NASA Still Trying to Verify Anti-Gravity Claims 430
uncoda writes "The L.A. Times has an article about NASA research into a phenomenon in which the effect of gravity is supposedly reduced. It sounds like cold fusion or polywater to me, but who knows?" We've posted two previous stories about Podkletnov's research: one from a couple of years ago and another more recently.
MicroGravity is Your Friend (Score:4, Interesting)
antigrav felines (Score:2, Funny)
which brings up a point in itself, the age old open-faced peanut butter sandwhich on the back of a cat argument.
Re:antigrav felines (Score:3, Funny)
Re:antigrav felines (Score:2)
Buttered Toast Feline engine (Score:2)
Wired magazine article (Score:4, Interesting)
Not the first $600K NASA dumped down this rathole (Score:5, Informative)
Re:Not the first $600K NASA dumped down this ratho (Score:2, Insightful)
Re:Not the first $600K NASA dumped down this ratho (Score:4, Interesting)
This is what passes for insightful around here? In case you slept through Science 101, the onus is on the discoverer to provide proof in the form of a repeatable experiment. As this has never happened, there's nothing there to disprove. $2.6 million is pocket lint to NASA, this is just someone scraping together the spare change from other projects, not a serious attempt to prove or disprove anything.
Re:Not the first $600K NASA dumped down this ratho (Score:3, Insightful)
In this case, the money spent on this project is rather small, in a NASA budget expense -- but even with a 2% chance of partial success, the amortized savings as a result of even a pointer in the right direction are enough to make the fool's rush more than worth it.
As was vaguely aluded to in the article, the possible PR cost to NASA's credibility was probably more of an impediment to funding this venture than the financial cost.
Think what would have happened if people had refused to fund semiconductor research? I mean, really! Electronics on silicon??? That stuf is almost an insulator!!!
Re:Not the first $600K NASA dumped down this ratho (Score:5, Insightful)
To be fair, most things that NASA does are crackpottery, until they work.
But in this case, they really are pushing the boundaries of credibility.
A (crack)potted history of Podkletnov goes something like this. Podkletnov throws together a bunch of superconducting junk that he has lying around his lab, and spins it up. He then waves some instruments at it, decides that he's seeing a 2% reduction in weight, and ascribes that to a reduction in gravitic mass (he can't test inertial mass, as he can't move the mass).
So far, so good. Stranger things have happened through serendipity. Podkletnov has no theory to explain it, but that's incidental. All he needs to do to obtain credibility is to publish all details of his experiment so that it can be replicated.
He fails to do this.
Instead, he publishes a vague description of the apparatus, and continues to make the claims. He refuses to disclose further details, or to let anyone examine his apparatus. Eventually, his university becomes so tired of his antics that they terminate his employment.
Various people with more money than sense try to replicate the experiment. Nobody who claims to have seen the weight loss will publish their details. Sound familiar? To anyone who reports that they cannot replicate the result, Podkletnov replies that they have the details wrong, but he still won't tell them what the details are.
Enter NASA. With some input from Podkletnov, NASA spends $1 million and thinks it maybe kinda might be seeing a 2e-6 reduction, sorta. Podkletnov suggests a few changes, but he still won't just give them his details, and NASA spend another $1 million, at the end of which, they stop claiming that they even might be seeing an effect.
And so here we are again. Someone's scraped together the spare change from other projects, and they've maybe, kinda, sorta got some details out of Podkletnov now. Or not. Who knows? Probably not NASA, and almost certainly not Podkletnov.
Podkletnov is a poor scientist, but a great publicist. Maybe that's what gets funding in NASA these days. It certainly gets publicity, as this discussion proves.
We need a revolutionary jump (Score:3, Insightful)
Re:Not the first $600K NASA dumped down this ratho (Score:2, Interesting)
I'm sorry, run that by me again? If they succeed at reducing the gravitational mass of an object but it requires expenditure of energy, you'd consider that a "null result"? I suppose next thing you are going to tell me is that electrostatic repulsion doesn't exist because moving the charges to measure it requires expenditure of energy.
2.6 Million bucks is a lot of money. It can fund many, many, many more real projects. Instead, it gone thrown into an unsubstantiated, non-peer-reviewed crackpottery by a guy who refuses to reveal the details of his so-called experiment.
Frankly, given the kind of uninspired, peer-reviewed, publicity-hungry junk I come across daily, I'm glad to see that some people are still spending money on long-shots and crackpots. If science were exclusively done by what one's peers think useful or interesting, we'd still be living in the stone age. I think this particular experiment is a long-shot, and after $2.6M it may really be time to start looking elsewhere. But, then, I think it's much less of a long-shot than the kind of nonsense theorists have been engaging in.
And it's not like the idea that there is something funny going on with gravity were completely unfounded. We know that Einstein's theory disagrees grossly with what we observe. It's not a question of if we can replicate this experimentally but how.
Re:Not the first $600K NASA dumped down this ratho (Score:2)
The president spends more than this much on fuel in his jet just running around the country during a typical term in office.
A side from that, it's the long shots that usually have the biggest pay offs.
