Slashdot Mirror
"Overwhelming" Evidence For Magnetic Monopoles
Thorfinn.au sends along big physics news: magnetic monopoles have been detected at low temperatures in "Dirac strings" within a single crystal of Dysprosium Titanate. Two papers are being published today in the journal Science and two more on arXiv.org, as yet unpublished, provide further evidence. "Theoretical work had shown that monopoles probably exist, and they have been measured indirectly. But the Science papers are the first direct experiments to record the monopole's effects on the spin-ice material. The papers use neutrons to detect atoms in the crystal aligned into long daisy chains. These daisy chains tie each north and south monopole together. Known as 'Dirac strings,' the chains, as well as the existence of monopoles, were predicted in the 1930s by the British theoretical physicist Paul Dirac. Heat measurements in one paper also support the monopole argument. The two, as yet unpublished, papers on arXiv add to the evidence. The first provides additional observations, and the second uses a new technique to determine the magnetic charge of each monopole to be 4.6x10-13 joules per tesla metre. All together, the evidence for magnetic monopoles 'is now overwhelming,' says Steve Bramwell, a materials scientist at University College London and author on one of the Science papers and one of the arXiv papers."
I think this is at least one of the Science articles to which the post (almost) refers.
It's only against the law to use your monopole to extort the market.
Kwisatz Haderach
Sell the spice to CHOAM
This Mahdi took Shaddam's Throne
Uncle Pennybags purchases Acme's Magnet making division to create magnetic monopoly.
Clearly we knew monopoles exist already since Microsoft is guilty of being one right?
2 stupid questions: - Can someone make a car analogy? - Are there any applications for it within our understanding of physics? When I hear of monopoles it's often in a bad context, and in combination with news about LHC creating blackholes and other Earth eating stuff. I don't think the LHC is a doomsday device but I don't really get magnetic monopoles.
They come in "pairs" huh. Sounds like the N S of a regular old fashioned magnet to me. If they could be separated ever then they really would be monopoles but otherwise how can you be sure its not just a regular magnet thats too small a scale to detect the flux coming from every angle around it?
"...that yin-yang dualism can be overcome. With sufficient enlightenment we can give substance to any distinction: mind without body, north without south, pleasure without pain. Remember, enlightenment is a function of willpower, not of physical strength."
-- Chairman Sheng-ji Yang, Essays on Mind and Matter
So, can haz magtube now plz?
Surely if they are two monopoles tied by a dirac string then they actually make a dipole. I was under the impression a monopole would create a dirac string (a discontinuity in the field) that extends to infinity. Interestingly by allowing the dirac string to extend first in one direction, then in the other and joining the two resultant fields gives a fully continuous description of the monopole without the need for a dirac string.
I think what the summary is refering too is similar to the creation of a electron and hole pair in a semiconductor rather than a fundamental monopole particle. So they are in fact creating both poles but that inside the spin glass they are not confined with respect to each other so each one appears as a monopole in the material.
is it possible to create pepetium mobiles now? ;)
most of the the 'free energy' designs are based around non-existing monopoles, and tricks to 'emulate' monopoles.
Comment removed based on user account deletion
Isn't this just in time for the new season of the show Big Bang Theory, where Sheldon is on an expedition to find magnetic monopoles? :)
Yea like that electric charge nonsense, you can't have a particle with a single electric charge! that'd be crazy whatever it is will allways have another side with the oposite charge!
Wait, how will this affect me tonight when I roll a big fatty and watch TV?
I mean, if you're traveling, you wouldn't want your houses and hotels to go flying off the board, so the magnets would be pretty helpful. I'm just wondering if the Chance and Community Chest cards are magnetized too? And how do you deal with all the money? These questions need to be answered before we can truly say there is overwhelming evidence for magnetic Monopoly.
Quidquid latine dictum sit, altum sonatur.
I thought we were talking about a Slashdot question that only had the CowboyNeal answer as a choice.
All my coins are shaped like mobius strips.
The Klein bottle manufacturer guarantees unconditionally the following:
I have contacted them to notify them of this and to request a refund of my Klein bottle purchase. If you also have a Klein bottle I highly recommend doing the same!
Yes, and the world being round is absolutely preposterous. How could you possibly move in the same direction and end up back where you started? That is ludicrous. Some sort of stupidity there.
> this is some sort of stupidity here
It certainly is. The physicists are not the ones exhibiting it, though.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
That tells me nothing. How many beard seconds is that?
A magnetic monopole is to a magnetic field what an electron is to an electric field.
This will, amongst other things, mean that Maxwell's equations become more symmetrical.
div D = rho; div B = 0
Will become
div D = rho_e; div B = rho_m
And there will be a magnetic current term for curl H.
It's long been known that if a magnetic monopole exists then charge must be quantized.
I've not looked at any of the papers but I'm interested to find out if they've got a mass estimate for them. Last I remember reading about this they were expected to be heavy (uranium nucleus sort of heavy) but I don't recall if that was an extrapolation from their non-detection or whether there was a more fundamental reason for them needing to be so massive.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Its not, its just like electric charge only for magnetism.
Monopoles? Dirac Strings? Did I just wake up in Star Trek? If so, where the hell is my Uhura?
Superconducting wires? Bah, impossible! Time moves slower the faster you go? Bah, that's not even remotely correct! The earth is round? Bah, it's flat and carried on the backs of turtles all the way down!
Data: "Magnetic monopoles have been detected at low temperatures in "Dirac strings" within a single crystal of Dysprosium Titanate"
Geordi: "If we generate a phase-inverted lepton pulse from the main deflector, we might be able to force a quantum pulse cascade which will counteract their effect!!!"
Can someone translate this into English for us non-Physics geeks? What exactly does this mean? Will it lead to new applications of magnets (the closest analogy I can come up with from this brief description)?
If you have a regular old magnet, it has North and South sides. The net force, or charge, between those two sides is zero.
A monopole would be North or South, but not both. It would have a positive net force, much like an electron.
