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Researchers Discover "Magnetic Current"
fsouto writes "Researchers have discovered a magnetic equivalent to electricity. From the article, 'The phenomenon, dubbed "magnetricity," could be used in magnetic storage or in computing. Magnetic monopoles were first predicted to exist over a century ago, as a perfect analogue to electric charges. Although there are protons and electrons with net positive and negative electric charges, there were no particles in existence which carry magnetic charges. Rather, every magnet has a "north" and "south" pole.'"
The only thing new here is the current, not the "magnetic charge" from the monopole. And it's theoretical physics ridiculously far from being used in magnetic storage or computing.
Mr Tesla, Were only 100 late
Magnet current? Like, in a transformer?
Abstract from the actual paper:
"Electrically charged particles, such as the electron, are ubiquitous. In contrast, no elementary particles with a net magnetic charge have ever been observed, despite intensive and prolonged searches (see ref. 1 for example). We pursue an alternative strategy, namely that of realizing them not as elementary but rather as emergent particles—that is, as manifestations of the correlations present in a strongly interacting many-body system. The most prominent examples of emergent quasiparticles are the ones with fractional electric charge e/3 in quantum Hall physics. Here we propose that magnetic monopoles emerge in a class of exotic magnets known collectively as spin ice: the dipole moment of the underlying electronic degrees of freedom fractionalises into monopoles. This would account for a mysterious phase transition observed experimentally in spin ice in a magnetic field, which is a liquid–gas transition of the magnetic monopoles. These monopoles can also be detected by other means, for example, in an experiment modelled after the Stanford magnetic monopole search."
If this is a discovery then why did I learn about this in my electromagnetics class I took a semester ago? And why did I have to work on problems with magnetic circuits if this phenomenom wasn't discovered yet?
Nope. Gauss's law (electricity) has some nice formula while the corresponding Gauss's law for magnetism has a big fat zero.
If magnetic monopoles were taken into account, the magnetism one will have a nontrivial div like the electricity one.
Thank you wikipedia. Now I know to ask for for christmas: A Student's Guide to Maxwell's Equations! The amazon reviews are good. Let's learn together, slashdot. div grad curl too, in case old Maxwell's a little heavy with the vector calc
div B = rho_b
I think so. It sounds more like "electron holes" in semiconductors. The spin ice contains tetrahedrons formed from ions. Because of this arrangement, adjacent ions must form a positive-negative pair, which then affects the way electrons spin and the resulting magnetic field. Bring in an external magnetic field and that runs the process in the opposite direction. That's where the storage idea comes from.
Vintage computer adverts: http://www.vintageadbrowser.com/computers-and-software-ads
Seriously? Magnetricity? That's the best name they could come up with? Really?
I hope if they can't do better figuring out what term to measure in it, they at least pander to the attention it would gather and call the unit "Colbert"
No, they aren't. Maxwell's equations don't preclude magnetic monopoles or the movement of net magnetic 'charge' (aka 'current'). In fact it's always been a mystery why monopoles didn't appear to exist. There was no theoretical reason why they shouldn't, we have just never found a particle carrying a net magnetic charge. We still haven't exactly, just a crystal structure in which you can find discreet units of net magnetic charge, but that's effectively the same thing. And now we've seen that these units can move through a structure, so magnetic current exists.
In a way this must be a relief. Electricity and magnetism are symmetric in so many ways, it was odd that in this one way they weren't since they're ultimately aspects of the same force (electromagnetism).
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More buzzwords and concepts for Trek to abuse.
...that whizzing sound is my karma, flying out the window.
Isn't that how a hard drive operates?
There was also no theoretical reason for monopoles _to_ exist. If charge exists, and moving electric charges create magnetic fields, who do you _need_ magnetic charges? Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
"Discrete units of net magnetic charge" may be a quantum effect of aligned, moving electrical charges. I still see no need for monopoles.
I just tried to think about negative mass, thanks for the headache.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
There was also no theoretical reason for monopoles _to_ exist.
Well, if there is so much as one magnetic monopole in existance, it would explain the quantization of electric charge. I call that a theoretical reason for monopoles to exist.
Maxwell's equations don't preclude magnetic monopoles
False. As you find them in a standard text book, they do exactly that. Div B = 0 means no magnetic monopoles. That said, the standard equations can be easily modified to accomodate magnetic monopoles (a few books do this -- Classical Electrodynamics by Julian Schwinger might be one).
ttp://en.wikipedia.org/wiki/Magnetic_monopole#Dirac.27s_quantization
Maxwell's equations don't preclude magnetic monopoles
Excuse me? Last time I checked, Maxwell's equations said that Delta B = 0.
The "Gauss' Law" for magnetism (in quotes because this isn't a universally accepted name) is commonly taken to be div(B) = 0, but that's not always the case. The law can be div(B) = rho_m (Gaussian units), where rho_m is the magnetic charge density, analogous to the rho_e electric charge density in Gauss' law. In this case there is also a non-zero J_m, magnetic current.
