Short answers, pulled from the story.
Petrus Peregrinus de Maricourt first visualized the structure of a magnetic field in 1269. He performed an experiment using a spherical magnet and iron needles to map the field lines crossing at two points he named poles.
The Earth's magnetic field is produced by the convection of a liquid iron alloy in its outer core creating a dynamo process. The most recent reversal of this field occurred 780,000 years ago.
Hans Christian Ørsted discovered that electricity and magnetism are related in 1820. He demonstrated that a current-carrying wire is surrounded by a circular magnetic field proving that moving electric charges generate magnetic forces.
James Clerk Maxwell developed and published his famous equations between 1861 and 1865. His first set of equations appeared in a paper entitled On Physical Lines of Force in 1861 and were completed in his 1865 paper A Dynamical Theory of the Electromagnetic Field.
Nikola Tesla received a patent for his electric motor in May 1888. He claimed to have conceived his work on rotating magnetic fields in 1882 and gained patents for this work just two months after Galileo Ferraris published his research.
Magnetars have the strongest known magnetic fields of any naturally occurring object ranging from 0.1 to 100 gigatesla. These fields measure between 10 to the 8 and 10 to the 11 tesla and can distort the electron clouds of atoms.