Re:Not the first $600K NASA dumped down this ratho (Score:3, Interesting)
OK, disclaimer here: Note that I said "GR", not "Newtonian" gravity - yes, I know that every textbook on the planet says that GR agrees with Mercury's orbit "phenomenally well" - but it's not really true. If you check out a decent astrophysics textbook (I -think- it's in Carroll & Ostlie) there were findings in the early 90s (I think... I'll try to look it up, but I figured I'd post this first so more people'll look around) that the discrepancies in Mercury's orbit could be mostly explained away due to non-sphericity of the Sun. When you take that into account, GR doesn't agree quite so well (unless someone's cleaned this up recently, which is possible. No one seems to care, actually).
That said, that wasn't what the poster was talking about - my guess is that the original poster was talking about stuff like continuous spacetime vs. quantum spacetime, but again, that's quantum effects.
I'm still of the opinion that the anomalous mass changes above a superconductor COULD be real (and could be quantum, keep in mind that superconductors produce weird quantum states of electrons) - after all, before people knew about the Casimir effect, no one would ever have thought to claim that sticking two pieces of metal very very close to each other would cause them to be strongly attracted to each other by anything except gravity.
That being said, I think it's probably experimental error, and I REALLY don't appreciate the way the original scientist handled it. The fact that he hid his experimental setup (or the complete details of it) out of fear of someone stealing his idea is such crap. Personally, if it had been me, I wouldn't've cared. If it does work, it's such a revolutionary breakthrough that I wouldn't've even cared about the economic benefits to me - the scientific benefits are too massive (besides, SOMEONE would've named the effect after me - or me and someone else - and that's all I really care about
If it is true... (Score:3, Funny)
Re:If it is true... (Score:3, Insightful)
Interesting but... (Score:3, Insightful)
A super cooled, electrically charged, rapidly spinning super conducting disc that reduces the gravity field above the disc is interesting. However, taken as a whole, the entire system would still crash to earth.
Sort of like putting a sail on one end of a skateboard and a fan blowing air on it on the other end. It still isn't going anywhere.
Re:Interesting but... (Score:3, Interesting)
Take a wheel, with the axle horizontal and place the axle directly over the edge of this thing, so half the wheel has its gravity reduced, and the other half doesn't. Then there is a net torque on the wheel. It will spin. You can put a generator on the axle and make free energy for nothing.
In other words, if this thing works, you can make a perpetual motion machine. You can interpret that fact any way you want -- I interpret it to mean this anti-gravity thing is a crock of shit.
Re:Interesting but... (Score:3, Informative)
Re:Interesting but... (Score:2)
Re:Interesting but... (Score:2)
Re:Interesting but... (Score:2, Informative)
Free except for all the energy you spent spinning that disc 5000+ rpm's...it's not free energy, it's a transference of energy in that case.
Re:Interesting but... (Score:2, Insightful)
The Human Mindset... (Score:2, Funny)
AntiGravy (Score:3, Interesting)
I love how the web has made every Kook with a website an "Editor"--and a reasonable source for story on a scientific topic.
The government is turning welfare moms into prostitutes! [lostbrain.com]
tcd004
(Editor, Lostbrain.com)
Re:AntiGravy (Score:3, Funny)
As opposed to the printing press?
(totally off topic - but all the web has done has made it even easier to be a kook)
Bron (Scientific Advisor: Slashdot.org, On The Web, In Crayon)
randal and dante (Score:5, Funny)
PM Article. (Score:2, Insightful)
I can just imagine it now, getting spam that reads: "Do you weigh over 200lbs? Well we have the solution for you! Loose over 4lbs INSTANTLY! Thats right, INSTANTLY! NO gimmicks, NO drugs, just pure science! Only $600,000! Act Now!"
What about a rotating would make mass 'change'? (Score:3, Insightful)
If so, could the rotating simply be acting to create a focus point of magnetic energy at some point on the axis of rotation, above the superconducting disc? If the object being tested has any magnetic substace in it at all, then a strong magnetic field could cause it to seem less weighted, right?
I also question the use of the Cavandish balance to measure the mass of the item above the spinning disk. We're dealing with a superconductor in a magnetic and electric field... What is preventing this device from causing some strange magnetic effect. What about ionization of the air around this device?
These are just my inital reactions to the article, and I'm no Physics expert. What are your thoughts, friends?
Re:What about a rotating would make mass 'change'? (Score:2)
Oxygen is paramagnetic. Any dipole molecule will act as a magnet in a magnetic field. Heck, even single electron spins act in that way (line-splitting, for example, in spectroscopy works this way).
All this was known forever. It was the first time, though, that anyone tried doing it with an object. And let's face it, levitation is cool - and highly news-worthy.
Basically, though, with a big enough magnet, you can float pretty much anything you'd come across in every-day life.
why this got funded... (Score:5, Insightful)
If I do an experiment where I can show gravity doesn't work like its expected to, they will look into it. Most of the time the result is that somone put an Acme magnet in the wrong place. NASA doesn't care what the experimentor's (or crackpot's) theory is, they want to duplicate the experiment and try to find out the real reason for the change in mass. If your respected enough to do an expirment, its worth their time to look into it even if your theory is the disk weighs less because of the magic elves.
Re:why this got funded... (Score:2)
Last report I heard was that waste heat was considered unlikely, because of symmetry (probe vs. probe) & energy budget. Can't find a like to the darned NASA white paper though.
