The Infinite Impossibility Drive

There’s been a lot of chatter on these here intertubes about the “NASA”1 validation of a new propulsion mechanism called the Cannae drive, which wouldn’t need to carry reaction mass with it into space2. It supposedly works by pushing against the “quantum vacuum virtual plasma” which sounds like something Gene Roddenberry might have typed at 2:00 am on the day of filming. The original Wired UK article spurred reactions from the physics crowd, which led Wired to post a rebuttal to the objections.  I haven’t seen a lot of counter-rebuttals, and now that the (non-peer reviewed) conference paper is out3, we can finally start digging into what they did and did not see.

(Edit:  Here are some great G+ posts by John Baez (Link 1, Link 2), who lent his voice to the articles linked above, but also wrote his own fantastic pieces. Thanks /u/Saivo)

There are several things to unpack when talking about this experiment.

  • What does the paper actually show? Are the objections raised by physicists about the experiment valid?
  • What is conservation of momentum, and why does this cause physicists to doubt the Cannae drive measurements?
  • Is the authors’ explanation of how the drive works valid?  What is the “quantum vacuum virtual plasma”?

I’ll be writing a series of posts to answer these questions to the best of my ability.  Keep an eye out for updates.

Update!  The momentum article is up now!

Update! A short relativity proof that argues against the feasibility drive is up now!

But first, let’s talk about the experiment as laid out in the paper.

What was tested:

There were, in fact, three drives tested: two types of the Cannae drive and a tapered cavity.  Each Cannae drive looks from the outside like a deranged vase with a tube coming out both the top and the bottom.  The difference lies in the bulb of the vase — in one, suitably called the “slotted” device, slots were cut in only the bottom half.  Cannae himself hypothesized that this asymmetry would cause the driving force.  The other was identical except that slots were not cut.  This is the “null drive” referred to in the other articles.  It isn’t really a control; it only tests whether the slots are necessary.  You can see the side view diagrams, generated with my earth-shaking Inkscape skills, which show the three devices in the test chamber.

g3228 g3255 g3268

All of these have a resonance cavity in the center.  In a resonance cavity, the incoming radio waves from the source bounce back and forth a lot before leaving one side or the other, adding together as they do so — the sensor is there to allow adjustments to the power or frequency.  This alone shouldn’t produce any thrust.  There has to be a difference in something moving to the left or the right to produce a thrust.  That something could just be radio waves — if more radio waves bounced back to the right, there would be a thrust to the left — but that wouldn’t be anything more than a complicated solar sail4. A simple calculation5 shows that the maximum thrust the photon radiation pressure of the radio waves themselves could be is 0.2 micronewtons, much less than the reported force.

The assertion in the paper is that the electromagnetic field of the radio waves confined in the pipes adjacent to the resonator is stronger on the right side than the left, and this is somehow responsible for the thrust.

The only device control is in the form of a 50 ohm resistor. More on that later.

The test:

The total force delivered by these drives at low power is minute, so a very sensitive experiment is necessary. Fortunately, that’s what the team appears to regularly do.  The measurement device is called a torsion pendulum.  In essence, it is like a super-sensitive spring scale on vertical rods.  Just like a spring scale shows you how much force of bananas you’ve added by how far the spring stretches, if the rods of the torsion pendulum are twisted by a force, lasers measure how much they move. This is calibrated to give a force, measured in the physics-y units of Newtons.

One way to test whether it was the drive making the force, as opposed to a hiccup from the testing environment, is to flip the drive over and try it again.  If it’s legit, the force direction should flip, too, but the amount of force should be about the same.  The experimenters did just that, but only once for each drive.

The results:

In each case, between 20 – 30 Watts of power were used (enough power to run a fan or charge four cell phones simultaneously), and 50 micronewtons of force were generated (enough to levitate a couple of mosquitoes that weren’t already flying) in the expected directions.  The flip test also seemed alright, if under-sampled — the force was of similar strength in the opposite direction.

