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EM drive, warp drive, gullibility without limits

In recent 7 days, about 100 news outlets have informed their readers about "progress" in the construction of EM drive, and sometimes warp drive, that will allow NASA and everyone else to get everywhere (L.A., Moon, Mars, other galaxies) very quickly, perhaps faster than the speed of light.

Off-topic, legit technology: GPS with sub-inch accuracy (100 times better) will come to your smartphone soon
Almost all the writers indicate that the information is trustworthy. Exceptions are rare. Ethan Siegel at Forbes is an example. The Skeptics Guide. Katie Palmer of Wired must also be praised for her explanations why it's still poppycock. (Needless to say, hundreds of aggressive kooks attacked Palmer (pic) and upvoted themselves in the comments. By upvotes, kooks defeated sane readers 100-to-1. Be aware that poppycock isn't a cock that pops, as they think, but an original Dutch word for a soft i.e. near-liquid šit.) Numerous comments in the Tesla battery thread were dedicated to this warp drive hype. I was overwhelmed and couldn't find energy to write a separate blog post about that topic. I didn't want to be attacked by thousands of flabbergasting imbeciles.

Now the density of this nonsense has sufficiently decreased for me to find the courage to write a serious blog post: hundreds of flabbergasting imbeciles is what I am used to and ready to face.




All the hundreds of the news reports were derived from a post (about an "evaluation" of those things) on a website called NASAspaceFLIGHT.com which only "tries" to look credible, as you can easily find out. Why do hundreds of "science journalists" find it adequate to spread such big claims that only build on such a website?




There are two possible names of the cool technologies that will revolutionize spaceflight: "warp drive" and "EM drive". Warp drive is gravitational – it's supposed to curve the spacetime in such a way that the superluminal motion becomes possible – while the EM drive is basically electromagnetic (most science journalists don't care about and can't spot the difference between electromagnetism and gravity, anyway). Concerning the former, in July 2013, there was another wave of this warp drive nonsense in the media and I explained why it's completely wrong.

Special relativity bans faster-than-light motion of massive bodies because it says that in all other inertial frames, physical phenomena may be described by the same and equally simple laws of physics. But if you transform a superluminal motion to a different inertial system by the Lorentz transformation, it turns into the motion that goes backwards in time! That's a problem because the existence of the superluminal spaceships would imply the existence of spaceships flying backwards in time (those can be mapped to each other by Lorentz transformations) and it would allow you to castrate your grandfather before he sleeps with your grandmother, and that would make (or have made or would have been made or whatever) your existence impossible and our Universe logically inconsistent.

Some people want to believe that general relativity allows one to "circumvent" the limitation on speed that results from special relativity. But this ain't the case. Special relativity is still firmly incorporated in general relativity and shows its muscles in many ways.

First, special relativity holds locally. Small regions of spacetime (much smaller than the curvature radius length scale) look like the flat Minkowski space and special relativity holds there. Warp drive is supposed to curve the spacetime so that it makes the space in front of you "shorter" and easier to fly through, while the irrelevant space behind you is "longer". Warp drive apologists think that it's possible – general relativity may curve the space in any way – but they're wrong.

To get this kind of curvature, you need a negative energy density at least somewhere. You need to violate some energy conditions. I wrote a text about energy conditions and warp drive on Quora which you may read to see some details.

The negative energy density is ultimately forbidden because if it were allowed, the vacuum would be unstable. Equivalently, it could create particles (tachyons) that move faster than light and revive the aforementioned grandfather paradoxes.

There is another way to see that spaceships can't fly faster than light. From the viewpoint of very long distance scales, the space looks flat and empty – up to small and local perturbations (objects etc.). So it's a Minkowski space and the behavior of the local perturbations (objects etc.) must obey the Lorentz invariance inherited from the surrounding space, too. For this reason, it doesn't matter at all whether the local perturbations (objects such as spaceships) involve some local curvature of the spacetime (as a part of their design) or not. They're still some local objects or perturbations. Their motion that would surpass the speed of light is forbidden by the rules of special relativity because those still apply in the almost empty surrounding space!

If some strong curvature were enough to defeat special relativity, special relativity would be completely wrong. For example, black holes or some clever bound states of black holes could move faster than light. But if black holes could do it, all elementary particles could also do it – to one extent or another – because elementary particles may be viewed as "very tiny black holes" (lighter than the Planck mass) for which the quantum corrections become very important.

So the existence of curvature doesn't really change anything whatever about the fact that the superluminal motion is prohibited in Nature. Some people just don't like (special) relativity because it "restricts" them and that's bad (the fact that the laws of Nature always restrict you and everything else must be eluding them). So they invent an ideology based on a wishful thinking or belief that the "next" theory must surely eliminate the rules that special relativity has brought us – in this case that the speed can't exceed the speed of light.

But that's not how science works. Science doesn't go through similar counterrevolutions. The advance known as "special relativity" really meant that "non-relativistic physics" with its simple-minded possibilities (including arbitrarily high speeds) has been falsified. Falsification is really an irreversible process. General relativity doesn't mean and couldn't mean that physics would return to the state when all speeds are allowed once again. If that were so, it would really mean that general relativity restores Newtonian physics – but the latter had been killed since 1905.

Reactionless drive

The case of EM drive is analogous. What is EM drive? The proponents and fans talk about some microwaves in a cavity that push you without any propellant. It's clearly an example of a reactionless drive. A gadget sits in the middle of the empty space. Someone pushes a button and it suddenly starts to accelerate. No, that's impossible because it violates the momentum conservation law or the third Newton's law, if you wish.

Some people will tell you that the law isn't violated because "the vacuum" is what gives the momentum to the spaceship. But that's nonsense. By definition, the vacuum doesn't carry any momentum – its momentum is zero both in the initial state and the final state because it's really the same state, the vacuum state. If it looks like the object is accelerating itself and nothing goes out of it (and if it quacks in the same way etc.), it's because it is accelerating itself and nothing goes out of it. This is a straight denial of the momentum conservation law, and that's why this spaceship is forbidden.

Now, the individuals behind this particular "breakthrough" say that they combine some random ingredients – a church bell, microwaves, a superconductor, a cherry pie, the U.S. constitution, a witch's gray hair, and a few others – and they do a certain measurement and obtain a nonzero force in micronewtons, or something like that, which they can't explain. (Even if it worked in principle, such forces could be attributed to a mosquito and be enough to move a mosquito but all of these people already speak about getting to Mars in seconds.)

