Physics-Defying Space Drive Confirmed by NASA, May Revolutionize Spaceflight

[Azuaron]

I'm sorry, I can't take your comment about not being able to trust science if the translation isn't properly formatted seriously when you misspell "sketchy".

Ah, the unwarranted arrogance of native english speakers
Also I have to question your literacy if you would summarize my post as "not being able to trust science if the translation isn't properly formatted". The experimental results are s[b/]k[/b]etchy either way, I was simply complaining about the illegibility in the translation of the theoretical explanation proposed by Yang for two reasons:
1) I'm interested and it's supposedly based on classical electrodynamics, so given some effort I could probably understand it within a reasonable time span
2) the escapist article we're supposedly discussing here specifically makes a statement about the theoretical side of the device ("physics-defying", "violating" momentum conservation etc.) so that's the relevant part.

The full explanation why I don't trust that translation is rather lengthy and boring. Being lazy, I simply pointed to the biggest red flag: the abyssmal, borderline unreadable format.

I was a making a joke. Here's your entire original thesis and argument regarding the Chinese paper:

Moving on to Dr. Yang ( http://www.emdrive.com/NWPU2010translation.pdf ) my eyes already hurt from the lack of LaTeX. If a freshman handed this in I would immediately give it back to him and tell him to make an effort at presenting his findings if he wants to be taken seriously. Now I know that Dr. Yang's team published it ONLY in Chinese and this is a translation, and they submitted it to peer review, but I really can't take this seriously in the way this is presented. Especially if we take into account that Dr. Yang's team is several orders of magnitude off the NASA results. In conclusion the current experimental data on the subject is scetchy at best.

You've got one point for it being off from the NASA results buried behind a paragraph of irrelevant complaining about the format of the paper. To highlight this, I complained about your misspelling. Both complaints are equally ridiculous.

 

[Lightknight]

Wait, the law persists at quantum levels? I was pretty sure this one broke down and was inconsistent in quantum mechanics. Is that not the case?

Even at the quantum level energy is conserved... ultimately. It at least has to be conserved "on average" at the quantum level, otherwise it wouldn't be true for the rest of physics right?

Hm, I don't think I'm smart enough to explain quantum field theory to a non-physicist without writing a book about it... err.. but the basics structure one would motivate it from is classical field theory, which knows an energy-momentum tensor that is a scalar (gives number at every space-time point). Examples of a classical field theory are electromagnetism and hydrodynamics. In such theories the energy-momentum tensor comes from "translational symmetry", which is just a complicated way of saying "we think the laws of physics should be the same everywhere". Through some cute maths this results in a conserved current which we call the energy momentum tensor.
Now, in a quantum field theory one can do the same (because it's formulated in the same way as classical field theory), but the "fields" are now "operators", which act on particle and vacuum "states" (vacuum = "there is no particle", "particle"="something is there with momentum p and mass m" etc.). One would thus have an energy-momentum "operator". This is basically the reason why you would get confused about the energy-momentum tensor in the first place - it's now tied to some weird operator which can only measured through his statistical properties.

I'm not sure how interested you are in the fine print, but quantum field theory (QFT) is actually rather complex when you try to entangle it and I've already deleted quite a bit of half-true junk I had written down... err... well the gist of it is:
If we look to deeply we will probably trip over our own feet. At large times (for example at scattering experiments) we will always find energy to be conserved. I've actually seen a talk (http://pirsa.org/11010111/ warning: super advanced) about a group of physicists working on a "unifying" theory with the idea that all QFT needs to do is give "large time results" (scattering amplitudes), so we should be happy with that statement... I guess

edit: Seems like it ended up being longish and nonsensical regardless. I can only attribute this to my inadequacy. I have only taught physics students so far and it doesn't seem to translate well to a more general audience. Sorry.

Even particles with no mass seem to have momentum so the classic Newtonian math of p(particle)=M(mass)X V(velocity) means dick all here. The math is fun to look at though and is why we can have things like solar sails. I would hazard a guess that these thrusters actually work in ways similar to a solar sail rather than traditional propellant that uses macro objects (such as molecules) to propel.

So, looking further into it myself as well, it looks like it does hold up to scrutiny in quantum mechanics. You only have to generalize for it in the areas that Netwons laws don't hold up (electrodynamics for example). Interesting subject to study.

 

[Lightknight]

Momentum, a measure of mass and velocity,

You did that on purpose, didn't you.

