NASA Probe Validates Einstein Within 1% 188
An anonymous reader writes "Gravity Probe B uses four ultra-precise gyroscopes to measure two effects of Einstein's general relativity theory — the geodetic effect and frame dragging. According to the mission's principal investigator, the data from Gravity Probe B's gyroscopes confirm the Einstein theory's value for the geodetic effect to better than 1%. In a common analogy, the geodetic effect is similar to the shape of the dip created when the ball is placed on to a rubber sheet. If the ball is then rotated, it will start to drag the rubber sheet around with it. In a similar way, the Earth drags local space and time around with it — ever so slightly — as it rotates. Over time, these effects cause the angle of spin of the satellite's gyroscopes to shift by tiny amounts." The investigators will be doing further data analysis over the coming months and expect to release final results late this year.
Finally! That took long enough. (Score:5, Interesting)
That project took way too long. I remember people working on it when I went through Stanford in the mid-1980s. It was something of a boondoggle; it mostly produced students, not flight hardware. I'm glad to hear it finally worked, though.
Re:Finally! That took long enough. (Score:5, Informative)
Re:Finally! That took long enough. (Score:5, Interesting)
There was a great lecture about this on this year's hungarian skeptics conference, spiced with the real life experience that Hungary was part of the soviet influence sphere at that time, so when one physicist was allowed to go to the USA for a year to do research. When he came back, his colleagues were flocking him, discussing the news and that the americans are setting up this experiment. The lecturer, now an old man, can finally see the result of the experiment they were discussing more than 40 years ago.
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Re:Finally! That took long enough. (Score:5, Interesting)
Every time someone (re)validates Einstein relativity theories, we actually know we're one step further from FTL (Faster than light - though I'd be surprised if any
Damm gravity.
Re:Finally! That took long enough. (Score:5, Funny)
No, my friend, what you need is a warp drive.
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An oscillation overdrive. That would be exactly what you need.
Now to find that rock and roll physicist that has the prototype.
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Well we still have wormholes (Score:2)
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1) your sig has a very lame typo 2) take comfort in the 1%.
First we had the deistic theory of physics - things fall because they fall, big guys hit harder because they're big, and so on.
Then we moved up to Newtonian physics.
Then Einsteinian.
Who's next? Bohr? Someone I've never heard of? Who knows, but it's an interesting question.
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Could anyone who actually is familiar with this overall project (Not a stats person, I'm sure they'll say it's insignificant) tell us if the margin of error is truly acceptable?
I understand that there is always a margin of error due to minimum measurable differences, but can physicists now go "Phew, we are now FULLY sure this is right, and not that there has been a measuring fluke" or is there still some doubt? I
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Layne
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I guess my answer to your question is nothing is ever sure nor can it ever be.
Maybe it took so long... (Score:2)
scooped by another frame-dragging results (Score:2)
Longest project ever (Score:2)
The Pitch Drop Experiment [uq.edu.au]
I can't wait for the tenth drop! WooHoo!
Slashdot: my source for news about... (Score:5, Funny)
Re:Slashdot: my source for news about... (Score:5, Funny)
A tip o' the hat to you, sir.
Soko
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Re:Slashdot: my source for news about... (Score:5, Insightful)
But I find simplifying matters this way a very noble way of getting knowledge about the universe across to the layman. Without the balls-on-rubber-sheets, we would have to be talking about Riemann geometry and differentiable manifolds and other wonderful stuffs. There are reserved places in heaven for people who can make these kind of analogies. Millions of clueless joes will tell you so.
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http://fetteredpleasures.com/product/rubber_beddi
The one percent factor... (Score:1, Interesting)
Re:The one percent factor... (Score:5, Funny)
Re:The one percent factor... (Score:4, Funny)
My sweaty Uncle Phil must have a 198 IQ.
funny you mention that... (Score:2)
Genius is one percent inspiration and ninety-nine percent perspiration. -- Thomas Alva Edison
Actually... (Score:5, Interesting)
- taking credit for his employees' inventions as if he personally and singlehandedly came up with them. (There are at least 28 inventors that Edison ripped off this way, including for example taking credit for inventing the motion picture camera. Actually, it was invented by W.K. Dickson.)
