## General Relativity Is At Least 99.95% Right 223

Posted
by
Zonk

from the happy-hair dept.

from the happy-hair dept.

ultracool writes to mention a ScienceDaily piece on compelling proof of general relativity. A team at the University of Manchester have used three years' worth of data on a pair of pulsars as a litmus test, against which they've benchmarked Einstein's theory. From the article:

*"Though all the independent tests available in the double pulsar system agree with Einstein's theory, the one that gives the most precise result is the time delay, known as the Shapiro Delay, which the signals suffer as they pass through the curved space-time surrounding the two neutron stars. It is close to 90 millionths of a second and the ratio of the observed and predicted values is 1.0001 +/- 0.0005 - a precision of 0.05%. A number of other relativistic effects predicted by Einstein can also be observed. 'We see that, due to its mass, the fabric of space-time around a pulsar is curved. We also see that the pulsar clock runs slower when it is deeper in the gravitational field of its massive companion, an effect known as "time dilation."'"*
## General Relativity Is At Least 99.95% Right (Score:4, Insightful)

## Re: General Relativity Is At Least 99.95% Right (Score:5, Insightful)

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You observations are just making a theory more or less likely to hold.

What does it mean to disprove a theory, in any case? Does special general relativity disprove Newton's theory?

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Does special general relativity disprove Newton's theory?Yes, it does. Newtonian physics are bound to certain limits, at those limits strange things happen that Newtonian physics do not predict. Relativity explains both the experimental results of Newtonian physics and those where they go bonkers. So, relativity proves that Newton was wrong in certain conditions. This does not mean that Newtonian physics are unusable and that's why they are still taught in high school.

Compare it to something we

## Re: General Relativity Is At Least 99.95% Right (Score:5, Informative)

Mathematics is a closed system, for which we know all the rules (because we define them). Thus, things can be proven as being objectively true, false, or unprovable (for as given set of axioms, there are many self-consistent sets).

Physics and the other sciences, on the other hand, are faced with the dilemma that we can never observe all the behaviour of everything in the universe at once, and thus we are forever working with partial data sets, and fitting our theories to them. As a result, the best we can say is that the theory we have put together fits the observed data to a high degree of precision - but that this may be invalidated at any time by new phenomena. See, for example, the progression from Newtonian mechanics to Relativity, or the long-running debate over the nature of light.

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relativity does make newtonian physics "wrong". relativity shows a story that matches better with reality, so now we see newtonian as more of an approximation that it was before. it is still a useful approximation, and we still use it, so in this way WE say it is correct.

EVERYTHING is an approximation except the position and momentum of the base particles.

Eventually we will have a better theorem than relativity, will that make rela

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Newtonian physics is still correctIf by correct you mean "approximation adequate for daily use," sure. But, not correct in the sense that it is an accurate conceptual modelling of the forces at work, which is generally what is meant in discussions along these lines.

## that's incorrect, too (Score:2, Insightful)

As a result, the best we can say is that the theory we have put together fits the observed data to a high degree of precision - but that this may be invalidated at any time by new phenomena. See, for example, the progression from Newtonian mechanics to Relativity, or the long-running debate over the nature of light.Well, no, that's not the "best" we can do. It is quite possible to prove theories to be correct experimentally, if you formulate the theories correctly and then conduct the right kinds of experi

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feelsright, but that doesn't mean itisright.## Re: (Score:2)

Well, no, that's not the "best" we can do. It is quite possible to prove theories to be correct experimentally, if you formulate the theories correctly and then conduct the right kinds of experiments.You can't conduct that kind of experiment. We have incomplete knowledge, exist in a noisy environment, and are hampered by the problem that at some basic level, observation changes the system that is being observed.

