Portrait of Hans Christian Oersted, a Danish physicist, 1777-1851. Oersted studied physical science and pharmacy in Copenhagen, where he later became professor of physics. In 1820 he showed that the needle of a magnetic compass is deflected when electric current passes through a wire close by. In retrospect his experiment is seen as the foundation of the study of electromagnetism. His discovery was published in 1820, and resulted in a whirl of activity in the field of physics. In 1934 a unit of magnetic field strength was named the oersted in his honour. He also obtained the first accurate value for the compressibility of water.