H. C. Ørsted (1777-1851)

1. H. C. Ørsted (1777-1851) Highlights of Ørsteds Life and Pioneering Works Prologue. Hans Christian Ørsted was born on 14 August 1777 in Rudkøbing, a small city at the small Danish island ”Langeland”. He was the first of 8 children of the chemist Søren Ørsted and his wife Karen. Hans Christian in 1797 passed the final University examination for the pharmaceutical degree and only 2 years later he became doctor of philosophy on a thesis with the title ”Basic features of the metaphysics in nature”. Earlier, in 1798, he had earned a gold medal reward from Copenhagen University for a dissertation on ”The origin and benefit of amniotic fluid”. In 1800 he started as lecturer in physics at the University. Foundation of Danish Technical University Through the initiative from H.C. Ørsted the Polytechnical High School (Technical University) was founded in 1829. He became its first director. In the charter for the institution the first article reads: §1.”The Polytechnical High School opens for all estates the access to education and excercise in mathemathics and experimental natural sciences with paricular emphasis on applications”. Here he conducted many physics experiments for the students and constructed a range of elaborate instruments. Travels around in Europe. In 1801-04 Hans Christian Ørsted traveled to Germany (Berlin) and France (Paris) and established profound contact with the european scientific communities. He was strongly influenced by the romantic philosophy and developments in natural sciences at that time. At his return to Copenhagen he continued teaching and was in 1806 appointed extraordinary professor at Copenhagen University. In these years he was strongly inspired by the appearance of sonorous (Chladni) figures formed in fine grane dispersed at a plate stroken by the bow. Such experiments whereby musical tones were converted into stringent mathematical shapes indicated to Ørsted the beauty and unity in nature and science and gave inspiration to some of his significant philosophical works. H. C. Ørsted and J. C. F. Gauss In 1834 H.C. Ørsted visited J. C. F.Gauss (1777-1855) in Göttingen and studied the geomagnetic instruments and the measuring methods developed there. Among other he noted an instrument consisting of a heavy (4 pound) magnet bar suspended in a silk wire. At the magnet bar was mounted a mirror which in combination with a light beam and a distant display will allow for sensitive detection of attitude changes. First geomagnetic observations Upon his return he had made a geomagnetic observatory with similar instrumentation at the Polytechnical High School and used students to regularly observe the deflections. Through comparison of simultaneous recordings made in Copenhagen and Milano (at 1100 km’s distance) he discovered that during a magnetic storm the deflections at these widely separated sites had the same appearance. This observation was published in ”Magnetiske Iagttagelser i Kjøbenhavn”. (1834-35) Inspiration from Germany and France. H.C. Ørsted was also strongly interested in physics and chemistry. In 1812-13 he again made a study excursion to Germany and France and was deeply impressed by the new trends in experimental physics which were developing there, particularly at the ”Polytechnical Universities” in France. During the stay in Germany he issued a dissertation ”Ansicht der chemischen Naturgesetze.” (Berlin 1812) which caused strong attention in the scientific community. In France he published his ideas in ”Recherches sur l’identité des forces chimiques et électriques” (Paris 1813). Two essential theories were forwarded in this work. One was a postulate that electricity can generate magnetism; the other was a postulate that light is electrical oscillations. Both were revolutionary and in strong contrast to the commonly agreed Laplacian concept that light, heat, electricity, and magnetism were different independent agents. At this time Ørsted had no experimental evidence to support the hypotheses. Routine Geomagnetic observations In 1842, on H.C. Ørsteds initiative a geomagnetic observatory was built at ”Gyldenløves Bastion”, one of the fortresses in the fortification of Copenhagen. Routine observations of the magnetic declination and field strength were performed from this location through more than 20 years. The observations were moved to ”Rosenborg Bastion” in 1862 but then they ceased and were stopped for some