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.
That's because the summary is just copypasta of the first paragraph of TFA, which goes on to say that monopole "quasti-particles" had already been observed.
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.
The monopole is at most a month old, so it's not like we're talking particularly old news. At worst it's an update on ongoing research.
Ok: Wake up! There are lots of electrons without protons. For example those which are created together with positrons.
But more to the point, what the OP asked for was not a north magnetic monopole where no south magnetic monopole is anywhere in the universe. What he is asking for is a north monopole where the south monopole is at a completely different place (especially not inside the same crystal as the north monopole).
Example: If you put an electric field on a metal, the electrons will gather on one side. If you now cut the metal in two pieces, where the cut is perpendicular to the electric field, you'll have a positively charged metal part and a negatively charged metal part (note that the electrons never left the metal during that procedure). You can now switch off your field and put both materials in different places; and the positive metal part will not have a negative pole, and the negative metal part will not have a positive pole, that is, both will be monopoles.
So now do the same with those spin crystals. If it works the same (i.e. if you get a north crystal and a south crystal after dividing), then you have real monopoles. However, if both parts exhibit a north and a south pole, you really have dipoles which are arranged so that they locally look like monopoles.
Abstract from the actual paper [nature.com]: "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."
Oh quasi-particles; on one hand you you think "well they're just mathematical constructs rather than physical things" but then you realize that regular particles fall into the same category. I heard of an interesting experiment where a Stern-Gerlach experiment [wikipedia.org] was conducted on a dark-state polariton [wikipedia.org] and resulted in the same effect as for nuclei. You can really only talk about how something behaves when a particular measurement is performed when treating it within whichever theory you're using, calling something a particle or a quasi-particle doesn't really matter.
by Anonymous Coward
on Wednesday October 14, @09:42PM (#29752835)
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?
Magnetic circuit analysis deals with magnetic fields and magnetic flux etc. Not magnetic current in the sense that there is a displacement of magnetic monopoles analogous with the displacement of electric monopoles (e.g. delocalised electrons in a metal) that is electricity. It's a different idea. Yes, a magnetic field and a conductive "circuit" in a magnetic field can be analysed using a loose analogy to electricity, but the actual physical phenomena are not the same thing, unless these guys are on to something.
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.
...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.
"...And so, the development of karmon storage marks the end of the Just Age; where consequences always hit the originator of the action. i.e.: The karmiker and the karmiked where always one and the same."
"Mr. Johnson. What were khores paid for, then?"
"As you may know, the term "khore" comes from "karma whore". At that time, they were called just "whores" and they were paid in exchange for sexual favours."
by Anonymous Coward
on Wednesday October 14, @11:53PM (#29753479)
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!
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?
I post the paper itself (not the abstract whose text cannot be accessed, not a derivative article in a divulgative magazine)
arXiv:0907.0956 [arxiv.org]
I know nobody is interested, because after so many posts no one had the urge. But anyway..
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?
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?
Nope. Gauss's law [wikipedia.org] (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
I think so. It sounds more like "electron holes" in semiconductors. The spin ice [wikipedia.org] 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.
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).
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.
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.
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.
There was also no theoretical reason for monopoles _to_ exist.
Well, if there is so much as one magnetic monopole in existance, it would [wikipedia.org] explain the quantization of electric charge. I call that a theoretical reason for monopoles to exist.
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.
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 [thefreedictionary.com] 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 [slashdot.org]
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 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 the
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).
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 [wikipedia.org] means no magnetic monopoles. That said, the standard equations can be easily modified [wikipedia.org] to accomodate magnetic monopoles (a few books do this -- Classical Electrodynamics by Julian Schwinger might be one).
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.
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 [wikipedia.org] 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 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 theoretic
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
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.
Maxwells equations are alive, magnetic flux [wikipedia.org] was already pretty much equivalent to a current.
It even has its equivalent to Ohms Law, Hopkinson's Law: Magnetomotive force = Flux * Reluctance. A real monopole world add a source term to Maxwell's
second equation, the Guass Law for magnetism. But its important to release that this aren't real monopoles, instead its a dipole with a almost invisible
thing middle. Even in these Spin Ice crystal, Div B = 0 everywhere. See, Slashdot from earlier in the september [slashdot.org].
Bad summary (Score:5, Informative)
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.
Re:Bad summary (Score:4, Informative)
That's because the summary is just copypasta of the first paragraph of TFA, which goes on to say that monopole "quasti-particles" had already been observed.
Parent
Re:Bad summary (Score:4, Informative)
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.
The monopole is at most a month old, so it's not like we're talking particularly old news. At worst it's an update on ongoing research.
Parent
Re:Bad summary (Score:4, Informative)
Ok: Wake up!
There are lots of electrons without protons. For example those which are created together with positrons.
But more to the point, what the OP asked for was not a north magnetic monopole where no south magnetic monopole is anywhere in the universe. What he is asking for is a north monopole where the south monopole is at a completely different place (especially not inside the same crystal as the north monopole).
Example: If you put an electric field on a metal, the electrons will gather on one side. If you now cut the metal in two pieces, where the cut is perpendicular to the electric field, you'll have a positively charged metal part and a negatively charged metal part (note that the electrons never left the metal during that procedure). You can now switch off your field and put both materials in different places; and the positive metal part will not have a negative pole, and the negative metal part will not have a positive pole, that is, both will be monopoles.