Basically, Maxwell's equations and the rest of EM theory accept a magnetic monopole freely, but as far as we have seen, none exist in nature. Paul Dirac has shown that the existence of magnetic monopoles would explain the quantization of electric charge.
There was also no theoretical reason for monopoles _to_ exist.
I think the point the GP was making was that there was no reason that they couldn't exist...
1178161 is prime...
---
Magnets and Magnetism Feed @ Feed Distiller
Do you have to have smision to be able to detect it?
sic transit gloria mundi
Okay, yes, I almost replied to myself to point out that the one equation based on the lack of the observation of magnetic monopoles would change. But none of the rest of the theory would change, and as you point out Maxwell's theory perfectly accommodates this change, so yeah, Maxwell's equations(plural) aren't "crying", except maybe with joy that now the expected symmetry has been discovered.
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Well, if there is so much as one magnetic monopole in existance
Look no further! I've got one right here in my kitchen (driving my microwave oven).
The Admin and the Engineer
No, they aren't. Maxwell's equations don't preclude magnetic monopoles or the movement of net magnetic 'charge' (aka 'current'). In fact it's always been a mystery why monopoles didn't appear to exist. There was no theoretical reason why they shouldn't, .
Yes and no. Its true that if you look at maxwells equations in the traditional form (with div and grad) the statement of no monopoles (Div B) is simply one of empirical observation: monopoles have not been seen.
However if you cast maxwells equations in differential forms it becomes intuitively obvious why there are no magnetic monopoles. electricity is a one form. Magnetism is a two form. Two forms cannot come from monopoles.
That's an equation, note lack of plural, and it's based on the lack of observation of a monopole. Observe one, change that one equation, and the rest of the equations compensate nicely. Neither Maxwell nor his equations are "crying" because of the discovery of monopoles and magnetic current. The theory doesn't preclude them, it was simply based on observation (as science should be). It's not like we observed that c was different in a vacuum for different inertial observers, which would undo the entire theory of Special Relativity. Maxwell's theory is compatible with magnetic monopoles. That was my point.
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I just tried to think about negative mass, thanks for the headache.
Think of the marketing potential!
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We could make billions!
What? Uhm, no.
Maxwell's 2nd equation, aka "Gauss' law for Magnetism", which is written in differential form as del * B = 0 (divergence of the magnetic field lines is zero). In integral form it's written as the double integral over a closed surface of the magnetic field lines is equal to zero).
Either way you look at it, that says "no magnetic monopoles". The law may need to be rewritten, but as written it does say no monopoles.
My favorite quote doesn't fit into 120 characters. Now no one will like me.
That's only an artifact of Maxwell's equations assuming there are no magnetic monopoles. Add them in, and the equations are perfectly symmetrical for electricity and magnetism, the only difference is the name of the variables and the quantities they represent are swapped. Their partial differentials are identical otherwise.
Electricity and magnetism are two aspects of the same force, electromagnetism. They are mediated by the same particle, the photon. The lack of symmetry in this one aspect is theoretically unnecessary, and philosophically kinda weird. That's not proof, of course. Demonstration of net magnetic charges is.
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The law may need to be rewritten, but as written it does say no monopoles.
Which is trivial to do, and doesn't contradict the rest of the theory, and hence they aren't "crying". The possibility of monopoles has been accepted for a very long time. It's simply the lack of experimental observation that ever caused them to be written in the first place. Re-write Maxwell's equations given the existence of 'magnetic charge', set that charge to always be zero, and you get the equations as written.
Maxwell's equations don't preclude the existence of monopoles. They are simply stated in terms that assume there aren't any based on the lack of evidence for them. His theory is fine, his equations are not "crying".
I don't understand why this is so hard to understand. Outside of the fact that you're all just being pedantic. I guess I should have said Maxwell's theory of electromagnetism.
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...that whizzing sound is my karma, flying out the window.
You've discovered the karmic equivalent to electricity!
The phenomenon, dubbed "karmicity", could be used in meta-moderation or in troll suppression. There were previously no known particles in existence which carried karmic charges. A net-positive karmic particle is known as a karmon; a net-negative particle, a moron.
LHC, eat my shorts.
I think the point the GP was making was that there was no reason that they couldn't exist...
Exactly. It isn't necessary that they exist, but there's no reason they could not exist and it makes a lot of sense for them to exist for various reasons (charge quantization and symmetry between aspects of the same force being big reasons). But we've never observed them, hence the equations as stated do not account for them. Observe one, and you can trivially modify the equations to account for the fact. The theory is pre-built to accept them. Hence they're not "crying".
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...we're 0.00317% closer to flying cars!
Table-ized A.I.
