Transcript Document

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.
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.
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.
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).
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.
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)
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.
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., ”Thermoelectricity”. (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 ChlorArgillium und Chlor-Silicium. (Copenhagen 1825)
Ørsteds Piezometer
Peter Stauning. Danish Meteorological Institute. September 2002. [email protected]