[austinz]

I am skeptical about the EmDrive (although I would very much like it to be real), and my opinion on the drive or its theoretical underpinnings is not really relevant, given my lack of knowledge about the field. But I don't think that writeup is very good either:

From the IO9 article:

> The experimental setup is so flawed that it’s continuing to produce measurable “thrust” while in null mode when it should do nothing.

From the Wikipedia page on RF resonant cavity thrusters (and corroborated by the citations):

> the 'null test article', was designed without the internal slotting that the Cannae Drive's creator theorised was necessary to produce thrust

> The null test device was not intended to be the experimental control.

The article's author seems to fundamentally misunderstand the purpose of the null test setup. Setting everything else aside, if the null articles did produce thrust, this would disprove the Cannae theory (which requires the slotted configuration), but would say nothing about the efficacy of RF thrusters in general.

Their quotes from various physicists about why the drive is probably nonsense are a lot more compelling.

[DavidSJ]

Pardon my ignorance, but I don't think anyone seriously doubts that the null article produces no thrust. So it's not a question of whether the null article's production of thrust disproves the efficacy of anything. It's a question of whether the experimental setup which measured that thrust is trustworthy.

[austinz]

I'm not saying the experiments were trustworthy or conducted properly. Only that the author of the article misunderstood the experimental setup.

(To be precise, the comment about the null thruster was made by the author in a comment on this article, and by a previous article written by the author, which this one references. It is not in the article itself.)

[DavidSJ]

I realize that, but I'm suggesting that you may have misunderstood the author.

It sounds like you think the author is asserting that the null test article was intended as an experimental control and that its production of thrust is evidence for the null hypothesis.

I read him/her as asserting that the null test article is an experimental apparatus calibration tool, and that the reading of thrust suggests the apparatus is improperly calibrated, so that no results at all can be inferred from the experiment.

[taneq]

Holy triple negative batman! Do you mean that nobody thinks the null article produces thrust? Or did I parse that wrong?

[DavidSJ]

You have the right parity but there is a slight semantic difference between that and what I said. Sorry that I wasn't so clear. I'll try again.

There's a difference between "I don't believe X" (which allows for ambivalence) and "I believe not X" (which does not). There's also a difference between "I believe not X" and "I have no doubt of not X".

I was pointing out that there is no dispute or even doubt about the null article's inability to produce thrust (and this would have been a better phrasing). So the question is not "what does the null article's thrust imply about various hypotheses?" It's "what does the apparatus' measurement of thrust from the null article imply about the apparatus?" GP seems to have missed this point.

[taneq]

Agreed on the semantic differences, I missed that one.

> "What does the apparatus' measurement of thrust from the null article imply about the apparatus?"

That makes sense, and I think it's a good question. Thanks for clarifying!