So now do the same with those spin crystals. If it works the same (i.e. if you get a north crystal and a south crystal after dividing), then you have real monopoles. However, if both parts exhibit a north and a south pole, you really have dipoles which are arranged so that they locally look like monopoles.
Parent
Article Abstract (Score:5, Informative)
Abstract from the actual paper [nature.com]:
"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."
Re:Article Abstract (Score:5, Informative)
Um. I think that's the wrong article. Look at the date: it's published in 2008; that's hardly news.
Here's the correct one [nature.com] published ... um, on 15th—probably in U.K., since it's still 14th here.
Parent
Re:Article Abstract (Score:4, Interesting)
Parent
Re:Article Abstract (Score:4, Funny)
Ow, my head.
Just put some spin ice on it.
Parent
"Discovered" magnetic current? (Score:4, Interesting)
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?
Re: (Score:3, Interesting)
I'm pretty sure you didn't learn about a current of magnetic monopoles in electromagnetics class.
This is not the same as a normal current of electric monopoles (charges) producing a magnetic field.
Re:"Discovered" magnetic current? (Score:4, Informative)
Parent
magnetic flux vs magnetic current (Score:4, Informative)
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.
Parent
Oh no, Rick Berman just came in his pants... (Score:5, Funny)
Whoa! (Score:5, Funny)
...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.
Parent
Re: (Score:3, Funny)
"...And so, the development of karmon storage marks the end of the Just Age; where consequences always hit the originator of the action. i.e.: The karmiker and the karmiked where always one and the same."
"Mr. Johnson. What were khores paid for, then?"
"As you may know, the term "khore" comes from "karma whore". At that time, they were called just "whores" and they were paid in exchange for sexual favours."
"Like computers?"
"Yes, Jimmy. Exactly like computers."
magnetricity? (Score:3, Funny)
So this means (Score:3, Funny)
...we're 0.00317% closer to flying cars!
We're going up the tech tree! (Score:4, Funny)
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!
So what do the field lines look like? (Score:3, Interesting)
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?
Re:So what do the field lines look like? (Score:4, Informative)
Yep. Same as like a static electric charge.
Parent
the article itself, and available (Score:5, Insightful)
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?
Re: (Score:3, Informative)
What are you talking about?
Probably something like this, for the first complaint:
roystgnr@mycroft:~$ wget http://arxiv.org/abs/0907.0956 [arxiv.org]
--2009-10-15 08:39:22-- http://arxiv.org/abs/0907.0956 [arxiv.org]
Resolving arxiv.org... 128.84.158.114
Connecting to arxiv.org|128.84.158.114|:80... connected.
HTTP request sent, awaiting response... 403 Forbidden
2009-10-15 08:39:23 ERROR 403: Forbidden.
roystgnr@mycroft:~$ wget --user-agent="Mozilla/5.0 (X11; U; Linux i686; pl-PL; rv:1.9.0.2) Gecko/20121223 Ubuntu/9.25 (jaunty) Firefox
Question on magnetic fields (Score:3, Interesting)
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?
Re:aren't the 2 linked? (Score:4, Informative)
Nope. Gauss's law [wikipedia.org] (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
Parent
Re:aren't the 2 linked? (Score:4, Interesting)
I think so. It sounds more like "electron holes" in semiconductors. The spin ice [wikipedia.org] 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.
Parent
Re:Maxwell Equations (Score:5, Interesting)
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).
Parent
Re:Maxwell Equations (Score:4, Interesting)
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.
Parent
Re: (Score:3, Funny)
I just tried to think about negative mass, thanks for the headache.
Re:Maxwell Equations (Score:4, Informative)
What, you haven't encountered the idea before? It's been around a while. Look here. [wikipedia.org]
Parent
Re:Maxwell Equations (Score:5, Funny)
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.
Parent
Re: (Score:3, Funny)
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.
Re: (Score:3, Funny)
And balloons filled with a negative mass equivalent of helium would sink.
Or you they rise faster?
This hurts my brain.
Re: (Score:3, Informative)
Re:Maxwell Equations (Score:4, Interesting)
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.
Parent
Re:Maxwell Equations (Score:5, Insightful)
There was also no theoretical reason for monopoles _to_ exist.
Well, if there is so much as one magnetic monopole in existance, it would [wikipedia.org] explain the quantization of electric charge. I call that a theoretical reason for monopoles to exist.
Parent
Re:Maxwell Equations (Score:5, Funny)
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.
Parent
Re:Maxwell Equations (Score:4, Informative)
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.
Parent
Re:Maxwell Equations (Score:5, Informative)
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 [thefreedictionary.com] 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 [slashdot.org]
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
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Re: (Score:3, Informative)
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 the
Re:Maxwell Equations (Score:4, Informative)
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).
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Note to self: physics-based sarcasm is a bad idea.
Re:Maxwell Equations (Score:4, Informative)
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 [wikipedia.org] means no magnetic monopoles. That said, the standard equations can be easily modified [wikipedia.org] 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
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Re:Maxwell Equations (Score:4, Interesting)
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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Re: (Score:3, Interesting)
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 [wikipedia.org] 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.
Re: (Score:3, Interesting)
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 theoretic
Precludes vs assumes (Score:3, Informative)
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
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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 equat
Re: (Score:3, Interesting)
Re: (Score:3, Funny)
Magnet current? Like, in a transformer?
No, that's a 'spark'. Still, it might be disguised as a magnetic current.
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Were should have stopped 10 beers ago.