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What we know about the EmDrive and Cannae Drive

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Re: What we know about the EmDrive and Cannae Drive

#121

Post by DennisP »

spott wrote: post #45
Steuard wrote: post #17

Earlier quoted context omitted.

Yes, sure, they've measured something surprising. I have no reason to doubt that. A few years ago, the enormously more respected folks at the OPERA experiment were willing to announce that they had seemingly detected neutrinos moving faster than light. Despite this coming from a large group of scientists with top-notch credentials, that was immediately doubted by almost the entire physics community, and sure enough,…

So, it is worth bringing up: GR doesn't require global conservation of momentum or energy.[0,1] I'm not saying anything about the experiment, but I think your statement that "conservation of momentum is more deeply embedded..." isn't quite so accurate. [0] http://www.preposterousuniverse.com/blog/2010/02/22/energy-i... [1] http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_g...

Hmm. So there's some indication that this device warps space. If that's true does that mean it could violate those conservation laws?

Re: What we know about the EmDrive and Cannae Drive

#122

Post by nine_k »

eli_gottlieb wrote: post #107
drzaiusapelord wrote: post #79

Earlier quoted context omitted.

This is one of the many reasons why I consider all "fururist" media as just sci-fi wish fulfillment for kiddies. Its just incredible how unreadable /r/futurology is, for example. Its just a lot of pats on the back about some amazing life-changing technology, that is eternally 10 years away. I don't have access to the Mondo 2000 stuff today, but if any of that was to believed we'd have AI masterminded rockets to moon…

>Its a shame that practical and real advances are often "boring" to the typical sci-fi obsessed INTJ males who dominate science on the internet. eh-hem implying the Myers-Briggs Personality Type is based on rigorous science /sardony /irony.

Myers-Briggs four-letters are usually self-imposed ("I am an ENTJ"), so it's as good a wearable marker as any other trendy trinket, useful or not.

Re: What we know about the EmDrive and Cannae Drive

#123

Post by mng2 »

MCRed wrote: post #56

I've some direct experience with a similar situation. I can speak to the issue of "why hasn't spaceX or other major company experimented with this". During the "Cold Fusion" era, when Pons & Fleishman had claimed to develop room temperature fusion, I worked for a major US lab doing superconductor research. (We invented the first superconductors that operated at liquid nitrogen temperatures-- Y1B2C3O) While fusion isn…

One of my profs told the class (NucE) that after the cold fusion announcement, people would come around the department to furtively ask for heavy water and such. So you can bet that smart people aren't going to pass up the opportunity to confirm what would be a major scientific discovery.

Re: What we know about the EmDrive and Cannae Drive

#124

Post by jcoffland »

tjradcliffe wrote: post #99
jcoffland wrote: post #46

Earlier quoted context omitted.

Really what's the difference. Either we can fit it in to our models or we have to change the models. It always bothers me that so many people in the scientific community speak of our scientific models of the physical world as if they were truth itself. All models are flawed and only imitate reality by definition. We must accept that our models are only a glimpse of the real thing. We barely manage to grok our own pla…

> Why can't we admit that what we currently know only seems impressive to a few moderately advanced apes but in reality it is likely only tiny drop in the bucket compared to the knowledge our universe holds. Because that would be to deny without any reason but empty speculation that what a small group of scientists have done in the past 300 years is a singularly impressive achievement, adding more to human understand…

> People don't know very much aren't impressed by what the discipline of publicly testing ideas by systematic observation, controlled experiment, and Bayesian inference has taught us about the world

I believe there are many who don't know very much who are easily impressed. I consider myself pretty well informed about science.

All you can say is that compared to humans of the past (and to other species that we know of) we know a lot and that our acquisition of knowledge is accelerating. To me, this is expected rather than awe inspiring. It's mainly impressive to us because our own minds are working at capacity and we were fairly recently huddling in caves in fear for our lives. Don't get me wrong, I'm rooting for team human, but we are very arrogant.

Re: What we know about the EmDrive and Cannae Drive

#125

Post by btilly »

danielweber wrote: post #92
bjourne wrote: post #61

Earlier quoted context omitted.

The heretic, Galileo Galilei, claimed that the earth revolved around the sun instead of the sun revolving around the earth. That the earth is (almost) spherical was known since antiquity.

I thought his name was Copernicus.

Copernicus came up with the theory. Galileo became a heretic for how he popularized it.

Re: What we know about the EmDrive and Cannae Drive

#126

Post by btilly »

Steuard wrote: post #52
dicroce wrote: post #21

Earlier quoted context omitted.

What about this well known, tested and well accepted effect: http://en.wikipedia.org/wiki/Casimir_effect I'm not sure this working implies what you think it does.

I'm not sure what you're getting at, either. The Casimir effect is real, absolutely. I think it was an exercise in one of my quantum field theory classes. In particular, the Casimir effect is something that you can compute entirely within the structure of existing physics, and it doesn't violate any conservation laws. Now, if you suggest that I can somehow extract the Casimir energy without having put the same energy…

...and if you did, then you'd be on shaky ground.

