Doubting The EM Drive

Figure 19, from the paper.
Figure 19, from the paper.

This article originally appeared on 5 December 2016, but I’m reposting it because interest in the EM Drive has renewed. RT reports, “China’s announcement would put them ahead of NASA in the race for an EM Drive.” Yahoo reports, “A video put out by a Chinese propaganda channel claims that Chinese scientists have a working prototype — something NASA has failed to achieve.” The doubts I express below have increased.

Heard of the EM Drive? EM is for electromagnetic. The idea is that, in an enclosed cone, some microwaves are bounced around, and that this bouncing somehow propels the cone, and presumably whatever is attached to it, forward.

Nothing comes out of the cone, mind. There is no propellant. The cone is sealed tight.

So how does it push, when nothing pushes back against it? As one popular article put it, the EM Drive appears to violate Newton’s third law, which is for every action, there is an equal and opposite reaction. In the EM Drive, there is an action but no apparent reaction. Conservation of momentum is no more. Apparently.

Another name for the machine is the RF resonant cavity thruster. A version of it was put to the test recently by NASA. And it seemed to work.

I have doubts.

The paper (which is free to read) is “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum” by Harold White, Paul March, James Lawrence, Jerry Vera, Andre Sylvester, David Brady, and Paul Bailey in the Journal of Propulsion and Power.

You have to read the paper for the introduction and apparatus and experimental description (there is no reason to repeat it here). Many readers of this blog won’t have trouble understanding the gist.

Wrong regression

Finished reading the paper? Let’s jump to the end.

Figure 19 is the summary of results of the tests of the forward and reverse thrust vacuum testing. The large, original version should be consulted instead of the smaller image which leads this post.

Power was varied and force estimated. The red circles are the results of the estimates of force from individual experiments at the given power levels. The purple circles/lines are only averages and can be ignored. A (dashed gray) line was over-plotted, the result of a linear regression of power and estimated force. Technically (and you can ignore this point), the uncertainty in the estimated force should be used in the regression, but it’s not clear they did this. That means the gray line, and subsequent equation Force = 1.16843 x Power will be too certain.

Skip the technicalities and notice something more important. The red circles at powers of about 40 W are tightly clustered and indicate a low level of estimated force. The red circles at powers of about 60 W are much more variable, but do indicate some (not all) higher levels of estimated force. But the red circles at 80-85 W look to be about the same, with a tad less variability, than the estimated forces at 60 W.

In other words, it appears as if the estimated forces tails off, or plateaus after 60 W. Might the estimated force jump or increase again at, say, 200 W or greater? Sure. It might do anything. But all we have is the data in front of us. And from that, it looks like it levels off.

If that is so—and I emphasize I am only guessing—then there are two things to consider. The first is that the equation reported by the authors of 1.2 ± 0.1 mN/kW isn’t quite right and is far too optimistic. If the force plateaus, then the better statistical estimate of force is roughly 100 micro-Newtons for powers greater than 60 W (with some plus and minus), which is at best more than 10 times smaller than the forces estimated by the regression. (The regression is also optimistic, because power levels didn’t even reach 100 W, let alone kilo-watts.)

But so what. 100 micro-Newtons is still greater than 0 Newtons, and any force north of 0 proves the concept of the EM drive.

That’s brings us to the second consideration. That leveling off casts suspicion that a form of energy leakage has not been identified. We’d expect greater thrust with greater power levels, but we didn’t see it, which is evidence, but far from conclusive evidence, that something has been missed. We’re talking estimated micro-Newtons here, so it wouldn’t take much leakage to provide the thrusts seen.

Now the force is estimated (via a chain of inference) at first via aluminum electrostatic fins, so it looks like leakage of magnetic field from the cone wouldn’t effect these; but where the aluminum connects, at the circuitry, there could have been induced fields (or maybe the aluminum was dirty or dusty?). And that’s just one of many places to look. But there’s no point me going over possibilities. Let somebody who is better do it. (Perhaps you?)

Error sources

I found this to be the most fascinating part of the paper. The authors took leakage seriously and went to great pains to measure potential errors. But from the language describing some of the sources, you have to wonder if a wee bit of over-confidence snuck in.

The second error is RF interaction with the surrounding environment, which has the potential for possible RF patch charging on the walls of the vacuum chamber interacting with the test article to cause displacement of torsion pendulum. Leaking RF fields are kept very low by ensuring RF connections are tight and confirmed by measuring with an RF leakage meter (levels are kept below a cell phone RF leakage level). Any wall interaction needs to be a well-formed resonance coupling and, because of the high frequency, will be highly sensitive to geometry.

Keeping the RF test article on resonance inside of the frustum volume requires a phase-locked loop system to maintain resonance as the test article expands during operation, so it is not likely that the RF test article can establish and maintain an effective external RF resonance. [Paragraph break mine.]

Well, it’s true at these frequencies geometry is important (ask anybody who builds antennas for gigahertz signals), it’s also true these same RF signals show up in the damnedest places. I merely mention this as one example of how one can fool oneself.

To the stars!