The problem is that General Relativity, like most physical theories, was pulled out of a h## um, right idea, but not far enough (Score:2)

However, your statements about math are off insomuch as you use the word "all": one of the most fundamental parts of math and logic were Godel's Incompleteness theorems in the 30s. This is the mathematical codification that Hericlitus ("We both step and do not step in the same rivers

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Me? I'm not confusing anything. The post I replied to made a blanket statement that was false... Theories CAN be proven true, and it's not my fault that the distinction you talk about was not noted there. "Theory" was the term used, not "Scientific rather than Mathematical Theory"And to continue the trend of utter pedantism (or is it pedanticism? I await correction) in this thread, you confuse the well-defined idea of a scientific theory with the vague notion of mathematical theory. Mathematical theori

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## Re: General Relativity Is At Least 99.95% Right (Score:5, Insightful)

. . .they are not a proof.Only mathematics has proofs, but observations that support a theory demonstrate that the model has predictive value. Observations that do not support a theory demonstrate that the model is, at best, incomplete.

Ignoring the predictive value of a model, whether it is complete or not, demonstrates that you are an idiot. Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.

Facts are not proofs, but they

arefacts.KFG

## Re: General Relativity Is At Least 99.95% Right (Score:5, Insightful)

Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.That's like saying "for whatever region of the hypothesis space a given theory gives usably correct predictions, it's useful." Of course that's true, however part of using a theory correctly is knowing how far it goes. Quantum theory has demonstrated that the fundamental concepts in newtonian physics (position, momentum, energy, time, etc) are not really meaningful when you boil things down to the lowest levels we can observe.

I mean, you can tell someone that a VCR works because there's a little man in there that knows when you said you wanted something taped and writes all the TV programs down on tape. I mean, I don't think people actually believe this, but their black-box model of a VCR is essentially equivilent to this. The reality of how a VCR works, of course, is much more complex in many ways, and involves failure modes that non-electronic type people will likely fail to predict because of their incomplete view of the situation.

Newtonian physics is not merely an appoximation error, the fundamental set of concepts and intuitions are just completely unhelpful at any scale but mezoscale (that on which we exist, somewhere between atom and star).

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Newtonian physics is not merely an appoximation error. . .It's errors are completely quantifiable.

. . .the fundamental set of concepts and intuitions are just completely unhelpful at any scale but mezoscale. . .Newton himself noted that there were observable limits to his model and that whatever fundamental concepts it provided were also extremely limited, giving no greater understanding of

mechanism. They are purely empirical observation.You will, however, find that if you wish to predict the path of a sim

## Re: General Relativity Is At Least 99.95% Right (Score:4, Interesting)

It's errors are completely quantifiable.Newton's formulas are not merely missing a few parameters... they involve concepts that simply stop making any logical sense once you get down to very small scales. The idea of a "particle" even existing in a single position, as far as we can tell with modern QM, is completely absurd and meaningless. The concept of an exact momentum is equally so. The "clockwork universe" which contains action at a distance (causal nonlocality) and non-discrete space, time, energy etc (rather than discrete geometry and quanta) is simply so far from the "truth" that our experiments reveal - namely that particles act as if they are in infinite numbers of places at once (or nearly so, given plank limits on spaceitme).

You will, however, find that if you wish to predict the path of a simple artillary shell or design an automobile they are "correct," they have predictive value, specifically because the phenomenon exist within the limits of the model's significance. Taking Relativity into account does nothing but complicate the math to provide a bogus level of significance and Quantum Theory is completely irrelevant.Back at university, I used these "wrong" theories all the time, as they are useful (if erroneous) abstractions. The problem is that theories are not merely useful for their ability to predict things within the realm of known experience, but also new and different things beyond the current frontiers. Newton's theories, as elegant and beautiful as they are, were long ago surpassed and are now almost useless when it comes to generating new predictions about unobserved phenomena in the universe. The mark of a truly good theory is not that it can compress the set of known expimental results well, but that it can predict entirely new ones, outside the original domain in which it was devised.

Newton was a far smarter man than anyone posting here on slashdot, but like Einstein, he got so very much fundamental very wrong. I think if he lived here today, he'd get new and exciting things wrong (like modern theorists) and that that's a very valuable part of science, but we really shouldn't pretend his theories are anything more than a bunch of mathematical approximations that reference intuitive concepts that have almost no meaning at very small (and possible very large) scales.

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. . .we really shouldn't pretend his theories are anything more than a bunch of mathematical approximations. . .That's what I said. In fact, it's what Newton said as well.

. . .that reference intuitive concepts. . .They reference only observable phenomenon and are valid only within the limits of those observations.