-- MarkusQ
hmmm...seems fishy (Score:2, Insightful)
as much as id love to see this kind of stuff a reality, this particular claim seems off to me. It happens way too often in the physics community that someone claims to have made some breakthrough, be it in superluminal light pulses, or cold fusion and really they are just full of it.
it seems most often that theyve put so much of their life and time into their work that when they dont get anything meaningfull they either fudge the results or "see" what they want to.
unfortunately that is probably the case here..a dead giveaway is Mr P's (i cant spell his name) initial secrecy, that always kind of says something about the authenticity of the claim...it also doesnt help that his hosting university throws him out and noone else can reproduce his claim...on the grounds that its too complicated to set up properly. bs
but im always the skeptic...even if im hopeful
good for nasa though in actually staking out the claim...and if they need to killing the hype
id like to know how Mr P measured his weight change too...if he use similiar ballances to nasa or something else he cooked up
Re:hmmm...seems fishy (Score:2)
Huh? It doesn't happen often at all. Out of the tens of thousands of physicists producing all those experiments and journal articles, maybe once every few years someone makes an extraordinary claim. The vast majority fit in just fine into modern physics thought.
Whats todays date? (Score:3, Funny)
The article states "The Podkletnov effect suggests it may be possible to effectively reduce the mass of the ship, thereby reducing the overall energy needed for acceleration."
Now as every semi-educated idiot knows, Mass and Weight are two different measures. Mass is an immutable constant, while weight is strictly based on the strength of the gravational field.
In other words wieght can vary, but mass will never.
I did a Google search on this "paranoid" scientist and I couldn't find anything negative.
---------------
Anybody recommend some reading for me? (Score:2)
I read 'The Physics of Star Trek' recently, and found that to have a very fascinating insight into how likely some of the fictional technology is. The author did a good job of explaining some of the more complex stuff in terms I could understand. Now I hunger for more. Anybody have a site or a book they could point me to?
Re:Anybody recommend some reading for me? (Score:2)
If you read this you'll understand why NASA is spending money on this kind of science. If we're going anywhere farther than the planets then we need a breakthrough. They are not ready to ignore the possibility that this guy might be right, even though he's acting like a crackpot.
And really, $600k -- or even $6M -- isn't that much money from the NASA budget, especially when spread over several years. I work on NASA projects and they spend hundreds of thousands per researcher per year to build and test prototypes of scientific instruments, rocket motors, what have you, just to incubate technologies that NASA thinks will be useful in the future. And it keeps industry and its talent ready and able to perform on future contracts.
Thanks everybody! (Score:2)
This sounds like.. (Score:2, Informative)
"..insists the gravity-shielding effect only occurs when all the experimental conditions are precisely right."
So we need a disc of special superconducting material spinning at just the right speed, etc., and then and only then the effect occurs.
If they can replicate the 2% weight loss in the experiment it'd be great. But only when they can tell what really triggers the effect, and how to do it with larger discs and at any RPM, then I'll raise my hat to true science. This is just lucky engineering, atleast to my views.
Hmm I wonder what would happen if they put multiple discs on top of each other. Would it multiply the effect..?
Okay, okay, maybe I should finally read that report he wrote some time ago.
podkletnov's paper (Score:5, Informative)
Pull the other one, it has bells on.... (Score:2, Insightful)
NASA must have contracted a bad dose of the "but they said Einstein was wrong" meme to even consider getting involved in this quackery.
Why its not antigravity.. (Score:3, Informative)
Re:Why its not antigravity.. (Score:4, Insightful)
Once the weight of these new scientists is great enough, there is a violent 'paradigm shift' to a new theory that fits all the old data and all the new.
Re:Why its not antigravity.. (Score:2)
Once the weight of these new scientists is great enough, there is a violent 'paradigm shift'
AH-HA! So this anti-gravity research is a plot by the old scientists to reduce the weight of the new scientists, and therefore retain their hold on power. Ingenious! I'd better eat more hamburgers to help counter this conspiracy.
How the mighty have fallen... (Score:2, Insightful)
The basis of science today is in testing phenomena and reproducing results. Podkletnov refuses to submit to this basic tenet of scientific society. He claims that people will steal his ideas and take his credit - yet if he's well known enough that NASA, let alone the LA Times, has heard of him, such intellectual thievery ought to be very difficult. In addition, by publishing a paper with all his procedures and results, he would not only prove that such "gravity shielding" phenomena do exist, he'd be able to defend himself against future intellectual thievery, and he would allow other scientists to build off of - note, not steal - his work.
However, Podkletnov chooses not to publish his actual procedures. This makes his experiments functionally untestable. This is fortuitous for him if he is a fraud. That way, if NASA does manage to discover "gravity shielding", he can claim that their procedure was his, and cash in on their prestige and fame. If NASA fails, as they are likely to do, he can simply claim that they didn't do it quite right, and continue to refuse to release his results. Given that he's kept the chemical composition of some of the components of his apparatus, namely, the spinning disk, secret, it's hard to see how NASA would succeed even if his claims were valid. Finally, if, as Podkletnov claims, "dozens of people" have matched his results, we could expect at least one of them to have come forward by now. Certainly, they can't all be hiding their data for fear of thievery - are we to suppose that not one of "dozens" of scientists has the bravery, initiative, far-sightedness, or even plain greed to publish these results, which could have such an impact on the world if verified? That seems highly unlikely...
