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

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BigTuk:
We'd need c thousand or so years at least to get to our nearest neighbor..and considering that we as a species under got global language shifts every 500 years or so and civillization uphevalas every thousand years or there abouts... theres almost a certainty that the explorers and the people back home would be speaking entirely different languages, coming from different cultural perspectives and references. The explorers we send would be as alien to us as any alien we could think of.

You should brush up on modern linguistics. Modern day language drift has drastically been reduced, and in part reversed. Most thank TV for that change. Accent Reduction is a nice change, and will defiantly impact your 500 year shifts.

Any explorers we send will almost certainly speak the same exact language they leave with. Maybe some minor changes. For 500 years, or more they won't have any significant updates to their technology, and to maintain the existing equipment they'll have to know the language it was written in. Language changes because things change, but if things stop changing (because you don't want to break your spacecraft) then language wont be affected by much drift.

TLDR;
Past performance is not indicative of future returns.

giles:

TL;DR: STOP MISREPRESENTING SCIENCE IN THE SCIENCE SECTION

QUIT TRYING TO SCIENCE MY GEEK NEWS SITE

Next you're gonna tell me the sinkholes in Russia aren't made from the Great White Worms that have come to devour us all..

Lightknight:
Wait, from the Nasa Abstract it says that the null drive also gave positive thrust results:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140006052.pdf

"Thrust was observed on both test
articles, even though one of the test
articles was designed with the ex
pectation that it would not produce
thrust. Specifically, one test article contained internal
physical modifications that
were designed to produce
thrust, while the other did not (with the latter be
ing referred to as the "null" test article). "

How the hell did the null drive test produce thrust if it was modified not to?

because when you heat an object it forces air around it to move.
They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

direkiller:

Lightknight:
Wait, from the Nasa Abstract it says that the null drive also gave positive thrust results:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140006052.pdf

"Thrust was observed on both test
articles, even though one of the test
articles was designed with the ex
pectation that it would not produce
thrust. Specifically, one test article contained internal
physical modifications that
were designed to produce
thrust, while the other did not (with the latter be
ing referred to as the "null" test article). "

How the hell did the null drive test produce thrust if it was modified not to?

because when you heat an object it forces air around it to move.
They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

One "was designed with the expectation that it would not produce thrust." That quote sounds like the opposite of the thing you said, "They were most likely expecting it".

That's why the part I quoted is significant to mention. They both produced thrust even though one was specifically designed not to. Did someone screw up and accidentally insert jet fuel or propellants of some kind?

Nowhere do I see NASA validating the idea or claiming proof of anything. The abstract just says that tests were inconclusive and that they need to automate the frequency control to get reliable results. Their obtained results can't be explained by our current understanding. It's only the news sites that claim proof or validation....

(also, if the device would emit Hawking radiation as reaction mass, it could conceivably conserve momentum while being a virtual particle exchange. "Splitting the quantum plasma" sounds Star Trekky enough to me ;) )

Lightknight:

direkiller:

They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

One "was designed with the expectation that it would not produce thrust." That quote sounds like the opposite of the thing you said, "They were most likely expecting it".

They built a 'dummy drive' that shouldn't work according to the proposed mechanism; measure both, and if the measured thrust is the same, the mechanism is bunk (or at least highly questionable).

It's like using a placebo in drug trials; you know that people improve if they think they're getting medicine, so you give them sugar pills, then see if there's a difference between the group getting sugar pills and the group getting the actual drug.

I have to correct you the "Conservation of Momentum" is an out of date theory that we have know to be wrong since the 1880's. The correct theory to use is the "Conservation of Energy", of which this device does not violate. I repeat there is no violation of physics with this device, all it does is convert electrical energy to mechanical energy in a way that hasn't been done before. Time will tell if a steam powered turbine will be more efficient then burning fuel. Or more correctly would the engine of a nuclear power aircraft carrier/ submarine, (replace the propeller with a generator), be better suited to space travel then that of a slow burning bullet, i.e. current rockets.

theluckyjosh:

Lightknight:

direkiller:

They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

One "was designed with the expectation that it would not produce thrust." That quote sounds like the opposite of the thing you said, "They were most likely expecting it".

They built a 'dummy drive' that shouldn't work according to the proposed mechanism; measure both, and if the measured thrust is the same, the mechanism is bunk (or at least highly questionable).

It's like using a placebo in drug trials; you know that people improve if they think they're getting medicine, so you give them sugar pills, then see if there's a difference between the group getting sugar pills and the group getting the actual drug.

QFT.

The control group (the null target) and the sample both showed positive, so the result isn't statistically significant. The way I read that abstract, the authors are fully aware of that and are proposing improvements to the experiment to increase accuracy.

raankh:

The control group (the null target) and the sample both showed positive, so the result isn't statistically significant.

