What did William Gilbert discover about the earth and its magnatism?

William Gilbert, in his seminal work "De Magnete" published in 1600, discovered that the Earth behaves like a giant magnet, with magnetic poles similar to those of a bar magnet. He proposed that the Earth’s magnetic field is generated by its rotation and its internal structure, laying the groundwork for the science of geomagnetism. Gilbert's research also distinguished between magnetism and static electricity, significantly advancing the understanding of magnetism in both natural and artificial materials.