The reason you don't see Maxwell's Equations with magnetic charge in textbooks is because it's pointless to leave them in unless you're specifically looking at the problem of "how would X change if magnetic charge existed?". I happen to have a textbook that assumes magnetic charge throughout the entirety of the text (Balanis, Advanced Engineering Electromagnetics) It doesn't mean that the equations preclude it. Heck, in antenna analysis we model antennas using magnetic current/charge.
It's simple, objects with negative mass would have a negative gravitational force on the surrounding objects. Say, two objects with equal mass, but one is negative. They wouldn't have an affect on one another gravitationally, because the net force is zero.
AKA negative masses would "fall" up.
So, what's the next breakthrough? According to the Alpha Centauri tech tree I'm reading, we can now research Unified Field Theory and Nanominiaturization now that we have Monopole Magnets!
Won't you feel funny when we do discover negative mass. It would actually make a lot of things easier. The accelerated expansion of the universe cries out for a repulsive force. Throw a negative sign on a mass and voila, repulsion! Also, it would lead to the possibility of negative energy, which we can then use for warp drives. At least according to my creative star trek esque imagination. Science has taught us to never say never until experiments tell us to say never.
Well.. maybe. Or Maybe not. But Definitely not sort of.
Okay, I'm replying to myself as I thought I should immediately after posting the above.
Yes, Gauss's Law of Magnetism, one of Maxwell's Equations, says the magnetic field has zero divergence, meaning there is no net magnetic charge.
That is an assumption based on the lack of experimental evidence for a monopoles.
This does not mean Maxwell's Equations preclude the existence of monopoles, because they don't. What's the difference between precluding their existence, and presuming their non-existence? Well, let's look at something that is both assumed and precluded by theory: the speed of light being different for different inertial observers, and Special Relativity.
Special Relativity assumes c is constant for all inertial observers. It also precludes the possibility of that not being true, because the entire theory is based on that assumption, and falls apart if that assumption does not hold. All the equations of special relativity contradict observer-relative speed of light. If you ever discovered a case where this was not true, you would have to scrap Relativity and re-write the theory from scratch. That's precluding.
Maxwell's Equations assume net magnetic charge is zero, but if that assumption doesn't hold, then you simply have another term in the equations and you don't need to go back to the drawing board. Gauss' Law of Magnetism simply becomes a special case where net magnetic charge is zero (though this 'special' case is the most common case). You don't need to re-write the theory of electromagnetism. These researchers are not claiming to be re-writing the theory of electromagnetism, because the theory does not preclude magnetic monopoles.
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Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful
Discussion of the existence of monopoles or true magneto current -- seriously, people -- this sentence is glaringly false. In fact, the use of magnetic charge and magneto have been integral* to electromagnetic analysis for more than 50 years now. Using the symmetric form of Maxwell's equations. The fields created by all sources and media inside an arbitrary closed surface can be analogously modeled as charge and current distributions over the surface. This is what allows you to equivalently model the open end of a driven waveguide as a rectangular patch of magneto current, an electric dipole antenna as a "cigar band" of magneto current wrapping around the feed gap. All of which, I should add, makes the equations much easier to solve. Hell if nothing else the addition of a magnetic boundary conditions can allow numeric models to converge much more quickly.
Arguing that the phenomenon discovered does not truly uncover a magnetic monopole is one thing. Arguing that there is no benefit to symmetrical equations is as silly as that there is no benefit to expressing the equations in the "bastardly" phasor vector notation when a simple set of 12 differential equations of 12 variables would suffice.
*No pun intended.
"Loose (sic) 50lbs without dieting, overnight! Just try our patented NegaBelt for the low low cost of only 40 payments of $19.99!"
Um, and if those payments were made in coins, your NegaBelt wouldn't have to do a thing. They'd lose 50lbs right there.
AKA negative masses would "fall" up.
Ah, like Helium balloons.
</sarcasm> <-- for the humour impaired, and those that think I might be posting from the Southern US.
What, you haven't encountered the idea before? It's been around a while. Look here.
There is negative energy. At least, there is negative potential energy.
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Well, in the interest of closing the loop, these aren't totally disjoint ideas ;^)
In the standard magnetic circuit with flux and field, the analogy between a magnetic circuit and an electrial circuit is
MMF = PATHINTEGRAL (H dot dl) vs EMF = PATHINTEGRAL(E dot dl)
Without any magnetic monopoles, this path integral that represents the magnetic circuit is merely analogous to a magnetic charge making a loop in the circuit creating a potential around the loop. Although this MMF is now taught as being generated by transformer/inductor coils wrapped around the magnetic circuit using the relationship MMF = N*i, but instead in a world with magnetic monopole current (i.e., magnetic current), in principle the same MMF relationships can be used.
Interestingly with magnetic monopoles this can also be extended like "electrical" circuit element.
R = dv/di, C = dq/dv, L = dF/di, M = dF/dq, i = dq/dt, and v = dF/dt
Historicall, only Resistance ~ Reluctance was the only one of the analogs that made sense w/o magnetic monopoles.