- patented stuff he didn't actually have yet, and/or wasn't even original
E.g., he applied for a lightbulb patent a full year before actually having a filament that was commercially viable: and Edison's, or shall we say, his teams, _only_ contribution there was a commercially viable filament. The light bulb as such had already been discovered, it just didn't last long enough to be worth buying. But wait, even the carbon filament wasn't new: Edison't patent application itself had come a whole 1 year after Joseph Swan had patented a working model in England (and was working at it since 1850, 28 years earlier). So basically it took Edison and his team two years to copycat someone else's invention and claim credit.
- bogus patents, e.g., a number of patents on ornamental designs
- using PR and bad science to win public support: see the "war of the currents", where Edison (who wanted to sell direct current) paid people to roam the country and conduct demonstrations of killing cats, dogs, and once even an elephant with alternating current. Just, you know, to show people that alternating current kills. (While supposedly his direct current at the same 110V doesn't. Yeah, right.) He's also the author of the electric chair, as part of the same campaign to prove that AC kills. The first execution had the guy pretty much fried alive over a time of more than a minute (he certainly was still alive and struggling after the first 17 second jolt), in a show that sickened spectators and was described by the New York Times as, "an awful spectacle, far worse than hanging." That's the kind of PR that served Edison's purposes.
- shafting the employees. E.g., Tesla was promised a (huge for that time) bonus of $50,000 if he succeeds in making an improvement to the DC generators. When he actually succeeded, Edison didn't pay him, and in fact told him, "When you become a full-fledged American you will appreciate an American joke." In fact, he even refused to at least give Tesla a raise.
- mis-treating his employees. They actually spread word of Edison's current mood, so they'd know to duck for cover if he's in a bad mood.
- speaking of Tesla, here's one thing he said about Edison's dumb trial-and-error methods, a.k.a., 99% perspiration: "His method was inefficient in the extreme, for an immense ground had to be covered to get anything at all unless blind chance intervened and, at first, I was almost a sorry witness of his doings, knowing that just a little theory and calculation would have saved him 90 percent of the labor. But he had a veritable contempt for book learning and mathematical knowledge, trusting himself entirely to his inventor's instinct and practical American sense." (Would explain why most "Edison" inventions were actually from employees who actually understood what they're doing.)
- various attempts at monopoly, including the infamous "Motion Picture Patents Company", a.k.a., the Edison Trust. You know, if you thought that MPAA is bad, the MPPC meant you couldn't even make independent films without Edison's blessing.
- showing more contempt to the artists than the RIAA today, and in fact, enough to make the RIAA look like the good guys. Edison refused to even print the artist's name on the label. You're buying Edison music, you peon, not some artist's music. On one occasion he stated, "I would rather quit the business than be a party to the boasting up of undeserved reputations." Yeah, who do you think you _are_ to be getting any reputation for your talent and popularity. Only the great Edison should get a reputation out of it.
- letting his personal moods and preferences be the only criterio
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To put it into context, Edison's efforts to protect his licenses on Motion Picture technology created Hollywood.
Yes, there was land and light a plenty in Hollywood but there was elsewhere too. LA was also the other side of the country to his enforcers. We can comfortably postulate that Hollywood was therefore created by a bunch of patent pirates.
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Sure, geeks like to bust on Edison. Real geeks prefer Tesla over Edison anyday. But either implicitly or explictly taking credit for people that work for you is common.