Not a typewriter
I think the stupidity is yours. Magnets are not just atoms lined up, atoms themselves have magnetic poles. In fact, the components of atoms (such as electrons) have magnetic poles as well.
It's perfectly conceivable to think of a point source of just North or South where the field lines radiate outwards in all directions. They would arc toward the nearest magnetic pole of opposite polarity. The diagrams are simple to draw and have been accepted by just giants in the field as Dirac for eighty years. The only question is: do they actually occur?
Let me wiki that for you: Magnetic charge
Magnetic charges fired in a customised photon torpedo were used in Voyager S96E10 to defeat the dudes with forehead that looked like vulva.
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;
I know what magnetism is, I also know what a magnetic monopole is, hell I even know what a dirac string is and what a spin glass is. Honestly your argument about coins made no sense at all.
I was attempting to point out that electric charge also has field lines but that they do not have two sides like a coin, the entire point of the discovery of a magnetic monopole is that it doesn't have two sides in the way that all the other magnetic dipoles we are used to have.
... run Linux?
They have units of ampere*meter instead of ampere*second. Don't listen to this "joules per tesla metre" non-sense.
Think of them as different causes of motion. Magnetic charges cause motion in magnetic materials and electric charges cause motion in other electrically charged materials. They are supposed to be linked in someway. Same goes for the "colour" charges of the strong force. And to generalize further, physicists hope to find a link to gravity which also causes motion (in all materials).
Guys, guys, calm down. Obviously this poster is making a joke. We all know that quantum particles come in pairs or groups; we all know that quantum particles are often monopoles, most famously electrons and positrons.
More than anything, we all know that quantum particles aren't like coins -- they are more like cars...
I'm sorry, but you're going to have to provide your credentials if you want me to accept that you know more about magnetism than four separate physics research teams, two with articles in Science and two more with draft articles on arXiv.org, all of which show evidence of the existence of magnetic monopoles.
Rule of Slashdot #0: You and people like you are not representative of the larger population. - A.C.
I'm wondering , if we have curl H = J(electric), if we'll end up have something like curl (something) = J(magnetic) (a new equation or I dunno)
how long until
...therefore, God exists.
You should do some more research, anarchyboy is right, there is no theoretical reason (aside from never having observed them) why magnetic monopoles cannot exist.
What this work shows is that they can exist, although it is not in the 'real world', but as effective particles in a solid state system. The mechanism will be similar to spin-charge separation that occurs in 1D systems, whereby the degrees of freedom of a particle separate into independently moving constituents. In this case, it will be the north and south poles of a dipole that become effectively independent and behave as distinct particles.
This doesn't mean that monopoles must be able to exist in a vacuum, possibly (probably?) they cannot, but the reason why will be due to the properties of the vacuum, not any fundamental restriction on monopoles.
I'm sorry, but you're going to have to provide your credentials if you want me to accept that you know more about magnetism than four separate physics research teams, two with articles in Science and two more with draft articles on arXiv.org, all of which show evidence of the existence of magnetic monopoles.
Christ, not to mention Paul fucking Dirac.
circletimessquare, you have one again exceeded yourself at demonstrating your truly incredible arrogance and stupidity.
There are all sorts of physical phenomena that defy intuition and do not exist in our day to day environment. That you cannot intuit their existence doesn't change the fact of their existence.
Neutron stars are somewhat less abstract than these monopoles appear to be (the stars are reasonably explained using high school physics), but they aren't exactly something that can compared to day to day macroscopic physical reality.
Nerd rage is the funniest rage.
How does an electric field line just stop somewhere?
We all know what to do, but we don't know how to get re-elected once we have done it
i thought they were talking about www.poloniasingles.com/
Now I've scanned one of the papers I see that they're not detecting the sort of magnetic monopole I was thinking of (i.e. a new sub-atomic particle)
Instead they've detected the equivalent of a charged molecule.
They give an analogy of the disassociation of water into H3O+ and OH-. They claim to have done the same thing with magnets - ending up with a disassociated north and south pole.
So their work doesn't appear to give any clue to the mass of a magnetic monopole particle. But AFAICT they have still created a type of magnetic monopole, exactly the same way as a proton is an electric monopole even though it has an internal structure.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
(Disclosure: I'm a physicist)
You could just as well ask: "how can an electric field line just stop somewhere?", and thereby conclude that there can be no such thing as an "electric monopole" (a positively- or negatively-charged particle). As long as the universe has no net electric or magnetic charge, all lines will terminate somewhere. If the universe did have a net charge the point is subtle, but that's irrelevant: the paper talks above pairs of opposite-pole monopoles created together, like a particle and its antiparticle. So this argument doesn't hold water.
Monopoles aren't impossible in principle (it would just be an extra term in Maxwell's equations) and are predicted in some theories, but fundamental-particle monopoles have never been observed. The summaries of this paper are confusing a lot of people: the authors are describing a crystal system with excitations that look like monopoles. They are NOT describing discovery of a new fundamental particle, but rather a new kind of solid-state phenomenon.
By having a non-zero divergence. Just like Gauss' law divergence D = rho (charge density), we have divergence B = rho_m (density of magnetic monopoles).
These are not the magnetic monopoles you're looking for.
A good place to start is by explaining to them what a magnetic field line is.
Sorry son, it is you who have been defeated by your own ignorance and closed-mindedness. You threw out one (dumb, totally invalid and irrelevant) analogy, somebody came back with a very proper analogy to something actually *related* to magnetism, and you shrugged it off as him not understanding magnetism. In fact, your narrow understanding of magnetism with your little coin analogy has been a convenient way to understand the concept for many years...until today. That's the point. Scientists have been researching monopoles for a long time, quite simply because the coin analogy never quite added up - there was no good reason why they *always* came as dipoles, besides that monopoles had never been observed. Now they have been, everything you know about magnets will probably be wrong once more data is gathered, and you will either have to take the scientists' word for it, or you will have continue using inaccurate mental models to make sense out of it for yourself.
"and not continue on its way around to the other side of a magnet?"
Yes! That's why it's called 'monopole'. It behaves like electric charge, but with respect to magnetic field. For example, moving monopoles create _electric fields_ with closed lines.
