The history of physics and astronomy

The history of physics

Magnetometer for earth-field measurements built by Weber in about 1885

The history of physics at Bonn University starts with Julius Pluecker, who worked here from 1836 to 1869. His work on gas discharges laid the fundament for spectroscopic investigations of atoms and molecules. Together with his assistant, a glass blower, he invented the Geissler tubes.

Pluecker was succeeded by Rudolf Claudius (1869 - 1888), a theorist whose work on thermodynamics, in particular on the concept of entropy, is well known even today. Next came Heinrich Hertz (1889 - 1894), for whom the unit of frequency is named. His discovery of electromagnetic waves was the basis for technological developments from radio and radar to TV and mobile phones. Tragically, Hertz died at age 36, of blood poisoning.

Gas discharge tubes from about 1850

In the next 50 years (Heinrich Kayser, 1894 - 1920; Heinrich Konen, 1920 - 1934; Christian Fuechtbauer, 1935 - 1945) physics at Bonn University was dominated by spectroscopy, which became the most important tool to investigate the dynamics of atoms and molecules. Methods developed here also found their way to industry, where spectroscopy was (and still is) used to identify ingredients of materials.

Ion trap from Wolfgang Paul

A new era began after the end of World War 2, when Wolfgang Paul (1952 - 1981) became director of the Physics Institute. He continued to work on atomic and molecular physics; in particular, his "Paul trap" for the capture of single ions in 1989 earned him the Nobel Prize in physics. Paul also introduced high energy physics to Bonn University. He supervised the construction of a 500 MeV electron synchrotron, which was the first accelerator capable of producing mesons at a German university. Its modern successor is ELSA, which is used today to investigate the dynamics of baryons. However, the "energy frontier" can nowadays only be explored with accelerators which are far too large and too expensive to be built and operated at a university. Experimental particle physicists from Bonn University therefore now also work at laboratories dedicated to high energy physics, such as DESY in Hamburg, CERN near Geneva, and Fermilab near Chicago.

Gold foil electrometer built by Hankel in about 1900

During the 1950s additional physics institutes were founded at Bonn University. The institute for nuclear and radiation science (now HISKP) built and operated a cyclotron. This was later turned into an isochron cyclotron by Erwin Bodenstedt (1962 - 1991) and Theo Mayer-Kuckuk (1965 - 1992), and used to explore nuclear reactions. It is now chiefly used for nuclear physics based solid state physics experiments.

Rudolf Jaeckel (1955 - 1963), the founding director of the Institute for Applied Physics (IAP), did seminal work on vacuum systems, which are indispensable e.g. for high energy accelerators. His successor Siegfried Penselin (1963 - 1992) introduced lasers to the IAP, which remain the most important research tools there; lasers also play increasingly important roles in technological fields from consumer electronics (CDs, DVDs) to communications (optical fibres).

Parabolic antenna built by Heinrich Hertz in about 1890

Up to the 19th century, physicists often did both theoretical and experimental work. For example, Heinrich Hertz calculated the electromagnetic fields around dipole antennas, one of the best-known results of classical electrodynamics. On the other hand, Walter Weizel (1936 - 1969), who first did theoretical work on the quantum theory of molecular spectra, later turned to experiment, and investigated gas discharges, thereby connecting back to Pluecker's work. The first pure theorist at Bonn University was the nuclear physicist Konrad Bleuler (1960 - 1980), whose work on the quantization of the electromagnetic field remains well known today. In the wake of the construction of the electron synchrotron, the particle theory group was greatly strengthened. Today research in theoretical physics at Bonn University runs the gamut from many-body and solid state physics over nuclear and hadron physics to the physics of elementary particles.

The history of astronomy

Astronomy was established in Bonn with the nomination of Friedrich Argelander (1836). He founded the "Sternwarte" at the "Poppelsdorfer Allee", which started operating in 1845. His great achievement was the "Bonner Durchmusterung" (the BD), a catalogue with accurate positions and brightness of some 300,000 stars of the northern hemisphere, including maps. Since then the stars listed have a name starting with BD. He and his successor were active in the hunt to find nearby stars and at some point more than half of the parallactic stars known were found from Bonn.

With the nomination of Kaestner (1899) a period of renewal set in. A "double refractor" was purchased, a 5m long lens telescope fit to determine very accurate star positions. The goal was to investigate star clusters to find motions of their stars to trace their kinematics. He continued the tradition of studies of the structure of the Milky Way. The photographic plates taken then are still valuable first records of the astronomical sky at that time.

In 1947 Becker became the director of the Sternwarte. He took on the modernization of the institute. He established in 1953 a new Observatory at the "Hoher List" in the Eifel mountain range with plenty of dark sky. The telecopes were moved there and a 1m reflector telescope was added. In the mean time radio astronomy developed and a telescope was built at the "Stockert" (1956) leading to the creation of the Radioastronomical Institute in 1962. The success of radio astronomy also led to the planning of a large telescope, for which the "Max Planck Institute for Radioastronomy" was established in 1966. It set out to build and operate the 100m Radiotelescope at Effelsberg. The exploration of space resulted in the foundation (1964) of the Institute for Astrophysics and Extraterrestrial Research.

Modern astronomy uses data from all ranges of the electromagnetic spectrum. In Bonn, the infrared, the ultraviolet and the X-ray domain are, in addition to data of optical nature, actively included in the research. Research covers stars and star clusters, galactic structure, structure of galaxies, cosmology, interstellar and intergalactic matter, star formation and stellar dynamics. Since astronomy does not work any more in a compartmentalized manner, the astronomy institutes of the university merged in 2005 into the "Argelander Institute for Astronomy"