I’d be thrilled to learn my doubts were baseless, or were quibbles, and the EM drive worked. But there are more doubts about how the EM drive is supposed to work. Quantum mechanical pilot-waves. If you don’t know about these, you’ll have to wait for another day. But the authors appear to mix up, as most do, what is from our knowledge of what is, of the ontic with the epistemic, with ontology and epistemology. I’ll save those criticisms, because what is above is enough for now.

Update Forbes is talking about it, and so are others.

Ritchie On Causes Of Evolution

Since we’ve been having fun discussing evolution, and because of YOS’s repeated plea to distinguish observation of evolution (he provided this link), i.e. change, between the causes of these changes, I thought we’d look at what a philosopher of science had to say on the subject.

To repeat YOS, everybody agrees on the observation of evolution. But not everybody agrees on the causes of these changes. Despite these cautions, what seem to be anyway, glaring and obvious differences, the equivocation fallacy looms. A man will say, “I do not believe in neo-Darwinian explanations of evolution”, and the second man, falling prey to equivocation, says, “The first man doesn’t believe in dinosaurs! What a rube!” or some such thing.

Then enters the false dichotomy fallacy, just as prevalent, and worse in consequence. A man will say “I do not believe in neo-Darwinian explanations of evolution”, and the second man, in the grip of the false dichotomy, will say, “The first man says God caused all evolutionary changes! He believes in intelligent design. What a rube!” When, of course, the first man was merely proposing that mechanisms other than those proposed by neo-Darwinian might be at work. YOS even lists one of these theories, due to Shaprio (in the link above). Other criticisms of neo-Darwinian theory, from non-theists like philosopher David Stove and David Berlinski, exist in plenitude.

We can only guess the blindness of the false dichotomy is due to the irrational fear that once we set aside (in whole or in part) neo-Darwinian theory we must open the door to God and abandon Science. YOS has pointed out the fallacies a dozen times, but as I say, his lessons don’t stick, so I don’t suppose yet one more exposure will eradicate them, either. And, anyway, as I also said before “Don’t Panic, But Intelligent Design Is Trivially True“, depending on what you mean by that term, of course.

Below, with all markings original, are comments by Arthur David Ritchie, from Studies in the History and Methods of the Sciences, Edinburgh University Press, 1958 (reprinted 1960), pp 131-134. The reader will recall there is no such thing as “chance”. (I did not use blockquotes to avoid italicizing the whole passage. I learned of Ritchie’s book from David Warren.)

Ritchie

[p 131] The fauna and flora of the most ancient fossil-bearing rocks are not the same species as the fauna and flora now living, although there are some very ancient types still surviving comfortably in the sea, an environment which changes little and very slowly. Even in the sea the predominant forms are relatively modern. This is plain matter of fact, a plain empirical generalization as well authenticated as any. But when it comes down to details, as to the history of any special group of forms there are difficulties because the evidence is fragmentary…

[Footnote on the last sentence.] Notice how cautious botanists (who are not themselves plants) are about the course of plant evolution compared with the cocksure zoologists who know it all leads up to their own noble selves.

[p 132] On the general question, once anybody has grasped the immensity of the time scale involved, there is no difficulty. Had it been explained to Aristotle he would have raised no objections…St. Augustine would almost certainly have raise no objection either. The ancient world had no bias in favour of a short time scale with strictly defined limits, such as grew up later. St. Augustine understood the process of Creation as a long-lasting continuous process. St. Thomas Aquinas might have hesitated a bit more because of that later tendency. But I believe the trouble began later and mainly with bibliolatrous, materially-minded Protestants who took to interpreting the Old Testament in legalistic and mechanistic terms, and cared nothing for the Prophets…

Undoubtedly biologists can point to one factor which must have operated to produce organic change; Darwin’s ‘natural selection’. This means that forms which are less suited to any environment in which they find themselves tend to die out in favour of those better suited. It does not however explain how they come to find themselves in that environment nor how the changes in their forms have come about. It is [p 133] customary to say changes come about by chance; legitimately, if to say so amounts to a confession of ignorance…

Granted that organic forms change in course of time, in the long run, though in the short run populations are generally stable; the question then arises: What makes them change? What are the causes of variation? It is an awkward question and it was wise of Darwin to leave it deliberately unanswered (quite in the Newtonian tradition: Hypotheses non fingo.) It is also a paradoxical question. Causes are discovered by observing regularities and in the physical sciences irregularities are dismissed as ‘errors’ or simply ignored. Our evolutionary question about a long term process of variation on the statistical scale affecting whole populations we should make out second one, because such variation is derived from primary or short term variations among individuals composing the population…

[p 134] Lamarckians have claimed from time to time to show direct influences from the environment producing a change in the genetic makeup of a race of organisms in a few generations. So far all such claims made for the higher plants and animals have been bogus…

The Mendelian geneticists oppose the Lamarckian claims and say, in elaborate technical terminology, that variation is due to chance, and evolution is the result of ‘natural selection’ of favourable chance variations. If, when they say ‘chance’, they mean simply that they do not know what causes variations to occur, then their position is secure, in fact impregnable. If they mean by ‘chance’ that they know that there are no causes of certain sorts at work, then their claims are no better than the Lamarckian. They have no evidence that Lamarckian inheritance may not occur over long periods of time. Nor have they any evidence that there is no kind of directive long term process, a Bergsonian élan vital, at work. Surely, on this whole question of how evolution works, in what direction if any, the truly scientific attitude is strictly agnostic. Speculative convictions on one side or the other range from dogmatic metaphysics, at the best, to superstition at the worst, though most of it is about the middle range of ‘science fiction’.

