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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

#21

Post by dicroce »

Steuard wrote: 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…

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.

Re: What we know about the EmDrive and Cannae Drive

#22

Post by kristjankalm »

ComputerGuru wrote: post #2

I'm not a physicist but as someone that's always looked at over-the-top headlines and groaned while internally wishing they were true, I just want to say: this is all so very cool and I'm so excited to see where this takes us. Even if it's not the start of a Star Trek-eseque future, this is some pretty neat stuff and I'm really anxious to hear more about what new gates of knowledge this unlocks. The plot line is righ…

the problem is that the excitement is generated by the use of exotic terminology. you wouldn't get excited if a single study reported that alzheimer's was reversed by copious praying and sprinkling of holy water.

Re: What we know about the EmDrive and Cannae Drive

#23

Post by Steuard »

waterlesscloud wrote: post #11
Steuard wrote: 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…

"But I also wish that I could cure cancer with a single magical kiss, and that I had my very own pet dragon" This kind of condescending response doesn't do science or scientists any good. It's actually actively harmful. Don't do it.

Fair point, and thanks for calling me on it. In retrospect, accurate or not, that sentence grew out of feelings of frustration more than a desire to teach, which is always a bad sign. I've rephrased it.

(I really do have much the same feeling about the magical cancer-curing kiss, though. Oh, how I wish...)

Re: What we know about the EmDrive and Cannae Drive

#24

Post by wbhart »

Comparing the Chinese results with the American results, it seems that raising the wattage by a factor of 50 raises the thrust by a factor of 15000. That's somewhat hard to believe. On the other hand, the linked pdf from the Chinese team suggests that at just 3 times the wattage of the American group, they got 1500 times the thrust. I think there is some confusion somewhere.

Re: What we know about the EmDrive and Cannae Drive

#25

Post by narrator »

I think this technology, if real, should be shut down and controlled by the government. Officially, it should be denied and declared to be quackery. It would likely cause grave security problems. Just think of the capabilities this would give the bad guys. We already went too far with technology with the discovery of nuclear weapons and enormous effort has been invested in controlling that technology for decades. The whole reason we went into Iraq was to prevent them from getting technology (WMDs) that we think they shouldn't have access to. I don't think humanity will be ready for this kind of technology until we have elevated our civilization to a "higher level".

Re: What we know about the EmDrive and Cannae Drive

#26

Post by TheLoneWolfling »

hliyan wrote: post #14
tlb wrote: 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.

How does one calculate this?

(1 micronewton / watt)^-1

Units cancel out to give m/s.

This is just specific impulse. Though Isp is generally measured in seconds (implied gravitational field of the Earth gives s * m/s/s = m/s.)

Re: What we know about the EmDrive and Cannae Drive

#27

Post by higherpurpose »

binalpatel wrote: post #3

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.

Re: What we know about the EmDrive and Cannae Drive

#28

Post by kristjankalm »

aetherson wrote: post #5
ComputerGuru wrote: post #2

I'm not a physicist but as someone that's always looked at over-the-top headlines and groaned while internally wishing they were true, I just want to say: this is all so very cool and I'm so excited to see where this takes us. Even if it's not the start of a Star Trek-eseque future, this is some pretty neat stuff and I'm really anxious to hear more about what new gates of knowledge this unlocks. The plot line is righ…

Understand that the most likely gate of knowledge that this unlocks is, "oh, there was some kind of magnetic interaction between the test drive and the harness," or something to that effect. The proper Bayesian approach to these tests is to downgrade your prior of "drives require reaction mass" from 99.99999999% to 99.999999%

exactly -- I'd guess not too many non-physicits realise what's a prior for 'conservation of momentum violated'

Re: What we know about the EmDrive and Cannae Drive

#29

Post by ngoldbaum »

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 reminds me of the story behind the "discovery" of cold fusion in the 80s. Sure, Pons & Fleischman may have thought they measured something, but in the end the whole effect could be attributed to careless experimental design and procedure.

See this paper: http://pus.sagepub.com/content/5/2/121.short (unfortunately behind a paywall)

Re: What we know about the EmDrive and Cannae Drive

#30

Post by heliumcraft »

tlb wrote: 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.

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