Is that a good amount of force?  Well, it isn’t great, but it’s not as bad as it might seem on the face of it.  First of all, 50 micronewtons doesn’t do anyone any good, but 20 Watts is an incredibly low power to drive a real system.  It could scale up with the application of more power.  For example, a shuttle’s engine, after the solid-fuel stage, burns at a rate of 30 billion Watts, a billion times more power than in the Cannae experiment.  However, that rocket also delivers a force of 5 meganewtons, one hundred billion times more force than the Cannae.

But, this drive isn’t meant to replace a rocket to get a satellite into space.  This is meant to replace the drive you’d use on something that was already in space.  A small force over a long period of time could have the same effect as a large force over a small period of time.  Without having to drag extra reaction mass around or burn out, it could work for much longer and achieve very high speeds in space.

The Control:

A… resistor? A 50 ohm  resistor? Not even inside a pipe like those attached to the resonant cavities of the Cannae drives.  I suppose this resistor matched the impedance of the resonant cavity/waveguide test objects, but it has nothing else in common. And I suppose this shows that the radio waves aren’t affecting the torsion pendulum of the measurement device, but it leaves something to be desired.  Generally, you’d like a control which is as close to your test objects as possible, but without the element you consider critical.  The “null” device was a decent control to the assertion that the slots would be necessary, but only if they can validate the force measurements generally.

 The Outcome

So far, the experiment seems reasonable, except for a poorly considered control.  Why all the hullabaloo?  Because the mechanism for generating the force is, let’s just say, uncertain.  As it stands, we must either question the experiment’s results, or we must question the Law of Conservation of Momentum and our understanding of the quantum vacuum.  We have a lot of evidence in support of those last two, the authors must present a lot more evidence in support of their results before they can gain much ground with the community at large.  That is, other labs (and not commercial ones, like EmDrive) must validate the results.  That’s science.

So, what about that Conservation of Momentum or the quantum vacuum dealy? What do we know about them, and what, if anything, do they have to do with this experiment?

You’ll just have to wait for my updates.

Update!  The momentum article is up now!

Edit: I’m commenting on a Reddit thread with my brand new account.  This is proof that /u/gildthetruth is me.

Edit 2: No, I’m not.  My account is too new. I’ve lurked for a couple of years without an account and made one today to comment. Anyway, just listen to /u/kleinergruenerkaktus.

1 It was a small team among NASA’s giant organization. While this is what they do for a living, they aren’t speaking for NASA.

2 It would still require energy. If they claimed it didn’t require energy, no one would be paying any attention at all. For more on how rockets use reaction mass to generate lift, see my upcoming article on conservation of momentum.

3 Though not public.  Since this is a federally funded agency, the research should be public eventually, as I understand it.

4 As long as the RF source remained external. For these drives, though, the source travels with the drive, which wouldn’t work as a solar sail any more than you can point a fan at the sail of your boat and hope to move.

5 They used about 30 Watts of power in the radio frequency signal. Each photon that hits a sail would impart an impulse of 2*p, where p is the magnitude of the momentum of the photon (assuming a single reflection isn’t enough to accelerate the sail much). The momentum of a photon is related to its energy by E = pc, where c is the speed of light. Since power P is energy over time, P = dE/dt = dp/dt *c = F*c, because F = dp/dt is the momentum form of Newton’s 2nd law. Thus F = 2*P/c = 2* 30W/3E8 m/s = 0.2 micronewtons.


Oh, yeah. Writing Links

It occurs to my that I haven’t been posting… well… anything in the past several years.  But, among the literally infinite number*of things I haven’t posted is a set of links to my writing.  I shall remedy this with haste.

*Well, it’s infinite if there is no character limit on a given post.  Otherwise it is merely absurdly large.


Under a previous name:

“Zhu Xaoshin and The Man of Clay”, Linguistic Erosion.

“A Thread Finer than Hope”, Mad Scientist Journal.

“Changing in the Pale Light”, Every Day Fiction.

“The Water Thief”, The Future Fire.

As Jackie Neel

“Flames in Flesh”, The Colored Lens, or buy the excellent e-book with other great authors here.


More to come as they are published.


