You have possibly heard of the Higgs boson. This indefinable particle was expected to exist long ago and helped clarify why the Universe works the way it does, but it took years for us to discover. Well, there is another indefinable particle that has also been expected by quantum physics, and it has been absent for an even longer time. In fact, we still have not discovered one, and not through lack of trying. It is known as the magnetic monopole, and it has a little unique property that makes it pretty special.
Those with curiosity in physics are possibly already familiar with an electric monopole, though you may know it by its more famous name: electric charge. Opposite electric charges attract and similar electric charges repel through the interaction of electric fields, which are well-defined as moving from positive to negative. These are the somewhat random labels for the two opposite electric charges. Electric monopoles occur in the form of particles that have a positive or negative electric charge, just like protons or electrons.
At first glimpse, magnetism looks somewhat comparable to electricity, as there exists a magnetic field with a direction defined as moving from north to south. Though, the similarity breaks down when we try to discover the magnetic matching part for the electric charge. Although we can find electric monopoles in the form of charged particles, we have never witnessed magnetic monopoles.
As an alternative, magnets are present only in the form of dipoles with a north and a south end. When a bar magnet is divided into two pieces, you do not get a discrete north part and a south part. In fact, you get two new, smaller magnets, both with a north and south end. Even if you divided that magnet down into single particles, you still develop a magnetic dipole. When we look at magnetism in the world, what we see is completely stable with Maxwell’s equations, which define the alliance of electric and magnetic field theory into traditional electromagnetism.
They were originally published by James Maxwell throughout 1861 and 1862 and are still used every day on a practical level in engineering, telecommunications, and medical uses, to name just a few. But one of these equations, Gauss’s law for magnetism, says that there are no magnetic monopoles.
The magnetism we detect on a day-to-day basis can all be ascribed to the movement of electric charges. When an electrically charged particle moves along a track, just like as an electron moving down a wire, this is an electrical current. This makes a magnetic field that wraps all over the place, in the direction of the current. The second reason of magnetism includes a property from quantum mechanics called 'spin'. This can be supposed of in terms of an electrically charged particle revolving on an axis rather than moving in a specific direction. This produces an angular momentum in the particle, making the electron to act as a magnetic dipole (which is a small bar magnet). This means we can explain magnetic spectacles without the need for magnetic monopoles. But just for the reason that our classical electromagnetic theories are reliable with our explanations, that does not indicate that there are any magnetic monopoles.
Once we begin to explore the gloomy depths of theory, we start to find some attractive arguments for their existence in the Universe. In 1894, Nobel Laureate Pierre Curie debated the possibility of such an undiscovered particle and could find no cause to markdown its existence. Later, in 1931, Nobel Laureate Paul Dirac presented that when Maxwell’s equations are stretched to contain a magnetic monopole, electric charge can occur only in discrete values. This 'quantisation' of electric charge is one of the necessities of quantum mechanics. So Dirac’s effort went towards presenting that classical electromagnetism and quantum electrodynamics were well-matched theories in this logic.
Finally, there are few scientists who can struggle the beauty of regularity in nature. And because the reality of a magnetic monopole would indicate a duality between electricity and magnetism, the theory signifying magnetic monopoles turn into almost intoxicating.
Duality, in the physical sense, is when two dissimilar theories can be connected in such a way that one system is parallel to the other. If it were the situation that the electric force was totally similar to the magnetic force, then possibly other forces would also be similar to one another. Perhaps then there would be some method to relate the strong nuclear force to the weak nuclear force, paving the way to an outstanding alliance of all physical forces. Just because a theory has an interesting regularity does not make it correct.
An individual magnetic monopole might be hiding out there somewhere. Credit: CERN/MoEDAL
Researchers have come close to seeing magnetic monopoles by creating monopole-like structures in the laboratory using difficult arrangements of magnetic fields in Bose-Einstein condensates and super-fluids. But, though these indicate that a magnetic monopole is not a physical impossibility, they are not the similar as finding out one in nature. Particle physics researchers have, on occasion, declared possible monopole candidates, but so far no one of these discoveries has been revealed to be undisputable or reproducible.
The Monopole and Exotics Detector at the Large Hadron Collider (MoEDAL) has taken up the exploration but has found no monopoles to date. As a result, magnetic monopole devotees have turned their visions to explaining why we have not discovered any monopoles. If the current generation of particle accelerators have failed to identify a magnetic monopole, perhaps the mass of a monopole is only greater than we are able to create at present-day. Using theory, we can guess the maximum probable mass for the magnetic monopole. Given what we already know about the arrangement of the Universe, we can estimate that the monopole mass could be up to a massive 1014 TeV.
An object this huge may have been formed only in the very first stages of the Universe after the Big Bang before cosmic inflation started. If the Universe cooled to a time that monopole creation was no longer vigorously possible before increasing, perhaps the monopoles are out there. Just a few and far between. The trick is to discover one.
This article was initially published by The Conversation.