Two essential factors which led to the founding of the
Physikalisch-Technische Reichsanstalt (Imperial Physical Technical Institute – PTR) were the determination of internationally valid, uniform measures in the
Meter Convention of 1875 and the dynamic industrial development in Germany in the 19th century. Already in the Franco-German War (1870/71), the stagnation in scientific mechanics and in the science of instruments had become evident in Germany. Increasingly precise metrology was required for industrial production. A considerable impact on the initiative for the founding of a state institute for metrology in order to promote the national interests of the economy, of trade and of the military was made – in particular – by the upcoming electrical industry under the direction of the inventor and industrialist
Werner von Siemens. In contrast to the units of length and weight, no recognized methods and standards existed at that time in the field of electrical metrology. The lack of reliable and verifiable measurement methods for the realization of electrical (and other) measurement units was a pressing scientific and economic problem. In 1872, some Prussian natural scientists joined forces and demanded the establishment of a state institute in order to solve this problem. The reason for this was that such a task was scientifically too ambitious for industrial laboratories and, in addition, not profitable for them, and classical training institutes were not suited for the task either. Among the supporters of the "Schellbach Memorandum" (named after its author Karl Heinrich Schellbach) ranked, among others,
Hermann von Helmholtz and the mathematician and physicist
Wilhelm Foerster. Prussia, however, initially rejected their demands. Not until some years later were Werner von Siemens and Hermann von Helmholtz, the "founding fathers" of the PTR, able to make their vision – the establishment of a research institute which was to link scientific, technical and industrial interests in an optimal way – come true. Finally, on 28 March 1887, the Imperial Diet approved the first annual budget of the PTR – the founding of the first state-financed, university-external, major research institution in Germany which combined free fundamental research with services for industry. Werner von Siemens ceded private land in
Berlin-Charlottenburg to the Reichsanstalt. Hermann von Helmholtz became its first president. At that time, 65 persons were employed at the PTR – among them more than a dozen physicists – who disposed of a budget of 263,000 Reichsmarks. In its first decades, the PTR succeeded in attracting important scientists and members of the Kuratorium as employees, among them
Wilhelm Wien,
Friedrich Kohlrausch,
Walther Nernst,
Emil Warburg,
Walther Bothe,
Albert Einstein and
Max Planck.
Birth of quantum physics The first outstanding scientific achievement at the PTR was also closely connected with Max Planck. To decide whether electricity or gas would be more economic for street lighting in Berlin, the PTR was to develop a more precise standard for luminous intensity. For this purpose, in 1895,
Otto Lummer and
Wilhelm Wien developed the first
cavity radiator for the practical generation of thermal radiation. Their measurements of the spectrum of the black-body radiation were so precise that they contradicted
Wien's radiation law at long wavelengths. This caused one of the cornerstones of classical physics of that time to totter. The measurements prompted a decisive impulse on the part of Max Planck to divide thermal radiation – in an "act of despair", as he later declared – into separate portions. This was the birth of quantum physics.
New structure and new physics In 1914, the PTR President
Emil Warburg discontinued the subdivision into a physical and a technical division and re-structured the PTR into divisions for optics, electricity and heat, with sub-divisions of a purely scientific and technical nature. Under Warburg's successor
Walther Nernst, the Reichsanstalt für Maß und Gewicht (Imperial Institute for Weights and Measures – RMG) was, in addition, integrated into the PTR. A newly established division took over from the RMG extensive tasks with regard to the verification system as well as the measurements of length, weight and volume associated with the verification system. The profile of tasks was thus similar to that of PTB today: Through its own research and development, and through services building on this, the PTR was to ensure the uniformity of metrology and its continuous further development. As regards contents, the PTB was dedicated at that time to the so-called
New Physics. This included, among other things, research on the newly discovered X-rays, new atomic models, Einstein's Special Theory of Relativity, quantum physics (based on the already mentioned work on the black-body radiator), and the investigation of the properties of the electron. Scientists like Hans Geiger, who established the first radioactivity laboratory of PTR, were involved in this research work.
Walther Meißner succeeded in liquefying
helium, which led him to the discovery of the superconductivity of a series of metals. In this connection, he recognized some years later – together with his colleague
Robert Ochsenfeld – that superconductors have the property of displacing from their interior a
magnetic field which has been applied from the outside – the Meißner-Ochsenfeld Effect.
Nazi Germany With the appointment of
Johannes Stark as president on 1 May 1933, the ideology of National Socialism found its way into the PTR. The convinced advocate of a
German Physics terminated diverse research projects on issues of modern physics to which he referred to as "Jewish", among them, in particular, works on quantum physics and on the
theory of relativity. Stark also tried to enforce the "
Führer principle" (Führerprinzip) at the PTR: in 1935, he dissolved the Kuratorium and took over its competences himself. Jewish employees and critics of the
NSDAP (such as
Max von Laue) were dismissed. After
World War II, Von Laue participated in the re-founding of PTB.