So, I’m way behind in my reviews.  I’ll never catch up, especially since I’m reading new books and getting behind in those.  So, I declare bankruptcy on the following books.  I’ll give them my rating, and maybe a sentence or two about it.  One day I might go back and do a full review, but I make no promises.

  • Stumbling on Happiness by Daniel Gilbert.  A pop-psych book that presents some very good research on the psychology of happiness.
  • Not in Kansas Anymore by Christine Wicker.  A study of magic and magical thinking in America.
  • Mainspring by Jay Lake.  Er… Sapient monkey sex?
  • Escapement by Jay Lake.  An improvement, largely effected by changing up the characters and ditching inter-species intercourse.
  • The Collapsium by Wil McCarthy.  Some serious hard sci fi in a world of abundance and immortality.
  • Wellstone by Wil McCarthy.  The same as the above, but with a bit less flow.

  • On Writing
    by Stephen King.  Half memoir and half guide to writing.
  • Norse Code, by Greg van Eekhout.

The Oubliette

Sometimes, for whatever reason, I just quit reading a book.  It doesn’t mean that the book is bad, though that is sometimes the case.  At times I’m in the mood for something else.  Or maybe I’m just not the right person at the moment to enjoy it – there have been times that I gave up on a book only to love it when I eventually returned to it.

I don’t review books that I don’t finish.  So what do I do with books that I don’t get through?  They go to the Oubliette.  (Metaphorically – I have a neurosis about allowing books to be damaged.)  Some of these books are bad.  Some merely competed with a new, more anticipated book that I got my hands on.  Some just didn’t tickle my fancy.

Some of these might hope to see the surface world again, and others shall be forever regulated to darkness.

The Oubliette currently (recently) includes:

  • The Summoner, by Gail Martin
  • The Child Thief, by Brom
  • Crystal Rain, by Tobias Buckell
  • The Unincorporated Man, by the Kollin brothers

Oh, and I do recognize the irony of keeping records in something called the Oubliette.

Redeem Yourself – The Graveyard Book

A man cannot step into the same river twice, Heraclitus taught, because it is not the same river, and he is not the same man.

Sometimes I read a book or watch a film and it just doesn’t gel with me. I can recognize the quality, perhaps, but I’m just not in the state in which I can enjoy it or appreciate it. Thus, in these Redeem Yourself segments – in which I return to a book that I’ve previously reviewed – I won’t specify whether it is the book or myself that I feel is in need of redemption when I get it another shot.  Feel free to speculate.

So I read Neil Gaiman’s The Graveyard Book again, and I think I have a clearer understand of why this book doesn’t wow me like so much of Neil Gaiman’s work does, as much as I liked it.  The book is arranged in chapters that are essentially short stories, much in the same mode that Rudyard Kipling’s The Jungle Book. The chapters span the years of Bod’s childhood and gradually weave into the larger story of those that murdered Bod’s family when he was but a baby.

This is the crux of lack of impact I feel.  Each chapter is terrific – some more than others, of course – but so many of them, while they develop themes and develop Bod as a character, don’t push along the plot.  The chapters that work the best for me are those which bring Bod closer to confrontation with his enemies.

The final chapter does much to tie together Bod’s adventures, but it is in some sense too late for me.  I didn’t feel the rising action all the while, so when we reach the climax, it seems as though I’ve only climbed a hill rather than scaled a mountain.  And so much of Gaiman’s work is Alpine.

Each story is a star, but they don’t, for me, assemble into a constellation.  So, while I enjoy the book and admire it, it doesn’t fill me hope, sentimentality, and joy (among other emotional cocktails) that I’ve come to expect from Gaiman’s work.



But, hey.  It won a Hugo, and nabbed both the Newbury and Carnegie Medals.  So, as LeVar Burton used to say, don’t take my word for it.

Winter Vacation Part 1: Malta

This New Year found me in Sicily, where my parents currently live. I’ll write about that next time, because our first adventure was to meet my parents in Malta a few days before the New Year.