Well, that shouldn't be surprising that these people can't explain the force. People doing these things are complete idiots so biology predicts that they can't calculate the force they should measure in a complex experiment and they can't explain anything in physics or engineering. So the observations exactly agree with the predictions by physics and biology: science predicts that these people will behave like complete idiots because they're complete idiots, and that's exactly what is observed, indeed, because these people behave as complete idiots, too.

Lots of fans of this nonsense will tell you that quantum electrodynamics and its "mysterious vacuum" will allow you to violate the energy conservation law. This wishful thinking (or, more precisely, the wishful absence of thinking) is completely analogous to the absence of thinking of the warp drive fans who think that general relativity "abolishes" the special relativistic limitation on speed.

There is absolutely no reason to think that quantum mechanics or quantum electrodynamics or their effects should "abolish" the momentum conservation law or to provide you with some exceptions. As we learned from Emmy Noether exactly 100 years ago, the momentum conservation law is just the other face of the invariance of the laws of physics under spatial translations. The laws of physics are the same here and on another place. And that's enough to see that a conserved quantity – which we call momentum – has to exist.

None of these relationships is modified by quantum mechanics. We have \([H,\vec p]=0\) which may be interpreted in two different ways. Either the momentum's time derivative is zero, thanks to the Heisenberg equations, so the momentum doesn't change in time (at all: it is an operator equation). Or the Hamiltonian \(H\) isn't changed if you transform it by the transformations generated by \(\vec p\), namely by spatial translations. Because \(H\) defines the dynamical laws of physics, the previous sentence is equivalent to saying that the laws of physics are translationally symmetric.

So many people are behaving completely irrationally. There is absolutely no reason why the "next layer" of a physical theory should "abolish" the particular insights of previous theories such as the momentum conservation law. But some people want to believe that any mystery that is incomprehensible to their eyes and peabrains – and needless to say, none of these people understands quantum mechanics – will make all their dreams come true.

An Islamist doesn't know what QCD is but if you vaguely tell him what QCD is, he will surely believe that QCD is able to calculate that he will get exactly 72.0 virgins in the heaven after he performs a terrorist attack. Well, that's not what QCD does. There is absolutely no reason why it should. Very analogously, there is absolutely no reason why general relativity should "reallow" superluminal motion or why quantum mechanics should "allow" violations of the momentum conservation law.

In any quantum mechanical theory, if a conserved quantity \(L\) (either \(H\) or another observable that commutes with \(H\) – in our case, \(\vec p\)) is known for certain to have the value \(V\) after a measurement, it is guaranteed that it will have exactly the same value \(V\) up to the next measurement. It's because the wave function in between these two measurements is an eigenstate of \(L\) with the eigenvalue \(V\):\[

L \ket\psi = V \ket \psi

\] When you make the second measurement, it depends what you measure. If you measure \(L\) or another observable that commutes with \(L\), \(\ket\psi\) will remain an eigenstate of \(L\) with the same eigenvalue \(V\). If you measure a different observable \(M\) that doesn't commute with \(L\), such a measurement inevitably influences the value of \(L\) – you can't measure things without distorting the measured object. In that case, the value of \(L\) no longer has to be \(V\) after the second measurement.

But if you talk about the total momentum of the observed system and the observer, their total momentum is exactly conserved – it may be verified by an external observer. There is no way to circumvent this fact. This fact holds in any quantum mechanical theory where \([L,H]=0\). And quantum electrodynamics, QED, is just another sophisticated example of such a theory. No, the energy conservation law cannot be violated.

People love to be extremely sloppy about the "character of the uncertainties" that exist in quantum mechanics. They think that the uncertainty principle surely allows them to violate any conservation law by a little bit. But it doesn't. What the uncertainty principle says is that by measuring \(M\) such that \([L,M]\neq 0\), you affect \(L\), so you no longer know \(L\) after the measurement.

But if you know \(L\) and if \([L,H]=0\), then you continue to know \(L\) up to the next (final?) measurement! In the case of the conserved energy (imagine the energy of the harmonic oscillator), the energy may be written as a function of positions \(x\) and momenta \(p\). In classical physics, you could measure all components of \(x\) and \(p\) to calculate \(H\).

In quantum mechanics, \(H\) can't be measured by measuring \(x\) and \(p\) because \(x\) and \(p\) can't be measured at the same moment. For macroscopic objects, the uncertainty principle only inserts a tiny uncertainty about the values of \(x\) and \(p\) – and their functions such as \(H\). But in the microscopic case and if you want to be completely accurate, it's important to realize that each observable – such as \(H\) – must be measured by a very special, separate procedure, and you can never imagine that the measurement of all conceivable observables may be reduced to the "universal" measurement of \(x\) and \(p\) and some \(H\)-dependent calculation. That's how classical physics worked but quantum mechanics doesn't work in this way! Every observable – e.g. every function of the operators \(x\) and \(p\) – is measured in a fundamentally different way.

Casimir effect and superstitions

On Monday, it's been 15 years since the death of Hendrik Casimir whom we remember for the Casimir invariants and the Casimir effect. I wanted to write a biography on Monday but I was still overwhelmed by the amount of EM drive or warp drive nonsense and wanted to avoid the topic while the concentration and self-confidence of crackpots was still high.

The Casimir effect is the purely quantum mechanical attraction between two parallel metallic plates whose distance is \(a\). The electric potential obeys \(\phi=0\) at both surfaces. This implies that in between the plates, in the interval \(0\leq z \leq a\), the electromagnetic waves may be expanded into discrete Fourier series instead of the continuous Fourier transform.

This "modification of the vacuum" changes the counting of the zero-point energy of the quantum harmonic oscillators carried by the electromagnetic field. With the two metallic plates, the vacuum energy density per unit area of the plates includes a sum over the Fourier series integer \(n\)\[

\eq{
\frac{E_0}{A} &= -K \sum_{n=1}^\infty \zav{ \frac{n}{a} }^3 =\\
&= -\frac{K}{a^3} (1^3+2^3+3^3+\dots) = -\frac{K}{120 a^3}
}

\] I have used the fact that the sum of third powers of positive integers is \(\zeta(-3)=+1/120\). It is a completely analogous result to the fact that the sum of positive integers equals \(-1/12\).