Now that we have magnetic monopoles, the other electrical circuit elements now have possible analogs in a magnetic circuit.
So this is actually a similar idea that shouldn't be dismissed out of hand.
You just failed physics. Congratulations.
There is no such thing as negative energy (without negative mass anyway).
What you're confusing with negative energy is relative energy--an object can be said to have negative potential energy if it has less potential energy than the arbitrary zero level. This is not the same thing as negative energy (any more than being in debt is having negative dollars, or being below 0 degrees Farenheit is having negative thermal energy).
The classic illustration of magnetic field lines is to put a big bar magnet on a table and sprinkle iron filings on and around it; they will end up tracing the magnetic field lines of the bar magnet.
So say they could construct the monopole equivalent of such a bar magnet, just one big lump of North or South. If we put that on a table and sprinkled iron filings on and around it, what (if any) lines would they end up tracing? Just rays away from the monopole?
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
Why make billions when you could make... millions!
Look no further! I've got one right here in my kitchen (driving my microwave oven).
I thought magnetic monopole was a way to play monopole during long family roadtrips.
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
Electricity and magnetism are symmetric in so many ways, it was odd that in this one way they weren't since they're ultimately aspects of the same force (electromagnetism).
And that, puny earthling, is why you are stuck on that backward planet. Even the stupid Omicron Persii 8 children know that electricity and magnetism are aspects of gravity. Blorga, it is time to go home.
The concept isn't foreign but the idea of an object with a negative mass but positive volume starts to have wierd implications for things like trying to hold it.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
Why not link directly to arXiv in all scientific posts? Maybe a divulgative link AND a link to the paper in the arXiv. I am crazy?
Would they though? Assume a negative mass which still has a positive volume. If you use the (probably way oversimplified) model of positive mass objects acting like a lead ball on a rubber sheet in space you'd wind up with negative mass objects pinching it and pulling it upwards.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
What, like a sphere you mean?
Sig (appended to the end of comments you post, 120 chars)
Here is a better article http://www.physics.rutgers.edu/grad/681/mpoles_physicstoday.pdf
Negative mass is easy.
You take one 1 kg of regular mass and place on a scale. The scale reads out 1 kg.
Now you place 1 kg of anti matter on the scale on top of the regular matter. Now there's no weight on the scale.
There's also no scale any more, but that's irrelevant for this thought experiment.
or being below 0 degrees Farenheit is having negative thermal energy
And you just failed physics by confusing temperature and thermal energy. Congratulations!
You must write The Book, and then tear away belief. Only you can save the light of man --Gary Numan
To which you would add a negative volume, otherwise nobody will notice the difference.
Non-Linux Penguins ?
Or if electric charges are quantized.
There was also no theoretical reason for monopoles _to_ exist.
Maybe not, but I can't help thinking of the positron. No-one knew they existed, but Dirac's equation allowed for the possibility. The Standard Model said that various particles should exist for symmetry reasons and they were discovered. Symmetry is no proof of existence, but I wouldn't say it's wise to bet against it.
There was also no theoretical reason for monopoles _to_ exist. If charge exists, and moving electric charges create magnetic fields, who do you _need_ magnetic charges? Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
"Discrete units of net magnetic charge" may be a quantum effect of aligned, moving electrical charges. I still see no need for monopoles.
If you have an analysis of Maxwell that explains the quantization of electrical charge without requiring the magnetic equivalent, you should show it to people. Dirac couldn't do it, so if you have it'd be well received. Not only did Dirac's equations require them, he predicted the magnetic charge quanta to be 68.5 times the electrical charge quanta. Proving Dirac wrong would have enormous consequences, since the 1983 theory of electroweak unification required them to exist and have the predicted charge magnitude, and the W+, W- and Z(0) intermediate vector bosons it predicted (based on the theory that required monopoles) have been detected. Not only that, they have precisely the charge magnitude predicted by the theory based on the predicted magnetic charge magnitude. And if you can show where Dirac went wrong, you can also show where t'Hooft and Polyakov went wrong, since they independently not only showed that any such unification theory required them, but also came to the same prediction of magnitude of magnetic charge as Dirac. Three independent theoretical analyses that make specific predictions which have been tested and shown to be correct would seem to be a tough nut to crack. But if you can show where these were all wrong, it'd be worth a Nobel, just as Weinberg, Salam, and Glashow shared one for the electroweak unification predictions that testing had subsequently and apparently mistakenly supported with data. In fact, if you can point to where Dirac et al. were wrong, you could save a lot of people a lot of money, since the search for the Higgs boson is based on symmetry breaking that requires the monopoles to exist and have a specific charge. If you could just point out where Dirac went wrong, say on the page at http://encyclopedia2.thefreedictionary.com/Magnetic+monopoles then we can call CERN and tell them to recalibrate the LHC because they followed Dirac's mistake when they built it. Or should they just trash it? It must really be hosed if it's based on a theory that predicts things, some of which have been detected exactly where they were supposed to be.