It's somewhat disheartening to see an institution like NASA following pseudoscience like Podkletnov's "gravity shielding". With current budget cuts, NASA would be much better off spending its diminishing money on developing technology that already exists, rather than chasing implausible alternatives. Everyone would profit off of an alchemist's ability to turn lead to gold, or a perpetual motion machine, or cold fusion, but, because those have been shown to be so implausible, for various reasons, we don't see serious research institutions researching them. "Anti-gravity", at least of Podkletnov's variety, should be placed in the same category, at least until the 'scientist' is willing to back up his claims with some real, verifiable, and repeatable procedures and data.
I've seen (Score:2)
It's until now I realized none has yet confirmed yet. Oh I shouldn't have read all these damn UFO-science books.
Gravitational vs. Inertial Mass (Score:4, Informative)
The law of gravity is one of science's most sacrosanct principles; any breaching of its walls would represent a major threat to the current theoretical framework.
Really? One of the few things I can remember from my Physics courses at school is that noone understands why gravitation mass is the same as intertial mass. The closest anyone's got to an explanation is Einstein with his Equivalence Principle [uidaho.edu], but even this seems a bit woolly (only works in a uniform gravitational field). So there are still aspects of mass (and so gravity) that are not fully understood.
Of course, this experiment sounds rather dodgy, and it's unclear from the article what they're measuring. Got me wondering though
Re:Gravitational vs. Inertial Mass (Score:2, Interesting)
Strictly speaking, they are not the same. That's why the gravitational constant (G) exists - it's the "scaling factor" between inertial and gravitational mass. Hence, g = GMm/(r^2), not Mm/(r^2).
Inertial and gravitational mass are equivalent, which is very nearly what you said, and probably what you meant. That's the thing that noone understands. It is the only force that behaves like that, and also the only force that we have only seen one charge for (eg electrical charges come in positive and negative, magnetic charges come in north and south, etc). All mass attracts all other mass, there is not a different type of mass that repells "normal" mass, at least as far as we've been able to see. I find that as intriguing as the equivalence of inertial and gravitational mass.
Cheers,
Tim
Re:Gravitational vs. Inertial Mass (Score:4, Insightful)
Not really: G is a conversion factor between mass and force, making it a coupling constant (like Coulomb's constant) - it's more a field strength than anything else.
Note that you can make G go away with a convenient choice of units (mass is mass is mass: they would still have the same units - grams - even if you had inertial and gravitational, just like kinetic energy, potential energy are both measured in joules). For the rest of this, we'll work in units (call them 'statgrams') such that G = 1 Newton-m^2/statgram^2.
When people say that gravitational mass is the same as inertial mass, we mean: force is equal to inertial mass times acceleration, and force is equal to gravitational mass of the two objects divided by radius squared.
OK, so F = (m_i)a , and F = (m_g)M/r^2. Now, when we say that gravitational mass is the same as inertial mass, we mean that if you set these two forces equal, so gravity's providing all the acceleration, the inertial and gravitational masses cancel, that is, g = (m_g/m_i) M/r^2 goes to g= M/r^2.
There are several ways to test this, and all any of them can test is that the ratio is constant (indep. of radius, indep. of inertial mass, etc.) and so we set this constant to 1.
It's a subtle difference, but there: there're two different things that're in the force equation, a coupling of matter to matter (G) and a conversion between gravitational mass and inertial mass (m_g/m_i). Setting one of them to 1 doesn't necessarily set the other to 1, but since they're both 'unit choices', you can freely set them both to 1. The important thing is that since all derivatives of m_g/m_i appear to be zero, it IS merely a unit choice. If there WAS a difference, you could set G to 1, but not m_g/m_i.
One other thing: quantum-mechanically, it's not surprising that gravity is solely attractive: it's a tensor (spin-2) field, which IS solely attractive. That part's understood (We know that a spin-2 field can mimic linearized GR - that is, GR in the weak field limit).
Re:Gravitational vs. Inertial Mass (Score:3, Interesting)
I think your terminology is correct here, but the reasoning is backward. There is no quantum field theory for gravity that has been tested in any way. People realized that a tensor boson would create an exclusively attractive force, so this is a candidate theory to explain the gravitational force. Hence the supposed "graviton". So to say that we know gravity is attractive based on quantum field theory is incorrect. We know that gravity is attractive based on experience. We have a candidate quantum field theory of gravity which has two major drawbacks: 1) it's untested (no exclusive predictions can be observed with our present technology). 2) it's inconsistent with GR, which has been tested to extremes.
I'm not an expert on general relativity, but AFAIK the equivalence principle, which is at the heart of GR, is in a sense the statement that gravitational mass and inertial mass are identical. In Newtonian theory, gravity is an external force that attract masses. In GR, Newton's gravitational force is a "fictitious force", not a force proper. A non-inertial reference frame is approximately the same as an inertial reference frame with an additional fictitious force. Mass (for some reason) creates curvature in spacetime, which is like a non-inertial reference frame in flat space-time.
I've never really understood the need for a quantum theory of gravity, since gravity is not a force to begin with. I hope that some string theorists can set me straight on this some time. (I just need the guts to walk down the hall and sask them point-blank. My fear is that I won't understand the answer.)
