Magnetic Monopoles

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Can anyone explain to me why magnetic monopoles don't (or can't?) exist?

 

[Michael]

Can anyone explain to me why magnetic monopoles don't (or can't?) exist?

Hmmm. Well, they would violate Guass's law of magnetism if they did exist?.

I'm not sure your question is really an answerable question. Given the genetic diversity of the planet, I can't really explain why unicorns do not exist, let alone why they could not ever exist under any circumstances. As far as we know they just don't exist, hence we call it a 'law' of magnetism. Until one is "observed" experimentally, Gauss's law is considered to be a 'law'.

 

[AstrophysicsStudent]

"Can anyone explain to me why magnetic monopoles don't (or can't?) exist?"

They may yet exist. And this would not violate Gauss' law for magnetism, but it would modify it at the quantum level by a factor of 4 x pi x density.

Imagine a coil of wire with electric current running through it. This produces a magnetic field as well, with one end of the solenoid a North pole and the other end a South pole.

If you cut it in half and take one of the halves and still have electric current running through that half-coil, you will still have one end as a North pole and the other end as a South pole.

The hypothesis is that as far as has been observed, electric charge is quantized (has a smallest possible value everywhere). If that is true, which seems to hold up in all observations, magnetic fields may have a quantized charge as well - and this would lead to the high probability of the existence of magnetic monopoles (a final, infintesimally-small cut of the coil, if you will, which leaves only ONE magnetic pole left).

 

[Agonaces of Susa]

Can anyone explain to me why magnetic monopoles don't (or can't?) exist?

Magnetic monopoles are a known scientific fact because they have been repeatedly observed.

Magnetic Monopoles Detected In A Real Magnet For The First Time

ScienceDaily (Sep. 4, 2009) — Researchers from the Helmholtz-Zentrum Berlin für Materialien und Energie have, in cooperation with colleagues from Dresden, St. Andrews, La Plata and Oxford, for the first time observed magnetic monopoles and how they emerge in a real material.

Results of their research are being published in the journal Science.

Magnetic monopoles are hypothetical particles proposed by physicists that carry a single magnetic pole, either a magnetic north pole or south pole. In the material world this is quite exceptional because magnetic particles are usually observed as dipoles, north and south combined. However there are several theories that predict the existence of monopoles. Among others, in 1931 the physicist Paul Dirac was led by his calculations to the conclusion that magnetic monopoles can exist at the end of tubes – called Dirac strings – that carry magnetic field. Until now they have remained undetected.

Large-Scale Cousin Of Elusive 'Magnetic Monopoles' Found At NIST

ScienceDaily (Oct. 8, 2009) — Any child can tell you that a magnet has a “north” and a “south” pole, and that if you break it into two pieces, you invariably get two smaller magnets with two poles of their own. But scientists have spent the better part of the last eight decades trying to find, in essence, a magnet with only one pole. A team working at the National Institute of Standards and Technology (NIST) has found one.

In 1931, Paul Dirac, one of the rock stars of the physics world, made the somewhat startling prediction that “magnetic monopoles,” or particles possessing only a single pole—either north or south—should exist. His conclusion stemmed from examining a famous set of equations that explains the relationship between electricity and magnetism. Maxwell’s equations apply to long-known electric monopole particles, such as negatively charged electrons and positively charged protons; but despite Dirac’s prediction, no one [except Edward Leedskalnin and the scientists last month] has found magnetic monopole particles.

Now, a research team working at NIST’s Center for Neutron Research (NCNR), led by Hiroaki Kadowaki of Tokyo Metropolitan University, has found the next best thing. By creating a compound that under certain conditions forms large, molecule-sized monopoles that behave exactly as the predicted particles should, the team has found a way to explore magnetic monopoles in the laboratory, not just on the chalkboard. (Another research team, working simultaneously, published similar findings in Science last month.)

BBC NEWS | Technology | 'Magnetic electricity' discovered

Researchers have discovered a magnetic equivalent to electricity: single magnetic charges that can behave and interact like electrical ones.

The work is the first to make use of the magnetic monopoles that exist in special crystals known as spin ice.

Writing in Nature journal, a team showed that monopoles gather to form a "magnetic current" like electricity.

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.

 

[AstrophysicsStudent]

Magnetic monopoles are a known scientific fact because they have been repeatedly observed.

