Hans-Christian ØrstedUnification of the fundamental forces is one of the big, recurring themes of theoretical physics: How to merge gravity with the rest of the standard model of particle physics? What is the GUT for the strong and electroweak force? Salam, Glashow and Weinberg were awarded the Nobel prize for the unification of electromagnetism with the weak interaction. We take so much for granted the idea that there should be a unified description of the forces of nature that it's hard to imagine that when physics started to be the science we know today, even electricity and magnetism were considered as completely disparate phenomena.
In April 1820, Hans-Christian Ørsted, professor at Copenhagen University, prepared an experiment he wanted to demonstrate to the students in his lecture class. His intention was to show how an electric current through a wire, created by the electric voltage supplied by a Volta-type pile, heats up the wire and lets it glow. By chance, a magnetic compass was standing close to the wire, and Ørsted noted that the needle of the compass was deflected when the current was switched on. Ørsted was magnetised. He didn't have time to have a closer look at this phenomenon immediately, but three months later, he sent a detailed four-page report about his discovery, written in Latin, to colleagues all over in Europe, Experiments on the Effect of a Current of Electricity on the Magnetic Needle. He had found a connection between electricity and magnetism, by quite a peculiar force pointing not along the direct line connecting the current and the needle, but perpendicular to it.
Hans-Christian Ørsted was the son of a pharmacist. He studied pharmacy, chemistry, physics and philosophy at the University of Copenhagen where he became a professor in 1806. Before, he had spent three years travelling and studying in Europe. In Germany, he was deeply influenced by Johann Ritter, best known today as the discoverer of ultraviolet light. Ritter was a proponent of the German "romantic natural philosophers" of that time, who were deeply sceptical about the Baconian method of doing science by isolating and dissecting natural phenomena in experiment. Instead, these thinkers believed in a deep unity of all nature, and a balance between the attracting and repulsive aspects of a single force responsible for all phenomena. a physicist who believed there was a connection between electricity and magnetism. As Ritter, Ørsted had speculated that galvanism and magnetism had one common cause in the motion of some fluid. Hence, in fact, Ørsted was not completely surprised by his discovery, since he had thought much about such a relation before.
Ørsted was a man with many facets. As a professor in Copenhagen, he continued his research with electric currents and acoustics, developed a comprehensive physics and chemistry program for the University, established new laboratories, and discovered the element aluminium. But he was also interested in language and literature, wrote poems, and was a close friend to Hans-Christian Andersen, the author and poet most famous for his collection of fairy tales.
Hans-Christian Ørsted was born 230 year ago today, on August 14, 1777.
Skål, Hans-Christian Ørsted!
- There is a beautiful web site about Ørsted, albeit in French, L'expérience de Hans-Christian Œrsted (1820), with biographical details, information about the experiment and its reception, and scans of Ørsted's original Latin report, Experimenta circa effectum conflictus electrici in acum magneticam, as well as the English and French translations, published as Experiments on the Effect of a Current of Electricity on the Magnetic Needle (Annals of Philosophy 16 (1820) 273-277) and Expériences sur l'effet du conflict électrique sur l’aiguille aimantée (Annales de chimie et de physique 14 (1820) 417-425), respectively.
- More background about the German tradition of "Naturphilosophie" in the early theories on electricity, including Ritter and Seebeck, can be found in The Form and Function of Scientific Discoveries, the Dibner Library Lecture by Kenneth L. Caneva at the Smithsonian Institution Libraries, November 2000
- A detailed account of the circumstances of the discovery of electromagnetism by Ørsted is given in (subscription required) Chance in Science: The Discovery of Electromagnetism by H.C. Oersted by Nahum Kipnis, Science and Education 14 (2005) 1-28, doi: 10.1007/s11191-004-3286-0.
TAGS: physics, Ørsted, electromagnetism