And impossibility of monopoles is not a fact. In fact, (pun intended) it's long been known that monopoles can exist within the framework of classic electrodynamics.
An interesting fact: existence of even one monopole in the Universe forces _all_ electric charges to be quantized. But all electric charges ARE quantized.
The whole crowd of people selling devices that use Zero Point Energy and magnetic suspension perpetual motion machines and people who write hundred page manuscripts in purple ink arguing why the Second Law of Thermodynamics must be repealed are going to come out of the wood work now.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
He knows what a magnetic field line is, just like you. He also knows what an electric field line is, which is where you need to catch up. Try to be less arrogant about your ignorance, especially to someone who is taking the time to try to educate you.
Having read at least one of the arxiv articles, it is clear to me that the authors have NOT detected magnetic monopoles, and don't actually claim that they have. They claim that a certain type of ordering in a very specific crystal at very low temperatures BEHAVES AS IF it was a magnetic monopole - it's an analogy at best. The energy required to trigger the effect is minute, so they can "see" lots of MMAs (magnetic monopole analogs [my terminology]), and hence study what would happen if lots of REAL MMs existed in some other situation. They confirm that setting up Maxwell's equations to include a monopole shows the same sorts of behavior as what they see. But a real, isolated magnetic monopole? Not this time......
Wrong analogy. An electric charge exists statically, whereas a magnetic field only exists by virtue of a nearby moving electric charge. Whenever something is moving, the first derivative of its position can be described with a vector, which, unless the vector has no magnitude, indicates that it must be moving away one position while simultaneously moving towards another. This duality is, roughly speaking, where it comes from that you cannot have a magnetic field with only one pole... it is approximately mathematically equivalent to the notion of a non-zero vector having no additive inverse.
What are the practical implications/applications of monopoles?
I'm not dissing the theoretical impact. I'm just curious if anyone has a use in mind for them.
Because you are better at physics and Paul Dirac was.
Yes. You can reason through this and find a magnetic monopole current induces a curl in the E field. Consider Lorentz boosts and see how the fields transform.
a magnetic monopole is a physical impossibility. point of simple fact
A monopole is just one end of a very, very, very long dipole - the other end is lost in space so to speak.
i read somewhere that magenetic monopoles can be used to convert protons directly into energy, as per e = mc^2. can anyone clarify what this new discovery means for this concept. it would be the ultimate energy source, i would presume.
I've been reading for decades about the search for subatomic-particle-type monopoles, and all the wondrous things one could do with them. This sounds more like some kind of group phenomenon, an emulation of a monopole, if you will. Sort of like holes in a semiconductor, which behave in some ways like positive "things", but are actually just the absence of an electron in a lattice.
I'm guessing that these aren't the kind of "real" monopoles that would let us build super-powerful motors, or compact proton disintegrators, or whatnot. On the other hand, even though the semiconductor folks can't isolate and sell bucketloads of holes, they do turn out to be quite useful.
curl-H = J_e + dE/dt
curl-E = -(J_m + dB/dt)
Magnetic lines seem to come from electrons as they move through the aether, the faster they move the more aggressive the magnetic flux gets and since electrons always orbit an atoms nucleus the lines go up through the middle and around the donut shape of its orbit. If an electron breaks its orbit there really isn't a distinct north or south, just the direction the lines are rotating around the electron (right or left - and whether they are actually physically moving is something we may never actually know but lines going in one direction wont combine with lines in the other direction). That being said I don't think the magnetism actually exists as something within the structure of the electron but only within the space around it like a pebble making a wave in a pool - the pebble doesn't "posses" the wave it creates even if the wave wouldn't exist without it.
I guess I'm trying to say the electrons don't actually have a magnetic pole as you assert.
Also how can you throw a pebble into the middle of a pond and get the waves to move in one direction from the pebble but not the other? I think envisioning the creation of a monopole is something like that and I'm still not convinced the people considering it are looking at it the right way.
I'm glad you provided the episode number, because the description didn't narrow it down much.
If you were blocking sigs, you wouldn't have to read this.
The equations for magnetism are similar to the equations for electricity, apart from an extra equation which states that there are no magnetic monopole. That equation comes from empirical evidence and can be removed without breaking anything. As a proof, electricity doesn't have that extra equation and works just fine.
Dirac's argument (and all the field-theoretic) arguments in favor of the existence of magnetic monopoles have had to do with an elementary particle exhibiting those characteristics. Sometimes this is phrased in the terms of a 0-dimensional topological defect, something that would be produced by certain kinds of symmetry breaking; and indeed one of the arguments in favor of cosmological inflation theories was the fact that we don't see fundamental-particle monopoles, and would expect to. Finding one of these guys would be amazing news.
What these experiements seem to have done, however, is detected the effect of what condensed matter physicists like to refer to as a quasi-particle, akin to the phonon, which is a different thing entirely.
Or am I missing something?
If I had a dollar for every time someone on /. claims to understand something without really doing so, your posts on this topic alone would already get me some beer. You need to brush up on the notion of quantum collective excitations - any advanced condensed matter book will do. After you do that, reading TFAs might provide you with some answers.
Contrariwise, you're free to apply your 'reasoning' to 'proving' how superconductivity should not exist either.
You know who else didn't believe in magnetic monopoles? Hitler, that's who.
If you were blocking sigs, you wouldn't have to read this.
Because you can't understand it, it's impossible?
Give me Classic Slashdot or give me death!
In principle, YES! Imagine the gravitational field lines radiating away from the Earth. If there were no other masses in the universe to bend the field lines, then ALL of them would go on forever.
Presumably you understand electric field lines, and gravitational field lines, and how they terminate at charges and masses respectively. Why is it so hard to visualize the field lines of a magnetic monopole? They work in exactly the same way.
From one of the articles:
They've managed to create the microscopic equivalent of a long skinny magnet or a long bendy solenoid: a set of dipoles aligned end-to-end, which acts just like a string with two "monopoles" at the ends.