Oh, and while you're taking a balanced equation and unbalancing it, the answer to your other question is on that page too. An electrical charge in motion creates a closed magnetic field, so a magnetic charge in motion creates a closed electrical field. You may feel free to not see a need for it either, but by now it should be clear why you don't see these things as necessary. This latter result would seem at second look to be dismissable since it predicts an essentially perpetual motion. However, the perpetual motion machine it describes is available for examination in every electron orbiting every nucleus. This closed electrical current has been detected at a classical scale as a persistent flow such as a superconducting current, in a normal resistive metal ring. This was announced in Science magazine a week ago and mentioned in http://hardware.slashdot.org/article.pl?sid=09/10/10/1338210
Actually it is understandable that some people don;t see the "need" for monopoles any more than they see the need for scalar waves. This is because it has become common to teach the essentials of Maxwell's equations by arbitrarily ignoring some aspects. this is done by setting some of the necessary variables to zero. While this allows one to examine the isolated na
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Just don't drop it outside.
What is a magnetic field composed of? The article says that a small magnetic field is formed around the muons. Is a magnetic field composed of particles?
Ermmm, what about emo kids ? They are negative all the way. Well, maybe not for the mass, but they are so close.
Actually antimatter has positive mass, too. And if you managed to keep the radiation created by the annihilation of matter and antimatter in a box (and arrange it so that all the antimatter in the box annihilates with the in-box matter before it reaches the walls of the box and destroys it), you'll find that the box doesn't lose even the slightest bit of weight.
The Tao of math: The numbers you can count are not the real numbers.
Don't forget the Negative Zone, a great place for a vacation, to find that really important knick-knack you need for universal dictatorship and a easy place to dispose of enemies, muties or idiotic wizards.
Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
You're saying two thinks. Of course symmetry doesn't make equations more valid, but elegant? In my opinion symmetry of different equations is one the most elegant things of nature.
And balloons filled with a negative mass equivalent of helium would sink.
Or you they rise faster?
This hurts my brain.
It's never too late to have a happy childhood.
Arrgh!
Or would they rise faster?
Like I said, my brain hurts.
It's never too late to have a happy childhood.
Oh, dear. You made a big whopper:
> However, the perpetual motion machine it describes is available for examination in every electron orbiting every nucleus.
They don't orbit. Get away from the pretty math and take a look at what an 'electron cloud' really means. And for elephants or onions, you should use as much as is necessary to explain the facts and keep Occam's Razor in mind.
That said, the Dirac equations are interesting and its descendants do try to explain an interesting problem.
just as soon as you can make coins with one side
You mean, Moebius strip-shaped? Those would have one side and one egde!
A bit tricky to manufacture and store, and therefore impractical, but still possible.
WYSIWIG, but what you see might not be what you need
There is a difference in that Dirac's treatment of the electron for quantum mechanics actually predicited the positron, the equations wouldn't work without it. Magnetic monopoles fall more into a "wouldn't it be neat if..." but are not actually required for electromagnetism to work. Where as positrons and antimatter HAVE to exist if you want a reletavistic quantum theory.
"If it doesn't agree with experiment, it's wrong" - Feynman
These "local monopoles" described in the experiment are really just super-long dipoles, and though they have interesting properties, they are not separable and not on the scale of fundamental particles.
This is expected because, though perpetual motion of the third (and wimpiest) kind already exists in atoms and in superconductors, real magnetic monopoles would provide perpetual motion of the first (and awesomest) kind, the kind that violates conservation of energy. And not only is conservation of energy an observed fact, it's also a beautiful theoretical result of Noether's Theorem.
So while the symmetry of magnetic monopoles existing is nice and all, I prefer conservation of energy. Sorry Dirac, but you don't mess with Noether.
As you find them in a standard text book, they do exactly that
In manifestly co-variant form, which is by far the more likely way for physicists to think about them, the lack of magnetic charge gets hidden in an abstract four-vector.
The form of the equations--their invariance under Lorentz transformations--is a far more important feature of Maxwell's equations than whether or not some particular vector component is strictly zero. If we were to find true magnetic monopoles the transformation properties of the equations would not change and physicists would happily go on calling them "Maxwell's equations", because that is what they still would be.
For both historical and practical reasons we teach undergrads Maxwell's equations as vanilla differential equations, which is unfortunate because a) it fixates them on irrelevant aspects of that notation and b) it hides the deep and profound elegance of their underlying mathematical structure.
Blasphemy is a human right. Blasphemophobia kills.
Note to self: physics-based sarcasm is a bad idea.
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The density difference between the negaHelium and air would be greater than that between Helium (classic flavor) and air. Hence, the negaHelium experiences a greater buoyancy force, and should rise faster.