Someone that lives in a custom home says they built it, but odds are they did not drive a single nail. The owner of a construction company can show you all of the building he "built", but again, odds are he did none of the physical construc
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AFAIK, the Edison quote is real (see http://en.wikiquote.org/wiki/Thomas_Alva_Edison [wikiquote.org]), and Tesla, Edison's arch rival, said something like "If Edis
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NOVA did episodes, helps visually (Score:4, Informative)
http://www.pbs.org/wgbh/nova/elegant/ [pbs.org]
Re:NOVA did episodes, helps visually (Score:4, Insightful)
String theorists will take these sort of statements as an attack, but they're just a blunt assessment of the situation. GR and QM are well-tested theories. String theory doesn't rise to the same level. It's possible that some version of it will one day -- it's certainly morphed into enough varieties -- but today, it's primarily mathematical speculation.
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My qualification "essentially untestable" was intended to address this. Sure, there are version of string theory that can be rejected. But positive confirmation of many of the artifacts of string theory seems elusive. Since the margins of this Slashdot comment are small, I'll let Sheldon Glashow respond on my behalf [pbs.org].
On the subject of "elegance", in the end, that
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I think you misunderstood my point.
First, re the pseudoscience issue, Greene comes in for that criticism because his books and video presentations rely quite heavily for their impact on emotional, aest
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Spinning Weights (Score:4, Insightful)
Re:Spinning Weights (Score:4, Informative)
On your second question, electrons and subatomic particles don't really spin, they have orbitals. Electron orbitals are the probability distribution of an electron in a atom or molecule. Take a look: http://www.orbitals.com/orb/ [orbitals.com] So it's not really like a gyroscope. But that is an interesting question, i.e. Do electron orbits effect the angular momentum of atoms? How would you measure that experimentally? Does Newtonian Physics operate on that level?
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Actually, you missed on both counts.
Putting more than one gyro in a box is the same as putting one in with a different angular momentum. Angular momentum is a vector quantity; two gyros add together and act like one with the corresponding angular momentum. So when you try to move the box it will act like a box with a gyro in it, and you won't be able to tell how many gyros there are.
Electrons orbit in orbitals, but they also spin, like how the Earth both orbits and rotates. See Quantum spin [wikipedia.org] for detai
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Particles have angular momentum, even though they're not necessarily rotating in the classical sense of the word (as a wheel does). Confusing? Yes. Useful? HELL YES. For one, MRI imaging relies entirely on quantum spin to work.
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Of course your orbital carries an angular momentum (i.e. the electron "spins around the core") if l>0, i.e. for most electrons. Its just very small.
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This was a stanford experiment (Score:4, Informative)
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links (Score:4, Informative)
http://cosmicvariance.com/2007/04/15/dragging-on/ [cosmicvariance.com] (4:33 p.m.)
Also of interest if you're into this sort of thing, what Beyond Einstein programs will be cut?
http://scienceblogs.com/catdynamics/2007/04/beyon
sad if you compare sticker prices to the $10 billion per month on the Iraq adventure.
The most interesting thing to me is apathy (Score:5, Interesting)
While some might think me a troll, think about it, Einstein was right. That means that we are that much closer to understanding how the universe works. Even 100 years ago such progression could only be imagined, not proven. In the time that we live in, science books have to be revised every year not because of a need to spend government money, but to actually keep them up to date!
So much change and investigation. People have become numb to the actual changes.
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I think the apathy comes from disappointment as much as anything. We all wanted FTL and Hyperspace and Warp drives. Phooey on that now, eh? Looks like stargate is our only remaining option for interstellar travel and exploration. That, or put our consciousnesses in robot bodies and suffer through thousands or millions of years of boredom / deactivation in transit ("Are we there yet?")