While this is an interesting microscopic state of matter, from the "discovering monopoles" point of view it doesn't seem fundamentally different than the macroscopic description of magnet "poles" that has been well understood for over a century (and observed for a lot longer than that). I call hype.
If a thing is not diminished by being shared, it is not rightly owned if it is only owned & not shared. S. Augustine
That it not entirely correct.
Magnetic monopoles have been observed.
The problem is that most student are told that magnetic monopoles haven't been observed,
and very few student check to see if that is correct.
Check out chapter 5 in
http://www.scribd.com/doc/4445/quaternionic-electrodynamics
for references to the articles.
a magnetic field is a relationship between a particle and its environment. it begins at the particle, it loops around, it ends on the other side of the particle
Mmm... can we say "begging the question"? You assume a magnetic field like must "[begin] at the particle" and "[end] on the other side of the particle", and then use that as proof that a field line must begin and end at a particle, thereby disproving the existence of magnetic monopoles.
Can you explain further why you think that a monopole implies perpetual motion?
This mentality is a good example of what Joel Spolsky calls fire and motion. You just keep moving, keep publishing, keep innovating, and your opponent is so busy trying to catch up or deal with your earlier work that you gain huge momentum. Sometimes unstoppable momentum. People just can't deal with the information overload.
For 30 years, physicists have believed that the universe is made up of tiny vibrating dimensional strings which only they are clever enough to understand. A fine idea, except it turns out not even they are clever enough after all. Nevertheless, they persist in this belief because the mathematics is beautiful. Likewise, many physicists persist in their belief in magnetic monopoles because the concept is beautiful, or some other such rubbish. Look! It even makes Maxwell's equations symmetric. So what? What's so important about having symmetric equations. Unsymmetrical ones are so much more interesting!
There's only one arbiter in physics, and science in general. It isn't a "flurry of papers". It isn't "beauty" or "symmetry" or "elegance" or "coolness". It isn't how many people agree with your viewpoint. It isn't how many journalists you can get to print words like "overwhealming evidence" in headlines. It isn't how much "supporting (online) material" you can find to back you.
The one, only, and final arbiter is the experiment. An honest to gods experiment. It finds things. It separates truth from fiction. You can try to twist the meaning of the result this way and that, throw back the grenade and carry on with your fire and motion, but in the end the results of all those experiments will finally weigh down your dishonesty and halt your advance.
There are no magnetic monopoles. You can try to separate north and south pole. You can even construct models of "magnetic charge" and dipoles if you like. But in the end, you can't get a north pole without having a corresponding south pole, very, very close by.
Modern science, and worst of all physics, is in a deplorable state. Cargo cult scientists,frauds, charlatans, fakes, and deluded true believers(Yes I'm serious about that last link) have saturated certainly the media circuit, but I fear many physics departments as well. Sensationalism and media attention are now as never before, deciding what the "consensus"* in science should be. It's disheartening to see the world lose its faith in the method of observation, hypothesis, experiment and above all skepticism that has served it so well for so many centuries.
P.S.
*Before the cranks jump in; No, I do not in fact, doubt the reality of anthropogenic climate change.
May the Maths Be with you!
More than anything, we all know that quantum particles aren't like coins -- they are more like cars...
In that it's fun to watch them crash into each-other?
I suppose you have never heard of a Mobius coin.
and you've been so consistently for years now. Congrats, I guess. Shithead.
I said electricity is not magnetism are similar, not the same.
They become the same after interchange of the electric and magnetic field.
It's not your whale vs elephant example. It's more like x^2=1 has two solutions in x, therefore y^2=1 has two solutions in y. This is because the equations are the same after interchange of x and y.
i don't fucking get it: a magnetic field starts and begins with the same point in space.
Actually, in a conventional dipole, it starts at one side of the dipole, and ends at the other side. as you can see in the magnet and iron filings experiments you do in school...
it does not start at a point and not end: that's not a magnetic field. such a field could exert no force, as its not grounded in anything
Gravity is such a field, as someone above pointed out. Gravitational field lines radiate out from the earch, and in a univers with only one mass, would not end anywhere..
The electric field of a point charge is the same, i.e. an electron.
Does that help?
Mathematically, well, others have put the equations and how it breaks down already, far better than I could.
To quote others, there is nothing impossible about the magnetic monople (and a lot of evidence that at least one *must* exist, we just haven't seen one.
Weather this is or is not a "true" MM is a different matter.
Years later, a doctor will tell me that I have an I.Q. of 48, and am what some people call "mentally retarded".
IAAP and I did do my PhD on this stuff, but it is a while ago now...
The Dirac string is not real, but is really just a failure of the coordinate system. Coordinate systems are always failing: just stand at the North Pole and ask which direction is South. All directions are, and the coordinate system is broken at that point. That's fine, it works everywhere else and we jsut remember to be careful in the rare cases where we are asking for directions at the North Pole. There is no fundamental breakdown of space and/or time going on, it's just because we chose to impose a silly coordinate system onto the physical world. The fact the it breaks down at the North and South poles is also a red herring - we just chose to make the polar axis the same as the axis of rotation of the earth.
The coordinate system used to simultaneously describe electric and magnetic charges is also broken, and the Dirac string is really just a way of fixing up this breakage. We imagine that one unit of magnetic flux arrived through a very narrow tube at the monopole and then spewed out in all directions (think toddlers or teenagers at this point). The tube is not real, it is just a way of patching up the failure of the coordinate system. In the same way that the Poles as points of failure is our choice, the direction that the tube arrives at the monopole is also an artifact of how we set up the coordinate system.
We can change the direction that the tube arrives at the monopole from transparently using what is technically known as a gauge transformation, but let's not worry about that here.
The tube is not real, so we must not be able to detect it. This leads to the concept of quantisation of electric charge. Normally, if you take a tube carrying g units of magnetic flux and then take an electrically charged particle round it in a circle, the wavefunction of the charged particle will change by a complex phase exp(i.theta) where theta is proportional to the product of q (its electric charge) and g. You can detect this phase using a quantum-mechanical interference experiment, if you feel the urge. If the Dirac string is to remain physically unobservable, no interference effects must be seen so the phase rotation must be a multiple of 2.pi, because exp(i.2.pi)=1.
