be generating thrust through some novel means, sticking the momentum into some unknown form? Yes. But I am EXTREMELY skeptical that they've measured anything real. And their comments about interaction with some quantum vacuum virtual plasma is pretty much just word salad. Nobody outside of NASA Eagleworks (who did the testing) uses that term, which should raise some red flags right away.
First, they are trying to do a torsion balance test, which are known for being extremely tricky and finicky (see Impossible Thruster Probably Impossible for some details on that front). This was tested over only a few days and only a few times, which is not much time for trying to iron out all of the issues. I would want to see months of testing to confirm any sort of results. Did I mention that Science is Hard?
Second, there are a number of real effects that could play a role. The tests were carried out at ambient pressure (confusingly, the original paper, which is mirrored here, talks about having a vacuum system to pump down the system--but then in their "Future Work" section they mention needing to change their RF circuitry to properly work under vacuum. Their official NASA abstract says the testing was done at ambient pressure), which means that there was plenty of air to interact with. If one side got warmer than the other, this would easily provide some thrust in a manner similar to a Crookes radiometer.
The report speaks of the difficulty of providing full shielding of the microwaves, and so any leaky waves (which would go about the distance of 1 wavelength, which for ~ 1GHz is about 1 foot) could interact with water vapor or other parts of the aparatus. They also mention several sources of error (they talk about waves from the Gulf Coast affecting measurements) but don't quantify how big they are. Major, major alarms here.
Third, their null test gave about as much thrust as their proper test. While one could argue that the null test was not "really" a null test as, since they don't really know how it works, maybe how they made it null (removing the slots) wasn't affecting it much, but it definitely kills their explanation of how it works (since their theory relied on the slots).
Fourth, this is a conference proceeding, not a paper. This means that nobody in the greater scientific community has formally vetted it (though now many are making comments in response to the news) and let me tell you, many many proceedings turn out to be wrong (I've caught mistakes in my own proceedings). These are more "interim" reports than anything final. So I'd give it fairly little scientific weight.
And, while this may sound a bit petty, the report looks sloppy, which does not inspire me with confidence. The fact that for their own proceedings they did things like take photos of graphs on their computer screens instead of downloading the data and putting it in nice graphs (which takes 20 minutes of effort, mostly to make the graph look nice): sloppy*. They talk about irrelevant things in the experimental set-up (like what sort of solder they used) and ignore important things like what the Cannae cavities are made out of (Copper? Or some kind of superconductor?). They have some inconclusive results and then end the report with some grand scheme of all the things that could happen if they scaled this up.
Just no.
This is the kind of thing I put out if I'm rushing to write a lab report for a class and am not putting too much thought into it. I will later accept the C grade and then never look at the report again. While you could have a shoddy paper for interesting results, this really does not instill any confidence in me that this test was undertaken with enough care and precaution to counteract all the sources of experimental error.
So I cannae vouch for the Cannae drive. Like the neutrinos we thought were faster than light (a measurement that was later found to be due to a loose wire) it's all too easy for these sorts of things to be some experimental hitch.
Science is Hard.
For more reading, I recommend John Baez's post: https://plus.google.com/1
*Alternately, you could just press "Print Screen" on your keyboard, open up MS Paint, and crop the image to get something that looks nicer. That takes 30 seconds. IT TOOK MORE WORK TO TAKE THE IMAGES OFF OF A CAMERA LIKE THEY DID.
