The Lecture Hall Technician Gerd
1950s and 1960s
Hello, my name is Gerd*, and I have been working at the 1st Physics Institute in Göttingen for 20 years. I even worked with Pohl before he retired—but that was more than a few years ago. As a lecture hall technician, I am responsible for preparing all the experimental setups and I also assist the lecturer during presentation of the experiments. This requires more effort than one might think, especially with a dynamic Pohl-style lecture, but I’ll explain more about that later. A lot has changed since his time. I know the old lecture hall only through photographs, but I can describe Pohl’s renovation plan in detail. He also designed some interesting devices that I’m sure you’ll appreciate learning about.
* Gerd is a fictional character.
Clear the Stage
The existing lecture hall fell far short of Pohl’s needs. In order to demonstrate his experiments properly, Pohl conceived a series of renovations that began in 1921. His conversions resulted in a significantly larger space that was surprisingly minimalist for its time, with immense white walls awaiting his famous shadow projections. The auditorium— once overcrowded and densely packed—now featured a large open stage, providing Pohl with a perfect setting for the dynamic presentation of his demonstration experiments.
The lecture hall before, during and after Pohl’s renovation. Large tables and a clutter of objects gave way to a clean, minimalist aesthetic.
Set the Scene
In contrast to many of his colleagues, Pohl embraced live demonstration to communicate the principles of physics. This generally meant a lot of work for his lecture hall technicians. Similar to the development of a theatre piece, set construction takes place “behind the scenes”. Then, there are on-stage dress rehearsals, and eventually an experiment is ready to be presented to a live audience. I am there through every step. Preparation and rehearsal can consume much more time than the actual presentation, especially when a lecture features multiple experiments.
Link to the induction motor collection of the University of Göttingen. Robert Wichard Pohl used shadow casting to present the experimental setup of an induction rotor demonstrating the principle behind the rotary field motor.
This experiment was filmed as part of the new multimedia edition of Pohl’s textbook authored by his son Robert Otto Pohl, seen presenting in this video. (Lüders, Klaus; Pohl, Robert Otto; Beuermann, Gustav; Samwer, Konrad: Induktionsläufer. Physikalische Experimente nach Robert Wichard Pohl (1884 – 1976), IWF (Göttingen), 2004. https://doi.org/10.3203/IWF/C-14887)
Raise the Curtain
Pohl refined many well-known devices for use in his demonstrations, and often called upon his machinists at the Institute to execute these upgrades or to custom-build his own inventions. Starting in 1926, many of Pohl’s devices were produced for distribution around the world by Spindler & Hoyer, a Göttingen-based company that manufactured a wide range of mechanical and optical products for industry and education. Of his inventions, the best-known is “Professor R. Pohl’s Rotating Experimental Table”. Although neither the table nor its individual components were new in and of themselves, Pohl’s innovative multifunctional design was an international success. Some of his teaching devices, first conceived in the 1920’s, are still in use today, including at the University of Göttingen.
An item from the Spindler & Hoyer catalog in the early 1930’s: Pohl’s swivel chair. (Aus: Spindler & Hoyer, Liste 61: Der Drehstuhl nach Prof. R.W. Pohl, Collection Paolo Brenni, https://vlp.mpiwg-berlin.mpg.de/library/data/lit18147 [letzter Zugriff 19.09.2022].)
Bright White Light
Carbon arc lamps entered common use in the late 19th century as street lamps, in search lights and later in movie projectors, amongst many other applications. With their very small, extremely bright and highly concentrated light source, arc lamps can create remarkably sharp-edged silhouettes over long distances. A relatively diffused light source like an incandescent lamp filament—or worse, a fluorescent tube—cannot provide such definition. Pohl used arc lamps in his lectures to project information from glass slides, to enlarge measuring device displays and magnify dynamic demonstrations onto the walls of his auditorium. Even with a tiny device on stage, the amazing detail visible in these shadow plays made it possible for the entire audience, including those in the back rows, to clearly follow Pohl’s presentations.
In this excerpt from the lecture “Robert Wichard Pohl’s long shadow: Physics for teaching in the 20th century”, Dr. Michael Markert (left) and Dr. Daniel Steil (right) demonstrate the difference between shadows cast by a halogen lamp (left) and an arc lamp (right). (Ausschnitt aus: https://www.youtube.com/watch?v=nhc18efqLlI [letzter Zugriff 26.09.2022].)
As in Pohl’s era, today’s lecture hall technicians today are responsible for the experimental setups and for ensuring the successful presentation of demonstrations. Joachim Feist, a lecture hall technician at the 1st Physics Institute, University of Göttingen, is interviewed about his work. His colleague Matthias Heisig, a mechanical technician since 1973 and later a lecture assistant at the HTW Dresden, reacts to the interview and reflects on his own experiences.
Heisig: If experiments are portrayed using two or more cameras, a new aesthetic approach must be adopted.1 of 3
Heisig: The lecture at our institute is based on the original content developed by Pohl, Bergmann-Schäfer and Recknagel.2 of 3
Heisig: We’ve been working with carbon arc lamps and Pohl’s silhouette projections since the beginning.3 of 3
Heisig: This is exactly the development that has taken place in recent years.1 of 3
Heisig: The demonstration with electromagnetic waves is pretty popular, but some of the electronic devices in the lecture hall are quite severely affected during this experiment.2 of 3
Heisig: We still like to work with Pohl’s original “old brass devices”—simple and functional!3 of 3
Heisig: As an alternative, we sometimes use Zenon light bulbs from car headlights.1 of 3
Heisig: We still use the original carbon arc lamps produced by the company Carl Zeiss Jena, which operate at 220V AC, but we disable the self-calibrating mechanism.
2 of 3
Heisig: I can only agree with all the points Mr. Feist made in this interview!3 of 3