So, we know if there is one magnetic monopole anywhere in the universe then q.g = 2.pi.n (where n is some integer) so that the Dirac string (a mathematical fix for a choice of broken coordinate systems) remains just a theoretical trick and not observable physics. We must then have that the electric charge of every particle in the universe is some integer multiple of e = 2.pi/g, where g is the magnetic charge of that monopole.
Whether you consider the smallest unit of electric charge to be the charge on the electron or the charge on a free quark (one third of this) doesn't matter. We do observe that electric charge is quantised (i.e. integer multiples of some base amount) and magnetic monopoles as fundamental particles provide a relatively elegant solution as to why this is true.
A monopole is supposed to be an elementary particle with a magnetic charge. This is--as the abstract itself says--a "tractable analog" of a magnetic monopole.
There are a lot of things in solid state physics that "behave like" some kind of elementary particle but aren't: phonons, holes, etc. This is just another instance.
circletimessquare's original post is perhaps one of the most insightful posts in this thread. It is in fact, and insightful comment on magnetic monopoles in general. The post reveals a true understanding of the magnetic monopole "problem", and a much firmer grasp of the topic than that displayed by the authors of these papers.
Magnetic dipoles are not like electric charges. They do not result from particles of non zero charge separating from one another. The difference is best understood by examination of the electron; an elementary particle.
Electrons have static charge. They are electrostatic monopoles in every sense of the word. But they also possess magnetic moment. A magnetic dipole moment, a vector quantity with both magnitude and direction. It is from this direction that designations like north and south pole come from, not from some imaged pair of opposite magnetic charges that reside somehow displaced from one another, within the point particle of the electron.
circletimessquare is correct. There is no such thing as a magnetic monopole, just as there is no such thing as a unit vector without a direction. A pity some moderators around here cannot take their heads off sensational headlines and summaries or out of their pulp science fiction novels long enough to recognise good sense when they see it.
May the Maths Be with you!
so i must be insane, or the whole lot of you are ignorant of what a magnetic field is
I'd like you to consider the possibility that it's neither of the above. I recognize your signature and remember you making many good posts in the past. I don't think you're crazy. I just think you don't understand the theory of electricity and magnetism very well.
Electric fields also begin and end at particles. And there are electric dipoles, just like there are magnetic dipoles. Why should magnetism only have dipoles and not monopoles like electricity?
Just as electric dipoles are made from positive and negative electric monopoles (charges), there is no reason magnetic dipoles can't be made from opposing magnetic monopoles. Electric monopoles are definitely MUCH easier to observe in nature, but that doesn't mean there are no magnetic dipoles.
Did you know that observers in different reference frames will disagree about the strength of electric and magnetic fields? Electric and magnetic fields vary (in a coordinated way) under Lorentz transforms. That is, what looks like a pure electric field to one observer might look like a combination of electric and magnetic fields to an observer in a different reference frame. Putting it differently, eletricity and magnetism are two aspects of a single force called, creatively enough, the electromagnetic force. That's a reason to believe that magnetic monopoles might exist.
Additionally, electric charge is observed to be quantized in nature. All free particles observed so far have charges that are integer multiples of the electron charge. Quarks are believed to have charges that are +/- 1/3 or 2/3 of the electron charge, but free quarks have not been directly observed, and in any case, even if the basic unit of charge quantization is 1/3 of the electron charge, charge is still quantized. And in the theory, the existence of magnetic monopoles automatically leads to charge quantization. That's a big reason many very smart folks with Ph.D.s in physics have been looking for magnetic monopoles for some time.
I remember a magnetic monopole detector that was sitting in a garage-like bay at HEP, the High Energy Physics group's building, at the University of Chicago in the late 1980s. I believe it was something Henry Frisch had set up really cheaply, so the risk was low, and the potential return enormous. Think of it as a low-budget HEP nerd experiment in Chicago. If you look at Professor Frisch's CV, you'll see that he's written a bunch of papers about magnetic mnopoles and their detection.
Only tangentially related: it has been 20 years, so I shouldn't have been surprised, but seeing Frisch's hair that white was a bit of a shock. Probably because of what it implies about my own age.
"It is nice to know that the computer understands the problem. But I would like to understand it too." --Eugene Wigner
those flying cars you keep promising.
Table-ized A.I.
Wasn't she the secretary that James Bond always flirted with?
Have you thought of the possibility of a field line starting at one particle and ending at a completely different particle? (a matched set of 2 monopoles?)
from what I'm reading this would seem to be what this is talking about, and it also solves the problem you describe.
A magnetic monopole is to a magnetic field what an electron is to an electric field.
Just what we need. More singularities.
Years ago, I learned that magnetism was really just a way of accounting for the way electrostatic forces and special relativity interact. So, it will be interesting to see how they reconsile the discovery of monopoles with special relativity. I wonder if they are saying that some sort of monopole particle really exists. I'm skeptical of this. Or, perhaps they have discovered a condition where the mathematics work out nicely if you pretend a monompole exists, but really under the hood it's all relativity and electorstatic forces.
http://skepticsplay.blogspot.com/2007/12/relativity-electrostatics-magnetism.html
http://www.newton.dep.anl.gov/askasci/phy00/phy00993.htm
http://van.physics.illinois.edu/qa/listing.php?id=2358
As I have stated in response to circletimessquare elsewhere in this discussion, there are a few good reasons to believe magnetic monopoles might exist. I remember circletimessquare's sig, and remember him or her making good posts in the past, but it's clear that he or she does not understand electricity and magnetism very well.
Classical electric and magnetic fields vary in a coordinated way between different Lorentzian reference frames. So where one observer might only observe an electric field with no magnetic field, an observer in a different reference frame moving at a constant velocity with respect to the first observer's frame might see a combination of electric and magnetic fields. Electricity and magnetism are different aspects of a single force, believed to be one of the four "fundamental" forces. It is called, shockingly enough, the electromagnetic force. That's one reason to believe that since electric "monopoles" (charges) exist, magnetic monopoles might too.