If you care, the full derivation gives you the normalization constant \(K=\hbar c \pi^2/6\).

So the energy is negative and extremely important for \(a\to 0\), and that's why the two plates attract by a force that scales like \(1/a^4\). This is the Casimir force.

The displayed formula above showed that the "energy density has a negative piece" which was attributed to the modified zero-point energies. The deluded fans of various EM drive nonsense (which is a group that, under certain circumstances, may include people like Kip Thorne and Stephen Hawking as well) totally misrepresent what this "negative piece" in energy density means, can mean, or cannot mean.

They claim that it is a step towards allowing negative energy densities in macroscopic situations, too.

But once again, this claim is completely wrong. The nonzero energy density in between the plates only arose due to quantum mechanics – it was proportional to \(\hbar\) i.e. to Planck's constant. So it is guaranteed to go to zero in the classical limit, e.g. if the distances between the plates become macroscopic.

Note that we were really not calculating the interaction energy of the two plates as a volume integral. Instead, we calculated the "total" value of the integrated energy for the vacuum state. So we can't really say what places contributed the negative piece that produced the Casimir effect. The conceptually correct answer to this question is that it is the metallic plates themselves that are necessary for the modification of the zero-point energies, and in a natural accounting, the plates themselves – with their modified boundary conditions for the electromagnetic fields – contribute the negative Casimir energy.

How we attribute the energy to regions is a question that slightly depends on conventions. Note that in Maxwell's theory, there are questions what the "right" stress-energy tensor should be. There are several options. Only the total (integrated) energy and momentum are conserved and convention-independent.

But whatever convention you choose, you shouldn't forget about the fact that the very small distance between the two metallic plates was a necessary condition for producing a sizable negative contribution to the ground state energy. If you make the cavities macroscopic, the effect goes to zero. And even when and if it is not zero, the force is only a new contribution to the force between two plates (just like the van der Waals force which is a related example of a quantum-mechanics-induced force). And the force between two plates obeys the third Newton's law, of course. The action and the reaction match.

Let me describe an analogy with quantum tunneling. In quantum tunneling, a particle is able to penetrate walls that would be classically impenetrable. It means that classically, the particle would need a negative kinetic energy while being in the wall, but the kinetic energy is \(p^2/2m\) which is a positively definite operator. Classically, the particle just can't be "in the wall" and you could be tempted to say that this is true even quantum mechanically because \(p^2/2m\) is a positively definite operator.

However, the uncertainty principle offers you a loophole here. If you ask whether the particle may be "in the wall", you know its position well enough, so there's some unavoidable error in the momentum. You may imagine the momentum to be small and imaginary. And that's enough for the particle to get through if it is quick enough. The appearance of the imaginary momentum may be controversial but I just used these words to describe the exponential decrease of the wave function inside the barrier.

However, the exponentially growing/decreasing wave function can't be extrapolated to the whole space because it would fail to be normalizable (it wouldn't even be normalizable to the delta-function). Equivalently, the momentum is a Hermitian operator so all of its eigenvalues (and expectation values) are real. That's why the description in terms of the "imaginary momentum" only has a limited validity, "inside the barrier", and one must be careful what we mean.

The case of the Casimir effect may be described in an analogous way. Locally, we may imagine that the electromagnetic field has \(\bra 0 E^2 \ket 0\lt 0\) or \(\bra 0 B^2\ket 0\lt 0\) at some points in between the plates. However, this description in terms of "imaginary electromagnetic fields" can't be extrapolated to macroscopic regions of space. Such things only occur due to the small distances between the metals.

At big regions of the space, you must be able to write the electromagnetic fields as the Fourier transforms allowing all real frequencies and the energy carried by those are positively definite again.

All of this may be confusing and I can't prove a rigorous "no-go theorem" for similar gadgets because I don't really know what the "most general gadget of this kind" that is supposed to exploit the "negativity of the Casimir energy" is supposed to do. But what I can do is to prove that completely mundane and ordinary arrangements of matter that are being shown as EM drive don't display any miraculous behavior. They're so big and ordinary that classical physics is really enough, classical physics works, and it prohibits the self-acceleration and similar wonders.

I have watched several minutes of talks by Harold Sonny White and one more guy who "invented" EM drive. It seems fair to compare them to the pseudoscience supported by Rudolph II when he was the Austrian Emperor with headquarters in Prague. I think that the guys who worked for Rudolph II – inventing elixir of youth and transmutation of elements to gold and lots of similar wonderful stuff – were actually much more scientific than the men behind EM drive and (Albucierre) warp drive.

They had at least some stories, some theories that have apparently passed some tests, some excuses why the latest elixir didn't work or why no gold emerged in their test tube. The theories were ultimately wrong and people could have seen that they were wrong but they have at least tried.

The men behind EM drive and warp drive don't have anything of the sort. They just randomly combine building blocks and hope that this will lead to some breakthrough. Once you get used to the nonsensical combinations of physics buzzwords that don't fit together at all, their talks are boring and virtually content-free – and some of their fans interpret this lack of content as their being careful researchers. Sorry, they are just vacuous inarticulate crackpots. They may have been employed by NASA but they're still pathetic morons, much like all of their apologists.

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reader R T Deco said...

Nevertheless, I'm sure that, any day now, Elon Musk will be telling us that Tesla plans to leverage its lithium-ion battery technology to produce "dilithium crystals" for this new warp drive.

Anything to get some publicity and make a buck off of the naive and gullible investor, eh?


reader MikeNov said...

It's technology appears to be packaging Panasonic lithium ion batteries into pretty packaging.


reader MikeNov said...

How does Interstellar do relativity wise?


reader NumCracker said...

Dear Lubos. In your opinion why even highly educated people as the Nobel Laureate Brian Josephson, and even prominent peer reviewed journals as Nature, are prone to believe/publish pseudo science as: "water memory" or "cold fusion" ?


reader Luboš Motl said...

It's a lot of totally accurate visualizations of black holes and wormholes based on precision analysis of situations in GR that make some understandable assumptions that physicists would make. Many of the concepts about the dilation of time and similar things are basically correct, too.


