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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

#71
post #47

Earlier quoted context omitted.

Also conservation of energy. Thrust can't vary by velocity because there's no such thing as absolute velocity. So your velocity (relative to whatever) keeps increasing linearly, while kinetic energy increases quadratically. At some point you start getting more energy out than you put in. For some reason, this disturbs a lot of people more than violating conservation of momentum. The alternative is that there really i…

You'd never get more change in kinetic energy than the energy you put into it, right?

Well that's the point: you would, so that's an argument why the device doesn't likely work.

Re: What we know about the EmDrive and Cannae Drive

#72
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,…

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)

Cold fusion is a bit more complicated than that. The early experiments were certainly flawed, and there were way to many people announcing results for publicity before they had checked their work.

After a few years, it was no longer socially acceptable for respected scientists to work on cold fusion. It didn't matter anymore how good your reputation was as a researcher, or how carefully designed your experiment was--if your research was in cold fusion, it would get largely ignored.

Unfortunately, this happened around the time a couple groups of respected researchers with good experiment design were getting interesting results pointing to real new phenomena, and perhaps explaining why prior results had been so erratic.

David Goodstein around this time wrote a great article [1] looking back at cold fusion, which included a discussion of these later results, and how socially science had reached a state where they could not be considered. Here are the last few paragraphs.

    All of this was much less important than the fact
    that Cold Fusion experiments, if they gave positive
    results at all, gave them only sporadically and
    unpredictably. When Bednorz and Mueller announced
    the discovery of high-temperature superconductivity
    in 1986, no one carped about control experiments,
    because, once the recipe was known, any competent
    scientist could make a sample and test it and it
    would work immediately. If, at their press
    conference, Pons and Fleischmann had given a
    dependable recipe for producing excess heat, they
    very likely would be Nobel Prizewinners now (as
    Bednorz and Mueller are) rather than social outcasts
    from the community of scientists. The essential key
    to the return of Cold Fusion to scientific
    respectability is to find the missing ingredient
    that would make the recipe work every time.

    Experiments done in the U.S. and in Japan, and
    reported at the Maui meeting indicate that the
    missing ingredient may have been found. In all the
    various Cold Fusion experiments, the first step is
    to load deuterium into the body of metallic
    palladium. The issue is how much deuterium gets into
    the metal. The ratio of the number of atoms of
    deuterium in the metal to the number of atoms of
    palladium is called x. It turns out, by means of
    electrolysis, or by putting the metal in deuterium
    gas, that it is rather easy to get x up to the range
    of about 0.6 or 0.7. That is already a startlingly
    high figure. If there are almost as many deuterium
    atoms as palladium atoms in the material, the
    density of deuterium (a form of hydrogen) is
    essentially equal to that of liquid hydrogen rocket
    fuel, which can ordinarily exist only at extreme low
    temperatures. In other words, palladium (and certain
    other metals including titanium) soak up almost
    unbelievable amounts of hydrogen or deuterium if
    given the chance. This is far from a new discovery.
    However, according to the experiments reported at
    Maui, x=0.6 or 0.7 is not enough to produce Cold
    Fusion. Both the American and Japanese groups showed
    data indicating there is a sharp threshold at
    x=0.85. Below that value (which can only be reached
    with great difficulty and under favorable
    circumstances) excess heat is never observed. But,
    once x gets above that value, excess heat is
    essentially always observed, according to the
    reports presented at Maui, and recounted by Franco
    Scaramuzzi in his seminar at the University of Rome.

    The audience at Rome, certainly the senior
    professors who were present, listened politely, but
    they did not hear what Franco was saying (that much
    became clear from the questions that were asked at
    the end of the seminar, and comments that were made
    afterward). If they went away with any lasting
    impression at all, it was just the sad realization
    that a fine scientist like Franco had not yet given
    up his obsession with Cold Fusion. They cannot be
    blamed. Any other audience of mainstream scientists
    would have reacted exactly the same way. If Cold
    Fusion ever gains back the scientific respectability
    that was squandered in March and April of 1989, it
    will be the result of a long, difficult battle that
    has barely begun.

    Recently, I told this story in a Philosophy course
    we teach at Caltech called "Ethics of Research." The
    first question, when I finished my tale, was, do I
    believe in Cold Fusion? The answer is, no.
    Certainly, I believe quite firmly the theoretical
    arguments that say Cold Fusion is impossible. On the
    other hand, however, I believe equally firmly in the
    integrity and competence of Franco Scaramuzzi and
    his group of co-workers at Frascati. I was disturbed
    when I saw that Franco had gotten caught in the web
    of science-by-news conference in April 1989
    (although I was truly pleased that he finally got
    the long overdue recognition his agency ENEA owed
    him), and I was even more distressed when I learned
    that Franco and his group had observed excess heat
    (the "bad kind" of Cold Fusion). However, I have
    looked at their cells, and looked at their data, and
    it's all pretty impressive. The Japanese experiment
    showing that heat nearly always results when x is
    greater than 0.85 looks even more impressive on
    paper. It seems a particularly elegant, well
    designed experiment, at least to the untutored eye
    of a physicist (what do I know about
    electrochemistry?) What all these experiments really
    need is critical examination by accomplished rivals
    intent on proving them wrong. That is part of the
    normal functioning of science. Unfortunately, in
    this area, science is not functioning normally.
    There is nobody out there listening.

    I suppose that, if nuclear fusion really does take
    place whenever x is greater than 0.85 in palladium,
    the world of conventional science will eventually be
    forced to take notice. If not, then the whole story
    I have told you is nothing but a curious footnote to
    a bizarre and ugly episode in the history of
    science. Either way, I think the story illuminates
    the inner dynamics of the scientific enterprise in a
    way that few other stories have done. For that
    reason alone, it may be worth telling.
[1] http://www.its.caltech.edu/~dg/fusion_art.html

Re: What we know about the EmDrive and Cannae Drive

#73
post #54
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...