There are electric dipoles, which are made of opposing electric "monopoles" (charges). Why couldn't magnetic dipoles also be made of opposing magnetic monopoles? That's another reason to believe magnetic monopoles might exist.
Dirac didn't just think magnetic monopoles might exist for no reason. He discovered in his calculations that the existence of magnetic monopoles would automatically lead to the quantization of electric charge. Since all electric charge observed in nature is quantized (in integer multiples of the electron charge for free particles and, we believe, in integer multiples of 1/3 of the electron charge if we include particles that are not observed "free"), we have yet another reason to believe there might be magnetic monopoles.
Very smart folks with Ph.D.s in physics have been looking for magnetic monopoles in creative ways for a very long time. In another post in this discussion, I mentioned Professor Henry Frisch of the University of Chicago. These people aren't just looking for magnetic monopoles to do something crazy. They're doing it because their deep understanding of the theory and the experimental data leads them to believe magnetic monopoles might exist.
"It is nice to know that the computer understands the problem. But I would like to understand it too." --Eugene Wigner
Unending magnetic field lines and a particle with a net magnetic charge does not result in "perpetual motion", where that term always means "perpetual motion in the face of friction or other counteracting forces", because minus that "perpetual motion" is just Newton's 1st Law and completely uninteresting.
In the case of a magnetic monopole, it's actually little different than electricity (I know you think otherwise but you're wrong, look at the force equation), and in the case of electric fields, a charged particle in that field has a certain amount of potential energy, and that potential energy may be converted into kinetic, and that kinetic energy may be enough to reach escape velocity for the universe, but it isn't perpetual motion.
I know it's pointless explaining this to the deliberately dumb troll, since even if you wanted to understand it'd require you knowing some of the actual theory and math behind the physics you only understand through inaccurate analogy, but it's entertaining anyway.
P.S. Yes you're insane and yes you're stupid.
The enemies of Democracy are
Only if they have non-integer spin. Otherwise it's kinda boring.
Holy shit, I think this is the first time someone on Slashdot has used the term "begging the question" correctly. Hats off to you!
Too bad I have no idea what this monopole business is all about.
1. By softball sized foam ball at Hobby Lobby.
2. By a couple hundred small neodymium magnets online.
3. Get a hot glue gun and hot glue one pole facing towards the surface and the other pole away.
4. Glue more magnets to the entire surface of the foam ball is covered in magnets.
5. You now have your very own "Macro-Sized, Monopole analogue!"
Tsukasa: All I really want, is to be left alone...
Wake me when this gets to market.
Too bad I have no idea what this monopole business is all about.
/. crowd!
It's that single, machined glass eye-piece worn by 19th century lumber barons and railroad tycoons. I had no idea there was so much math behind it, or that it was such a point of contention with the
God has the only monopole in the universe and it is currently floating over the N pole of a large planet sized Neodymium magnet he keeps on his desk.
He uses the magnet as a paperweight and once he got a new metal desk and needed Chuck Norris's help in moving his paperweight around. Chuck Norris then told the magnet to behave so God could move it and the magnet obeyed so now God doesn't have to keep asking Chuck Norris to move it all of the time for him.
Tsukasa: All I really want, is to be left alone...
am i insane? is everyone here stupid?
Normally, when you arrive at a point where everyone in the world has to be retarded, is out to get you or has to hate you personally for the situation to be understandable, it is safe to assume that the reverse is to true. You're ignorant, paranoid or hate everybody. Sort of like if you keep dating assholes, the problem is with you, not with the world.
Those who can, do. Those who can't, sue.
You claim argument from authority, I claim argument of ignorance: I cannot conceive of it, therefore it cannot be true. Quite frankly, I'd rather trust Dirac on matters of physics that some random poster on a random website with absolutely no knowledge of physics.
Those who can, do. Those who can't, sue.
There's not as much difference as you think. True, magnetic fields are not caused by "charges" as far as we know, unlike electric fields. But there's no theoretical reason why that's not possible. Electric fields can be caused by things other than static electric charges - for example, changing magnetic fields or (hypothetically) a magnetic current - a flow of magnetic monopoles.
The electron does indeed have an electric monopole and magnetic dipole, but there could conceptually be a magnetic monopole - we just haven't seen any. The monopole charge density would be a scalar, just like the electric charge, so I don't know what you're getting at with your "unit vector without a direction" remark.
IANAP (I am not a physicist), but perhaps it's some relation between magnetic and gravitational fields? Certainly gravity is related to mass, so perhaps there is some relation or parallelism in magnetic fields?
Hear, hear! Thank you for the appropriate and physically literate statement of what I would have liked to tell GP.
Disclosure? It isn't a disclosure, it's more of a disclaimer.
AFAIK you disclosure when you have a potential bias about the subject matter, and want to be honest about it. What you have here is bragging rights.
(Disclosure: I'm a physicist too)
entropy happens
These are simply sets of atoms that, together, act like monopoles. What has been discovered is not a single particle with one pole. It is a place inside a material that acts like a monopole. Real 'Dirac strings' connecting real monopoles are not long chains of molecules, these long chains of molecules simply act like Dirac strings. Please. This is the most misleading title and summary I've ever read here, and that is saying A LOT.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
""Overwhelming" Evidence"
"Theoretical work had shown that monopoles probably exist..."
Overwhelming Theory seems more appropriate when you look at it this way; Overwhelming evidence that monopoles may probably exist in theory. :)
The physics of magnetic monopoles is not widly known, mostly because its slightly complicated and their existence is (was) purely theoritical. But its not new and they can be incorporated into maxwells equations quite easily. In fact it makes electricity and magnetism appear much more symetric which is in some ways nice since we allready know they are the "same thing". I think the problem is you have a definition of magnetic field lines which is fine when there are no magnetic monopoles present (which is pretty much all the time) but the fact that magnetism allways comes in dipoles is not written in stone in the equations or in the idea of magnetic field lines. There is no problem with field lines not terminating (like in the case with a single point charge) its just that this doesnt normally happen for magnetism.