Magnetic Monopoles Detected In A Real Magnet For The First Time

Large-Scale Cousin Of Elusive 'Magnetic Monopoles' Found At NIST

BBC NEWS | Technology | 'Magnetic electricity' discovered

- Actually, in regards to the first source cited, the detected "magnetic monopoles of spin ice" in 2009 declared by the Science journal has been challenged and not accepted by the general science community for reasons given here:

scientificamerican.com/article.cfm?id=magnetic-monopole-spin-ice

They are not seen as "genuine" due to the fact that there still is a North and South pole, just that only one of the poles manifests itself due to the extreme conditions. It IS very important work and no one disputes that it is VERY intriguing, but it does not result in a discovery of the quantized magnetic charge, which is the fundamental property of the hypothesis.

- Your second source from NIST is not a magnetic monople, but is likely a big stepping stone towards one.

- Your third source is further work with the "magnetic monopoles of spin ice" from 2009, which (for lack of better wording) is seen in science as a kind of "faux" monopole until more research is completed and a more informed concensus can be reached.

 

[Michael]

For the record...

The ice experiments with "molecules" is really NOT an example of a monopole, and in fact it causes the molecule next to it to hold the opposite spin. That is really just a molecular curiosity that creates an usual magnetic field alignment in the atomic lattice, it's not an example of an actual 'monopole'.

FYI, this all comes back the transfer of kinetic energy in a plasma. The transfer of kinetic energy occurs between 'charged particles'. The transfer of EM field energy to charged particles is called 'induction' and the photon is the carrier particle of that type of kinetic energy transfer. Since charged particles and photons do the actual kinetic energy transfers inside of a plasma, there is really no need for 'monopoles' to exist, nor do we have any empirical evidence that such things do exist in nature. In physics, the transfer of energy in a plasma occurs in discrete units between 'charged particles'. Photons are the carrier particles (of kinetic energy) of the EM field, not monopoles.

 

[Wiccan_Child]

Can anyone explain to me why magnetic monopoles don't (or can't?) exist?

Simply because such a magnetic monopole has never been discovered. They may well exist, but there's no evidence that they do.

 

[Agonaces of Susa]

Actually, in regards to the first source cited, the detected "magnetic monopoles of spin ice" in 2009 declared by the Science journal has been challenged and not accepted by the general science community

So? Heliocentrism was challenged and not accepted by the general science community. Darwin's hypothesis of biological evolution has also been challenged and is not accepted by the general science community. What's your point?

"Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you're being had. Let's be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus. There is no such thing as consensus science. If it's consensus, it isn't science. If it's science, it isn't consensus. Period." -- Michael Crichton, author, January 17th 2003

 

[Naraoia]

So? Heliocentrism was challenged and not accepted by the general science community. Darwin's hypothesis of biological evolution has also been challenged and is not accepted by the general science community.

Is that an implicit admission that the ToE is right?

 

[AstrophysicsStudent]

So? Heliocentrism was challenged and not accepted by the general science community. Darwin's hypothesis of biological evolution has also been challenged and is not accepted by the general science community. What's your point?

"Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you're being had. Let's be clear: the work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus. There is no such thing as consensus science. If it's consensus, it isn't science. If it's science, it isn't consensus. Period." -- Michael Crichton, author, January 17th 2003

You should read my entire post before you answer. What's my point? Not only that it is challenged and not accepted, but I gave the reasons WHY it is challenged and not accepted with a link as to why scientists say about these "monopoles of spin ice" that they are NOT monopoles in the definitive sense.

It would be best if you respond to my entire post ... not just the first sentence.

 

[AstrophysicsStudent]

Is that an implicit admission that the ToE is right?

At first, I thought "Theory of everything? He didn't mention that one. Ohh wait ... I'm slow."

 

[AstrophysicsStudent]

For the record...

The ice experiments with "molecules" is really NOT an example of a monopole, and in fact it causes the molecule next to it to hold the opposite spin. That is really just a molecular curiosity that creates an usual magnetic field alignment in the atomic lattice, it's not an example of an actual 'monopole'.

FYI, this all comes back the transfer of kinetic energy in a plasma. The transfer of kinetic energy occurs between 'charged particles'. The transfer of EM field energy to charged particles is called 'induction' and the photon is the carrier particle of that type of kinetic energy transfer. Since charged particles and photons do the actual kinetic energy transfers inside of a plasma, there is really no need for 'monopoles' to exist, nor do we have any empirical evidence that such things do exist in nature. In physics, the transfer of energy in a plasma occurs in discrete units between 'charged particles'. Photons are the carrier particles (of kinetic energy) of the EM field, not monopoles.