KFG

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I don't think you are giving classical mechanics enough credit. Sure, it is wrong on several accounts. But it some ways, it seems to have gotten things fundamentally right, in a way that I personally think almost seems to transcend the mathematics.The reason it seems so right is that it accurately describes the physics approximation that's hard wired into your brain. Do remember that instinct formed some science too.

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Please don't enga

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Within its limits of significance Newton's theory of gravitation is still just as "correct" as Relativity.That's like saying "for whatever region of the hypothesis space a given theory gives usably correct predictions, it's useful."

No, it isn't. What he said compares the utility of accuracy to the demands of daily use, and thereby displays the lack of contrast in daily life between two progressive states of the understanding of physics. What you said is a tautological observation that a usably accurate p

## Re: General Relativity Is At Least 99.95% Right (Score:5, Insightful)

Yes the position/momentum/energy/time *operators* themselves have meaning, but giving a particle these properties, which it doesn't strictly even appear to have... that's simply ridiculous. Our intuitions don't work at these levels, the best we can do is trust to the math and come up with great ideas based on the equations we find in QM.

Relativity is still "classical" physics in that it's deterministic, but its very concepts of mass, energy, time, space, and propagation of information are fundamentally different. I'm sorry, but it's just so very different from what Newton had in mind.

## You can measure position in quantum physics (Score:2, Interesting)

You can't measure position in quantum physics [...] As far as we known, the "particle" *NEVER* has an exact position or momentum, but rather is at an infinite set of locations.At least in principle, you can measure position in quantum physics. The particle is temporarily put in a position eigenstate with an exact position eigenvalue associated with it (the momentum is completely indeterminate, however). This only lasts for an instant, however, before the state evolves into a superposition of position eige

## Re: General Relativity Is At Least 99.95% Right (Score:4, Informative)

Well you certainly can measure position! What about a single slit experiment? The electron going through the slit has a quite well-defined position, but a less well defined momentum and that is the crux of quantum mechanics. Indeed, as you imply, it is not possible to say the position of the particle is exactly such-and-such because that would violate the uncertainty principle. I would prefer not to mention infinite spreads of position/momenta because this is not helpful; given you mention information propagation, do you not think that this notion might have issues with an infinite wavefunction? The wavefunction in any phase space must be normalizable and this is surely the most important concept. I'll except tunneling as there even the smallest of tails causes the finite barrier to "leak"... eventually.

An illustration - it is well known that C60 can be made to diffract [univie.ac.at]. What do you mean then that position is meaningless? Do you mean to say that the atoms within the fullerene have no spatial relation to each other? How then do we know the symmetry of the molecule (from the number of absorption lines)? Of course postion is meaningful! Whether it is well defined is quite another matter.

I would also question your belief that the operators have any more meaning than the objects that the theory puports to describe! And I would certainly not advise trusting the math (although I'm a theoretician) - surely one must actually trust experiment!

I happen to be a physicist (but I don't particularly think that's relevant). I'm quite sure you grasp QM (the famous quote from Bohr aside), but I'm not sure I agree with the way you have chosen to explain it :-)

It is very common to say that "position, etc. are meaningless" but that simply isn't a correct statement at all, as I hope I've shown. Sorry for dragging this off topic (and for the profusion of exclamation marks)

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It's not hard to pin an electron's speed to within a few KeV.

It's vector +/- 90 degrees.

And it's position to within 1 AU.

The first limit is a product of the uncertainty in velocity and position so you can know a lot about one, but the more you learn about one the less you can know about the other.

The second problem is an apparent limit on how much you can know about velocity and position period.

Outside of these

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You can't measure position in quantum physicsOf course you can. It's one of the two locus collapses of the Heisenberg Uncertainty Principle. You can measure location perfectly if you're willing to accept indeterminacy in time.

I do have a degree in physicsThis seems highly unlikely. In fact, your degree too may be subject to the uncertainty principle: you can measure location accurately if you're vague about time (you might, for example, have a physics degree from MIT circa 1885) or time accurately if

## Re: General Relativity Is At Least 99.95% Right (Score:4, Informative)

Only mathematics has proofs## Re: (Score:2, Informative)

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It really shouldn't be surprising that when a system is powerful enough to talk about itself we can end up

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Only mathematics has proofsAnd logic, semantics, many subfields of philosophy, tactics, game theory, economics, and other purely theoretical rigorous fields. But, your point remains valid.