Viewed this way, there's no theoretical reason for ANYTHING to exist - the laws of physics don't REQUIRE there to be any matter. Particles are either allowed, or they aren't. And our experience has shown that particles that are allowed, exist. Except for magnetic monopoles. Which is kind of weird.
It should be noted that the "monopoles" discussed in TFA aren't "real" monopoles - they're quasiparticles that have the same properties as monopoles, but don't "really" exist. They're much the same as "holes" in electrically conductive materials - holes have the same electrical properties as positrons... but they aren't really positrons. The best evidence for now indicates that true magnetic monopoles don't exist, and we don't really know why.
No, no... Negative masses would sit UNDER the sheet, pushing up on it.
Simple.
You're all making this harder than it has to be.
You have just discovered the secret to marketing. Now how about a pet rock for $20?
The purpose of language is communication, If the idea is clear the grammar ain't important
It's only buoyancy that makes them float. Do they have negative density? What that even be implied by negative mass or is our equation wrong?
And it really does make your head hurt. From Newton (let's just leave Einstein out of this for now... please?): F=ma, and F = Gm1m2/r^2. Let's say that we're dealing with two bodies, one with mass m, and one with mass -m. So, substituting: the negative mass body feels -ma = Gm(-m)/r^2. The minus signs cancel, and the negative mass body is attracted to the positive mass body. But the positive mass body feels ma = Gm(-m)/^r2... so it's repelled by the negative mass body. In other words, set up these two bodies, and they'd chase each other across the universe at ever increasing speeds, forever. Which would appear to violate conservation of energy.
It gets even stranger when you consider that "mass" is not a completely well-defined term. You can talk about inertial mass, active gravitational mass (essentially, how much gravity a mass produces) and passive gravitational mass (how much force is produced when an object interacts with another object's gravity). For normal mass, it's been shown that these are all equivalent (at least, active and passive gravitational mass either have to be equivalent, or you have to give up conservation of momentum, and inertial and passive gravitational mass have to be equivalent, or general relativity doesn't work anymore). But it turns out that as long as you're speculating, you can go ahead and give these different kinds of mass different signs for the same body. Then you get even weirder results - for example, the negative mass might repel the positive mass, but still move toward it because such objects would accelerate in the opposite direction of forces applied!
I told you this stuff made your head hurt.
I dunno. How heavy is it ?
Religion is what happens when nature strikes and groupthink goes wrong.
No, he was illustrating the point that 0 degrees Fahrenheit is kind of an arbitrary value, and that 0 here has no meaning.
But if you can show where these were all wrong, it'd be worth a Nobel
I don't think the bar for a Nobel is quite that high.
In what sense is "being in debt" different from "having negative dollars"? If I have a credit card balance of $1000, and no assets, and then I make $100 and send them in the direction of my credit card account, the credit card balance will annihilate the $100 and reduce itself to $900. I think "negative potential energy" is a perfectly valid concept.
Also: I don't think he really failed physics.
Although you don't run into it in any real-world situation, negative energy is useful in modeling the vacuum.
Instead of a rubber sheet, imagine a thin, infinite sheet made of water*. A normal mass would act like a straw sucking at the water, pulling it inwards more quickly. Anything that entered that region of spacetime would be 'attracted' to the object.
Using this analogy, a negative mass would act like a straw 'blowing' at the water, so anything moving close to it would be repelled.
* Resting on a giant turtle, naturally
GP poster, I think you can consider yourself smacked down.
A "field" in math is an object that assigns a value to every point in space. A "magnetic field" assigns a vector that has to do with the amount of force experienced on an electrically charged particle moving with a certain velocity at that point. So it's not really "composed of" anything, any more than the earth's gravitational field is composed of anything. It's just a property.
THIS is the year of absolute-zero-chilled, neutron-and-muon-bombarded memory on the desktop!
Populus vult decipi, ergo decipiatur...
"Force shits upon Reason's back." - Poor Richard's Almanac
It does not help the original confusion to illustrate the point with a confusing analogy.
You must write The Book, and then tear away belief. Only you can save the light of man --Gary Numan
Div.B=0 That '0' explicitly says that magnetic monopoles don't exist. So Maxwell's equations DO claim that they don't. Now, those equations are based on experimental observation, so really it's saying that "we've never seen one" rather than expressing any deep underlying reason that they shouldn't exist.
These "local monopoles" described in the experiment are really just super-long dipoles, and though they have interesting properties
Talk about understatement of the year... sheesh... the whole point of this spin ice exercise is to show that the predicted behavior of monopoles (or monopole-like entities -- happy now?) match the data. And it does. Obviously this is not about studying natural monopoles in deep space or something. It's about "if it walks like a duck and talks like a duck, it's a flippin' duck".
-l
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Are these objects actually monopoles? Well, yes and no. They fall into an interesting gray area:
No, they are not the fundamental monopoles that Dirac proposed. They are not fundamental particles, but only quasiparticles arising from the dynamics of some substrate. In this case, the substrate is quite exotic: a spin ice, which is a kind of material (dysprosium titanate) with polar atoms arranged into tetrahedra.