The main overall story is of course impossible. There can't be traveling backwards in time and there can't exist traversable black holes, either. They require the negative energy density, much like the "warp drive". However, it's still possible to do calculations in GR with the assumption that the energy is negative, whatever is needed, and Interstellar showed the rather accurate answers what you get.


As I wrote before, there are things that are physically impossible in that movie, but those are absolutely needed for the story. This puts the movie in a much higher league physically than many other sci-fi movies with tons of errors and stupidities that are not needed for the plot at all.


reader Luboš Motl said...

Dear NumCracker, I think that Brian Josephson - who believes in telepathy - hasn't just lost it. He must be technically evaluated as a psychiatrically ill person.


reader AlainCo said...

What about MiHsC and it's idea that Unruh radiation explains inertia...
not going backward to no relativity, but forward to improving relativity.


removing darkmatter would be nice. It is modern epicycle?


reader Luboš Motl said...

I spent quite some time with that a month ago, and rediscovered some ideas later found in papers by Milgrom etc. At some moment, my belief that this replacement of dark matter is right increased to 15%.


I got back to senses, partly because these MOND theories just don't work well for clusters - they only "explain" galaxies well. So one can't live without *some* dark matter at the end. Without too much specific evidence, dark matter only seems like a better solution than dark matter plus MOND. Only a rigorous enough argument or strong enough empirical data would change my attitude.


reader R T Deco said...

What do you expect of a company that is <5% R&D and >95% sales and marketing?! Their flagship product (the electric, battery-powered car) has been available for over a century.


reader Rehbock said...

"The distance between insanity and genius is measured only by success. -Bruce Feirstein.


reader Uncle Al said...

Fabricate a drive going forward in space and backward in time ("conservation of spacetime" - find the Noetherian symmetry), thus getting from any here to any there instantaneously. Matching here and there relative velocities.... Popping from the Czech Republic (50°05′N 14°28′E) to the SA Agulhas II cruising between South Africa and Antarctica (50°05′S 14°28′E) is OK. Arriving at Dutch Harbor, Alaska (53°53′20″N 166°31′38″W) will have your nether aperture rocketing through your mouth or vice versa.

The Scharnhorst effect breaks lightspeed no problem, though it is a small step for mankind. Consider a finite temperature in electromagnetic Rindler space

http://www.npl.washington.edu/AV/altvw43.html
http://arxiv.org/abs/1110.1919
Not. Local lightspeed speed exceeds c only when the Casimir energy is negative. Finite temperature Casimir energy is positive.


reader Billy Bob said...

NASA is rightly revered in American culture but any association whatsoever even a janitor at NASA is taken as scientific gospel and so invoking those four letters certifies that what follows is fact. Look up Thomas Campbell and his TOE as another example of someone "associated with" NASA who's gone scientifically to the quiet room.


reader kashyap vasavada said...

Among proponents of warp drives using negative energy blankets by casimir effect, we should include the famous TV theoretical physicist Michael Kaku also! I have heard him saying this and also read his articles about it. I sent an email to him once, but he did not reply! This goes back to the point that even well known physicists cause confusion in public by their rash statements and we cannot blame only journalists for such confusions.


reader imho said...

Hi Lubos,


Re: the Casimir effect. I don't necessarily disagree with what you are saying, and again, I'm not advocating the correctness of the EM drive, but I do think you are missing some subtleties. First, as you mentioned, the Casimir effect works by restricting the available quantum states at a microscopic level, but nature is clever and there are many more ways to achieve this affect. This simplest examples are the destructive and constructive interference patterns that occur among electrons in crystalline matter. These destructive regions are called band gaps and manifest by restricting waves of specific momenta and energy. These restricted waves with exponentially decaying amplitudes (otherwise known as evanescent modes) indeed have imaginary wave vector, and within the crystal this results in an electronic energy density that is smaller than that in vacuum. This microscopic effect does indeed scale up to macroscopic length scales. Furthermore, an exactly equivalent mesoscopic process occurs with photons in things called photonic crystals.


BTW, I have no idea how this is applicable to the EM drive, but negative electronic or photonic energy density relative to vacuum is possible in macroscopic systems.


I've never given any thought to super conductors and their ability(inability) to restrict available quantum states outside the material? They certainly expel magnetic fields.


reader Ralph Hartley said...

You may think that persistent proponents of impossible devices are all total idiots, but that isn't true. Many are, but not all.



Some are frauds. A true fraud knows perfectly well that what he is saying is gobbledegook, and that it is impossible for the device to work as claimed, but he knows that gullibility has no limits.



Frauds and idiots can be hard to tell apart. Knowing how to prove that energy is conserved won't help you tell if the inventor of a perpetual motion machine is deluded, or trying to fool people. You need to find the hidden power source. If it is something that could be done by mistake, he may be deluded. If it was cleverly constructed and hidden, probably not.

I certainly can't claim to know about the current incarnation. I lost interest pretty quickly.


reader Art Hays said...

I thought they were saying the drive was somehow making photons and shooting them out, a 'photon' drive. I guess sort of the reverse of a solar sail.


reader Rehbock said...

Well not really. Based o. http://www.bloomberg.com/news/articles/2015-05-06/tesla-s-new-battery-doesn-t-work-that-well-with-solar
It seems possible that Panasonic batteries would be superior.:-)


reader QsaTheory said...

I have shown many times that your knowledge of the history of the area is very weak. Many of the Arab countries were already under the British and French sphere of influence to varying degree with KSA already an ally of US. Only some Palestinians who understandably were furious with the British supported Hitler.


As for Ottoman Empire, It was the Arabs in the end who brought it down, what a meager knowledge you have.


reader davideisenstadt said...

no, it certainly wasnt "the arabs"


reader QsaTheory said...

The Empire by 1914 held only Turkey and some Arab Lands, the British and The French would not have succeeded without the local Arab population revolt, Only to be stabbed in the back.


reader davideisenstadt said...

so the turks didn't do it?
the turks dont consider themselves to be arabic you know....


reader NumCracker said...

On the other hand, I have learned by reading TRF that even perfectly sane Nobel winners may be sometimes adepts of crazy pseudoscientific ideas as "cold fusion" (http://motls.blogspot.com.br/2008/07/julian-schwinger-died-14-years-ago.html ). This makes me wonder how much one shall believe in scientific disciplines out of HEP, which is well known by its "5-sigma" standard. Do you agree ?


reader Steve Presse said...