As for Podkletnov, I'm genuinely surprised that anybody is taking him seriously. (taking seriously = non-zero funding to investigate his claims.) The LA times article suggests that he is affraid of the credit being stolen if he publishes the details in a peer-reviewed journal. This is crazy since publishing the explicit experiment and its results is his only gaurantee that he will be recognized as the discoverer of the effect!
His other paper that he put on the preprint servers last year was a masterpiece of bogus science, and I can see why he has such a hard time holding a job or publishing anything. There were several logical flaws in that paper, and the experimental technique was horrible and imprecise. For example, there were no measurement errors quoted, which wouldn't even earn him a passing grade in a high school physics course.
My favorite line of reasoning in the paper was that the impulse imparted by his "anti-gravity beam" was proportional to the mass of the test subject. Thus, by extrapolation, if he were to put a hugely massive test subject in the beam, it would receive more kinetic energy than the amount of energy put into the beam. He then sites this as a violation of the equivalence principle! No, it's a violation of conservation of energy, and no one in their right mind would believe that he's observing violation of conservation of energy based on an absurd extrapolation, hundreds of times further than his actual data reaches. If you think about it, this "little goof" invalidates his whole anti-gravity explanation.
After reading that, I just shook my head in amazement. And now he's getting folks at NASA to take him seriously? NASA is desperately hurting for funding, and really shouldn't be dabbling in quackery right now.
- Topher
Re:Gravitational vs. Inertial Mass (Score:3, Interesting)
However, if we assume GR is true (which it looks like it is, in a gross sense) then at some level, it has to be spin 2, as in the small field limit, it IS a spin 2 field.
So, we really have two observations:
1) gravity is a spin-2 field. (not a quantum field, true, but I didn't say it was a quantum field
2) spin-2 fields in quantum field theory are solely attractive.
Based on this, we can say it's not a surprise that gravity is solely attractive. We CAN'T say that gravity is a spin-2 quantum field in the sense that we understand quantum fields now, but we can say it's not really a surprise that gravity is solely attractive.
That is, if you didn't have the volumes of empirical data saying "gravity is solely attractive", your first guess would be that gravity is solely attractive based on the fact that it is a spin-2 field in the linearized approximation, and spin-2 fields in quantum field theory are solely attractive. It's similar to calculating energy level transitions using quantum mechanics: it shouldn't work, you're crossing realms of validity, but it does, because it's a general 'macroscopic concept' - in this case, energy. In the spin-2 gravity case, it's conservation of momentum which is driving the spin-2 necessity. A theoretician would probably say "conservation of momentum is such a strongly held symmetry that we can bend it a little with no problem" or some bull like that (no joke - I've heard similar).
As for Podkletnov, I agree that he's a quack (will never argue that) and that his research is sloppy and all the extrapolations/reasonings are junk. The main thing that people are trying to replicate, though, is not the antigrav beam (which I almost printed out to go alongside the other antigrav devices I've seen on arxiv) but the anomalous mass reduction over a spinning superconductor. This one... ok, I can see the desire to try to replicate it (especially because they had trouble previously) but it probably won't work (PROBABLY... but, eh, who knows).
That said, I should also point out this is almost definitely funded via Millis's BPP program, which is a perfectly valid program. There's some random financial realm of thinking which basically says "if you have an idea which has a very low probability of success, but an infinitely huge return, you should invest some small portion of money into it", and this is what Millis's program is being funded out of. It's valid. They'd probably be better off futzing around with the Casimir effect, but that's probably next year.
Re:Gravitational vs. Inertial Mass (Score:3, Informative)
Incidentally, my background's in experimental particle physics AND in gravity - grad and undergrad, respectively, just so you know where I'm coming from. The lack of a diple moment in gravity is just conservation of momentum: think of it this way.
Electromagnetism:
No scalar moment: conservation of charge, so (d/dt) sum over q_i = 0.
Dipole moment: perfectly allowed: (d/dt) sum over (q_i*x_i) need not be zero.
(all higher moments are fine)
Gravity:
No scalar moment: conservation of mass, so
(d/dt) sum over m_i = 0.
No dipole moment: conservation of momentum, so (d/dt) sum over (m_i*x_i) = 0. (that is, dm_i/dt * x_i = 0, from cons. of mass, and m_i*dx_i/dt = 0 from cons. of momentum).
Quadrupole moment: perfectly allowed: (d/dt) sum over (m_i*x_i^2) need not be zero. (that is, dm_i/dt*x_i^2 = 0, cons. of mass, 2*m_i*x_i*dx_i/dt need not be zero)
Of course, you can substitute "dipole" for "vector", and "quadropole" for "tensor" before, so gravity is a tensor field (spin 2), and electromagnetism is a vector field (spin 1).
Using a tensor field for gravity is therefore justified mainly from its presence in linearized GR, and supported by the singularly attractive potential. Its downfall is, of course, the fact that it doesn't work.
Re:Gravitational vs. Inertial Mass (Score:2, Interesting)
Time dialation (Score:2)
This would obviously be a very weak effect, but then gravity is a very weak effect. And, as I said, I can't do the math, so it might be wrong. But that's the way it seems to me.