The Apoplectic Reaction to the Nashville Statement

Liberty Conservative: The Apoplectic Reaction to the Nashville Statement

Apoplectic, nearly universal condemnation was the reaction to the Nashville Statement, the dry reminder that, to Christians, homosexual acts are sinful, that two men cannot be married to one another, and that a man who thinks he is a woman is a man.

Yet when the kumbaya crowd heard these things, it was as if it were announced their cell phones were to be taken away. The by-now standard cries of “hate”, “bigotry”, “hypocrisy” were made, with many paradoxically calling the Statement “anti-Christian.”

The Nashville Statement was not political. Many prominent “never Trumpers” signed; for instance, Russell Moore of the Southern Baptist Convention.

The Statement does have debatable points, but theological niceties weren’t what triggered the credentialed Left. After all, it is no secret what the Bible actually says about sex. What galled must have been their discovery that large numbers of people still believe things like this:

For this cause God delivered them up to shameful affections. For their women have changed the natural use into that use which is against nature.

And, in like manner, the men also, leaving the natural use of the women, have burned in their lusts one towards another, men with men working that which is filthy, and receiving in themselves the recompense which was due to their error.

The New York Times said “The Nashville Statement Is an Attack on L.G.B.T. Christians“. Attack?

Turns out gender dysphoria sufferers and the same-sex attracted “have disproportionately high rates of suicide and of anxiety and depression”, which is so. The NYT claims that these folks being reminded that their lusts are “objectively disordered” will cause them to kill themselves faster.

If that is so, we’re going to have to ban and burn the Bible, Old and New Testaments, lest a homosexual chance upon God saying “You shall not lie with a male as with a woman; it is an abomination.” Sites which give comparative translations of verses like that one are also going to have to go.

So too must we rid our shelves of Robert Gagnon’s magisterial The Bible and Homosexual Practice: Texts and Hermeneutics, a book which stuns in its erudition and painstaking argument, a book which leaves those who help to find even a scrap of scriptural support for aberrant sexuality with no hope.

How many LGGBDTTTIQQAAPPand even normal—folks will go to Hell if they act on their disordered desires and do not seek forgiveness, critics of the Nashville Statement do not say. It’s a good bet that, if pressed, Statement critics would say none. The only sin they would probably recognize is the “sin” of recognizing sin.

[…]

You know where to go for the grand finale.

The editor at Liberty Conservative, Gavin Wax, asked me to contribute a few pieces, which I was most happy to do. Readers might recall that it was LC Google put over a barrel a couple of weeks back, by threatening to cut off their ads unless they removed a harmless article, but one which ran afoul of the SJWs at that once-great tech company.

It was a requirement to publish that I create an “avatar”. Its moustache, which certain homefront powers forbid, is a wish and not a reality.

Pope Francis Says Ask Scientists About Their Uncertainties In Global Warming. Good Idea

Stream: Pope Francis Says Ask Scientists About Their Uncertainties In Global Warming. Good Idea

A reporter asked the Holy Father about the recent hurricanes in the Atlantic, adding the questions “Is there a moral responsibility for political leaders who reject collaborating with the other nations to control the emission of greenhouse gas? Why do they deny that climate change is also be the work of man?”

The Pope answered in part:

…if we don’t turn back we’re going down, that’s true. Climate change, you see the effects and scientists say clearly which is the path to follow. And all of us have a responsibility…to accept from the opinion or make decisions, and we have to take it seriously…

I would say: everyone has their own moral responsibility, first. Second, if one is a bit doubtful that this is not so true, let them ask the scientists. They are very clear. They are not opinions on the air, they are very clear. And then let them decide, and history will judge their decisions. Thanks.

The Pope is right. It is a good idea to ask actual scientists about their best guess of the uncertainties involved in climate change. One thing every climate scientist, myself included, will tell you is that it is 100% certain the climate will change.

It is as certain that nothing can stop the climate from changing. Let me emphasize that “nothing”. It means just what it says. Nothing.

The climate of the earth has never stood still, and never will. That means efforts to “battle” or “stop” climate change are futile. This position in physics is known as climate realism.

[…]

The big question is how much influence does mankind have? And the answer is nobody knows.

[…]

The Pope replied to the reporter (the ellipsis are original):

Why? A phrase comes to me from the Old Testament, I believe from the Psalm: Man is stupid. He is stubborn one who does not see, the only animal of creation that puts his leg in the same hole is man…the horse, no, they don’t do it…There is arrogance, the sufficiency of “it’s not like that,” and then there is the “pocket” God, not only about creation, so many decisions, so many contradictions (…) depend on money.

And there (we must suppose) is […]

I, an expert, recommend clicking here and reading the rest.