In essence, this is an experiment that strongly suggests your car can't get you to MegaCon, and you'll probably die alon
Re:The most interesting thing to me is apathy (Score:5, Interesting)
Not all religions think that technology is evil/pointless, but the ones that are most dangerous do. This doesn't disprove the existence of god, or prove it. It disproves irreducible complexity, and thus the theory of intelligent design. ID is that theory that would not explore or experiment because it cannot be understood, things just are because god created them that way. Evolution didn't happen, the big bang didn't happen... all that claptrap. god may well exist, and may well have caused the big bang, or the chain of evolution to begin... who knows. The point is that understanding how things work is important to us as a species. Those that would oppose such investigations and the evidence they produce are dangerous to all of us. Scientists are heroes. Not even 1000 years ago men were killed or imprisoned for knowing less than we take for granted as common knowledge today.
wikipedia article and cool picture (Score:3, Informative)
And the probe itself is just astounding: http://en.wikipedia.org/wiki/Image:Einstein_gyro_
I knew it! (Score:1)
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It works bitches! (Score:1)
http://www.xkcd.com/c54.html [xkcd.com]
Smart (Score:1)
From TFA: (Score:1)
Wish I had mod points. (Score:2)
More info (Score:4, Informative)
Frame Dragging Effect (has NEVER before been measured): 1.1x10^-5 degrees per YEAR
Geodetic Effect: 1.8x10^-3 degrees per YEAR
Clearly then, these were not merely "minuscule" shifts...the potential for error is great.
More information can be found at http://www.nasa.gov/mission_pages/gpb/index.html [nasa.gov]
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Speaking of the potential for error, here's something funky. Einstein's equations are real-number equations. That is, they describe computations performed using infinite-precision numbers. But any operation involving infinite-precision numbers must involve infinite operations from an information-theoretic point of view -- think bits, the number of, required to represent an infinite-precision number, and now think of the computations required to process such numbers. Since the universe obviously hasn't graun
It's called "Zeno's Paradox" (Score:3, Informative)
oops (Score:5, Insightful)
The goal was to measure the frame-dragging effect of the Earth, which is of the order of 40 milli-arcseconds per year; the current calibration (http://einstein.stanford.edu/content/aps_posters
The problems turn out to be really crazily subtle issues in solid-state physics -- the deposited metal films on the gyroscope and on its housing retain charge in patches large enough that they have to be modelled rather than averaged out -- plus an annoying issue from classical mechanics where the motion of a rigid body around three axes XYZ depends on the ratio of the differences of the moments of inertia X-Z and Y-Z. Whilst the gyroscopes are absurdly precisely made, so the moments of inertia are very close, the ratio of the differences of the moments of inertia is a macroscopic number; this is the same effect, and even a similar cause, to some of the oddities with low-precision floating-point arithmetic.
They'll probably be sorted out, sigma might be reduced by a factor ten after another year's modelling effort, but it seems unlikely that they'll get it down by the factor 200 they were hoping for.
The frame-dragging has already been measured indirectly by looking at the flickers of X-ray sources caused by frame-dragging-induced precession of the accretion discs around black holes, and most of the theories that suggest relativity is wrong would suggest that any oddities would be more pronounced in the huge gravitomagnetic fields near black holes than in the tiny fields near a mass as small, as non-dense and as slowly rotating as Earth.
Re:oops (Score:4, Informative)
This is a project that has been rolling along for four decades. Over that time, many of the things this experiment was designed to test have been indirectly tested using observations about binary pulsars. Now they're getting hit by incredibly subtle systematics in their apparatus (note that the apparatus was not misconstructed or anything, there are just some surprises that were too subtle to measure until the thing actually reached space). The worry is that the experiment is now not so interesting, even if they managed to beat down their error bars through blood, sweat and tears. If they confirm the predictions of GR everyone will say "gee, great". If they don't, people will be concerned about how well they really understand their error bars. Either way, they don't make the splash one might have hoped all those years ago.
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The snarky joke was that this was truly a null experiment : if it agreed with General Relativity, it would be believed, but it would change nothing. If it did
not agree with General Relativity, it would be viewed as being in error until it could be confirmed, which would likely take more decades. So, no matter what the result, it wouldn't change fundamental physics, which was the whole point.