The detection of monopoles may be news but the theoritical plausibilty is not and you would find mention of them in many quantum field theory, quantum electrodynamics and electromagnetism text books.
make believe our planet had a net mass. it would interact with our sun's gravitational field lines, and keep moving orthogonal to those lines, looking for equilibrium. but it wouldn't find it, because unlike a normal mass-dipole, its a monopole
so our planet would loop around, move through mostly empty space, and whatever aspect of our planet that was still in existence as a monopole would still continue orthogonal to those field lines, never stopping movement, just looping forever orthogonal to a field line
thats a perpetual motion machine. thats mass. thats impossible bitches
And light is a wave of energy propagating through space time...until it interacts with a solar panel and suddenly we are discussing photons and the photoelectric effect. Many people cannot fathom the wave-particle duality of light, but that does not make it true. They are no dumber than you and you no dumber than they.
Actualy, Dirac in his later years decided that the lack of evidence together with the effort spent on finding them was a good indication that monopoles do not exist. He was invited to a conference on the subject (one a year some round number of years after his paper on monopoles) and he declined to attent, explaining that he had stopped thinking the subject of interest for that precise reason. His response letter is included in the conference proceedings, and makes for an amusing read :P
Well, now you'll have to change your /. signature. :D
how long until
They were proposed by one of the greatest physicists of all time, in his area of expertise and their existence makes things "nicer" in terms of symmetry.
Yes they may not exist. But you declaring they can't because you can't conceive how they would work doesn't cut it. Especially given physicists who know way more than you about their field of expertise that is this area can conceive of them.
Time dilation makes no fucking sense either, so that's impossible then?
Amazing that you in your wisdom can determine something can't exist, while those idiot physicists build huge underground detectors to look for them
That's interesting - it's not a history I'm well versed in.
Uhh, how about providing the theoretical groundwork not only for being able to reverse the polarity of the phase inducers (which is the answer to most of life's problems), but also for being able to reverse the polarity of the main deflector dish to fire a tachyon pulse? Generally speaking, it allows you to reverse polarity on things, thereby providing an extremely simple and elegant solution that somehow was never conceived before.
Well, sir, there's nothing on earth
Like a genuine,
Bona fide,
Crystalized,
Nano-sized,
Monopole!!
Do daemons dream of electric sleep()?
You may be insane, but it's not that a lot of people don't understand what a magnetic field is -- it's that you don't understand what a magnetic field is.
"Magnetic field lines" aren't real, anyway, they're a theoretical construct to visualize the magnetic field. Their apparent behavior -- going in a loop from one side of a dipole to another -- is a consequence of the Maxwell equation (div B = 0). Really, it's div B = rho_m (magnetic charge density), but if no magnetic monopoles exist, rho_m is zero everywhere. You cannot use a consequence of (div B = 0) to show (div B = 0), which is what you're doing.
The magnetic field behaves exactly like the electric field. If you want to know what a particular magnetic construct would behave like -- it's exactly the same as the corresponding electric construct. So, for example, you claim that a monopole in the presence of a dipole forms a perpetual motion machine. We certainly have electric dipoles and electric monopoles (charges). There are even crystals that form permanent electric dipoles (ferroelectrics), the electric analogue of a ferromagnet. So, is an electric monopole in the presence of an electric dipole a perpetual motion machine?
Impossible magnet
On selfish pole
Burma Shave
Great post. I'm sorry I used up all my mod points.
Comment removed based on user account deletion
To be fair, TFA (Nature) wasn't much better. It never actually broaches the topic of molecular vs. particle monopoles which is kind of central to anyone not in the know understanding that this isn't the big deal everyone's been talking about for the last decade+
Yes, but don't go putting anyone's eye out with it.
There's nothing trollish here. At the least it's an honest counterarguement, and worth replying to rather than burying.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Field "lines" are a convenient way to visualize magnetic fields, but they aren't the fields themselves.
Electromagnetism is one force. We know electric monopoles exist (electrons, protons, positrons, etc), so what do their field lines look like? The field lines of a lone electron spread out in all directions, infinitely. They of course get weaker as you get farther from the electron (lower field density), but they do go "forever." Indeed, even magnetic field lines go "forever" in the same way: the line directly between the two poles extends straight out, never turning back. Thus, a simple visualization of the field-lines of a normal magnet will have the same "problem" as the monopoles must have.
Wikipedia has a nice image showing two electric charges and their field lines. Look at the horizontal line for an example of such an inifinte line. You will see the same thing with a magnet and iron filings or by any sketch of magnetic field lines. What you percieve to be a problem isn't a problem, it's just a bit of difficulty visualizing it. I hope the images help.
Not a sentence!
Exotics are always the best way to finance those hellbore cannons. Will will bring the Ur-Quan to their knee equivalents, yet!
A government is a body of people notably ungoverned - AC
The end of a good solenoid (long cylinder of wrapped wire with current flowing through it) is a good approximation to a magnetic monopole. A short fat solenoid isn't so different from a bar magnet â" it's a dipole field, all right. But the longer and thinner the solenoid is, the more its magnetic field looks like two well separated monopoles. The Dirac monopole is precisely the mathematical limit of an infinitely long, infinitely thin solenoid, whose ends are then true monopoles. The vanishingly thin solenoid running between them is the 'Dirac string'.
What seems to have been seen in this crystal is something like a quite thin, quite long solenoid. It's not a new elementary particle with a magnetic charge, and in a way it's no different from the long thin solenoid you could make in your basement and power with a D cell battery. But in another way it's actually very big news, maybe even almost as good as it sounds, because the point is that nobody sat down to engineer a tiny solenoid. These things form spontaneously, for reasons that probably have to do mainly with physics on much larger scales than the solenoid thickness. And if that's so, then saying they're not 'real' monopoles is a fairly irrelevant quibble, as far as modern physics is concerned.
That equation comes from empirical evidence and can be removed without breaking anything.
It would break the empirical evidence... And I think you mean extra "term".