Malta is a gorgeous place in the winter. Like many parts of the Mediterranean, the summer months are sun scorched and barren, while in the winter the moderate climate allows plants to grow. But I wasn’t there for the flora – I wanted to see history.

There are three major eras for which Malta remains a mecca for amateur historians. It contains some of the best preserved neolithic ruins in the world, including temples much older than Stonehenge. The early Renaissance Knights of St. John refortified the island with structures that still frame many of the coastal cities. And Malta played a significant role in Allied effort in the European theater of WWII.  I was particularly interested in those first two.

And History did I see.

Tarxien Temple This is the front of the southern Tarxien Temple, one of a cluster of neolithic temples constructed between 3300 BC and 3000BC, and probably used at least into the Bronze Age.  Sadly, the pillars you see are reconstructions, but all the other megaliths at the site are authentic (though some were short-sightedly covered with cement in the 60’s to preserve them.  Fortunately, the cement is already coming off on its own.  I have no words.)

Valletta, the capital, simply oozes Medievalality and Renaissanceness all over the place.  This is the fountain at the bus station, which consists of a few concentric lanes filled with yellow-striped buses dating back (in many cases) to the 50s (which does harsh the mood a touch).

Then there’s the Co-Cathedral of St. John.  This place is simply slathered in ostentatious ornamentation.  Any one piece could be unpacked into an hour’s study, and each section – say, this Chapel, one of eight – could stand up to any degree of scrutiny you’d like.  I just snapped a pic or two.

The city itself is steeped in its military history.  It’s a walled city, basically made out of a fort.

We had a wonderful time, even when we were exhausted.  I recommend spending more than three days.

The Half-Made World


Author: Felix Gilman

I think the allure of Westerns comes down to two points: the mystery of the frontier and the simplicity of the white hats versus the black hats (though often those white hats are trying to wipe clean the tarnish of their past). 

It’s hard to capture the spirit of exploration these days.  There are few mysteries left to the surface of the Earth.  I can crack open Google right now and see any place on the planet.  Mention the name of an exotic culture, and I can find out most of what there is to know about them from Wikipedia in a few minutes.  How do you capture the since of vastness of the world that Westerns have provided to generations past when the whole of the world seems known?

In The Half-Made World, Felix Gilman solves the riddle.  Set, roughly speaking, in a parallel 1860s, the world exists on a continuum between the well-known, well-solidified East, and the mysterious, tumultuous West, where Creation itself is not yet complete.  In between is the vast frontier of the Half-Made world, stable enough for living, but plagued with Powers unintentionally called forth from mankind’s subconscious.

It would be easy to label Half-Made World as Steampunk.  After all, it’s got steam – in the form of the demonic Engines that rule the bureaucratic army that is the Line – and it’s got punks – the chaotic Agents of the Gun.  But to label it as such overlooks the fantastic (in both senses) elements.  The Line and the Gun are engaged in a Great War between mankind’s lesser attributes – as the Agent Creedmore put it, humans made the Gun out of their spite, and the Line out of their fear.

While Gilman solves the riddle of the frontier by making the world only half-made, our heroes are not white hats.  One might be, the Doctor Liv Alverhyusen, who is broken but ultimately recognizable as a civilized person.  But Creedmore, possessed of a demonic Gun and a certain joie de guerre, is complex but ultimately sympathetic.  The clear villain, Lowry, is a middle manager of the Line, proud and ambitious despite the Line’s distain for individualism.

All three are charged with recovering a General whose mind was nearly destroyed by a weapon of the Line.  But this General may know a secret would could forever change the balance in the Great War.

The book charges through at a bullish pace, but if you cling to, you’ll come to learn a lot about these conflicted characters as the evolve under the pressures of their missions.

If I have a criticism, it’s that the book feels almost unfinished (I’ll spare you the wordplay).  This isn’t quite fair, the story promised in the opening is the one that is closed.  But there’s a cliffhanger – a clear invitation to a sequel.  The story I wanted to see finished will carry on, probably for many books to come.

But, really, if the worst you can say about a book is that you want to read more of it, that’s hardly so bad, right?