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Re:oops - Bingo (Score:3, Informative)
I was going to post this myself. The goal was to measure frame dragging. The geodetic effect has been measured before (LLR and binary pulsars),
and is not nearly as interesting (i.e., its hard
to see why you wouldn't have it). It's the frame dragging that motivated the decades of effort and expenditure.
If they can't do frame dragging, the experiment will be deemed a failure.
Late to work. (Score:3, Informative)
Peter
1%? (Score:2)
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"99% accuracy" does not mean "1% error". It simply means that's how sure we can be that it's correct. The remaining 1% is unknown. If there was a known, repeatable 1% error, that would be big news because the theory would then be known to be wrong. To find said error would, however, require a measurement that was more like 99.9% accurate.
Re:1%? Consider Newton, Galileo, et al (Score:3, Informative)
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I was just showing how nitpicking the numbers can sometimes lead to new discoveries as well as confirming old theories.
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Now, for General Relativity (GR), effects start to come in at (v/c) squ
That's awful! (Score:2)
It's not like guns are that hard to acquire (Score:1, Offtopic)
One thing you can't do in such a country is defend yourself against someone with a gun. That someone can kick in your front door, shoot your entire family before your eyes and you'll just sit there and watch and there won't be a damn thing you'll
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Generally speaking, a society that has them everyplace is going to be far more democratic than one where only the ruler has one, and it doesn't make an anorexic rats ass difference whether that ruler started out as a saint, or a thug. The existence of a ruling class with guns to enforce their rule, will in time convert that saint to a thug simply because even the saint will
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So tell me, do you support private citizen's rights to own thermonuclear weapons?
Re:I'll hazard three guesses. (Score:4, Funny)
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I like what you have to say about every moving object emitting Hawking radiation.. kinda reminds me of Mach's Principle [wikipedia.org]. Perhaps every object in the universe emits particles in sympathy to a moving object.
Doesn't make much difference to its status (Score:3, Funny)
We need a probe to test GR at L1 point if the gravity there is significantly weaker than a0 to distinguish between MOND and DM. This IMHO is the most important test. If it is not possible to test MON
Translation to English (Score:2)
Jargon/Bogon Filter output to console:
"Even though this test is not being done on Earth, it is still being done pretty far down a deep gravity well. It might be interesting to repeat this test at the Lagrange point between the Earth and sun (L1). The only other choice to find flat space is to shoot the sucker out of the solar system, which would take too long."
Re:I'll hazard three guesses. (Score:5, Interesting)
Firstly, I'm going to guess that frame dragging is verified at no better resolution than the curvature of space/time, but that as far as they can tell, it exists and meets the values expected by Einstein.
Frame dragging is the name of one particular way in which spacetime curves. It is curvature. To say something about frame dragging or curvature is to say something about the other. I don't know if the parent statement makes sense or not. The group has not released their frame dragging measurements yet, just the geodetic precession measurements (the precision of which will likely go up as they isolate more systematics in their data as they move toward making a statement about frame dragging). Frame dragging is about 100 times harder to measure than geodetic precession, for the mass and spin of the Earth.
Secondly, I'm also going to guess that QM experts will start to get a little nervous. The properties any future QM model of gravity must have contradict the GR model. They cannot both be right. The more "right" the GR model, the more problematic a QM model. This doesn't mean a QM model does not exist, only that it is most undesirable (from a QM perspective) for the GR model to make highly precise and accurate predictions.
GR is arguably the most successful physical theory to date (I would say that electrodynamics rivals it since it has been formulated classically in curved spacetime and also has been quantized successfully in flat spacetime, but that is another discussion). Newton was not "right", but note that GR simplifies to Newtonian mechanics in the weak field and non-relativistic limit. Any theory which supersedes a highly successful physical theory must reproduce said theory in the proper limits. A quantum theory of gravity must reproduce GR in the macroscopic limit, just as quantum mechanics has a correspondence principle which allows it to reproduce classical wave and particle phenomena in the appropriate limit. I don't think any physicist is nervous about these results - everybody expects GPB to verify the predicted frame dragging. Deviations from the values predicted would excite fans of MoND, SVT theories, and other alternative theories of gravity.