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Gravity only attracts, the magnetic monopoles would be kept in motion because there is a repulsive force.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Which is more or less true of every magnetic field we have ever observed. It is not true of every magnetic field we can imagine.
Please explain. We have electrical monopoles that don't cause perpetual motion. We work with the ones called "electrons" all the time. How could we get energy out of a magnetic monopole?
We don't know if they're anything real, but if you want to convince me they're a failure of reasoning you'll have to provide reasons for me to believe you and not Dirac and a horde of other physicists.
So far, you've claimed that a magnetic field is necessarily the sort of magnetic field we've always observed, that there's no room for discovering something new in the Universe. You've claimed that a magnetic monopole would imply perpetual motion, apparently unlike the electric monopoles we use all the time, without showing why the two are different.
Unless you can provide me with reasons why a magnetic field is necessarily closed, unlike an electric field, or why a magnetic monopole would screw up physics in ways electric monopoles don't, I'm going with Dirac.
This being Slashdot, there's real physicists here, who are as non-ignorant of what a magnetic field is as anybody on the planet. You might want to look for a third alternative.
"When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
A magnetic monopole would be attracted to one end of a magnet and repulsed by the other. So you could set up a wheel with identical magnetic monopoles on the edge and a magnet parallel to that edge, and the wheel would accelerate indefinitely. Unlike an electric motor no energy would be required, it would be better than a perpetual machine, it would be a free energy machine. This of course would violate conservation of energy, which for me indicates that an isolated monopole is impossible.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Citation Please
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Not a bad book, but its discussion on magnetic monopoles is hardly conclusive.
"The ability to delude yourself may be an important survival tool" - Jane Wagner -
Assuming you weren't being snarky, they're two sides of the same coin -- electromagnetic force, which is one of the four fundamental forces, along with the strong nuclear force, the weak nuclear force, and gravity. That's why you can generate an electromagnet by passing current through a wound wire, or generate electricity by passing a magnet along the same.
https://www.eff.org/https-everywhere
I guess Simon & Garfunkel got it wrong. The words of the prophets are written in e-mag textbooks.
make believe our planet had a net mass.
I can't imagine thiiiiiis!
The Science article is just as bad. The editors should have insisted that this article be entitled something like:
"Solid-State Analogs of Dirac Strings and Magnetic Monopoles in Spin Ice Dy2Ti2O7"
The existence of H3O+ and OH- shows that an electric monopole exists, even though it is not directly observed; you cannot construct these molecules/ions from dipoles only. Similarly, it looks like this experiment shows the existence of magnetic monopoles. To me that is more interesting than the details of the elementary monopole particle. For one thing, it explains (via Dirac's proof) why electric charge is quantized.
Escher was the first MC and Giger invented the HR department.
Are you serious? All this fuss about "fake" monopoles? Honest questions. I read one news article about this and it seemed they had found real particle monopoles. But then, I'm not a physicist.
Normally, all cars are diaxles. But these guys have created a stretch limo so long and stretchy that when a few dozen of them are wrapped around one another in a parking lot, and the front of one is sticking out, it looks like it's a free-standing monoaxle.
If there are independent monoaxle vehicles, then gasoline is a homogeneous liquid. Otherwise, according to Maxwell's equations, it's a bunch of tiny pebbles.
Shop as usual. And avoid panic buying.
Your Jedi mind tricks do not work on me!
There would be no net force once equilibrium was reached. The magnetic monopoles on the other side - the ones nearer to the unfavorable pole - would feel just as strong a repulsion trying to turn the wheel the other way, and no net motion would result.
a magnetic field begins at a particle/ bar magnet/ planetary core, loops around, and ends at the other end of the same particle/ bar magnet/ planetary core
Your first argument seems to be, "I've been told by my teachers that magnets are always dipoles. You cut one in half, and you have two dipoles. Therefore, if you tell me you have a monopole, it cannot be possible by definition.
The only thing I can say to that is that your definition of magnetism is incomplete. Monopoles have never been said to be impossible, they've been said to never be found. They are predicted by many theories. Maxwell's equations are more symmetric with their existence: they're even more elegant. No, that's not proof of anything directly, but the universe appears to like symmetry.
Your second argument is even weirder:
make believe our planet had a monopole at its core. it would interact with the sun's magnetic field lines, and start moving along those lines, looking for equilibrium. but it wouldn't find it, because unlike a normal magnet, its a monopole
I know you seem to refuse comparisons between electric and magnetic fields, but that really doesn't make any sense because they behave very similarly. Hell, they're part of the same unified force: electromagnetism. You can't have the one without the order. However, if you want to treat them separately...With magnets north is attracted to south, north repels north, south repels south. There are magnetic fields and magnetically charged particles are affected by them. There are electric fields and charged particles want to move along them. With electricity negative is attracted to positive, negative repels negative, positive repels positive. There are electric fields and charged particles are affected by them. The equations guiding those fields are the exact same equations: they would behave in exactly the same way.
So why can't you build a perpetual motion machine with electricity? Because you think there are no electric dipoles? You'd be wrong. We can and have manufactured dipole electrets. You can buy them.
Now let me give you an example. You have a perfect vacuum. You have a massive object. You have a second massive object in a perfect circular orbit around it. Will its orbit ever end? Perpetual Motion!!!
Perpetual motion is perfectly fine in physics. In fact, it's Newton's First Law: An object in motion will continue to be in motion unless you exert a force upon it. Perpetual motion machines are impossible in physics. When you try to extract energy from that system, the motion will necessarily change and you won't be able to do it forever.
I'm not a physicist either, but slashdot poster ajs is and he backs me up on this, so I think I read it right.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
The thing that bugs me about magnetic monopoles is that magnetism is the special relativistic correction to electric force. It seems like a side effect rather than something with an independent existence.
Of course, in a way most of physics seems like that: "broken symmetry".
For example, the normal "kinetic energy = 1/2 m v^2" is just an approximation of the relativistic mass minus the rest mass.
And classical behavior is a statistical approximation of quantum behavior.
Physics is freaky. That's why I love it!