What's the deal with magnetic monopoles?
So what are magnetic monopoles, and why are they important?
A monopole is just something with only one pole (enlightening, I know). Normal permanent magnets (or the Earth) are dipoles, they have a North and a South pole. If you cut a magnet in half you don’t get one North and one South pole, you get two smaller and weaker dipole magnets.
Imagine an electron. You probably picture it as a point in space, and you probably picture its electric field as lines pointing radially outward. That’s a monopole, an electric monopole. Now if you switch from it having electric charge to having magnetic change, you’ll have a magnetic monopole.
You might be saying right now, “Well that’s all well and good, but I’ve never seen one of the magnetic monopoles, why should I think they exist?” If you are thinking that, then you’re on to something. No one ever has seen a magnetic monopole. If you look at Maxwell’s Equations, you won’t see any magnetic charge anywhere. But Maxwell noticed that it could easily be added, but the lack of evidence for them dissuaded him from including them.
I just said that no one has seen a magnetic monopole, and this is true, in a sense. Valentine’s Day 1984, Blas Cabrera, my advisor, saw a signature on a detector that is exactly what you’d expect if a monopole had passed through. However, further experiments made it vanishingly unlikely that this was an actual monopole, and Blas will tell you it almost certainly was not. (Personally I’d like to believe it was, and I’m impressed Blas can admit that it wasn’t.)
Now you’re probably thinking, “If we’ve never seen one, why do we care about them?” That’s also a good question. It turns out that if you take quantum mechanical principles and mix them with electrodynamics, you can prove that if there exists one magnetic monopole anywhere in the universe, then both electric and magnetic charge will be quantized. This is called Dirac’s quantization, and is a pretty stunning result. I’ve seen the calculation done and it’s quite beautiful (but too complicated and lengthy for a blog entry). There’s no real reason for the quantization of charge without this (at least that I know of), so the fact that charge is indeed quantized is a good indicator that there is a monopole somewhere out there (maybe it did go through Palo Alto in 1984). Unfortunately for any monopole lovers, there’s probably less than one per cosmic horizon, which means your odds of finding one are just about nil.
Besides that, Grand Unification Theories and other high-level theories, such as String Theory, demand their existence. For a while, theories demanded too damn many of them, and people were concerned about why there were so few. Alan Guth’s Inflationary Cosmology did a fantastic job of explaining the small level of monopoles, which is one of the many reasons it’s so widely accepted.
I hope that now you have a decent grasp of magnetic monopoles, what they are and why they matter.
A monopole is just something with only one pole (enlightening, I know). Normal permanent magnets (or the Earth) are dipoles, they have a North and a South pole. If you cut a magnet in half you don’t get one North and one South pole, you get two smaller and weaker dipole magnets.
Imagine an electron. You probably picture it as a point in space, and you probably picture its electric field as lines pointing radially outward. That’s a monopole, an electric monopole. Now if you switch from it having electric charge to having magnetic change, you’ll have a magnetic monopole.
You might be saying right now, “Well that’s all well and good, but I’ve never seen one of the magnetic monopoles, why should I think they exist?” If you are thinking that, then you’re on to something. No one ever has seen a magnetic monopole. If you look at Maxwell’s Equations, you won’t see any magnetic charge anywhere. But Maxwell noticed that it could easily be added, but the lack of evidence for them dissuaded him from including them.
I just said that no one has seen a magnetic monopole, and this is true, in a sense. Valentine’s Day 1984, Blas Cabrera, my advisor, saw a signature on a detector that is exactly what you’d expect if a monopole had passed through. However, further experiments made it vanishingly unlikely that this was an actual monopole, and Blas will tell you it almost certainly was not. (Personally I’d like to believe it was, and I’m impressed Blas can admit that it wasn’t.)
Now you’re probably thinking, “If we’ve never seen one, why do we care about them?” That’s also a good question. It turns out that if you take quantum mechanical principles and mix them with electrodynamics, you can prove that if there exists one magnetic monopole anywhere in the universe, then both electric and magnetic charge will be quantized. This is called Dirac’s quantization, and is a pretty stunning result. I’ve seen the calculation done and it’s quite beautiful (but too complicated and lengthy for a blog entry). There’s no real reason for the quantization of charge without this (at least that I know of), so the fact that charge is indeed quantized is a good indicator that there is a monopole somewhere out there (maybe it did go through Palo Alto in 1984). Unfortunately for any monopole lovers, there’s probably less than one per cosmic horizon, which means your odds of finding one are just about nil.