"They think that the uncertainty principle surely allows them to violate any conservation law a little bit."
I think the misunderstanding of the uncertainty principle is the foundation for all (?) scientifically baseless theories some more lucrative than others (cue the hydrino).


reader Cesar Laia said...

well, HEP surely wouldn't happen without the technology that comes from other scientific disciplines.


reader John Archer said...

"John has on many occasions given the white power Nazi signal tendencies. So if you like to cooperate with him just like some of your ancestors did, fine with me, but don't blame people calling you the self hating."

Oo-oo!

Why so circumlocutionly circumspect? Is there is some mysterious reason that you can't say it outright—such as it lacking a factual basis perhaps—so, as muslimes' needs must, you have to resort to innuendo? It's certainly typical. We see it all the time with the kid-glove treatment muslimes get when interviewed by the media here. Any old incoherent rubbish is accepted — indeed it's all that's ever proffered. And if, heaven forbid, the mandatory peecee interviewer inadvertently asks what turns out to be a difficult™ question the level bluster, incoherence and emotional incontinence in response just goes through the roof. Mega Joules of heat and no light. Oh, and the lying of course. The lying is mandatory.

So, there's a challenge for you: say it straight so that there's no possibility of it being misunderstood or being construed as vague in any way. I'm not much of a linguist but I know this is possible in English.

But this is not just about me of course. You refer to David's self hating too. Please spell out exactly what you mean here. In addition you make it sound as if I'm some kind of threat to him. If that's what you're attempting to imply please be very specific.

Thanks awfully.


reader John Archer said...

Haha. History of pisslamic bedlam is the history of civilisational pollution. And QSA is its apologist.


reader space_fountain said...

I'm one of the people arguing on the linked Wired article so I'd like to add another element to this if possible. I think 9,999 10,000 the EmDrive is some strange systematic measurement flaw. Personally, with no scientific background, I think about the possibility of vaporizing something on the outside of the cone maybe just water or the possibility and the fact the rf frequency needs tuned seems to me a possible avenue to add confirmation bias or it could just be cheating. Regardless, I had two main issues with the Wired article, first like almost all news sources they seem to conflate the reactionless drive with the warping of space. Dr White the guy testing this at NASA has for years thought it was possible to push against the quantum vacuum he called any thruster that could do this a Q-thruster. Based on this he theorized that you would see a warping of space time in the supper vacuum left behind. This is what he says he's found. It's still crazy, but it's a different crazy than the one Wired implied. Second Wired seems to imply that it isn't even worth looking into. To me that seems crazy, it's basically a hobby and is only costing about 50,000 dollars a year along with other things they are doing. It might be worth it just from a employee retention standpoint.


reader NumCracker said...

Dear Cesar, well, most likely I think it seems just another circular thinking pattern, hence most "low energy" technology currently really needed by HEP (e.g. vacuum tubes, magnets, electron sources, etc) basically derives from what in the past was considered to be HEP. Please, just remember the status of Eletrodynamics in 1870's; Chemistry around 1920's or Nuclear physics in 1930's ;-)


reader MikeNov said...

I thought the traversable black hole is OK, since they never leave it except for some way in the future construction of unspecified nature.


reader Luboš Motl said...

That would work well, in principle, but that's probably too mundane for them. ;-) In practice, we can only get enough photon pressure to measurably push the thinnest foils we can make. The idea that we will have to use it in practice seems extremely far-fetched here, too. We would have to create macroscopic amounts of antimatter and annihilate it against matter to get huge photon pressures. We would need nearly perfect mirrors not to burn the spaceship, and so on.


reader davideisenstadt said...

of course it was the proud arab nation that threw off the yoke of the ottoman empire...not the turks...


reader Luboš Motl said...

Hi, your criticisms of the Wired article are completely wrong.


First of all, as I discussed in the text above, EM drive *is* a reactionless drive because no physical excitations or particles are said to leave the "spaceship". The proponents sometimes try to pretend that they're not proposing the most hardcore kind of stupidity - reactionless drive - so their "gadget" isn't a reactionless drive. But by the actual evaluation of what it is supposed to do, it is totally obvious that it *is* a reactionless drive. You may call it a "gadget pushing against the quantum vacuum" but a gadget that accelerates itself by "pushing against the vacuum" (and the vacuum around us is always a quantum vacuum - and nothing quantum is really needed to nicely explain big simple gadgets like theirs - so the addition of the adjective "quantum" is just another piece of the scam) is by definition the same thing as a reactionless drive. It's just a fucking synonymous term for the same thing.


One can't accelerate himself by "pushing against the vacuum" because it's prohibited by the momentum conservation law - because it would be a reactionless drive!


Second, you conflated warp drive and EM drive - the first mistake by the stupidest fans of these crackpotteries that I began my text with. The newest wave of hype was about EM drive which is something else than the warp drive that you describe in the rest of your comment. At any rate, both of these things are exactly as crazy and their fans are exactly as stupid as the Wired article described it - and you are a textbook example of these uneducated deluded irrational morons.


reader Luboš Motl said...

Kaku has said quite a lot of stupid things about similar matters. Sometimes his comments looked like deliberate exaggerations he said semi-jokingly - but he probably does want the listeners to absorb all this nonsense literally.


reader Luboš Motl said...

Dear imho, one can never restrict "quantum states of the whole physical system" because they form the Hilbert space and the laws of physics say that all states in the space - and all their linear superpositions - are allowed.


So you probably meant that the Casimir effect restricts the "state of one photon" by the presence of the metals. You may say it in this way. But one only restricts the electromagnetic field at the locus of the metallic plates and their surfaces - by the boundary conditions that the metals impose upon the electromagnetic field. One is not really "restricting" anything about the behavior of the electromagnetic field in open regions strictly in between the plates. The electromagnetic field over there is as free as it has always been!


Your example starts by saying that your effect is caused by constructive or destructive interference. But in quantum mechanics, *everything* is caused by constructive or destructive interference. Feynman's path integral approach to QM makes this point manifest.


