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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

#131

Post by Steuard »

zamalek wrote: post #102
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...

Furthermore momentum is only conserved in classical mechanics. It is actually information that is preserved. E.g. In a particle accelerator momentum is converted into energy, but information is not lost. Conservation of momentum is not more deeply embedded than c in that it isn't even a law (outside of classical mechanics) to begin with.

Conservation of momentum can be derived as a necessary result in any theory whose basic laws are translation invariant (that is, if the defining equations are unchanged if you move everything in the universe 6.2 cubits to the left). This is true in classical physics, relativistic dynamics, quantum mechanics, quantum field theory, or even string theory). You can prove it in various ways depending on which formalism you're working in, but the most elegant proofs I know are based on Noether's Theorem (http://math.ucr.edu/home/baez/noether.html). It's beautifully general, and it applies equally strongly to classical or quantum systems.

Re: What we know about the EmDrive and Cannae Drive

#132

Post by Steuard »

Dylan16807 wrote: post #114
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,…

>Despite this coming from a large group of scientists with top-notch credentials, that was immediately doubted by almost the entire physics community You make it sound like the scientists reporting it didn't doubt it.

Well, that's a funny question, right? On the one hand, they really were careful in their announcement to indicate "we're not sure about this". They were clearly making a real attempt to exercise proper scientific skepticism of such a remarkable result.

But on the other hand, they were willing to make that public announcement in the first place. If they'd really felt the same level of skepticism that most of the rest of the community did, they might have done the tests that eventually found that loose cable before they stuck their necks out. (But then, part of their intent was clearly to get help and suggestions in figuring out what the lingering errors might be, and to get broader input on how feasible superluminal neutrinos might be theoretically. I can't judge them too harshly, even if they did wind up looking a step or two more willing to believe than they should have been.)

Re: What we know about the EmDrive and Cannae Drive

#133

Post by Steuard »

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.

I can't begin to tell you how much more likely I would consider a lunar McDonald's publicity stunt than a demonstration that "momentum isn't conserved after all". The first is so implausible as to be laughable. But the second makes the first look mundane. The future behavior of large groups of people is enormously more complicated and less understood than quantum field theory and the standard model.

Re: What we know about the EmDrive and Cannae Drive

#134

Post by Retra »

mng2 wrote: post #123
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.

That is one of my arguments against homeopathy: We've got a world full of bright young medical students looking for cheap and easy research to do that will lead to positive results. If they haven't proven homeopathy effective, it's because it isn't.

Re: What we know about the EmDrive and Cannae Drive

#135

Post by Retra »

zamalek wrote: post #102
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...

Furthermore momentum is only conserved in classical mechanics. It is actually information that is preserved. E.g. In a particle accelerator momentum is converted into energy, but information is not lost. Conservation of momentum is not more deeply embedded than c in that it isn't even a law (outside of classical mechanics) to begin with.

Translation invariance has been a core assumption of every physics theory because we've observe it to be true. That's what a law is: that which you've observed.

Besides, classical mechanics is one of the assumptions of quantum mechanics.

Re: What we know about the EmDrive and Cannae Drive

#136

Post by Retra »

issa wrote: post #76
digitalzombie wrote: post #15

Sweet. Best case, we get a new awesome thrusters. Worst case, we get the learn new things. So far these drives have pass tests and stumped experts and researchers. So even if it doesn't violate the current laws of physic, it'll paint a better picture of the current laws of physic and better testing method in the future.

This is exactly my attitude. I'm shocked that people don't think twice about spending money on frivolous or even harmful things, but balk at the idea of paying for pure research.

You don't want to shovel fuel into a crackpot industry. That actually prevents real science from being done.

Re: What we know about the EmDrive and Cannae Drive

#137

Post by api »

raverbashing wrote: post #86
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…

> When you get to the fringes-- that's where the action is-- but it's also where you can have confusing or odd results. I think this phrase sums it the best I also usually remember that the Casimir effect, a tested and true effect, used to take a lab of experts some years to reproduce results

Was the Casimir effect highly controversial like this? Is there a good example of a discovery that was both challenging to reproduce and initially dismissed by many but was later vindicated? We hear lots of examples of the inverse of this like Pons and Fleischmann but I'm sure there have to be cases like this.

Re: What we know about the EmDrive and Cannae Drive

#138

Post by api »

Steuard wrote: post #131
zamalek wrote: post #102

Earlier quoted context omitted.

Furthermore momentum is only conserved in classical mechanics. It is actually information that is preserved. E.g. In a particle accelerator momentum is converted into energy, but information is not lost. Conservation of momentum is not more deeply embedded than c in that it isn't even a law (outside of classical mechanics) to begin with.

Conservation of momentum can be derived as a necessary result in any theory whose basic laws are translation invariant (that is, if the defining equations are unchanged if you move everything in the universe 6.2 cubits to the left). This is true in classical physics, relativistic dynamics, quantum mechanics, quantum field theory, or even string theory). You can prove it in various ways depending on which formalism yo…

Must it be local conservation? In other words can we rule out systems that push against something nonlocal or against everything in the universe at once?

Edit: elsewhere in the thread you explain that yes, it must be local.

So if this isn't experimental error or some other minor effect, it seems safe to assume that however it works it is not violating conservation of momentum. Either that or the universe is much weirder than we thought.

Re: What we know about the EmDrive and Cannae Drive

#139

Post by techdragon »

I would like to suggest to anyone really interested in understanding this topic better, read about the Casmir effect http://en.m.wikipedia.org/wiki/Casimir_effect

The Casmir effect and the Casmir-Polder Force is considered by many scientists to be a result of asymmetrical forces being generated by and or from the quantum vacuum based on the materials and geometries being used.

It did take decades to verify to the level people don't consider it experiment error, and we're sill arguing over if it's really a quantum mechanical effect. Some people do not like the whole quantum field theory thing and their efforts to disprove things related to it is important for science.

Personally QFT makes a lot of sense to me so I look at the work being done at Eagleworks and wish there was a way to help accelerate the pace of research because this thing isn't the LHC its not trillion dollar stuff, a few million is probably the total bill to do all the work and the subsequent re verification by JPL, NASA and Johns Hopkins that they want to do. This could be "done" in a year if we stop going slowly. It's 2015 and I would like my hover car next year thanks.

Re: What we know about the EmDrive and Cannae Drive

#140

Post by Dylan16807 »

Steuard wrote: post #133
Dylan16807 wrote: post #118

Earlier quoted context omitted.

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.

I can't begin to tell you how much more likely I would consider a lunar McDonald's publicity stunt than a demonstration that "momentum isn't conserved after all". The first is so implausible as to be laughable. But the second makes the first look mundane. The future behavior of large groups of people is enormously more complicated and less understood than quantum field theory and the standard model.

I'm not really talking about this specific thing. (Though are you sure it even requires momentum to not be conserved?)

I'm just trying to say that our knowledge is incomplete enough that I would very solidly bet on certain "impossible" things being more likely than certain "possible" things. So sure people are bad at judging highly unlikely things, but even possible/impossible is not a reliable criterion. (As long as you don't cheat with hindsight.)

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