Ignoring the predictive value of a model, whether it is complete or not, demonstrates that you are an idiot.Well, either that, or that he's trying really hard to be academically proper, and doesn't know how. Cut the kid some slack.

## Even Newton is 99.995% right for most stuff (Score:4, Informative)

However, General Relativity is not a proof, but a model. The various models that give us a way of understannding the world are only that: models, not laws per se.

When Newton explained gravity, he did not say that he was right. Indeed he said that the model he proposed was the best he could come up with given the limitations of his apparatus. He even predicted that his model would be superceded. And, for most people of today, the physical objects that they interact with can be adequately understood with Newtonian physics.

Einstein even said "As far as the laws of mathematics refer to reality, they are not certain; as far as they are certain, they do not refer to reality.". Just like Newton's models had limits and fell apart at some point, likely the same will happen to General Relativity when we're one day able to observe things beyond what the model can handle.

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is, only how it behaves.## Re: (Score:2)

One could argue that the objective of science is to provide models that accurately describe our Universe and allow us to make predictions about its evolution. That's finding out "how". The question of "why" is of a different nature -- it can't be answered using the tools of science -- and falls into the problem domains of philosophy and theology. So don't really expect science to answer all possible questions, but keep in mind it does answer quite a few of them as it stands. :)

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Yes, you're quite right. Obviously, my naïve use of the words "how" and "why" opens up a lot of interpretations -- I was hoping for an intuitive one in the spirit of the GP poster. I do agree intuition often fails in this situation, and only exposure to the inner workings of science can help one grasp the difference between the two "kinds of question".

I would further add that, in

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Absolutely, and with General Relativity despite its stunning success we know that it must fail at some scale because as a classical theory it simply does not match what we know about space at the very small scale.

The vacuum is a much more active place and while at the long scale it can be described my a nice smooth m

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and the univese is asymptotically deSitter spaceEr, I thought it was an anti-deSitter space? The two are fairly different.

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## Who do you trust more, Einstein, or astronomy? (Score:5, Funny)

Let's not go attempting to invalidate any theories I've spent hundreds of hours trying to understand, ok?

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## time dilation (Score:4, Funny)

all we need are 20 pounds of trash and 1.2 jigawatts from the town square clock at midnight!

## Re:time dilation (Score:5, Funny)

Not really.

What you need is to sit bare-assed on a hot furnace. Look at your watch and take note as to how slowly the seconds pass.

See?

## Completely offtopic... (Score:2)

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1.21jigawatts! Learn your basics of time travel!## Re: (Score:2)

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It's not. Check it again.

## 99.95% acurate? (Score:5, Funny)

I think 99.95% is about as close to dead-on-balls-accurate as it gets with our current knowledge of the universe; I mean, there's always a margin for error in absolutely everything, it's just one of the facts of the chaotic universe in which we live. Still, it just goes to show how far ahead of the game (and of the times) Einstein was.

Einstein's still my hero. He's the Samuel L. Jackson of science.

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## Re:99.95% acurate? (Score:5, Funny)

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But regarding your "I think 99.95% is about as close to dead-on-balls-accurate as it gets with our current knowledge of the universe", allow me to take this opportunity to point out that Quantum Electrodynamics (the extension of electromagnitism and quantum mechanics into a quantum field theory) surely is the most accurate theory we have today.

In some circumstances its predictions have been verified to an astounding 14-15 decimal places! (Thats something crazy like 99.999999999

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Get these mother-f'n Newtonian physicists out of my mother-f'n audience!

Do they speak English in when they give you the Nobel Prize? English mother-f'r! Do, they, speak, it?

God, I'm sorry.

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## The Devil is in the details (Score:2)

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## Sooo.... (Score:5, Funny)

(sorry)

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> (sorry)

Generally, yeah.