Well, I didn't read any details on amount of thrust vs whatever the input is (the physics are a bit beyond me), so I don't know about statistical significance one way or another. But you have one drive that shouldn't give you thrust that did, so ...

raankh:

The way I read that abstract, the authors are fully aware of that and are proposing improvements to the experiment to increase accuracy.

Yeah, that was my take away on the comment about 'automation'.

Lightknight:

direkiller:

Lightknight:
Wait, from the Nasa Abstract it says that the null drive also gave positive thrust results:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140006052.pdf

"Thrust was observed on both test
articles, even though one of the test
articles was designed with the ex
pectation that it would not produce
thrust. Specifically, one test article contained internal
physical modifications that
were designed to produce
thrust, while the other did not (with the latter be
ing referred to as the "null" test article). "

How the hell did the null drive test produce thrust if it was modified not to?

because when you heat an object it forces air around it to move.
They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

One "was designed with the expectation that it would not produce thrust." That quote sounds like the opposite of the thing you said, "They were most likely expecting it".

That's why the part I quoted is significant to mention. They both produced thrust even though one was specifically designed not to. Did someone screw up and accidentally insert jet fuel or propellants of some kind?

it was designed to not produce thrust in a working fashion. So any thrust generated would be from environmental influences(heated metal).
That's the point of the null, you eliminate influences that can change the data.

Lightknight:

direkiller:

Lightknight:
Wait, from the Nasa Abstract it says that the null drive also gave positive thrust results:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20140006052.pdf

"Thrust was observed on both test
articles, even though one of the test
articles was designed with the ex
pectation that it would not produce
thrust. Specifically, one test article contained internal
physical modifications that
were designed to produce
thrust, while the other did not (with the latter be
ing referred to as the "null" test article). "

How the hell did the null drive test produce thrust if it was modified not to?

because when you heat an object it forces air around it to move.
They were most likely expecting it, so they wanted to see if the working one generated any additional thrust over the null.

One "was designed with the expectation that it would not produce thrust." That quote sounds like the opposite of the thing you said, "They were most likely expecting it".

That's why the part I quoted is significant to mention. They both produced thrust even though one was specifically designed not to. Did someone screw up and accidentally insert jet fuel or propellants of some kind?

I think the idea behind the quote is not that the null drive was designed so that it could not produce thrust, but that the designers didn't think it would produce thrust. It's not that it was modified not to product thrust, it was more like following the directions to make it and thinking, "this will never work" but then it did.

Jeremy Robison:
I have to correct you the "Conservation of Momentum" is an out of date theory that we have know to be wrong since the 1880's. The correct theory to use is the "Conservation of Energy", of which this device does not violate. I repeat there is no violation of physics with this device, all it does is convert electrical energy to mechanical energy in a way that hasn't been done before. Time will tell if a steam powered turbine will be more efficient then burning fuel. Or more correctly would the engine of a nuclear power aircraft carrier/ submarine, (replace the propeller with a generator), be better suited to space travel then that of a slow burning bullet, i.e. current rockets.

http://en.wikipedia.org/wiki/Energy-momentum_tensor#Conservation_law

Conservation of the energy momentum tensor is a cornerstone of just about every relativistc theory I can think of (be in quantum field theory or general relativity). It is NOT an outdated concept. I'm not even going to MENTION the rest of that crazy post.

COMaestro:
I think the idea behind the quote is not that the null drive was designed so that it could not produce thrust, but that the designers didn't think it would produce thrust. It's not that it was modified not to product thrust, it was more like following the directions to make it and thinking, "this will never work" but then it did.

That is most definitely not what "designed with expectation" means. It means, in every scientific context, "designed with a goal in mind".

I would keep my pants on until this is accurately confirmed 20 times over by different parties.
This thing could have easily affected the result by sheer magnetic forces, heat difference or plainly manipulating the instruments.

Yes I could see an electron cannon working in the proposed way, but at that point electrons become the propellant that is lost so we are back to square one.

lacktheknack:

COMaestro:
I think the idea behind the quote is not that the null drive was designed so that it could not produce thrust, but that the designers didn't think it would produce thrust. It's not that it was modified not to product thrust, it was more like following the directions to make it and thinking, "this will never work" but then it did.

That is most definitely not what "designed with expectation" means. It means, in every scientific context, "designed with a goal in mind".

Exactly.

What we really need to know is the difference in thrust performance between the null thruster and the thruster in question. Big difference and it doesn't matter, same or similar number and the environment is causative or flawed somehow.

direkiller:
it was designed to not produce thrust in a working fashion. So any thrust generated would be from environmental influences(heated metal).
That's the point of the null, you eliminate influences that can change the data.

The wording of the abstract is that they made it not to produce thrust and were actually surprised when it did.

That's why the abstract says both produced thrust "EVEN THOUGH". Implying that the null one should not have produced thrust. I'm unsure why you disagree. It may not have provided thrust in amounts similar to the other article.

