Hans Christian Orsted

Hans Christian Orsted was a Danish physicist and chemist who in 1820 discovered that an electric current flowing through a wire deflects a nearby compass needle, demonstrating for the first time that electricity and magnetism, until then treated as entirely separate phenomena, are physically connected. This result, now known as Oersted's law, showed that a moving electric current generates a magnetic field around itself, and it launched the new field of electromagnetism, directly inspiring the more complete mathematical treatments of the electricity-magnetism relationship soon developed by Andre-Marie Ampere and others and, much later, the unified theory of electromagnetism built by James Clerk Maxwell. Orsted also carried out chemical research, and in 1824 he was the first to produce metallic aluminium, though only as a small, impure sample, several years before Friedrich Wohler achieved a purer isolation of the element. Orsted is additionally credited with coining the term thought experiment, used to describe a reasoned hypothetical scenario worked through mentally rather than physically carried out, a concept and phrase that became widely used across science and philosophy.