"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 Two papers are being published today in the journal Science and two more on arXiv.org, as yet unpublished, provide further evidence.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 The two, as yet unpublished, papers on arXiv add to the evidence.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."

Comments

not a "real" monopole

[anarchyboy]

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.

Re:Analogy

[gardyloo]

Are there any applications for it within our understanding of physics?

The existence of monopoles is a possible "explanation" for the quantization of electric charge. Maxwell's Equations are only self-consistent if:
            1. magnetic monopoles don't exist, and charge is not quantized;
OR
            2. magnetic monopoles do exist (at least one, somewhere), and charge is quantized.

As charge is quantized, it has always been a strong argument for monopoles' existence. Of course, perhaps Maxwell's Equations aren't applicable at the quantum level, but so far they've done a damned good job of being consistent and predicting and explaining things.

Re:why a monopole implies perpetual motion

[Chris Burke]

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.