Hans Christian Ørsted (August 14, 1777 – March 9, 1851) was a Danish physicist and chemist, influenced by the thinking of Immanuel Kant. He is best known for discovering the relationship between electricity and magnetism known as electromagnetism. In April 1820 he noticed a compass needle deflected from magnetic north when the electric current from the battery he was using was switched on and off. This deflection convinced him that magnetic fields radiate from all sides of a live wire just as light and heat do. The CGS unit of magnetic induction (oersted) is named in honor of his contributions to the field of electromagnetism.