Superconductors are a simpler example of "scaling a microscopic effect" to macroscopic size than your crystalline example. The wave function of a Cooper pair is scaled - it becomes a complex classical scalar field - because there are many Cooper pairs in the same state so their originally probabilistic "shared" wave function becomes non-probabilistic - a field - by the law of large numbers.


But that may only occur *within* the materials where the Cooper pairs are located (the same is true about your crystals). One needs to find a new effective field theory for the bulk of superconductors - and it turns out that they contain the new complex scalar field. But this may always be viewed as an effective description of the complicated arrangement of nuclei and especially electrons in the bulk of the superconductors. The point is that you *never* modify the vacuum outside in similar ways. So you can never change the basic features of the vacuum such as the fact that it carries no momentum, so one can't "push against it".


You are using the words "restrict available quantum states" in a very sloppy way and all your wrong conclusions result from this kind of sloppiness.


reader Clarence said...

You know who the biggest idiot is? You.
Not because you don't know your physics: but because experiment always trumps theory. Now I will admit that at this point it is likely this is still some spurious affect that will go away; but if ...IF it turns out not to be and is replicable at other labs then idiots like you - who while an expert in Physics are certainly no Einstein and have not yet succeeded in putting Gravity in its proper place so please try to deflate that sizeable ego somewhat- will have to modify your precious theories to account for the new evidence. I expect you will try to do with the arrogance and lack of grace you have shown here. There are plenty of legitimate critics of this research who show more maturity in their criticism and at least will wait to see what comes of future experiments. You instead choose to uphold a monkey (ANYONE can parrot 'conservation of momentum') simply because she is pretty. I hope she gives good head, silly boy.


reader Luboš Motl said...

Hi, obnoxious mental cripple. Experiment may trump theory or not but that doesn't matter because all theory and all experiments are 100% supporting me and 100% opposing hacks like you.


reader Luboš Motl said...

Dear NumCracker, many disciplines are important and produce trustworthy results.


In every discipline, one could use stronger standards or less robust standards. This is mostly due to sociological traditions.


And in every discipline, including physics, there can be "qualitative uncertainty" about certain conceptual things that makes the quantitative counting of sigmas irrelevant.


So I can't endorse your idea of a strict separation between HEP and the rest of science. There is really just one science that is arbitrarily divided to HEP and many other disciplines. In all of science, there may exist diverse levels of certainty about statements and diverse levels of quality of arguments.


Of course, "what is good for you" or "what the climate is going to do in 2050" are generally softer disciplines than HEP. But even generally softer disciplines have some insights that are known rather accurately and supported by rather solid arguments.


reader Luboš Motl said...

Dear MikeNov, it is a wormhole, not a black hole, that is traversable. The adjective implicitly says that the object has two sides and one may get from one to the other. A black hole normally has one throat only.


And the word "traversable" means *nothing else* than that you may leave it. So your statement that "traversable [...] is something that one cannot leave" is the opposite of the truth, by definition.


Traversable wormholes can't exist because they would violate special relativity in the big picture; and, which is equivalent, they would violate the energy conditions locally (by having negative energy densities etc.).


reader Luboš Motl said...

I don't believe that the tens of million of sane Americans who realize that there are the likes of Gavin Schmidt filling many buildings in NASA do keep the kind of respect towards NASA that you have described.


There are some isolated places that are amazing but in the average, the organization has clearly deteriorated beyond recognition.


reader Brett_Bellmore said...

Well, of course the theory of the EM drive is utter garbage. For one thing, they've explicitly stated that they're using different reference frames for different parts of the system!


But, as Clarence says, experiment trumps theory, and if they do get a thrust out of their system, so much for all that theory, you'll need to suck it up, and revise it.


"If". The measured effect isn't nearly large enough to compel that yet, and I'm betting never will be. But if it does happen, all your theory won't matter a hill of beans.


reader Ilja said...

The problem with torture is that once it is accepted, it will be applied not only to terrorists. Democracy has no possibility to prevent such misusage, because those who will be tortured will be named terrorists. And usually it does not take a long time until simple politically incorrect joke will identify you as a terrorist to be tortured.


reader David Nataf said...

Thank you for writing this.


reader Mike said...

I've heard (perhaps mistakenly) that Kaku works on M-theory. Have his contributions to it been strong - like Brian Greene's? Of course, I don't know whether Greene's contributions are strong; but I take your prior word for it that they are.


reader Luboš Motl said...

Dear Mike, yes, Kaku's contributions are comparable to Brian's, but they mostly came in the 1970s, a decade or more before Brian's greatest ones.

See

https://scholar.google.com/scholar?q=michio+kaku&hl=en&lr=&btnG=Search



You see papers by Kaku and Kikkawa from 1974 or so. Papers about the pomeron interpretation of strings; and papers founding "string field theory", a way to describe string theory in as close analogy with quantum field theory as possible.


This is often misunderstood - string field theory is a nontrivially large sub-subject of string theory but it is still a small minority of the research in string theory because string theory isn't quite an ordinary quantum field theory, and there's no strong reason to pretend that it is. So although it can be done, it is in no way "necessary", and string field theory has in practice has led to only a small number of insights that can't be obtained by other string methods.


But he has several papers in the territory of 500 citations which are famous, so he's surely not a guy who only pretends to have had links with the top string research. He's been a relative big shot.


reader BobSykes said...

NASA, like EPA (arsenical DNA) and other federal science/regulatory agencies, has degenerated into a clown show staffed by charlatans and Lysenkoists.


This is important because scarce resources are diverted to scams, and the scams drive public policy. Germany, for example, appears to be about to deindustrialize because of carbon dioxide hysteria.


If only there were a God to save us.


reader Mike said...

Thanks. You write that 'string field theory isn't quite an ordinary quantum field theory'; do you mean that strings cannot be thought of as excitations of a quantum field spread throughout space-time but rather as related in a different way to objects called branes, which are embedded (how?) in a higher-dimensional space?


reader Luboš Motl said...

Dear Mike, quantum field theory is ultimately described by operators that may create or destroy point-like particles. So quantum fields are functions of x,y,z,t, the spacetime coordinates where a point-like particle exists.


String theory, when formulated in an analogous way - string field theory - is based on operators that may create or destroy a string, i.e. a curve in space. So the quantum fields are functionals of x^i(sigma) where sigma is between 0 and pi (convention), a parameter along the string.