Besides that, Grand Unification Theories and other high-level theories, such as String Theory, demand their existence. For a while, theories demanded too damn many of them, and people were concerned about why there were so few. Alan Guth’s Inflationary Cosmology did a fantastic job of explaining the small level of monopoles, which is one of the many reasons it’s so widely accepted.
I hope that now you have a decent grasp of magnetic monopoles, what they are and why they matter.
Labels: electromagnetism, magnetic monopoles, magnetism, physics, science
posted at
4/26/2007 09:06:00 AM
Measured Against Reality Feed
4 Comments:
The difficulty with the magnetic monopole is that, according to the Dirac theory of the electron, if a monopole existed, it would have a string of singularities tied to it which would determine a preferred direction in space and hence violate rotation invariance (and thus conservation of angular momentum).
By
Anonymous, at 7:19 AM, May 02, 2007
The Large Hadron Collider [LHC]at CERN might create numerous different particles that heretofore have only been theorized. Numerous peer-reviewed science articles have been published on each of these, and if you google on the term "LHC" and then the particular particle, you will find hundreds of such articles, including:
1) Higgs boson
2) Magnetic Monopole
3) Strangelet
4) Miniature Black Hole [aka nano black hole]
In 1987 I first theorized that colliders might create miniature black holes, and expressed those concerns to a few individuals. However, Hawking's formula showed that such a miniature black hole, with a mass of under 10,000,000 a.m.u., would "evaporate" in about 1 E-23 seconds, and thus would not move from its point of creation to the walls of the vacuum chamber [taking about 1 E-11 seconds travelling at 0.9999c] in time to cannibalize matter and grow larger.
In 1999, I was uncertain whether Hawking radiation would work as he proposed. If not, and if a mini black hole were created, it could potentially be disastrous. I wrote a Letter to the Editor to Scientific American [July, 1999] about that issue, and they had Frank Wilczek, who later received a Nobel Prize for his work on quarks, write a response. In the response, Frank wrote that it was not a credible scenario to believe that minature black holes could be created.
Well, since then, numerous theorists have asserted to the contrary. Google on "LHC Black Hole" for a plethora of articles on how the LHC might create miniature black holes, which those theorists believe will be harmless because of their faith in Hawking's theory of evaporation via quantum tunneling.
The idea that rare ultra-high-energy cosmic rays striking the moon [or other astronomical body] create natural miniature black holes -- and therefore it is safe to do so in the laboratory -- ignores one very fundamental difference.
In nature, if they are created, they are travelling at about 0.9999c relative to the planet that was struck, and would for example zip through the moon in about 0.1 seconds, very neutrino-like because of their ultra-tiny Schwartzschild radius, and high speed. They would likely not interact at all, or if they did, glom on to perhaps a quark or two, barely decreasing their transit momentum.
At the LHC, however, any such novel particle created would be relatively 'at rest', and be captured by Earth's gravitational field, and would repeatedly orbit through Earth, if stable and not prone to decay. If such miniature black holes don't rapidly evaporate and are produced in copious abundance [1/second by some theories], there is a much greater probability that they will interact and grow larger, compared to what occurs in nature.
There are a host of other problems with the "cosmic ray argument" posited by those who believe it is safe to create miniature black holes. This continuous oversight of obvious flaws in reasoning certaily should give one pause to consider what other oversights might be present in the theories they seek to test.
I am not without some experience in science.
In 1975 I discovered the tracks of a novel particle on a balloon-borne cosmic ray detector. "Evidence for Detection of a Moving Magnetic Monopole", Price et al., Physical Review Letters, August 25, 1975, Volume 35, Number 8. A magnetic monopole was first theorized in 1931 by Paul A.M. Dirac, Proceedings of the Royal Society (London), Series A 133, 60 (1931), and again in Physics Review 74, 817 (1948). While some pundits claimed that the tracks represented a doubly-fragmenting normal nucleus, the data was so far removed from that possibility that it would have been only a one-in-one-billion chance, compared to a novel particle of unknown type. The data fit perfectly with a Dirac monopole.
While I would very much love to see whether we can create a magnetic monopole in a collider, ethically I cannot support such because of the risks involved.
For more information, go to: www.LHCdefense.org
Regards,
Walter L. Wagner (Dr.)
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is complicate to predict the next event related with this theme, you know with all the problems and the many ecollogical issued that we have to solve, this problem is just one of the concequences that we have pay.
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