years. In 1889 a new magnetic observatory was built by the Danish Meteorological Institute and the routine geomagnetic observations were resumed by DMI in 1891 to continue the work initiated by H.C. Ørsted. Aurora and magnetism Auroras are occasionally observed from Denmark. During the first solar maximum in 1705-06 following the extended Maunder minimum around 1600-1700 a number of large magnetic storms occurred during which auroras were observed from Copenhagen. Drawings of the aurora were made by the Danish astronomer Ole Rømer (1640-1710). Later in the century Olof Peter Hiorter (1696-1750) observed the relations between active auroral displays and geomagnetic disturbances. The connection between aurora and magnetism was further substantiated by the works of Christopher Hansteen (1784-1873), professor at the University of Christiania (Oslo), Norway. Discovery of Electromagnetism. In April 1820 during a lecture given to students at the University of Copenhagen Ørsted observed the effect from electric currents in a wire on a compas needle. In June 1820, 3 months later, he repeated the experiment in presence of official vitnesses. When the electric current in a wire held over a compas needle was turned on then the needle was deflected to the side. The electromagnetic effect was discovered. H.C. Ørsted published his observation in the paper: Experimenta circa effectum conflictus electrici in acum magneticam. (Hafniæ 1820). Ørsteds Compass Ørsteds Contribution to Auroral Research H.C. Ørsted was interested in auroras and aware of the magnetic effects from aurora. He suggested in 1824 that the magnetic variations observed during auroras could be caused by electrical currents in the upper atmosphere along the auroral curtains. His theory, which at that time was revolutionary, was published in ”Bemærkninger over Nordlysets Theorie” (1823-24) [Reflections over the theory of auroras] Aurora observed over Copenhagen on 1 February 1707. Drawing by Ole Rømer. H.C. Ørsted and Meteorology Ørsted had a profound interest in Meteorology. In 1827 the Danish Royal Society for Science and Letters, on Ørsteds initiative, founded a permanent ”Meteorological Committee”. The Committee encouraged meteorological sciences and initiated meteorological observations at various places in Denmark and in the Danish oversea colonial territories. H. C. Ørsted issued several publications on meteorological topics, among other, ”Over Skypompen” (Copenhagen, 1836) [”Above the waterspout”]. Ørsteds Barometer and Thermometer Ørsteds setup to demonstrate the magnetic effect of electric currents H.C. Ørsted Painting A painting of Ørsted made by the renowned Danish painter Eckersberg now resides at the National Museum at Frederiksborg Castle in Hillerød. In the painting is included reference to some of the most important accomplishments by H.C. Ørsted. In the foreground to the right is seen a compass with an electrical wire stretched across it. At the table to the left is seen a plate with sonorous figures. In the background is seen the instrument used for compressional experiments and some chemists tubings. The globe may symbolise Ørsteds interest in geography and geomagnetism and his many travels to other European countries. The pile of books just behind his arm may signal his immense scientific publication activity. It is worth noting that H.C. Ørsted mastered German, French, English and Latin (in addition to Danish) and wrote his many publications in any of this variety of languages. Important Experimental Works H.C.Ørsted conducted many experiments to study the chemical and physical nature of various elements and compounds. •He studied the compressibility of fluids and gases through a series of comprehensive and accurate experiments published e.g. in: ”Ueber die Zusammendrückung des Wassers. (Copenhagen 1817), ”On the relative compressibilities of different fluids at high temperatures” (1827) •Ørsted studied the electricity from galvanic elements, e.g.: ”Versuch über Zamboni’s zweigliedrige galvanische Kette” (Copenhagen 1821), and thermoelectricity, e.g., ”Thermo-electricity”. (Copenhagen 1830) •In 1925 he produced the worlds first sample of Aluminium metal from Alumina (Clay soil) and published his results in: Vorläufige Notiz über die Darstellung des Argillium, des Chlor-Argillium und Chlor-Silicium. (Copenhagen 1825) Ørsteds Piezometer Peter Stauning. Danish Meteorological Institute. September 2002. pst@dmi.dk