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?
What we know about the EmDrive and Cannae Drive
71–80 of 180 posts
Re: What we know about the EmDrive and Cannae Drive
#72Earlier 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)
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.htmlRe: What we know about the EmDrive and Cannae Drive
#73Earlier 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.
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
#74Earlier 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?
Re: What we know about the EmDrive and Cannae Drive
#75Earlier 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…
Re: What we know about the EmDrive and Cannae Drive
#76Sweet. 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.
Re: What we know about the EmDrive and Cannae Drive
#77I'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 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
#78This 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)
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
#79I'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…
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
#80Earlier 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…
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