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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

#101
post #95

Earlier quoted context omitted.

Given the small amounts involved, it's worth the money just to figure out the source of experimental error. NASA isn't giving money to random kooks off the street, these are actual physicists in labs doing the work.

Steuard is too polite to point this out himself, so I will do it for him: he is a physics professor. That the amount of money is small is a measure of how incredibly unlikely he thinks any useful result would come from the experiments.

Thank you for the pointer, I have a bad habit of not noticing usernames anyway. That said I still think my argument is valid, if you are seeing an incorrect result in a simple experiment it's still worth lab time figuring out which of your instruments or equipment is introducing it, even if you have 0.00% confidence that it's anything special or interesting.

Re: What we know about the EmDrive and Cannae Drive

#102
post #45
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...

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.

Re: What we know about the EmDrive and Cannae Drive

#103
post #4

This is not worth getting excited about. Really. Extraordinary claims require extraordinary evidence. These drives would violate conservation of momentum.[0] Conservation of momentum is built in to the known laws of physics at an extraordinarily deep level. It is obviously not impossible that our known laws are wrong, but the alternative would be to somehow produce a radically different set of physical laws that neve…

> Extraordinary claims require extraordinary evidence So what do you call a second, replicated experimental setup conducted in vacuum, if not extraordinary?

I want to be pithy and say "N=2", but it's not even that. As the experimental controls get stricter, the effect becomes more negligible. That hurts the likelihood, not helps it.

Re: What we know about the EmDrive and Cannae Drive

#104

I know it's unlikely that the EmDrive is real, and even more unlikely that the "warp drive" effects that some have been talking about are real. But...I really hope they are. What a world it'd be if these things prove out to be real.

I think even if it proves real, it would still take around 50 years to put in flying cars and such. But perhaps a bit less for using it in satellites. Still it's not too long on the humanity scale of time.

Even if this turns out to be 100% real, flying cars coming from it seems rather unlikely. The highest amount of thrust they supposedly got from it was 750mN at 2.5KW. Sounds pretty lame compared to an electric motor or jet engine. It might be a world-beater for space propulsion, but unless the efficiency can go up multiple orders of magnitude, it doesn't sound like anybody would bother using it for getting around on Earth.

Re: What we know about the EmDrive and Cannae Drive

#105
post #17

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 doesn't have to violate conservation of momentum to work. We don't understand how it works yet, which precludes us from saying that it violates our current understanding of physics.

I'm no physicist but this guy[1] is, and his paper — which is based off of research with evidence backing it up in the 1970's — suggests that the EmDrive creates propulsion from Unruh radiation[2].

[1]http://physicsfromtheedge.blogspot.co.uk/2015/04/light-in-bo...

[2]http://www.ptep-online.com/index_files/2015/PP-40-15.PDF

Re: What we know about the EmDrive and Cannae Drive

#106
post #39

Earlier quoted context omitted.

isn't that super low? if 1 micronewton = 1 newton * 10^-6 then to push against 1kg it would require 1.000 MWatts?

Super-low compared to pushing against matter. But 300x higher than pushing against photons.

Not to mention you don't have a high-powered beam of photons cooking everything behind you.

Re: What we know about the EmDrive and Cannae Drive

#107
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…

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.

Re: What we know about the EmDrive and Cannae Drive

#108

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…

I love reading /r/futurology comments for comedy purposes, but I have a weird sense of humor

Has anyone told them how gaudy their banner looks?

Re: What we know about the EmDrive and Cannae Drive

#109

Earlier quoted context omitted.

This is less like flush toilets and more like computers. It took nearly 50 years for the first computers to sit in consumer's home offices. It took time for the technology to be miniaturized and cheap enough to make its way to consumer electronics. Or even cell phones. We were using radio signals in hand held devices for nearly 50 years before a vast majority of consumers were walking around with phones in their pock…

If this were proven true, there would be a completely manic gold-rush of capital into the area. Flying cars that operate at less than 1/10th the energy of cars on the road now? This would very quickly move from "let's wait for NASA to do more tests" to "let's beat NASA to the test." That's all assuming it's real, of course. I'd bet against it.

Who says this will use less energy? The remarkable property of it is the (seeming) violation of conservation of momentum, not its efficiency.

Re: What we know about the EmDrive and Cannae Drive

#110
post #7

1 micronewton / watt is a surprising amount of thrust. The implied velocity of whatever it's pushing against is 1e6 m/s, which is 1/300 the speed of light.

What's more surprising is that every number I've seen for the higher power Chinese test was 750 milinewtons for 2.5kw of power. That's 300 micronewtons per watt of power.
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