Magnetism is a class of physical phenomena that includes forces exerted by magnets on other magnets. It has its origin in electric currents and the fundamental magnetic moments of elementary particles. These give rise to a magnetic field. A magnetic field is a region of space near a magnet, electric current, or moving charged particle in which a magnetic force acts on any other magnet, electric current, or moving charged particle. All materials are influenced to some extent by a magnetic field. Large objects, such as the earth, other planets, and stars, also produce magnetic fields. Photograph originally captioned: Steel filings show the magnetic field around a loop carrying an electronic current.