 Electrostatic forces and magnetic forces have both been discovered over thousands of years ago. These seemingly unrelated interactions have one major similarity. That is, they both are a type of attractive or repulsive force. Our current understanding of electric forces is through electric fields, which we've just covered. So naturally, our current understanding of magnetic forces is through magnetic fields. While humanity has been aware of electric and magnetic forces for a long time, not much progress in understanding these forces was made until the 19th century. Volta's pile gave us a reliable way of producing electricity at the beginning of the 19th century in 1800. This opened up the door to test for the relationship between electricity and magnetism. However, the link proved to be elusive. It took 20 years and many experiments until an accidental discovery finally unified electricity and magnetism into electromagnetism. This accidental discovery was made by Hans Christian Erstedt on the 21st of April in 1820. While setting up an experiment for an evening lecture, he noticed the deflection of a compass needle when an electric current was run through a wire. Prior to this discovery, compass needles have only been known to react to other magnetized objects. Running a current through a wire made the needle turn, indicating that there was a magnetic field due to the electric current. We know that charges generate an electric field, and Erstedt's discovery can be summarized by moving charges generate a magnetic field. A current is comprised of lots of moving charges, so we generally say a current creates a magnetic field. Hans Christian Erstedt demonstrated that a compass points tangential to the magnetic field at every point, and that it would point in opposite directions when placed on opposing sides of the current, which is a fancy way of saying that the magnetic field is circular. We'll look at this magnetic field in later videos. After this revelation, Erstedt left this discovery for a few months before returning to investigate it further. His notes on how exactly he made this discovery was also incomplete, which has left an unfilled hole in scientific history. He also never quantified the strength of the magnetic field around the current. Due to these events, Erstedt is mostly forgotten to history these days, with names like Ampere and Maxwell that are much more synonymous with electromagnetism.