Forget Antigravity, how about a Gravity device? (Score:3, Insightful)
Hrm? (Score:2)
Re:Hrm? (Score:2)
Re:Forget Antigravity, how about a Gravity device? (Score:4, Interesting)
That said, unless you can do VERY weird things, simulating gravity REALLY sucks. Think about the energy cost! If you can 'simulate' gravity, then all the matter that's put in that 'simulated' gravity field suddenly has a LOT of potential energy. Where do you think that potential energy has to come from? Gravity can't be free.
We don't need simulated gravity. We need ways of dealing with zero-gravity. If you absolutely have to have a gravity-like force, spin the ship. The only problem with that is that you need a BIG ship so Coriolis forces and a sharp pseudogravity gradient don't screw you up.
Simulated gravity won't happen until we are as good at manipulating gravity as we are at manipulating electromagnetism. The initial gravity field would take A LOT of energy to set up (hell: it took the Earth's mass times c^2 to set up the Earth's gravitational field! We sure as hell don't have easy access to that much energy!)
Re:Forget Antigravity, how about a Gravity device? (Score:2)
Make a spacecraft that can, say, put out enough thrust to continously accelerate at 0.5G acceleration. Flip the ship at the halfway point, and decelerate at 0.5G.
Re:Forget Antigravity, how about a Gravity device? (Score:2)
Re:Forget Antigravity, how about a Gravity device? (Score:3, Insightful)
Maybe I'm missing something, but can't you just create a windowless torus, spin it about an axis going through its centre perpendicular to the plane of the torus, and use the outer wall as the floor? (Pretty much how it was done in 2001, iirc).
There's no disorientation, as there's nothing visibly moving. Sure, if you think about it too hard, it might cause you a few conceptual problems, but surely no more so than thinking about people on the other side of a planet.
the moon is a shitload closer and we cant convince anyone to fork over funding to go back there
I'm hopeful about a Mars mission; after all, we've sent people to the Moon, and there are no more political points to be gained from doing so again. Mars, on the other hand, is another "Species First" thing - the first time a human being has set foot on another fully-fledged planet. I can see Bush now - "not only are we successfully waging war on terror and making the world a safer place, we're expanding our reach to the rest of the Solar System too, furthering the cause of all humankind. God Bless America!"
I just have to hope that he sees it that way, too, and not just as a waste of valuable dollars that could be better spent on expanding America's reach on this planet.
Cheers,
Tim
Re:Forget Antigravity, how about a Gravity device? (Score:5, Informative)
Then there's the problem of gravity gradients. Centripetal acceleration (the 'gravity') is a linear function of radius; thus, there is a 100% gravity gradient running from the axis of rotation to the outer rim. An object weighing 10 kg on the 'floor' (rim) would weigh 5 kg if moved half-way up towards the 'ceiling' (axis). The percentage weight change an object moving from a point Ra to a point Rb experienced is given by:
W1/W2 = (Ra - Rb)/Rb
Thus, an object raised to a 1 meter shelf in a 4-meter rotating station (from Ra = 4 m to Rb = 3 m) would lose 25% of its weight. It is unknown how this sudden weight loss would affect materials handling; e.g., would a suddenly lightened box tend to fly out of one's hands?
In addition, a 2-meter tall astronaut standing in a 4-meter rotating station would feel literally 'light-headed'; the head (nearer the axis of rotation) weighs 50% less than the feet!
Despite these concerns, the gravity gradient appears to be the problem of least concern in designing a rotating habitat, and was considered a 'non-problem' in NASA's recent Artificial Gravity Working Group.
cross post (Score:2, Funny)
still, i won't have to worry about my diet...
Tying In The Higgs Boson (Score:3, Informative)
What this would mean. (Score:2)
Consider a localised column around the earth in which gravity is lessened. This means that the potential energy is higher in this area... here on earth we have very negative energy, and out to infinity we define zero energy. The area of lesser gravity has a higher potential energy.
The upshot of this is that it requires a force to "push" something into this area of microgravity. Why? because otherwise you could have two stairwells, one for going up in the microgravity area, and one for going down (normal gravity). You could get energy for free.
So, if your missile, or what ever, has sufficient energy to make it into the microgravity column, it slows, and then comes out the other side, at its original velocity. If it doesnt have this critical velocity (let's call it escape velocity), it bounces back. At its original speed. Ouch. Most notably, if you put your arm in there, your heart can't pump the blood with enough pressure to keep the blood in your arm. Bugger.
I think it is kinda interesting, not only because it is fundamentally a cool thing, but all the cooky side effects that could come about from it.
Re:What this would mean. (Score:2)
No, there is no need for an external force. The energy comes from the field that is responsible for the local reduction in the gravitational force. When an object enters it and gains energy, the field must somehow restore its energy level, or fade. That comes down to drawing more energy from whatever's powering it. Assuming the field is artificial, that will probably, ultimately, be an electrical supply of some sort - a battery will be drained, more coal will have to be burnt, whatever.
You're not gaining free energy (which is impossible, at least macroscopically, and for "long" periods of time), you're just changing its form.
Cheers,
Tim
hmmm (Score:2, Informative)
Plus his error analysis was crap and also had graphs consisting of a number of smiley faces IIRC.