OK, so they're not fundamental, but they're still quasiparticle magnetic monopoles, right? Sort of. These quasiparticles still have to obey the standard laws of electromagnetism, and those laws still forbid the existence of magnetic monopoles. Every magnetic monopole is actually a member of a monopole-antimonopole pair connected by a Dirac string. To quote the paper:
So this is the key innovation here. A normal magnetic dipole like a bar magnet can be thought of as being like a stick: it has two ends; if you break it, both pieces have two ends; when you wave the stick around, both ends wave around. But this system is like a rope: it still has two ends; if you break it, the pieces still have two ends; but when you wave one end of the rope around, the other end can remain fixed. So the end of a rope can act like an object independent of the other end.
This makes it a great model system for playing with monopoles, as long as you close your eyes and pretend the rope doesn't exist. But it does exist, Maxwell's equations are obeyed and all is well in the universe.
real magnetic monopoles would provide perpetual motion of the first (and awesomest) kind, the kind that violates conservation of energy.
LOL, no. Not at all. Magnetic monopoles are not magic. They're basically an analog of the electric monopoles, which also don't violate conservation of energy.
Sorry Dirac, but you don't mess with Noether.
He didn't, which is why he got a Nobel. A hundred years of physicists didn't fail to consider conservation of energy when positing the existence of monopoles.
The laughability of the Peace Prize notwithstanding, you don't get a Nobel Prize for Physics by claiming to violate Conservation of Energy.
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Read the rest of this thread for understanding.
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I would think they would be very happy! Those oddball zero terms can be filled in. Symmetry is restored.
But, I wanted socialized health insurance!
-1, Missed the joke
it depends on whether the negative mass occupies a negative or a positive volume.
he predicted the magnetic charge quanta to be 68.5 times the electrical charge quanta
68.5 = 137/2 (half the fine structure constant). I'm guessing that's not coincidental.
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when i point out that monopoles are an impossibility?
it's like saying you want to feel the wind in your face, to turn around, and then feel no wind at all on your back. as if a magnetic field flows out, but not in, or in, but not out. you understand why you can't have a coin with one side, right? if you understand that you understand conceptually why monopoles don't exist: there is no such thing as a magnetic field that goes out, but never returns. logically, belief in a monopole is the same as belief in a perpetual motion machine
and, interestingly enough, monopoles are frequently featured in perpetual motion machine schemes. perhaps because that, indeed, if monopoles existed, you really could have a perpetual motion machine. a monopole, under the influence of a magnetic field, would begin moving and never stop. you understand that right? doesn't that tell you something about what a monopole really is in terms of reality/ not reality?
but for the sake of argument, let's say i'm wrong. ok, show me a monopole. i'm waiting
it's not like i'm a flat earth advocate arguing against the existence of the globe, or a creationist arguing against the existence of evolution. i'm simply pointing out that a monopole is a conceptual impossibility, and i get treated like i'm the electric universe troll
whatever
i just don't understand where this weird fervent certainty of monopoles comes in to the point where i have to be modbombed every time i point out that they don't exist and can't exist. its like i'm questioning the existence of god to a bunch of religious fundamentalists. this site is apparently overwhelmed with excitable physics freshman
i don't understand this bizarre certainty of belief in monopoles
there AREN'T ANY folks. pfffffft
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Yes and no.
You had to bring Schrodinger's cat into this, didn't you?
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About 10^-8 libraries of Congress
The purpose of language is communication, If the idea is clear the grammar ain't important
They would affect each other, but their relative distance would not close. In the example you posit, the whole system would continually accelerate in the direction connection the centre of mass of the two bodies, at a rate of g, where g is the gravitational acceleration exerted by the positive mass body.
Thus, if we could make a structure of positive and negative masses, we could create a continuous acceleration vehicle. Unless my intuition is wrong here.
Yes and no.
You had to bring Schrodinger's cat into this, didn't you?
That depends on how you look at it.
Interesting thought experiment.
I think that the answer is reasonably simple though based on the understanding of a standard dipole magnet. If you "look" at a dipole magnet, you see the north (south) pole is populated by more positive (negative) charge. If you cut that magnet in half, you still have the same configuration.
Therefore, I believe what you would get is a migration of electrons toward the north pole of the dipole magnet you touch to the wire. You get electrons moving since they are more "free" than protons in matter. as the electrons propagate, even just a little, you get tiny bar magnets forming along the wire. The new magnet would completely form when the dipole field was reached at the far end. Depending on the resistance of the material, etc it would be a time related to the ability of the electrons to move in the material.
The interesting part would be the fact that there maybe (I don't know the answer as I am not a specialist in material science nor EM physics) tiny magnetic perturbation fields that propagate along the wire do to the small "shift" in the electrons (electron motion is a current - current produces a magnetic field).