Chris Mattern

## hey (Score:2, Funny)

## That is great but... (Score:4, Insightful)

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## But What About the Boomerang Project...? (Score:3, Interesting)

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## Not good enough for me (Score:4, Interesting)

The measurement is still in the range of first order parametrized post-Newtonian accuracy. What the Donkey Kong that means is that these are the coefficients to the metric that are being tested:

dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2) dt^2

- (1 + 2 GM/c^2 R) dR^2/c^2

- R^2/c^2 dtheta^2

- R^2/c^2 sin^2 theta dphi^2

It is the 5 integers there (1, -2, +2, -1, -2) that are confirmed by this experiment. That is NOT NEWS, because it is not new. Shapiro got the same results. What would be news is if the experiment got to second order parameterized post Newtonian accuracy. I asked Prof. Clifford Will an expert on experimental tests of GR when where the data hunters going to gather that data. He said he knew of no one even discussing it. The reason is that the data must for 2nd order PPN effects must be a million fold more accurate, so we need data that is 99.99995% accurate.

I care a lot about 2nd order PPN tests, since that is were my proposal to unify gravity and EM using a 4D wave equation differs. GR says the metric should go here:

GR:

dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2 -3/2 (GM/c^2 R)^3) dt^2

- (1 + 2 GM/c^2 R + 3/2 (GM/c^2 R)^2) dR^2/c^2

- R^2/c^2 dtheta^2

- R^2/c^2 sin^2 theta dphi^2

GEM (gravity and EM):

dtaU^2 = (1 - 2 GM/c^2 R + 2 (GM/c^2 R)^2 -4/3 (GM/c^2 R)^3) dt^2

- (1 + 2 GM/c^2 R + 2 (GM/c^2 R)^2) dR^2/c^2

- R^2/c^2 dtheta^2

- R^2/c^2 sin^2 theta dphi^2

At first order PPN accuracy, the coefficients (1, -2, 2, -1, -2) are the same. At second order, they are different. That's the data I need. I'll probably be dead before it shows up.

doug

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I am afraid to tell you that your theory isn't sensible.

For instance, in equation (2), if you make the mass density equal to the charge density, then you get nothing. But with opposite charge, you do get something. That's just a simple example.

Your action, equation (1), contains neither E&M nor linearized gravity. Where is F_mu,nu F^mu,nu? Where is D^2 h_mu,nu D^2 h^mu,nu ?

I'd suggest that if this is something you are really interested in, you take some courses and

## Newton Was Closer (Score:2)

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That's a rather vague way to put it. Relativistic effects on a body moving at 1 m/s are negligible to the point that Newtonian mechanics can be considered 100% correct for all practical purposes. Take another body moving at a speed close to the speed of light (we deal with those every day in modern Physics) and it's a very different story -- I can assure you the effects are very much

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It's all relative (pun intended), and the news that Einstein is off by so much is not so flattering to Einstein.

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Isn't Einstein's relativity just a much smaller magnitude extra term on Newton's mechanics?God, no. Einstein's relativity is a complete inversion of physics, that recasts all fundamental processes as related to time and the speed of light. Relativity and Newtonian Mechanics are as similar as a paintbrush and spraypaint, in that they achieve generally the same results, but through a fundamentally completely different approach.

[[0.05%]] Negligible at human scales.0.05% of a six foot tall man's height is

## No such thing (Score:2)

There's no such thing as proof of a scientific theory, so talking about how a theory is "almost proven" is just plain wrong.

And trying to quantify the "provenness" of a theory with a figure also shows a deep misunderstanding of how science works. There are any number of quantifiable tests that have matched general relativity's predictions, and each of these have different error bars. So picking one at random and using it as the measure of how "proven" general relativity is doesn't make any sense at all.

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There's no such thing as proof of a scientific theory, so talking about how a theory is "almost proven" is just plain wrong.The word "almost" does not occur in either the article or the Slashdot summary. You might as well lambast them that claiming iron is made from honeybees and old shoes is just plain wrong.

And trying to quantify the "provenness" of a theory with a figure also shows a deep misunderstanding of how science works.This is probably why nobody attempted to do so.

There are any number of qu## Space is big. Really big. You just won't believe.. (Score:2)

Since when is 99.95% a big number when we're dealing with astronomy? I think

Newton'slaws are precise within 99.95%.99.95% of

what?## Re:Space is big. Really big. You just won't believ (Score:2)

I think Newton's laws are precise within 99.95%.Well, they are (up to about 0.6 c, at least,) but that's not the point. Indeed, the disparity between expected and measured data is less than 0.01%, which is also specifically mentioned in both the writeup (phrased as the measurement ratio and posited as 1:1.001) and in the article.