Also for a year, some RA was hired by Sheffield uni to try and recreate his results. Yes there was a weight loss effect once (out of many many attempts at the experiment) but the guy who did the experiment did some proper error analysis and concluded it was an error. In the end, they could not recreate his experiments.
Thats not to mention the anecdotes he used to explain his accidental discovery of the effect. One of his colleagues was smoking his pipe on the floor above when the smoke hit an invisible column and rose (or something similar to that).
Interesting situation, terrible article (Score:2)
Re:Interesting situation, terrible article (Score:2, Insightful)
Mmmmm.... spinning disks... (Score:3, Interesting)
Maybe they somehow generate some sort of bogosity field;) Or perhaps it's just because so many people have at one time or another personally encountered the bafflingly counter-intuitive behavior of a toy gyroscope when you try to alter the axis around which it is spinning, and it tries to move off in an approximately 90-degree offset direction. There was a time when I was studying physics at university when I could write down the relevant equations and calculate what would happen, but even then I never intuitively understood the "cause" or where this unexpected force "came from". Quantum theory and relativity seemed transparently obvious in contrast.
Superconductor and Anti-magnetism (Score:2, Interesting)
Since superconductors already possess one unique attribute (anti-magnetism), it would be very intriguing if it might possess a second (anti-gravitiationl). The other passing thought is that the world has longed for an anti-gravitational engine, but maybe it was right in front of our noses all the time but it was called something else, an anti-magnetic engine. The Earth along with many planets and stars in the universe possess magnetic fields.
Let's be pro-gravity, not anti-gravity (Score:2)
Gravity holds all of our stuff down, so let's not be so negative about it. All kidding aside, from a physics point of view, anti-gravity is like de-accelleration - there is no such thing. There is accelleration with a reversed vector -- which has the same effect as so-called "deaccelleration." With gravity there is simply the Graviton. It is just a theoretical particle but it fits in well with Super String Theory and Quantum Gravity. I suppose it implies there is an Anti-Graviton, but the article in question doesn't suggest the manufacture of Anti-Gravitons.
--Peter
T( H)GSB [slashdot.org] Apr 21-27
Quantum leap? (Score:2)
Wow, I thought the quantum leap effect was restricted to time travel!
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Falsifiability (Score:5, Insightful)
However, suppose the experiment fails to demonstrate the sought-after effect. This does not constitute a victory for the existing models, because Podkletnov just says, "Oh, you didn't use the right superconductor," or the right temperature, or something.
There is no way to disprove his theory. That's called "non-falsifiable". Non-falsifiable theories are generally unproductive because you can never stop trying to prove them; you're caught in an infinite loop. Eventually you just lose interest, or start to apply Occam's Razor.
It does not bother me that NASA should pursue research with a low likelihood of yield when the potential benefits are high. But whenever someone posits a non-falsifiable theory you must be suspicious, because it's the mark of somebody who is trying to get you to waste time and money.
Note that "falsifiable" is different from "not easily proveable". I can't really go out and check that those points in the sky are really massive hot balls of gas. But at least theoretically it's possible, just not convenient. And I can run other tests which could disprove my hypothesis. I can prove that they're not real close, for example, by sending up a rocket ship. I can check that they happen to produce light in the same fashion that really hot things do. If these tests fail, you know that my theory is wrong.
Inventing non-falsifiable theories is easy; you just leave a variable unbound. (That's the more general, and more useful, form of saying "you can't disprove a negative." You _can_ disprove a negative; I can prove that there's no elephant between me and my monitor right now.)
Because creating non-falsifiable theories is both easier and less productive than creating real scientific theories, but make it possible to fool people into believing something they want to believe, such theories must be treated with extreme suspicion, especially when somebody has something personal to gain out of it. The theory is not necessarily wrong, but the odds decrease drastically, to the point where the probability * cost is lower than the potential value.
The potential value may be very high here, but $2.6 million is non-trivial money, even for NASA, and the probability is vanishingly small.
Interesting Intellectual Experiment (Score:3, Interesting)
There are, in my mind, many different questions:
1. Over what range would the shield have an effect?
2. Could the shield shield itself?
3. Is it bidirectional?
4. If particles in the umbra of the shield are no longer fully subject to gravitation, how would the effect of other forces be expected to perturb the particles?
4a. For example, how would ordinary air in the umbra of the shadow be expected to behave?
5. If an object in the umbra of the field was subject to reduced or near zero gravitational force, how would such an object be expected to behave in regards to angular momentum forces in effect on a rotating planetary body?
And so on.
It seems to me on superficial consideration that a "gravitational shield" would likely cause extraordinary and obvious side effects in even the most simple of circumstances. Living as we do in a heavy gravity zone, we take all of the effects of gravity for granted. An area of even limited exemption to gravity would likely have highly perturbing results in its domain of influence.
Anyone want to play this game?
C//
Re:Getting Dizzy... (Score:4, Funny)
Re:Getting Dizzy... (Score:2, Interesting)
I've also got a stupid joke:
Future hard drive technology may allow super-lightweight Linux distributions.
Re:Getting Dizzy... (Score:2, Informative)
Re:Getting Dizzy... (Score:2, Insightful)
If photons are absorbed by matter to cast a shadow proportional to the absorption rate, then gravity must as well under the right circumstances. Problem is: matter generates gravity, hence a fancy way to mask gravitons (which by the way have never been detected) is needed to cast a weight reducing shadow.
