NASA's Peer-Reviewed EM Drive Paper Has Finally Been Published (opens in new tab)

I agree this incident has educational value, because it's like a toy research project. The science behind the EM drive and the means to understand why it could never work are accessible to laymen who only have to trust our most well-tested physical laws.

If you're curious, you can find an easy to understand theory about why breaking the conservation of momentum lets you build a perpetual-motion machine, creating infinite energy.

Then, you can find a paper from the inventor of the EM drive explaining why it won't allow that to happen. His explanation spectacularly violates special relatively in a way we could easily detect.

Ahh, it looks like I didn't notice the PDF link. My mistake.

Professionals don't always get things right, either, and reactionless thrust doesn't really fit into our best current physical model. That doesn't mean it can't exist - but, given the general usefulness of our current model in predicting how things will behave, there's reasonable cause for extraordinary skepticism in response to claims that one of its "can't happen" conditions is inaccurate.

Maybe the paper's conclusion is accurate! Maybe this physical "can't happen" actually can, and the model needs extending to account for that. It wouldn't be the first time. But it also wouldn't be the first time that a "can't happen" really can't happen, and the result suggesting otherwise is an artifact of the way an experiment was run, rather than an accurate description of a previously unsuspected physical phenomenon. Going by past examples, the latter is much more likely than the former. So there's nothing unreasonable, even for people like myself who aren't knowledgeable enough to evaluate the paper on its own merits, in reserving credulity until the result is shown by other experimenters to be reproducible.

This is the best part of the internet. Amateurs and 2nd year college students challenge professionals to make their months/years of hard work comprehensible. They take all this work and question it unless presented with hard, verifiable facts and data, sometimes over a coffee.

The internet is full of amateurs and they are very very eager to point out when they are not fully grasping something, in one way or another.

Lets be clear here, the people who ran published this test are also skeptical about this. However they did everything possible to reduce and remove errors from their calculations. This means one of two things, either our present understanding of physics is incorrect, or our present understanding of experimental physics and the ways errors creep into our experiments is incomplete. The scientists who did this test suspect the latter, however they've done everything they know to remove mistakes. Much like when we are troubleshooting why our computer won't start we don't jump to the CPU is dead, they also don't just jump to the big conclusion. It's still neat though because we'll still learn something meaningful, and you never know it really could open new understanding of reality.

This is true, but don't you also think that once extraordinary claims have this much publicity they warrant extraordinary investigation? If for no other purpose than to prove it wrong?

Chances are that this is just experimental error. But part of me really wants this to be true. That it's possible some crack pot shoved some microwaves in a tin can and created a device that may reveal a new phenomenon.

Those forces are actually pretty well behaved and can be readily measured and accounted for. Also, light sails have a order of magnitude less power, and the Pioneer Anomaly [1] was smaller yet. Space is probably the best place to test something like this.

[1] https://en.wikipedia.org/wiki/Pioneer_anomaly

Couldn't many of those effects be accounted for by having a non-operating unit in the same orbit as the test unit, and looking for differences in the motion of the two?

The 'commitment' from that article is: "No launch date has been set just yet, but it could happen in as soon as six months' time."

The effects are small enough that there's some possibility that it's just measurement error. If you produce a drive that actually moves something in space, you have a real effect.

Space is a vacuum and has negligible gravity effects; put it in space, turn on the engine, see what happens. In theory it could propel something to nearly infinite speeds if it checks out.

So you know if it works in space.

By far the most likely scenario is that something subtle but utterly mundane is happening and no useful thrust is actually being produced. You say that:

1. studies consistently are showing that this seems to produce thrust without expelling any matter

but this is in fact the first peer reviewed study, so we really only have a sample size of one (not to say other experiments are invalid, just that we have no reason to trust them). Even assuming it is down to subtle experimental error, we may still learn something interesting, of course.

Far less likely is that this is actually producing useful thrust, and regardless of how it is doing it, that would be extremely interesting, and in all probability, new physics. Even if true, I don't expect it to completely overturn our understanding of physics, but it would be very exciting.

>studies consistently are showing that this seems to produce thrust without expelling any matter

Nope, others have been unable to reproduce their results. As for Eagle Works ... their data is crap. The paper consists of 18 data points and large amounts of variance. The largest thrust measurement comes from the middle power setting.

Furthermore, they are measuring (at most!) 120 micro-newtons of thrust. Someone correct me if I am wrong, but that's ~1/100 the weight of a penny[0]. Even if they can produce these tiny amounts of of thrust reliably, they still need to eliminate other sources of error.

Other false-positive results of similar devices have either generated thrust in the null condition or were later retracted after correcting for measurement error.

>I think most people are excited about this not because they think we just proved 2 to be wrong, but instead because we know 2 must be true, so what the hell is going on with 1???

The EM drive literally entails perpetual motion. We know that's impossible, yet someone always manages to sell a new version of it every few years.

>Most likely we will find out that we are NOT violating the known laws of the universe, but we're "not violating" them in a very interesting way.

There is a reason this is in a journal dedicated to publishing experimental results from aerospace engineers and not a physics journal. Peer review isn't magic, it just means two out of three people signed off on a paper being published.

[0]: Seems crazy small, math may be wacky off due to lack of sleep.

> Most likely we will find out that we are NOT violating the known laws of the universe, but we're "not violating" them in a very interesting way.

Most likely is still some sort of experimental error. I'd like it to be real but there is still tonnes of room for skepticism.

I see no connection to the EM drive. The paper you mentioned suggests an alternative inertia formula, however it doesn't break conservation of inertia as far as I can see.

The "theory behind the EM drive" [1] is completely based on classical electrodynamics and therefore it's flawed. Classical electrodynamics conserves momentum and energy. It doesn't mean that the EM drive can't work though, it just means that this theory can't work.

[1] I only found this: http://www.emdrive.com/theorypaper9-4.pdf

Is this what you refer as the "theory behind the EM Drive"?

>Hubble-scale Casimir effect Isn't casimir effect very short range phenomenona? Seems like distances involved would reduce it to negligible levels compared with huge EM fields. Its like claiming weak nuclear force is relevant at galactic distances because "all the atoms add up". http://math.ucr.edu/home/baez/physics/Quantum/casimir.html

Why is it that EM advocates always seem to be dark matter-deniers? There's observational evidence for DM, a lot more than for the EM drive.

I don't know anything about this field but the language seems sound to me.

Is there a consensus on this interpretation v. "just adding more dark matter"?

$200 bucks it doesn't pan out, what you say?