99.95% of what?The ±0.05% refers to the accuracy of the measurement used to glean the data, and has nothing to do with the theory or the difference between the expected

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How can they say anything is 99.95% right, have they never heard of the Cartesian method of doubt. . .Yes, that's

whythey said what they said, i.e. that they have only shown the predictive accuracy of Relativity to a margin of error of. . .so all in all I'd say about 1-5% doubt - but you can never knowAnd this makes no sense whatsover, because you are just pul

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Perfectly cromulent word.

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## Mr. Secretary, is that you? (Score:2)

--Donald Rumsfeld

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Maybe I don't know about the "Cartesian method of doubt", but it doesn't have anything to do with physics.Uh, yes it does. The Cartesian Method for Doubt was introduced by Reneé Descartes as a method for seperating expectation from measurement when learning to interpret experimental data (as well as existentialism and skepticism as worldviews tolerant of "false senses.") Rule of thumb: if you don't know what something is, don't contradict the person talking about it. Even if it sounds incorrect,

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What they mean by "99.95% right" is not that there is a 99.95% probability that Einstein's theory is dead right, and correct, and a 0.05% probability that it is dead wrong.Horseshit. The ±0.05% isn't about relativity at all. It's the precision of the measurement used to gather data from the star. What they're

actuallysaying is "we have data which is accurate to ±0.05% and the data fits relativity."## Re: (Score:2)

least 99.95% accuracy.## Re:Maybe, but I don't think so! (Score:5, Insightful)

there is no such thing as "fabric of space-time". It's a convenient buzzword but it doesn't mean anythingOf course it means something: it is a summary of the distance and time measurements we make, and can be described in terms of geometrical curvature. If it didn't mean anything, then it wouldn't have any observable consequences.

Things work as if Einstein was right, but there is no evidence that he was right.You're splitting hairs that don't exist. "Working as if Einstein was right"

is"evidence that he was right". It's the only kind of evidence possible.If you pass a current through a wire it generates a magnetic field. If that field crosses another wire it generates a current in that wire.That's not necessarily true. A static magnetic field doesn't induce a current in a wire. You might be talking about alternating current, which produces a time-varying magnetic field.

It's exactly as if the magnetic field moved from one wire across the other.I don't know what you mean by a magnetic field "moving", but certainly the magnetic field of one wire can intersect the position of another wire.

The flaw is that if you wrap both wires through an iron donut all the field is inside the iron - absolutely NO field is detected anywhere around either wire.Perhaps I'm visualizing the geometry wrong, but your statement appears to be false.

The theory is false, but it is "exactly as if" it were true.What theory? That the (time-varying) magnetic field produced by one current can induce a current in another wire? That theory is always true. (Of course, you have to take into account induction from other objects which may cancel that current.)

Likewise, Einstein's theory may give correct answers even though nobody actually knows why.It is not possible to know "why" a theory is true, at least if that theory regards some fundamental phenomenon. It's possible to explain "why" some approximate theory is true by deriving it from a more fundamental one, assuming the more fundamental theory is true.

For one thing, plasma physicists can easily explain a lot of effects in electrical terms, relying on laboratory observations instead of imagined theories.Nonsense. Plasma physicists use theories just like any other physicist does. Those theories of course are electromagnetic in nature.

Astronomers ignore plasma physics because nobody ever taught it to them.More nonsense. Plenty of astronomers use plasma physics. What are you, an Alfven plasma cosmology crackpot?

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"...there is no such thing as "fabric of space-time""...It's just a way at looking at the WSOGMM (Whole Sort of General Mish-Mash). A way of defining things from our perspective. It may have been a joke, but I think that Adams was on to something.

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To me this just seems like a play on words. Observation is the only way in which we can test the validity of a model. If the model fits experimental data consistently and throughout a large number of experiments, we can only conclude it is right -- at least until someone makes an experiment whose results disprove it, but that's part of the nature of a scientific theory.

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canexist under General Relativity.