If their claims are correct, the weight of an object will be reduced, but the mass itself will remain unchanged since that is a property of the object itself.
They beleive the cooper pairs in the superconductor are somehow responsible for this absorption, though I have a hard time believing this is true since amorphous superconductors have been spun up and exposed to large RF pumping with no effect.
My idea is it is more likely an effect brought about by the alternating conductive and insulating layers of the composit superconductor that might produce the effect, creating a pseudo cassimer barrier with a negative net energy ballance which could attenuate gravitational flux.
By the way: any attempt to measure the mass will not find any mass reduction, though the weight will decrease due to the gravitational shadow being cast by the device. I imagine that the 2% reduction is optimistic at best, since the umbra and penumbra of any gravitaional shadow would be rather acute, due to an inability to mask the gravitation coming from mass off-center to the device.
Then again it could be another cold fusion episode, though NASA lends it more credibility, though Pod could held and give them the real scoop.
Talking to plants. (Score:2)
Tone of voice, no. CO2 yes. Sweet-talk a plant for a few minutes and you give it a strong shot of a relatively rare gas that it requires for its metabolism.
Re:Poor Article Poor chances (Score:4, Informative)
Actually, gravity depends on three things,
1) The mass of the object that is being attracted
2) The mass of the object 1) is attracted to(typically much greater than the mass of 1))
3) The distance separating the two.
This relationship is called Newton's law of gravitation:
F(gravity) = G*(mass(small)*mass(big))/(distance)^2
Re:Poor Article Poor chances (Score:2)
Re:Poor Article Poor chances (Score:2)
I actually did cover that situation in the post. Basically what I'm saying is that you WON'T be able to use this device to cheat in getting out of orbit unless you break conservation of energy.
Re:Poor Article Poor chances (Score:2)
Re:Poor Article Poor chances (Score:4, Informative)
Check your high school physics notes again. Gravity has everything to do with mass. Gravity is the attraction of objects to each other because of their mass. Every object posessing mass has a gravitational field. The strength of that field is proportional to the amount of... wait for it... mass.
If you witness/measure less gravitational force in a system, you can conclude at least one of three things, according to the high school physics you speak of:
1. The universal gravitational constant has been reduced.
2. One or more masses in the system have been reduced.
3. The distance between the masses has been increased.
Re:Poor Article Poor chances (Score:2, Funny)
Actually my wife found a handy little dial on the bottom of her scale that lets her reduce the apparent mass at will. It's especially effective after parties the night before.
Re:Poor Article Poor chances (Score:2, Insightful)
4. Gravitational mass is no longer tied to inertial mass.
Re:Poor Article Poor chances (Score:4, Funny)
Just an observation.
Re:Poor Article Poor chances (Score:2)
Gravity has EVERYTHING to do with mass. (Score:2)
As previous posters have noted mass and gravity are intimately related.
Re:Poor Article Poor chances (Score:3, Insightful)
Leaving aside the trivial counterexamples some others have offered (F=GM1M2/R^2), this is actually 100% wrong, as would be known if you consulted anything higher than a high school physics textbook. Even if you want (as the post seems later to imply) to disavow a connection between gravity and inertia, you'd be wrong. Gravitational mass is the same as inertial mass. This has been both empirically validated for 350 years and theoretically established by the Equivalence Principle in General Relativity. Gravity and inertia are one and the same, in ways we don't entirely understand.
So if you could actually reduce G, which is what these guys basically claim, you would indeed be reducing the inertial mass as well. Of course other weird effects would have to propagate, as well.
Re:less gravity is good for fat people (Score:5, Interesting)
I had the same reaction to this comment that I did when an 80 year old man was found dead on an airplane the other day. There was some debate as to whether or not he died before he got on the plane, or after.
One of the officials said "I'm pretty sure we wouldn't have allowed a dead man to board a plane." (true story)
In any case, lower gravity would help obese people move around more, but in the long term it wouldn't be such a good idea. The problem is that it'd make their condition worse as they'd be burning less energy trying to walk.
I realize you were probably just being silly, but it got me thinking. Lets say one day we had gravity reduction devices in our home to make us more comfy. Would that lead to a weaker speices down the road? Some would see the mass production of cars to have had a similar effect on our species.
The thought of gravity reduction devices scares me a little, although their applicates would definitely change the world we live in.
Re:less gravity is good for fat people (Score:2, Insightful)
But if the entire continent/earth whatever had this same gravity reduction, then youre fit in the same sense you are today.
Re:DBZ (Score:3, Funny)
Re:less gravity is good for fat people (Score:2)
One consequence of that would be an evolution towards truly spherical people.
Maybe, too, we'd start to develop tentacle like tethering arms.
Also, perhaps, without the usual gravitational based means for propulsion (legs, walking) we'd develop more general means, such as high powered flatulence.
Ah, but this is /., so you're probably way ahead of me on this one...
It would work great in space. (Score:3, Funny)
Re:Nothings Free (Score:2)
Re:Levitation Movies on ArtBell.com (Score:2)
Re:*sigh*.. (Score:2)
In the words of Thomas Edison when asked how he felt about failing a thousand times while trying to create a lightbulb, he replied, "I don't look at it as 1000 failures, but 1000 steps." (verbatim)