So based on this physics, I would say no, this is not a "current of magnetism" as you put it. Monopoles are not moving, electrons are.
There is indeed a theoretical reason for the well validated nonexistence of magnetic monopoles. The electromagnetic potential A must exist in the Lorentz gauge so that charged particles can be a source of gravity that is conserved over time. Then, given any reasonable A, the Bianchi identity, namely ddA = dF = 0 - "The boundary of a boundary equals zero.", is a topological theorem that specifies precisely the impossibility of magnetic monopoles.
Michael J. Burns
Hey, we've already worked out that electromagnetism and the weak force are the same. We're still working on gravity!
In terms of galactic civilizations, we're barely out of our brachiating simian stage. Cut us some slack!
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Negative mass would suggest negative inertia... now THAT gives me a headache. How the heck would you describe negative inertia? Would an object made of negative mass have a tendency to move unless force is exerted to keep it still?
There's also no scale any more, but that's irrelevant for this thought experiment.
I use a photon scale, you insensitive clod!
Ah, you found the symmetry. In Einstein-Davis (unadulterated spacetime) a negative oriented volume of blue-shifted space is equivalent to a red-shifted and positive oriented volume.
Anyway, regions of blue shift repel other regions, but are attracted by regions of red shift.
In the contest of mechanics, red-shifted volumes contain positive mass, and a blue shift implies negative mass.
Michael J. Burns
The only things I can think of that might have negative mass would be a tachyon or a satanic church.
Well, if you have any kind of experiment to sustain the claim, I'm quite sure you'll get it. You probably won't even need to get old before getting the prize.
But, ok, enough nitipicking.
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Well yeah that was my point. A theory that claimed to violate conservation, when obviously there is no experimental evidence for such, is going to get laughed out of Bob's Discount Journal of Non-Retarded Physics, much more so the Nobel Prize committee.
I mean it's not like these guys would have developed the entire electroweak theory and tested it without at some point noticing it broke conservation of energy... if it did. Which it doesn't. :)
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What about the 8th ray that enables Martian air ships to float?
I drank what? -- Socrates
Great post man. Congratulations.
Math is beautiful... e^(pi*i)+1=0
Funny then how the top google results for "lorenz gauge magnetic monopoles" are papers solving for the existence of magnetic monopoles in the lorenz gauge.
But I'm sure it comes down to a single integral, and that the Nobel-winning work of Dirac, Salam, Glasow and Weinberg could be obviated by such a simple observation. Too bad they missed it; we could have avoided wasting all this time building the LHC!
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I'd say it depends on *when* you look at it.
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Your scale is photons now, yes.
You are not a brain: http://books.google.com/books?id=2oV61CeDx-YC
"Sorry Dirac, but you don't mess with Noether."
Sadly not - it would've been a May-September romance - and he married Margit Wigner instead... but in mathematical physics fan-fiction......
http://en.wikipedia.org/wiki/Emmy_Noether
http://en.wikipedia.org/wiki/Paul_Dirac
You are not a brain: http://books.google.com/books?id=2oV61CeDx-YC
What I find funny is all the people insisting divB=0 is "just" a reflection of the experimental inability to find a magnetic monopole. All of those equations are "just" reflections of the experiments they summarize. I think any experimental result that contradicts the thousands that preceded it deserves a fair amount of skepticism.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
No, it depends on if you look at it.
This ain't rocket surgery.
Yes, all of those distinguished physicists were untrained in, and not knowledgeable about, the utility of the Bianchi identity taken together with the full application of the principle of general covariance.
Take two solid rings interlinked; embed monopoles in one and charges in the other. Give one a spin and then watch the ensuing unbalanced creation and destruction of angular momentum. Travel past at near light speed and see the no longer simultaneous transfer of energy from one ring to the other.
Magnetic monopoles are not a target of the LHC that I have heard of. But Higgs bosons are a publicized target, and they seem to be distorted versions of what would be better studied with a knowledge of general relativity.
Michael J. Burns
So the whole issue is a misinterpreted electrostatic polarization then.
Michael J. Burns
So it would create a larger duration of space where it existed due to a negative volume? Combine that with someone else suggesting a negative mass also having a negative inertia and I think I just had an aneurism.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
Well done, sir!
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Why is this particular form of prejudice allowed and even encouraged on Slashdot (by being moderated "Funny")?!?
If Tanktalus had written "... and those that think I might have darker skin than average" or "... and those that think I might be a woman", then he/she would be rightfully modded down to -1 and there would be multiple posts by now justifiably calling him/her a bigoted asshole.
Bigotry is bad, ok?
Of course, but only as long as there's a certain ratio of electric monopoles to magnetic monopoles satisfied. It simply is just another kind of gauge.
Thank you veddy much.
This ain't rocket surgery.
No, it says you can't create magnetic charge, just as you can't create electric charge. The sum of all electromagnetic charges in the universe is zero.
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Space, time, what's the difference?
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