As far as heated metal producing significant thrust, I'm not convinced it would ever produce significant thrust or anything along those lines. Maybe if you pass propellants across a heated metal grid or something, but that's a traditional thrust generation technique.

giles:

Jeremy Robison:
I have to correct you the "Conservation of Momentum" is an out of date theory that we have know to be wrong since the 1880's. The correct theory to use is the "Conservation of Energy", of which this device does not violate. I repeat there is no violation of physics with this device, all it does is convert electrical energy to mechanical energy in a way that hasn't been done before. Time will tell if a steam powered turbine will be more efficient then burning fuel. Or more correctly would the engine of a nuclear power aircraft carrier/ submarine, (replace the propeller with a generator), be better suited to space travel then that of a slow burning bullet, i.e. current rockets.

http://en.wikipedia.org/wiki/Energy-momentum_tensor#Conservation_law

Conservation of the energy momentum tensor is a cornerstone of just about every relativistc theory I can think of (be in quantum field theory or general relativity). It is NOT an outdated concept. I'm not even going to MENTION the rest of that crazy post.

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?

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. :(

Rhykker:
Momentum, a measure of mass and velocity,

You did that on purpose, didn't you.

Godamnit, science, hurry up and make a warp drive already.

I thought it was a relatively simple thing to work out how this fits with our existing laws of physics.

Thrust = Release of energy

Microwaves = energy carrier

The drive takes the energy carrier and releases the energy from it.

Release of energy = Thrust

Steve the Pocket:

Rhykker:
Momentum, a measure of mass and velocity,

You did that on purpose, didn't you.

I... am not sure what you are referring to... The alliteration?

So yeah RADAR imparts physical energy onto the cone that pushes the ship forward. Based on the angle of impact on the cone. they might get a better thrust if they use a proper feed horn into the cone. Theory is based on knowledge of RADAR gained from electronics training, standing under an antenna feeling the prickly's when getting pulsed, and figure 1 from this abstract http://www.emdrive.com/NWPU2010translation.pdf page 3. I would really need to see a better schematic of their antenna to prove my theory, and find the exact wave guide dimensions they used. The thrust wouldn't be all that much though and probably has been happening since we invented RADAR. We just couldn't measure the effects till now. Could eventually build up to something great in a vacuum.

Wow, the author needs to learn some basic physics before writing articles that claim laws of physics are broken. First and foremost, every law we know is technically wrong at some level of scale, all laws of physics as we know doesn't work at the moment of the big bang or in the center of a black hole. We're still missing a unified theory of everything.
Having said that, this device does NOT violate the law of conservation of momentum. Most devices we build today requires more than classical physics to explain. Momentum is NOT the same as mass! That's what the author seems to imply. Rocket fuel is heavy, aka mass. No rocket fuel, no mass. The classical definition of momentum is mass times velocity, so no mass, no momentum. But as I said, modern day devices requires more than classical physics, enter relativity and quantum mechanics. Microwave is EM radiation, like light, just longer wavelength. Light has no mass, but it most definitely has momentum. Therefore this device propels a ship in the same way a conventional rocket engine does, exchange of momentum. (This is sometimes known as radiation pressure, the idea of using giant solar panels as "sails" in space is based on radiation pressure from the sun's light.) So in reality, the conservation of momentum is NOT violated in anyway.

Kevin Cross:
This may not require propellant, but that doesn't mean it doesn't require FUEL. You still need to be generating power to generate microwaves.

yes but you can pluck an atomic reactor there and be set for hundreds of years of travel. no refills either.

giles:
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.

sorry but i cant take any person seriously who will ignore science for some imagined nicer style (latex isnt as beatiful as its called upon and nowadays is pretty much useless to begin with)

BigTuk:

It's best to think of NASA the same way you think of Peter Molyneux . Big on vision, big on selling that vision... but the reality will always fall well shy of the mark. Just as Pete is limited by the 'available tech' NASA will always be limited 'physics'. They know, that most solar exploration is going to be done by ships upon people will have to live and work for years if not decades . ANything outside our solar system fuggedaboutit.

Except that NASA has constantly delivered on the promises for decades and Peter Molyneux hasnt even once. so i would not consider it a good comparison.

also your second pragraph is why were not actually sending people out there but instead searching for a way to do it faster.

Rhykker:

Steve the Pocket:

Rhykker:
Momentum, a measure of mass and velocity,

You did that on purpose, didn't you.

I... am not sure what you are referring to... The alliteration?

Oh. It was worded exactly like a quote from Portal.

giles:

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 :D
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 sketchy 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:

giles:
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.

giles:

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.

Steve the Pocket:

Rhykker:
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.

image

(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.

...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.

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.

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.

giles:

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.

Suhi89:

giles:

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.

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

This is still pretty cool though!

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