The function x^i(sigma) describes an embedding of the line interval (or circle) sigma to the real spacetime. And for each embedding like that, one gets one quantum field. So the string field depends on a number of parameters that is infinitely larger than in quantum field theory of point-like field particles.


You may also convert this string field theory where string fields are functionals of x^i(sigma) to quantum field theory where quantum fields are functions of x,y,z,t only, like in quantum field theory, but you still need infinitely many quantum fields - which are in one-to-one correspondence with the mass/energy eigenstates of the vibrating string, and x,y,z,t is the "center of mass" of the function x^i(sigma), the embedding into space.


So the Standard Model has 30+ or so particle species that may be created at the point x,y,z,t. String field theory has infinitely many species that may be created at x,y,z,t. Those particles are really strings vibrating in one of the ways - and x,y,z,t is the center-of-mass of the extended string.

The fact that you need infinitely many fields as functions of x,y,z,t leads to some differences. In some respects, the generalization from normal quantum field theories to string field theory is straightforward and SFT behaves like a QFT. In other respects, SFT is qualitatively different. I don't want to go into that.


Also, SFT only works really well for calculations involving open strings as external states only. The reasons are technical. Because quantum gravity is carried by closed strings, this immediately reduces the power of SFT to study characteristic questions of quantum gravity.


SFT was assumed to be useful to understand string theory nonperturbatively but it wasn't so. Matrix string theory really became the first known well-defined definition of string theory that is exact at any finite value of the string coupling. SFT turned out to be just another way to organize the perturbative calculations.


But D-branes are defined as boundary conditions for open strings. That's why SFT is actually very useful to study allowed D-brane configurations, and especially problems like tachyon condensation on D-branes (instabilities of D-branes etc.).In all these calculations, D-branes play a different role than fundamental open strings. In SFT, D-branes look like solitons - much like magnetic monopoles which are described by similar classical solutions in ordinary field theory.


At a finite "g", branes and strings become morally equally good as each other - they may be exchanged by S-dualities as well - but none of this democracy is visible in string field theory.


reader Cesar Laia said...

Point partially taken ;) All those devices are indeed indebted to previous HEP, but most of the technological breakthroughs that allowed their use were away after, when they were already LEP. Anyway, what I am generally saying is that there are a lot of serious people in other scientific fields too.


reader Cesar Laia said...

What about using the principles of particle acelerators and beam the protons out of the spaceship at a fraction of c?


reader Luboš Motl said...

Great idea, Cesar. Why don't you propose to shoot the protons from the LHC to outer space, and promise that they will be rearranged to the astronaut's body at the end?


In that way, we may fly in outer space at the speed of 99.9999% of the speed of light.


With some P.R., I am sure that NASA will create a facility for you to investigate this new propulsion system, too.


reader Mike said...

Thanks again for the thoughtful reply. It contains much for me to chew over. I think if I research well while reading it, it will begin to make more and more sense to me; I will be sure to reread it many times. Have a pleasant day.


reader David Brown said...

The "some" dark matter might be axions.


reader Cesar Laia said...

lol.

I am too worried with other things, so I will not work in interstellar traveling soon. ;) But I do think miniaturization of particle acellerators may find interesting applications in the near future. For now, I am happy that you endorse the general concept. ;)


reader MikeNov said...

I didn't say traversable means you can't leave it.



You wrote that traversable black holes can't exist. I argue that the movie doesn't show a traversable black hole because they do not leave it.


reader Michal Deák said...

It seems, that finally NASA dumped this nonsense:
http://www.nasa.gov/centers/glenn/technology/warp/warp.html


reader AM said...

If vacuum can't be used, maybe rowing in waves of quntessence? At least, never head before about such idea. Just joking.


reader AM said...

sorry,quintessence, (kind of) rudeness was not intentional


reader RN said...

Theory is *built* on experiment, so saying something contradicts theory in an area where it was well-tested *implicitly means* that it is contradicting the past experiments that went into building the theory. Yes, experiment trumps theory, but this doesn't mean that every data point anyone bothers writing down is worth considering when it tries to overturn some of the most robustly understood principles of physics. I don't doubt that they actually got the numbers they did, but I'm allowed to claim that it was obviously a mistake somewhere. When this fails, and one of the original inventors comes back saying "no, you need to change the slope of the sides!" do we test that? How about when they want to add ridges, or whatever else? At some point you have to be able to say "No, there is no logical reason why this won't work, it's never worked before and this is not sufficiently different for me to consider this experiment worth doing". Well that's what everyone else is saying right now, but with respect to the experimental history of all of electromagnetism. This is a small permutation on a repeatedly failed idea and it will obviously fail again.

Note that physicists who *actually* want to find new fundamental physics always look for where old theories were merely *extrapolated* rather than directly tested: build the LHC, or theorize any number of things on *small scales*. Because contradicting theories where they've been robustly established for over a century is basically a logical contradiction, and actual physicists aren't stupid enough to waste their time with those.


reader EndSong said...

Out of topic: I would be interested in blog post related to pair production. It is so mysterious to me. =)
Intuitively I would think that if phonon can transform to positron and electron and a photon has a magnetic/electric field, it is logical to assume that a photon is made of Electron/positron pair. But since nobody seems to think that, it must follow that the whole idea is ridiculous.
Ok, some will say that positron/electron has mass and photon has none, so it can´t be made of anything. But personally I think (assumedly "illogically") that it is to suggest that their mass is transformed in photon's case into a force that holds the pair together.


reader Luboš Motl said...

Mike, do you suffer from dyslexia?


I wrote you in the previous comment that the traversable thing we discuss are traversable wormholes, not traversable black holes. In this way, I attempted to politely point out that you sound like a complete idiot when you write about "traversable black holes". Maybe my attempt to bring you to the correct path was way too subtle.


Why do you write about "traversable black holes" once again?


Your other statement is also wrong and I have already explained why. Interstellar surely does describe a *traversable* wormhole because they get in, and they get out. In fact, repeatedly.


reader space_fountain said...

Hi, thanks so much for replying. I clearly didn't explain myself well, sorry. My entire point was that people could have a point with arguing and still agree the drive is almost unequivocally nonsense. As to my critiques and your answers.