Extracting energy from the zero-point energy all around us no more violates conservation of energy than extracting energy from E=mc^2 does. And we can no more figure out how to do so than Einstein could figure out how to do so a century ago.

Heck, simply finding an efficient way to store lots of energy that way would be a nice trick as well! We know of no reason why you can't beat any existing battery technology by many orders of magnitude!

The trick is that we cannot think of any plausible way to do these things. And once you open up the window of, "This would be amazing if we could, and we can't prove you can't," then you've got something of great interest to cranks who convince themselves that they have done so. So you'd be on safe grounds promptly excusing yourself from any conversation where someone is trying to convince you that it has been done.

But dismissing them with a general wave of the hand and appeal to conservation laws makes you as wrong as they are.

Re: What we know about the EmDrive and Cannae Drive

#127

Post by api »

spott wrote: post #45
Steuard wrote: post #17

Earlier quoted context omitted.

Yes, sure, they've measured something surprising. I have no reason to doubt that. A few years ago, the enormously more respected folks at the OPERA experiment were willing to announce that they had seemingly detected neutrinos moving faster than light. Despite this coming from a large group of scientists with top-notch credentials, that was immediately doubted by almost the entire physics community, and sure enough,…

So, it is worth bringing up: GR doesn't require global conservation of momentum or energy.[0,1] I'm not saying anything about the experiment, but I think your statement that "conservation of momentum is more deeply embedded..." isn't quite so accurate. [0] http://www.preposterousuniverse.com/blog/2010/02/22/energy-i... [1] http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_g...

I would not even go so far. Assuming this isn't a mirage, we don't know what it's doing. It could be conserving momentum but in some weird non-obvious way, or even doing something weirder. First question is whether it "works" at all, then how... and I would look for ways it might work while conserving momentum before challenging a conservation law.

It's important to note that these are separate questions. The inventors of these devices seem to have their own theories, but these may be wrong even if the devices do work.

At this point this is interesting but I won't get excited unless there are more replications. I would say that it seems to not be an "e-cat" situation. There are a minimum of two independent replications. So it would likely be error rather than fraud if it is mistaken.

Re: What we know about the EmDrive and Cannae Drive

#128

Post by titanomachy »

Dylan16807 wrote: post #118
Steuard wrote: post #78

Earlier quoted context omitted.

I guess this is really the point: space elevators and commercial fusion are many, many orders of magnitude more likely to pan out than this is. Both of those are engineering challenges, and materials science challenges. They may be insurmountable ones, or they may not. But neither one would unconditionally require changes to the bedrock principles of physics. Human beings are not good at distinguishing between levels…

Well here's the thing. We could put a fully-functioning fast food restaurant on the moon by 2020. It's an engineering challenge and 100% surmountable. But we won't. It's more likely that we've fundamentally misunderstood physics than we would actually put in the effort to do that.

But the economic consequences of, say, commercial fusion would be enormous. Whoever mastered it would stand to become the wealthiest nation/corporation/person on the planet. Can't say the same for a Jack-in-a-box on the Sea of Tranquility.

Re: What we know about the EmDrive and Cannae Drive

#129

Post by Steuard »

DennisP wrote: post #121
spott wrote: post #45

Earlier quoted context omitted.

So, it is worth bringing up: GR doesn't require global conservation of momentum or energy.[0,1] I'm not saying anything about the experiment, but I think your statement that "conservation of momentum is more deeply embedded..." isn't quite so accurate. [0] http://www.preposterousuniverse.com/blog/2010/02/22/energy-i... [1] http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_g...

Hmm. So there's some indication that this device warps space. If that's true does that mean it could violate those conservation laws?

Nope! :) That's the point of the "locally conserved" clarification I made in a sibling comment: these conservation laws hold at every individual point in space, regardless of whether the point is part of a curved manifold or a flat one. (Curvature can definitely interfere with attempts to define a global conservation law, like "total momentum in the universe is constant". But the essential feature of a manifold is that near any given point it is locally equivalent to simple flat space.)

Re: What we know about the EmDrive and Cannae Drive

#130

Post by cowkingdeluxe »

Steuard wrote: post #17
creamyhorror wrote: post #9

Earlier quoted context omitted.

According to physicist Harold White, leader of the NASA Eagleworks team, it can't simply be a "photon rocket": The NASASpaceflight.com group has given consideration to whether the experimental measurements of thrust force were the result of an artifact. Despite considerable effort within the NASASpaceflight.com forum to dismiss the reported thrust as an artifact, the EM Drive results have yet to be falsified. After c…

Yes, sure, they've measured something surprising. I have no reason to doubt that. A few years ago, the enormously more respected folks at the OPERA experiment were willing to announce that they had seemingly detected neutrinos moving faster than light. Despite this coming from a large group of scientists with top-notch credentials, that was immediately doubted by almost the entire physics community, and sure enough,…

This statement is extremely dishonest and inaccurate.

The folks at the OPERA experiment stated that they found something that needed further testing. They even said that they doubted faster than light particles. They wanted their experiment audited and repeated and stated that they wanted help from the scientific community.

The media is who turned it into a circus.

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