Yes, it would be more precise if I had prepended "local" every time I said "conservation of momentum" above. With that clarification, I'm happy to stand by what I've said.

"local" seems like a fairly large assumption for something hypothesized by at least some to work through quantum mechanics, of which a central tenant is non-locality. In fact, given the consistency of qm experimental results over the past 50 or so years, it seems entirely plausible to think that it would be a field of study which could upend classical physics.

All that being said I agree extreme skepticism is healthy here, though arrogance or dismissal doesn't seem quite appropriate as these results continue to be reproduced.

Re: What we know about the EmDrive and Cannae Drive

#74
post #47

Earlier quoted context omitted.

Also conservation of energy. Thrust can't vary by velocity because there's no such thing as absolute velocity. So your velocity (relative to whatever) keeps increasing linearly, while kinetic energy increases quadratically. At some point you start getting more energy out than you put in. For some reason, this disturbs a lot of people more than violating conservation of momentum. The alternative is that there really i…

I'm not understanding this argument. Wouldn't the same amount of thrust get you less and less delta velocity as your velocity increases?

Velocity compared to what? You have an infinite number of velocities, depending on what you compare to. But you can only have one acceleration at any given time. So how can your acceleration depend on your velocity?

Re: What we know about the EmDrive and Cannae Drive

#75
post #66
post #47

Earlier quoted context omitted.

Also conservation of energy. Thrust can't vary by velocity because there's no such thing as absolute velocity. So your velocity (relative to whatever) keeps increasing linearly, while kinetic energy increases quadratically. At some point you start getting more energy out than you put in. For some reason, this disturbs a lot of people more than violating conservation of momentum. The alternative is that there really i…

> Also conservation of energy. Thrust can't vary by velocity because there's no such thing as absolute velocity. So your velocity (relative to whatever) keeps increasing linearly, while kinetic energy increases quadratically. At some point you start getting more energy out than you put in. Can you explain why photonic rockets are not breaking conservation of energy using this reasoning? They have the same property yo…

Because a photon rocket is throwing stuff out the back like any other rocket. It doesn't really matter that it's just photons due to mass-energy equivalence.

Re: What we know about the EmDrive and Cannae Drive

#76

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.

Re: What we know about the EmDrive and Cannae Drive

#77
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…

Wishful thinking, if not base motives, overpowers most common sense.

This seems to be about "reaction-less drives" - I remember reading about how hard-headed SF editor J.W.Campbell had a weak spot for such devices, several decades ago. He entertained a few demos, if memory serves.

Didn't pan out then, probably won't now.

Re: What we know about the EmDrive and Cannae Drive

#78
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…

Why isn't it worth getting excited about? I get excited about lunch. It costs me nothing to follow the progress on low-probability, high impact technological advancements (see: space elevators, commercial fusion power, etc)

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 of "very low probability". Getting excited about space elevators is awesome, even though we're awfully unlikely to see them in our lifetimes and they might never pan out. But these drive theories are pretty literally too good to be true.

Re: What we know about the EmDrive and Cannae Drive

#79
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 condos and eternal life by now. The big advances were actually missed as things like interchangable and standardized protocols, power saving SoCs, incremental battery improvements, touchscreens, and fast networks are "boring" compared to spacetravel and robots and such.

I feel I'm also seeing the same hype train today with VR, which has unsolved major issues like motion sickness and questionable applications in gaming, let alone anywhere else. To a lesser extent I see the same thing with electric cars that are always somehow 2-3 years from affordability and economic and range parity with ICE cars. These 2-3 years keep blowing past us, but there's no 200 mile range $20,000 car yet, if there will ever be.

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. I see so much spilled ink about SpaceX and very little about the upcoming SLS and its planned pioneering manned missions or NASA's robotic and science missions, which are all mindblowingly amazing to me. Sadly, this has all become politicized in the most asinine way possible with a dedicated libertarian group on the web voicing this private vs public rivalry to attack NASA, which is ironic as SpaceX is more or less a welfare program of NASA and the US taxpayers.

I hope this fad doesn't last long and good science, real breakthroughs, and the largely unpredictable and usually unsexy, in terms of whiz bang space operas, future continues to unfold before us in a wonderful way. The SLS will have us on an asteroid with just boring old chemical rockets, while the futurists continue to sell snake oil to the low information true believers and diminish the amazing and real accomplishments of the day.

"Everything's amazing and nobody's happy." - Louis CK.

Re: What we know about the EmDrive and Cannae Drive

#80
post #68

Earlier quoted context omitted.

Happens the other way too. In the 80s high-temperature superconductors were discovered, which were 'impossible' by previous understanding. The theory is still catching up to that.

And even low-Tc superconductors looked "impossible" under the physics of their day. No question about it! Science thrives on surprises: it's the very best part of what we do. But maybe non-physicists don't have a sense of the range of meanings that "that isn't possible within current theory" can have. High-Tc might have been "impossible" under basic BCS superconductivity theory, but BCS theory itself taught us that i…

I agree completely. I´ll try to explain this with a simpler example.

A long time ago, people thought that the faster than sound planes were impossible, perhaps some wrote that formally. The materials didn't have enough strength, it would become too hot, the pressure at some point would be too high, ... To model a faster than sound plane you need to model a lot of complicated interactions between a lot of atoms, and then you need some simplifications, and with the simplifications used at that time it was impossible.

The conservation of momentum is a very low level result, so you don't need to put a lot of simplifications to prove it or measure it. For example you can measure the conservation of momentum when a photon hits an electron almost directly: http://en.wikipedia.org/wiki/Compton_scattering

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