The Earth itself behaves like a giant magnet (represented in the image), with the magnetic north and south poles situated close to the geographic poles. The magnetic field that is formed is strong enough to protect us from the hazardous solar wind particles and disastrous effects of solar flares.
Magnetism is the force exerted by the electrons (negatively charged ions) of a magnet. It is the force, by which metallic elements like iron attract or repel each other. It also can be defined as the force between electric currents, which attracts when they are parallel to each other, and repels when they are in opposite directions.
Each magnet has two poles: north-seeking and south-seeking poles. The magnetic strength is maximum at these points. If a magnet is freely suspended, it automatically aligns itself in the north-south direction. The two 'like' poles (N-N) of the magnets repel each other, and the 'unlike' poles (N-S) attract each other. Other than iron, there are many other materials like nickel and cobalt that get magnetized when placed in a magnetic field.
History of Magnets
The word magnetism is derived from a region called Magnesia in Asia Minor (Crete in Greece), where a naturally magnetic iron ore lodestone or magnetite (iron ferrite Fe3O4 was found by a shepherd called Magnes around 4000 years ago. He was walking while herding his sheep, and on a particular spot, he observed that his iron staff was getting attracted towards a strange looking black colored stone. This rock was named as magnetite after his name 'Magnes', and probably, this is how the study of magnetism started. This mineral comprised iron oxide (a chemical compound of iron and oxygen, or Fe3O4), and is even called ferric ferrite or iron ferrite.
In the 6th century B.C., a Greek philosopher called Thales was credited with the discovery regarding the theory of magnetism. He was a great researcher and he studied the forces of attraction between magnets and resin amber. Around 500 B.C., an Indian surgeon called Sushruta started using magnets in surgical procedures.
According to another story, the legendary Greek researcher called Archimedes used the property of magnetism to destroy enemy vessels. This was made possible by removing the enemy ships' metallic parts that were a part of the hull, in order to make them sink in the water.
The ancient Chinese are also considered as one of the pioneers of research studies regarding magnetism. In the 11th century, Shen Kuo, a Chinese scientist wrote a book that described the working of a magnetic compass needle.
In 1600, an Englishman called William Gilbert was the first to systematically research on the phenomenon of magnetism by using several scientific methods. He first came up with the theory that Earth itself behaved like a giant magnet, and also experimentally confirmed that on heating of a magnet, there is a gradual decrease in its magnetic field strength. Early theoretical investigations on the Earth's magnetism were performed by the German scientist called Carl Friedrich Gauss, in the early 19th century.
During the eighteenth century, the quantitative studies of magnetism phenomenon were started by Frenchman Charles Coulomb. He developed the inverse square law of force, which states that 'the force of attraction between two magnetized objects is directly proportional to the product of their individual fields, and inversely proportionate to the square of the distance between them'.
Hans Christian Oersted, a Danish physicist, was the first to suggest a relation between electricity and magnetism. Many experiments focusing on the effects of magnetic and electric fields on each other were performed by Andre Marie Ampere and Michael Faraday. But in the nineteenth century, James Clerk Maxwell provided the theoretical foundation to the physics of electromagnetism, proving that magnetism and electricity represent different aspects of the same fundamental force field. In the late 1960s, Steven Weinberg and Abdus Salam conducted theoretical synthesis of the fundamental forces, by proving that electromagnetism is a part of the electroweak type of force.
The modern understanding of magnetism in condensed matter originated from the work of two Frenchmen: Pierre Curie and Pierre Weiss. Curie analyzed the effect of temperature on different magnetic materials, and noticed that the magnetism disappeared suddenly beyond a certain critical temperature (Curie point) in materials like iron. Weiss suggested a theory of magnetism, which was based on an internal molecular field that was proportional to the average magnetization, which immediately align the electronic micro-magnets in a magnetic matter. The present day magnetism phenomenon, which depends on the theory of the motion and interactions of electrons in atoms, came from the work and theoretical models of two Germans: Ernest Ising and Werner Heisenberg.
Until 1821, only one kind of magnetism was known, which was generated by iron magnets. But today, the characteristics and applications of magnetism are well-known in the field of science and technology. New concepts like study of magnetism in organic matter and diamagnetism continue to be the areas of interest for many physicists and scientists.