[Relationship between Copenhagen and Göttingen regarding earth magnetism]

Hans Christian Oersted is mostly known as the discoverer of electromagnetism and for being one of the physicists who were deeply influenced and fascinated by the romantic natural philosophy. In this article another side of Oersted is presented. What is underestimated until now is Oersted's contribution to the research of geomagnetism. Oersted stood in close contact with Carl Friedrich Gauss and Wilhelm Weber, whom he visited in 1834 in Göttingen. Oersted's aim was to learn the new developments in geomagnetism. Afterwards he was crucial in the building of a new magnetic observatory in Copenhagen as well as a second one with better equipment. Oersted formed a huge team for magnetic observations and the gathered data were sent to Gauss and Weber who published them. The correspondence between Oersted, Gauss and Weber was mostly dedicated to the transmission of these data, details about instruments and the best way of building a magnetic observatory. Unfortunately, Gauss and Weber had to stop their very successful collaboration in 1843, because Weber belonged to the Göttingen Seven and later on Oersted stopped his observations, because he had lost his partners in this research project.