Except in quantum mechanics where mass can be nonexistent (or so small as to be considered non-existent) and thereby require you to deal with shenanigans like the de Broglie wavelength and a reduced Planck's constant when doing your math instead of using mass of the particle and velocity.

http://upload.wikimedia.org/math/8/c/8/8c82061917fd7de92e9c614460f77d53.png

(relativistic momentum)

So if it is dealing with quantum vacuum plasma as the material for thrusting then we're going that way instead of the traditional Newtonian mechanics. Is it still mass and velocity? I guess it's expressions of it. But when you've got mass-less particles you've got to do some dancing to figure out why a mass-less object would have any momentum when the classical equation is mass times velocity.

 

[Baresark]

...or our fundamental understanding of classical physics is completely wrong.

That is a bit dramatic now, isn't it. It would simply show that there is holes in the knowledge we do have, holes we didn't know even existed. It's like when people quote the laws of thermodynamics and conclude that life can't exist because the laws don't account for the spontaneous complex order of life. It doesn't mean there aren't living, highly ordered things in the universe, it simply means our understanding of it is incomplete. Or the oft quoted, "Bee's shouldn't be able to fly because on paper it's not possible". C'mon, are you really going to sit there and say what they do is impossible or admit that our understanding (at the time) was incomplete.

OT: It's always exciting to see stuff like this. A bunch of folks have confirmed thrust is possible, even NASA. So it really seems to come down to whether any meaningful amount of thrust is possible with such a device.

 

[Lightknight]

...or our fundamental understanding of classical physics is completely wrong.

That is a bit dramatic now, isn't it. It would simply show that there is holes in the knowledge we do have, holes we didn't know even existed. It's like when people quote the laws of thermodynamics and conclude that life can't exist because the laws don't account for the spontaneous complex order of life. It doesn't mean there aren't living, highly ordered things in the universe, it simply means our understanding of it is incomplete. Or the oft quoted, "Bee's shouldn't be able to fly because on paper it's not possible". C'mon, are you really going to sit there and say what they do is impossible or admit that our understanding (at the time) was incomplete.

OT: It's always exciting to see stuff like this. A bunch of folks have confirmed thrust is possible, even NASA. So it really seems to come down to whether any meaningful amount of thrust is possible with such a device.

Or it doesn't imnpact classical physics at all. As I stated in my post above yours, this is pushing against the quantum vacuum plasma. So we're stepping out of classical physics into quantum mechanics which can have some significant differences between the Macro laws we have that hold true.

 

[Suhi89]

Wait, the law persists at quantum levels? I was pretty sure this one broke down and was inconsistent in quantum mechanics. Is that not the case?

Even at the quantum level energy is conserved... ultimately. It at least has to be conserved "on average" at the quantum level, otherwise it wouldn't be true for the rest of physics right?

Hm, I don't think I'm smart enough to explain quantum field theory to a non-physicist without writing a book about it... err.. but the basics structure one would motivate it from is classical field theory, which knows an energy-momentum tensor that is a scalar (gives number at every space-time point). Examples of a classical field theory are electromagnetism and hydrodynamics. In such theories the energy-momentum tensor comes from "translational symmetry", which is just a complicated way of saying "we think the laws of physics should be the same everywhere". Through some cute maths this results in a conserved current which we call the energy momentum tensor.
Now, in a quantum field theory one can do the same (because it's formulated in the same way as classical field theory), but the "fields" are now "operators", which act on particle and vacuum "states" (vacuum = "there is no particle", "particle"="something is there with momentum p and mass m" etc.). One would thus have an energy-momentum "operator". This is basically the reason why you would get confused about the energy-momentum tensor in the first place - it's now tied to some weird operator which can only measured through his statistical properties.

I'm not sure how interested you are in the fine print, but quantum field theory (QFT) is actually rather complex when you try to entangle it and I've already deleted quite a bit of half-true junk I had written down... err... well the gist of it is:
If we look to deeply we will probably trip over our own feet. At large times (for example at scattering experiments) we will always find energy to be conserved. I've actually seen a talk (http://pirsa.org/11010111/ warning: super advanced) about a group of physicists working on a "unifying" theory with the idea that all QFT needs to do is give "large time results" (scattering amplitudes), so we should be happy with that statement... I guess

edit: Seems like it ended up being longish and nonsensical regardless. I can only attribute this to my inadequacy. I have only taught physics students so far and it doesn't seem to translate well to a more general audience. Sorry.

If it makes you feel better I understood what you wrote. I did do a course in QFT at uni though. Actually I think it might be just such a complicated idea that you couldn't possibly be explained over the internet. You talk about translational symmetry, tensors, currents, vacuum states, operators, all of which require varying degrees of explanation. It pretty much took 3 years of a top class university education before we were introduced to QFT.