You are right in that there is no empirical evidence they exist. And I will agree that there MAY be no need for them to exist (providing of course that then we do find the reason for how electric charge is quantized ... and why then would there be no such thing as a magnetic charge and a magnetic current?) But if monopoles do not exist, then these questions must certainly have answers that lie in a different direction.

But I am not as certain as you seem to be that they do not exist (if I am reading you wrong, please correct me). In the string hypothesis, magnetic monopoles are strongly coupled with photons. And of course, photons are clearly the force carriers between charged particles; that is not in dispute.

The coupling constant between monoples and photons would be equal to the coupling constant ratio of photons and electric charge. This is given by
g^2/h-bar times c = e^2/h-bar times c

with g being the magnetic charge and e being the electric charge and the monopole in a variety of possible energy domains within its theoretical lower and upper limits.

Consequently, there is an EM "induction" method used to search for magnetic monopoles in labs using a solenoid and a and a detector attached to a SQUID.

A magnetic monopole, moving through the loop, induces an electromotive force and a current (Δi ). If the coil has N turns and its inductivity is L, the current is Δi.
If magnetic monopole passes through a superconducting loop there will be a magnetic flux change of PHI sub B = 2pi*h-bar*c/e which would be the flux of the monopole and independent of the monopole's velocity.

(Source:

Accelerator Based Magnetic Monopole Search Experiments (Overview) ​

Vasily Dzhordzhadze, et al, Brookhaven National Lab)

None have been found thus far by any of the different methods. Do I think they do exist? I don't know, but if they don't, then how is electric charge quantized? Hmm ... the mystery makes the effort worth it all on its own merit, doesn't it?

 

[Naraoia]

At first, I thought "Theory of everything? He didn't mention that one. Ohh wait ... I'm slow."

No, you just live in a different meme pool

 

[sfs]

None have been found thus far by any of the different methods.

Not counting the one seen in Blas Cabrera's lab in 1982, that is.

 

[Michael]

You are right in that there is no empirical evidence they exist. And I will agree that there MAY be no need for them to exist (providing of course that then we do find the reason for how electric charge is quantized ... and why then would there be no such thing as a magnetic charge and a magnetic current?) But if monopoles do not exist, then these questions must certainly have answers that lie in a different direction.

But I am not as certain as you seem to be that they do not exist (if I am reading you wrong, please correct me). In the string hypothesis, magnetic monopoles are strongly coupled with photons. And of course, photons are clearly the force carriers between charged particles; that is not in dispute.

The coupling constant between monoples and photons would be equal to the coupling constant ratio of photons and electric charge. This is given by
g^2/h-bar times c = e^2/h-bar times c

with g being the magnetic charge and e being the electric charge and the monopole in a variety of possible energy domains within its theoretical lower and upper limits.

Consequently, there is an EM "induction" method used to search for magnetic monopoles in labs using a solenoid and a and a detector attached to a SQUID.

A magnetic monopole, moving through the loop, induces an electromotive force and a current (Δi ). If the coil has N turns and its inductivity is L, the current is Δi.
If magnetic monopole passes through a superconducting loop there will be a magnetic flux change of PHI sub B = 2pi*h-bar*c/e which would be the flux of the monopole and independent of the monopole's velocity.

(Source:

Accelerator Based Magnetic Monopole Search Experiments (Overview) ​

Vasily Dzhordzhadze, et al, Brookhaven National Lab)

None have been found thus far by any of the different methods. Do I think they do exist? I don't know, but if they don't, then how is electric charge quantized? Hmm ... the mystery makes the effort worth it all on its own merit, doesn't it?

From my perspective at least, you and I do not seem to be that far apart on this topic. I just have yet to see any particularly compelling evidence to demonstrate that they do exist. I'm not suggesting that they could not exist under any circumstances. If evidence emerges to suggest that monopoles do exist at some point in the future, so be it.

However, that said, to the best of my knowledge they do not exist, their presence isn't necessary to explain EM field energy transfers in plasma, and the quantized aspect of QM seems to be directly related to photons. In terms of the transfer of discrete amounts of particle kinetic energy to charged particles, it appears that photons, not monopoles do the act energy transfer. AFAIK monopoles simply do not exist, nor is there any specific "need" for them to exist in terms of the effectiveness of current MHD theory to explain the behaviors of plasma.

