> Since then, something interesting has happened. Various teams around the world have begun to build their own versions of the EmDrive and put them through their paces. And to everyone’s surprise, they’ve begun to reproduce Shawyer’s results. The EmDrive, it seems, really does produce thrust.
That's a misleading statement. I'm passingly familiar with a few of the experiments they're referring to, and none of them both produced significant results and were performed by groups which seemed un-suspect. I'm not aware of any peer reviewed paper on this stuff, and I don't personally know any non-laypeople who believe there is anything actually remarkable happening here.
The sort of problem with relying on peer review is kinda shown in this bit from the Wikipedia article:
Eric W. Davis, a physicist at the Institute for Advanced Studies at Austin, noted "The experiment is quite detailed but no theoretical account for momentum violation is given by Tajmar, which will cause peer reviews and technical journal editors to reject his paper should it be submitted to any of the peer-review physics and aerospace journals."[46]
Basically, merely having a lot of replicated experiments isn't a high enough standard--one has to have a theory of why is works. This somewhat makes sense, but kinda fails miserably for things for which we currently have no mechanism for explanation.
Imagine if empiricists were faced with the nonsense of peer-review a couple hundred years ago before they had any of the knowledge of chemistry or physics to really explain electricity. Hell, imagine how Alessandro Volta would have had trouble publishing his work today when all he had was the empirical evidence of a voltaic pile but no knowledge of the electrochemistry that made it work.
I just want to parrot that what rimunroe is saying is true. The article is presenting empirical demonstration as certain and done. That is far from the case. These experiments are still highly contested and the proponents of "the thrust is real" are still a decided minority.
Fair points. Paul March of Eagleworks has claimed that a peer reviewed paper is under review for publishing currently, but who knows what the rigor of this publisher is. I badly, badly want this to be real, but I've accepted that it likely isn't.
TL;DR - a small, experimental division within NASA called Eagleworks tested the device. They are a very small group with very limited funding tasked with exploring unconventional theories around advanced propulsion. Their results were not published in a peer-reviewed journal, and there is considerable disagreement as to the validity of their experiment. They are continuing to refine their experiments, and the last update provided is that they intend to publish a peer-reviewed paper describing an experiment that successfully breached 100uN of thrust, which was the target needed for JPL and others to attempt to replicate their results.
4. A test at 50 W of power during which an
interferometer (a modified Michelson device)
was used to measure the stretching and compressing
of spacetime within the device, which produced
initial results that were consistent with an
Alcubierre drive fluctuation.
Which is just really cool. The followup sums up my fascination with the whole thing niceley:
Test #4 was performed, essentially, on a whim
by the research team as they were bouncing ideas
off each other, and was entirely unexpected. They
are extremely hesitant to draw any conclusions based
on test #4, although they certainly found it interesting.
That right there is science in progress: a hint of something interesting, a test leading to another test leading to another, each interesting in their own right. It's still not clear if something spectacular is going on, but I think it's undeniably interesting. Careful reexamination can yeild all manner of useful insights!
(Off topic, but along the lines of closer examination, see https://news.ycombinator.com/item?id=9020065 for how some careful (and extensive!) experimentation helped illuminate sodium's reaction with water. Not just how much work was needed to tease out the details!)
If that thing is really stretching and compressing spacetime, and a Michaelson Morely interferometer can see that in theory, then something like LIGO would be equipped to measure it.
sorta, kinda...
It is true that some scientists at NASA have done experiments with this where they claimed to have found some result. A lot of other scientists were very sceptical about these results and said they weren't rigorous enough in eliminating possible errors. The same scientists have done other controversial experients and made claims that other scientists found overhyped.
NASA is a big institution. It's a very different thing to say "NASA said XY" or "someone at NASA claimed to have found XY".
It's true - I think the general issue is that the forces produced are tiny, so it's hard to rule out some other effect coming into play and for the EM drive to work would mean overturning a decent amount of 'settled' physics understanding so the evidence needs to be pretty incontrovertible.
That's a misleading statement. I'm passingly familiar with a few of the experiments they're referring to, and none of them both produced significant results and were performed by groups which seemed un-suspect. I'm not aware of any peer reviewed paper on this stuff, and I don't personally know any non-laypeople who believe there is anything actually remarkable happening here.
[edit] fixed some grammar