Humans have long known of the existence of magnetic forces. Compasses relying on the magnetic field of the earth have been used for centuries as navigational aids. Until the nineteenth century, however, the cause and source of magnetic fields remained a mystery. Even after scientists began to learn about magnetism, the field remained complete separate from the study of electricity; at the time, it seemed inconceivable that the two could be related in any way. The connection between the two, and the resultant study of electromagnetism, is quite counterintuitive. For this reason, it is important to learn a little history of the development of magnetism before diving into the physical theory behind the complex phenomenon.
We begin by going through the history behind the discovery of the relation between electricity and magnetism, and then examine some basic principles of magnetic fields that can be derived from these early experiments. Next, we'll take a theoretical approach to the topic, deriving the existence of magnetic fields from the study of relativity.
Through these two methods we'll gain an important qualitative understanding of the topic before delving into it.