Thirdly, frame-dragging occurs at a non-zero distance from an object.
Frame dragging curves spacetime globally, but falls off to asymptotic flatness. The parent statement probably makes sense.
This doesn't matter, for the purpose of these observations, as they're nowhere near accurate to measure the relativistic effects that apply to the information passed that creates the effects in the first place. Nonetheless, such an affect must exist, or you'd end up with infinitely fast rates of change of state, which is expressly forbidden in GR.
The NSF and NASA don't spend this much money to throw an instrument into space unless they think it will actually measure what it's supposed to. The gyros are the most spherical macroscopic manmade objects, which used superconducting quantum interference devices (SQUIDs) to precisely measure their precession, blah blah blah, read about it on their web site. I sure hope they're accurate enough to measure those relativistic effects, because that's exactly what they've been designed to do. I don't know what information you are talking about. The Einstein Field Equations are local, so there is an inherent limit on the speed at which 'information' (curvature) propogates through spacetime.
It's a gross simplification and it's not an "obvious" conclusion to reach by any means, but if the curvature (and restoration) of space/time has nothing analogous to Hooke's Constant, then after a gravitationally massive object has move
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MOND approximates to GR in strong field. (Score:4, Informative)
There is a big misconception about MOND, that it is a theory. It is not, it is a law that works very well at the Galactic Level and somewhat at the cluster level. MOND fits all galactic level data to the limit of their expected accuracy. This it does so with a single universal constant. But nobody knows why it works so well.
As such it is very obvious there is something behind MOND. GR cannot explain MOND without fine tuning DM in such a way to give rise to MOND. But since MOND uses only Baryonic matter, it leaves DM with no degrees of freedom, which is not possible, so DM must not exist at the Galactic level.
At Cluster level situation is different MOND does not match up with the missing mass. Which means either there is Dark Matter at the Cluster level or MOND itself is a reasonable approximation of the correct theory of gravity only in the galactic limit. Beyond the galactic level it ceases to be a good approximation.
If there is dark matter at the cluster level then there must be a reason why it does not exhibit itself at galactic levels. This would meant that the dark matter is hot and moving at a high velocity, which allows it to form stable structure only at the cluster scales.
The interesting thing about the universal constant (a0) of MOND, is that if a particle is accelerated by a0 for the whole life of universe then we will get the speed of light. This would seem to provide a hint that a0 is due to the curvature of the universe.
This actually solves a problem in GR. If GR is absolutely correct then the curvature of the universe cannot be determined, which is also called the flatness problem. This problem is currently avoided by assuming that there was an inflationary era when the universe expanded so much that we only see a very small part of the universe which is flat. So that GR equations are correct. But if that is not true and the universe is not really that big then GR will break down because of no fault of itself, but simply because of the curvature of the universe.
So in my opinion GR is correct but the curvature modifies GR in such a way that we observe MOND.
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Re:I'll hazard three guesses. (Score:4, Informative)
>Who moded this person a troll, without posting a response?
You can't mod and post. One or the other, but not both.
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MOND is, as its name implies, a Newtonian theory of gravity, which means it predicts no frame dragging at all. As such, this experiments shows it to be incorrect, just like Newtonian gravity. This is expected.
What it would affect is alternate theories of gravity that are equivalent to general relativity but reduce to MOND instead of Newtonian gravity in the non-relativistic limit. I understand TeVeS is one such theory, but I don't know what its predictions of fra
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There's obviously nothing wrong with the model, but people tend to forget that multiple models can exist (and be applicable) simultaneously.
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To those claiming it to be a straw man, it is not! I see people in here backing scientific method that in global warming threads claim it to be a proven fact. You can not have both! So when people ask why it is 99% and not 100%, maybe we should look at the myths that are put forward as science and stop pushing the myths.