Albert Einstein, who had been thrown out of the Kuratorium already before its dissolution, broke ties to PTR/PTB. Under Stark and – after 1939 – under his successor
Abraham Esau, the PTR strongly dedicated itself to armament research. A newly founded laboratory for acoustics was not only to investigate general – but mainly also military – fields of application. This included, among other things, the acoustic finding of artillery, the military utilization of
ultrasound and the development of decoding procedures. In addition, researchers of PTR developed acoustic mines and a steering system for torpedoes which orientated itself on the sound field of traveling ships. Due to its classical metrological tasks, the PTR was also closely connected with the armament industry of the Third Reich. Since exact measures are a basic requirement for the manufacture of military equipment, the PTR gained a key role in armament production and defense. The extent to which the PTR was also involved in the German nuclear weapons project is controversial. It is, however, known that – prior to his time as PTR president – Abraham Esau conducted – until 1939 – a group of researchers dealing with nuclear fission. Later, he took over the specialist area "nuclear fission" in the Reich Research Council which supervised, from spring 1942 on, the German uranium project. Shortly after that,
Hermann Göring subordinated the working group under the former PTR physicist
Kurt Diebner to Division V for atomic physics at the PTR. Esau received the title "Authorized Representative of the Reichsmarschall for Nuclear Physics", a post which he, however, ceded to
Walther Gerlach already at the end of 1943. To escape the
bombing raids of the
allies, the PTR was, in 1943, relocated at the initiative of the president and Thuringian privy councillor Abraham Esau to different places in Germany (for example to
Weida and
Ronneburg in Thuringia and to Bad Warmbrunn in Lower Silesia). During the attacks on Berlin, the buildings of the PTR were heavily damaged. In 1945, the Reichsanstalt was virtually destroyed and the few departments which still existed were scattered all over the country.
Re-founding of PTB in Braunschweig and other PTR successors Approximately from 1947 on, successor institutes were developed in addition to the PTR in Berlin-Charlottenburg, i.e. one in East Berlin – for the Soviet Occupation Zone – and one in the
Bizone – and later
Trizone. With the well-meaning support of the British Military Government, parts of the old Reichsanstalt were established in Braunschweig. The idea for this re-founding had been developed by the former PTR advisor for theoretical physics, Max von Laue, already during his internment in
Farm Hall. In 1947, he succeeded in convincing the British authorities to make the former
Luftfahrtforschungsanstalt (Aeronautical Research Institute) in
Völkenrode near
Braunschweig available to the PTR successor. In 1948, Wilhelm Kösters, who had been the director of Division 1 in Berlin for many years, became its first president. Many former PTR employees from
Berlin, Weida and
Heidelberg followed him to Braunschweig. The new institute was named ꞋꞋPhysikalisch-Technische AnstaltꞋꞋ (PTA) and, since 1 April 1950, ꞋꞋPhysikalisch-Technische BundesanstaltꞋꞋ. In 1953, the West Berlin PTR was integrated into this institute as ꞋꞋBerlin InstituteꞋꞋ while respecting the four-power status of Berlin. In the German Democratic Republic (GDR), the Deutsches Amt für Maß und Gewicht (DAMG) had established itself with its principle seat in Berlin. After several renamings, this institute was designated Amt für Standardisierung, Meßwesen und Warenprüfung (Office for Standardization, Metrology and Quality Control – ASMW) during the last GDR years; the name already indicates that this office of the GDR had more extensive tasks than PTB in the
Federal Republic of Germany (FRG), namely additional tasks in the field of
standardization and
quality assurance and in the area of activity of the
Bundesanstalt für Materialforschung und -prüfung (BAM).
Growth and reunification The young PTB grew rapidly in the years after its founding – both in terms of staff and in terms of financial resources. Not only its scientific metrological profile was extended, but also its palette of services rendered to industry, in particular in the form of
calibrations of measuring instruments. In the 1970s, this led to the founding of the Deutscher Kalibrierdienst (German Calibration Service), which delegated service tasks to accredited, privately run laboratories and allowed PTB to concentrate itself on more demanding measurement tasks. From 1967 to 1995, PTB operated the Experimental and Research Reactor Braunschweig. This reactor served in particular as
neutron source for
fundamental research, not for the investigation of nuclear energy. PTB dealt with this controversial subject from 1977 to 1989, above all due to the fact that the task "long-term management and disposal of radioactive waste" had been assigned to it. Later on, this field of work passed over to the ″Bundesamt für Strahlenschutz″ (
Federal Office for Radiation Protection) after same had been newly established. Today, PTB’s Division 6 deals with
ionizing radiation in general. This also includes a highly sensitive trace survey station for radionuclides which has been measuring radioactive substances in ground-level air for more than 50 years. The "
Wende" ("political change") in Germany in 1990 also led to a "reunification in metrology". PTB took over parts of the ASMW (Office for Standardization, Metrology and Quality Control of the former German Democratic Republic), among them 400 employees, and the site Berlin-Friedrichshagen as additional field office (this has since been given up again). Other parts of the ASMW were integrated into the
BAM. Despite a phase of staff reductions – after the strong expansion following reunification – PTB ranks today among the largest national metrology institutes in the world. As such, it is in charge of the realization and dissemination of the
physical units and promotes the worldwide uniformity of metrology. == Journals ==