"First of all, as I discussed in the text above, EM drive *is* a reactionless drive" I even called it a reactionless drive in my text so in absence of of someone who really knows what they are talking about and is able to argue intellectually I'll totally agree. It's a reactionless drive and violets physics, yep agree moving on.

"One can't accelerate himself by "pushing against the vacuum" because it's prohibited by the momentum conservation law - because it would be a reactionless drive!" I really wish I understood physics enough to understand exactly why. I expect it's one of those subtleties that gets left out from the more simplistic version. I've heard it explained that the reason this is impossible is that the quantum vacuum is indestructible and immutable, but it seems you were saying there are more fundamental reasons why it's impossible.

"Second, you conflated warp drive and EM drive" actually my whole point was that that's what it sounds like the Wired article is doing which really annoys me. Dr White even before claiming these results has claimed that if q-thrusters were real they would allow for this. He talked about it in a lecture he gave here (https://youtu.be/Wokn7crjBbA). I once again want to make it clear I don't think any of this is real, I just think it's interesting.

"would avoid wasting $50,000 a year for something this stupid" I don't know, it sounds like you'd know more, but it seems like given the rewards if true it would have to have odds way less than the 1 to 1000 I gave it.

"[space fountain's comment above was retroactively edited and my comment below responds to the original, substantially different text. Please don't rewrite history like that.]" I'm really truly sorry I gave that impression. I was just trying to fix some typos. For context I'm in the middle of finals week and really should be studying for that rather than arguing with people online so I don't really have time to totally proof read. I don't know that there's any way for me to dig up the original, but you probably had it emailed to you, but I think it was only 1 or two words.

"and you are a textbook example of these uneducated deluded irrational morons." Don't you think this is a bit harsh? I'll readily admit I don't fully understand physics, but I almost guarantee you don't know what this would output:


int *i = new int;
i = 2


println((*i++%2 == 0)?"1":"2");


would it print:


A) 1
B) 2
C) an error.


Lets assume the above is c++


The right answer was C because I omitted * in front of i as was need to set it's value. Instead I modified the pointer value and made it point to a new value that isn't actually owned by the program (probably). The facts of whether or not you got that right does not imply anything about your general education just that it didn't include a class on c++


reader Luboš Motl said...

Sorry, space fountain, the momentum conservation law is one of a small number of the most important universal laws valid across diverse scientific theories we use to describe Nature. Its knowledge is a part of someone's being a cultural human.


If you compare the momentum conservation law to different conventions of C and C++ concerning asterisks when a value of a variable is set, which is one of millions of similar man-made technicalities and irrelevant conventions that randomly developed when people were deciding how to codify programming languages, you only highlight your absolute inadequacy and it makes me wonder why you don't see it would be vastly more appropriate for you to shut up throughout your life when something like science is debated.


reader space_fountain said...

OK, I understand the momentum conservation laws are can never actually be violated, but to me as a lay person it can seem reasonable that you could do something like push against the quantum vacuum (I understand you apparently can't, but it's not the same at all as not knowing about conservation of momentum). If the universe was filled with something like air or perhaps the "ether" you'd think you could push against it, regardless though that really isn't my main point. My main point seems to agree with you that the warping (note not warp drive) and the EmDrive are mostly separate things and the Wired article gets that wrong.


reader Luboš Motl said...

Dear EndSong, pair production - or any process - that obeys universal laws such as conservation laws (momentum,energy, electric charge, angular momentum, and perhaps a few more) always has a nonzero probability to occur.


That's the so-called "totalitarian principle" by Gell-Mann although this principle may be phrased in different ways, with different focuses.


The number of particles is not conserved. Their identity isn't conserved in time, either. That's how Nature works. Quantum field theory makes this fact obvious.


A photon is in no way composed of one electron and one positron. The particles may be created out of nothing, out of pure energy.


When the LHC collides two protons, you only have two protons - that are just fast enough so that they carry 6,900 times higher energy than they have at rest. But from their inertial system, they're the same protons as all other protons at rest.


When they're accelerated by the electric field and when 2 protons collide, lots of new particles may be created.


One collision may produce 1 Higgs boson, 2 Z-bosons, 4 protons, 3 antiprotons, some neutrons, neutrinos, antineutrons, pions, muons, photons, and so on - all this stuff arises from the 2 protons at the beginning only. It's a fact that this is possible. In every interesting collision, the number of particles in the final state exceeds that in the initial state.


I understand that a kid or a baby is first assuming that particles are conserved separately like marbles of a sort, and they may only be rearranged, but that is simply not the case.


In particular, a particle and antiparticle carry no charges (in total) and may carry no angular momentum etc. So the only constraining conservation laws are energy-momentum. In the center-of-mass frame, the momentum is zero and only the energy matters.


So if you have enough energy, you may always create as many particle-antiparticle pairs as you want. They were not there in the initial state, but they are there in the final state. This is allowed in Nature and the kid's expectation that it must be forbidden is just wrong. With E=mc^2, energy may be converted to matter and vice versa.


Lots of elementary processes in quantum field theory may make this point specific. Particle decays create particles that were not there to start with. When you shine light - a very simple things - you may create as many photons as you wish. They were not there to start with. Feynman was explaining this point to his dad and invented the analogy with the "word bags". You can repeat a word many times - say it, say it again, and so on - and you don't run out of the words even after a day of talking. There was no "word bag" inside your throat that you are "depleting".


The capacity to create words is unlimited and the same comment applies to photons - and other elementary particles. As long as you have enough energy, you may create as many particles (or particle pairs) as you wish.


There is also a specific process called "particle production" - the automatic creation of particle-antiparticle pairs caused by the curvature of the underlying spacetime or by the acceleration of an observer. One needs the Bogoliubov transformation, to distinguish different Hamiltonians and different ground states of these Hamiltonians etc. It is too technical. But there is nothing wrong about particle production - at the microscopic level, it is omnipresent.


reader Luboš Motl said...

"Pushing against the vacuum" and "violating the momentum conservation law" are exactly synonymous. They just allow an object to change the speed without changing the speed of anything else that is in principle observable.


This is impossible. I have already explained these trivialities to you and if you were not retarded, you wouldn't have needed any explanation in the first place. If you're lost even after the third attempt, you are a pure troll. A giant waste of time. At any rate, you are banned.


reader Luboš Motl said...

How does the link above - or any other information - imply that NASA dumped it?