Magnetism

Magnetism is the capacity to induce attractive and repulsive phenomena in a magnetic field created by electric currents. Magnetism and electricity make up the combined phenomena of electromagnetism. Ferromagnetic materials such as iron, cobalt, and nickel can be magnetized to become magnets, producing magnetic fields themselves.

Some organisms can detect magnetic fields, a phenomenon known as magnetoception. Some materials in living things are ferromagnetic. Chitons, a type of marine mollusk, produce magnetite to harden their teeth, and even humans produce magnetite in bodily tissue. Magnetobiology studies the effects of magnetic fields on living organisms; fields naturally produced by an organism are known as biomagnetism..

History
Magnetism was first discovered in the ancient world when people noticed that lodestones, naturally magnetized pieces of the mineral magnetite, could attract iron.

An understanding of the relationship between electricity and magnetism began in the 1800s with Ørsted, Ampère, Gauss, and Faraday. Then James Clerk Maxwell unified electricity, magnetism, and optics into the field of electromagnetism. In 1905, Albert Einstein used these laws in motivating his theory of special relativity. Only when both electricity and magnetism are taken into account, is electromagnetism fully consistent with special relativity. Perturbations in the magnetic field propagate at the speed of light.

Magnetic dipoles
A common magnetic field found in nature is a dipole, with a "South pole" and a "North pole", dating back to the use of magnets as compasses. Since opposite ends of magnets are attracted, the north pole of a magnet is attracted to the south pole of another magnet.

Magnetic monopoles
With the new laws of physics, a monopole was a new and fundamentally different kind of magnetic object. It would act as an isolated north pole, not attached to a south pole, or vice versa. Monopoles would carry "magnetic charge" analogous to electric charge.