To make it worse, I did understand it (at a very basic level, I only learned the Hamiltonian formulation of QFT, I don't even really know what a path integral is), but in the two years since my graduation I've forgotten most of it. I don't remember how to show that translational symmetry leads to conservation of momentum, I've forgotten exactly what a current is, I barely recall what each term in the SM Lagrangian means and am clueless how to use it to get Maxwell's or the Dirac equation (all these things make me sad). Laymen don't stand a chance unless they're very well read and extremely gifted.

As for those saying that our understanding of Physics may be wrong, you are of course right, but on the balance of probabilities it's unlikely. Conservation of momentum is pretty fundamental and it's unlikely that this piece of tech can produce such freaky conditions that it isn't conserved, even assuming such conditions exist in reality.

 

[Lightknight]

Wait, the law persists at quantum levels? I was pretty sure this one broke down and was inconsistent in quantum mechanics. Is that not the case?

Even at the quantum level energy is conserved... ultimately. It at least has to be conserved "on average" at the quantum level, otherwise it wouldn't be true for the rest of physics right?

Hm, I don't think I'm smart enough to explain quantum field theory to a non-physicist without writing a book about it... err.. but the basics structure one would motivate it from is classical field theory, which knows an energy-momentum tensor that is a scalar (gives number at every space-time point). Examples of a classical field theory are electromagnetism and hydrodynamics. In such theories the energy-momentum tensor comes from "translational symmetry", which is just a complicated way of saying "we think the laws of physics should be the same everywhere". Through some cute maths this results in a conserved current which we call the energy momentum tensor.
Now, in a quantum field theory one can do the same (because it's formulated in the same way as classical field theory), but the "fields" are now "operators", which act on particle and vacuum "states" (vacuum = "there is no particle", "particle"="something is there with momentum p and mass m" etc.). One would thus have an energy-momentum "operator". This is basically the reason why you would get confused about the energy-momentum tensor in the first place - it's now tied to some weird operator which can only measured through his statistical properties.

I'm not sure how interested you are in the fine print, but quantum field theory (QFT) is actually rather complex when you try to entangle it and I've already deleted quite a bit of half-true junk I had written down... err... well the gist of it is:
If we look to deeply we will probably trip over our own feet. At large times (for example at scattering experiments) we will always find energy to be conserved. I've actually seen a talk (http://pirsa.org/11010111/ warning: super advanced) about a group of physicists working on a "unifying" theory with the idea that all QFT needs to do is give "large time results" (scattering amplitudes), so we should be happy with that statement... I guess

edit: Seems like it ended up being longish and nonsensical regardless. I can only attribute this to my inadequacy. I have only taught physics students so far and it doesn't seem to translate well to a more general audience. Sorry.

If it makes you feel better I understood what you wrote. I did do a course in QFT at uni though. Actually I think it might be just such a complicated idea that you couldn't possibly be explained over the internet. You talk about translational symmetry, tensors, currents, vacuum states, operators, all of which require varying degrees of explanation. It pretty much took 3 years of a top class university education before we were introduced to QFT.

To make it worse, I did understand it (at a very basic level, I only learned the Hamiltonian formulation of QFT, I don't even really know what a path integral is), but in the two years since my graduation I've forgotten most of it. I don't remember how to show that translational symmetry leads to conservation of momentum, I've forgotten exactly what a current is, I barely recall what each term in the SM Lagrangian means and am clueless how to use it to get Maxwell's or the Dirac equation (all these things make me sad). Laymen don't stand a chance unless they're very well read and extremely gifted.

As for those saying that our understanding of Physics may be wrong, you are of course right, but on the balance of probabilities it's unlikely. Conservation of momentum is pretty fundamental and it's unlikely that this piece of tech can produce such freaky conditions that it isn't conserved, even assuming such conditions exist in reality.

I think the post did a wonderful job explaining it well enough. Hence why my response to Giles was conceding the point that conservation of momentum does extend to quantum particles.

I did posit though, that these thrusters don't have to be defying those laws in the same way we think they are. This could be a solar sail scenario in which it's pushing against something we're just not aware of yet. I've seen someone theorize anything from dark matter to the quantum vacuum plasma Nasa thinks it is.

The problem with Quantum Mechanics is that there's still so very much we don't know about the subject. It opened up a huge universe to us and we're only just beginning to piece things together. Hopefully time will discover all and it won't get to a point that we're incapable of delving further.

 

[XMark]

Aw man... the headline made me think that NASA had proven the physics behind the Alcubierre warp drive.

This is still pretty cool though!