The mimetic tradition in experimental physics

My introduction to history of science started in 1994, when I restored the experiment you can see in the photo, originally undertaken by the Norwegian physicist Kristian Birkeland at University of Christiania (Oslo), in 1913.
Birkeland had a strong interest in the Aurora Borealis and tried to simulate the effects around an electromagnetic ‘terrella’ in a large vacuum chamber. Scaling down large natural phenomena for scrutinizing them in the laboratory was part of the mimetic tradition of the period; other scientists experimented on weather phenomena, ocean currents and geological processes in the lab. Terrellas, or small models of the Earth had been used since the late sixteenth century to investigate and demonstrate magnetic, electrostatic, and electromagnetic phenomena. Birkeland used his one as a magnetized electrode in an electric discharge arrangement. The flickering light that he was able to create around the poles of the terrella, while suspended in vacuum, was interpreted as Aurora Borealis in miniature, thus confirming his theories about its causes.
To me, the restoration process became like a journey back in time, to the role of a lab-technician at the turn of the last century. I had to become familiar other instruments, tools, texts, materials, technologies and methods than what I usually worked with. I soon realized that the information in Birkeland’s official reports from the experiment was insufficient to get the equipment in a workable condition. Many of the records from Birkeland's laboratory practice has disappeared, and he left few technical details on how the chamber should be operated. A study of the technician’s own notes and sketches was in fact more helpful. The actual process of restoring the experiment using the old components revealed much that could not be inferred from the published documentation. But it also shed light on texts that were well known but not fully understood. Practical skills and laboratory techniques taken for granted at the beginning of the century had to be learnt again from scratch. The importance of tacit knowledge to run this particular experiment became evident, the only way to achieve it was to redo it. In addition to learn much about the early twentieth-century understanding of the Northern Lights, this project also taught me much about the contemporary air-pump (vacuum) technology. Moreover, Birkeland’s terrella is now depicted on the Norwegian 200 kr. bank note.