 

[thatotherguy]

They cannot exist because it violates Maxwells second equation.
any magnet emits a field around itself
(it wont let me post a link atm i just googled bar magnet and the first image shows good field lines)
the lines represent the direction of magnetic force if you placed an imaginary north pole (monopole) in that position, this is simply convention.
the trouble arises due to the fact that this field has to go somewhere
Maxwell's second equation (a rewording of Gauss' law) states that the divergence (upside down triangle pronounced "nabla" dot B) equals 0 so any field lines you draw have to come back on themselves to close the loop. In a monopole this would not happen and so violates the equation.
if i remember correctly you can get a pseudo-monopole where the other pole is contained WITHIN the first (a ping pong ball within a tennis ball) but i can't find any citations
despite them not existing lots of money has been spent on finding them (personally i don't think they'll ever find a true one)
Peace.

 

[Wiccan_Child]

They cannot exist because it violates Maxwells second equation.

Maxwells equations are formulated with the assumption of closed magnetic field lines. We can easily reformulate his equations using the more general case of magnetic monopoles:

becomes

, where ρ[sub]m[/sub] is the hypothetical magnetic charge density.

any magnet emits a field around itself
(it wont let me post a link atm i just googled bar magnet and the first image shows good field lines)
the lines represent the direction of magnetic force if you placed an imaginary north pole (monopole) in that position, this is simply convention.
the trouble arises due to the fact that this field has to go somewhere

But that only holds true if there are magnetic dipoles, creating closed loops:

With a magnetic monopole, you would have something like this:

I.e., the closed loop integral over all space doesn't yield zero, as every 'out' isn't countered by an 'in'.

Maxwell's second equation (a rewording of Gauss' law) states that the divergence (upside down triangle pronounced "nabla" dot B) equals 0 so any field lines you draw have to come back on themselves to close the loop. In a monopole this would not happen and so violates the equation.

Indeed. So? Science is descriptive, not prescriptive. If reality violates Maxwells equations, then so much for Maxwells equations.

 

[thatotherguy]

updating Maxwell's law like that would mean you could designate a piece of metal (or matter) as having a north or south magnetic charge like an electron having negative electrical charge. this is nonsensical due to north and south not existing it's the combination that exists since it's the alignment of the spin magnetic moments within the material, each one having an up and a down. since you can't separate the up and down a magnetic monopole cannot exist even on an atomic level.
i agree that the field lines would look like that if there were a monopole in existence i just don't see how one could exist

 

[Michael]

updating Maxwell's law like that would mean you could designate a piece of metal (or matter) as having a north or south magnetic charge like an electron having negative electrical charge. this is nonsensical due to north and south not existing it's the combination that exists since it's the alignment of the spin magnetic moments within the material, each one having an up and a down. since you can't separate the up and down a magnetic monopole cannot exist even on an atomic level.
i agree that the field lines would look like that if there were a monopole in existence i just don't see how one could exist

IMO the search for the elusive monopole seem to be motivated by "magnetic reconnection" theories. They seem to believe that magnetic fields disconnect from and reconnect to other magnetic fields lines. In order for that to actually occur, it would require something like a monopole, otherwise it wouldn't actually be a unique energy transfer event. The transfer of particle kinetic energy to another particle is not "magnetic reconnection". The transfer of photon kinetic energy to a charged particle already has a proper scientific name, "induction'. In order for there to be a "third" and unique energy exchange mechanism a "monopole' would have to transfer the energy from one field to another. That's why we sometimes see them theoretically associated with magnetic reconnection theory, and that's what drives the interest in finding a monopole IMO.

 

[Wiccan_Child]

updating Maxwell's law like that would mean you could designate a piece of metal (or matter) as having a north or south magnetic charge like an electron having negative electrical charge.

No, since metal is made up of magnetic dipoles, which are, in this hypothetical scenario, made up of magnetic monopoles - you cannot have a metal made up of one kind of magnetic monopole, since that would fundamentally alter its structure to the extent that it would no longer be a metal.

this is nonsensical due to north and south not existing it's the combination that exists since it's the alignment of the spin magnetic moments within the material, each one having an up and a down. since you can't separate the up and down a magnetic monopole cannot exist even on an atomic level.

Well that's rather the point, isn't it: a magnetic monopole is a particle with a net magnetic charge, the combinations of which yield the magnetic moments in the first place.