XLIII Scientific Instrument Symposium - SIC 2024

Session Chair: Julien Gressot (Université de Neuchâtel, Switzerland)

Preferred precision: The Nobel Prize in Physics to Guillaume in 1920
Author: Karl Grandin
“I cannot but prefer works of high precision” Bernhard Hasselberg wrote to Hale in 1907. Hasselberg was a member of the Nobel Committee for physics 1901–1922, so how might his preference for precision have influenced the Prizes in physics? The 1920 Nobel Prize to Guillaume is claimed by historians to have been given out of homage to Hasselberg late in his life. And the quote for the prize to Guillaume read “in recognition of the service he has rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys.” In a present materials database, it is stated that this Nobel Prize “shows the importance of this alloy in scientific instruments.” So, what where the scientific instruments that might have swayed the committee in 1920? Guillaume worked his whole career with the International Bureau of Weights and Measures and succeeded in 1895 to find an alloy of nickel and steel that registered almost no change in length and volume due to temperature fluctuations. This alloy, called invar, came into use in pendulum clocks and for high precision land surveying. So, what instrument arguments were used in the evaluation of Guillaume? Hasselberg, the Academy’s physicist, was the Swedish representative to the International Bureau of Weights and Measures. So, he was well acquainted with Guillaume’s work. Other members of the Committee had been involved in the Swedish-Russian surveying expedition to Svalbard 1899–1902 with the purpose to extend the earlier Struve meridian measurements North of the European mainland.

Nature depicted, but in action
Author: Peter Heering
At the SIC meetings in 2006 in Krakow and 2015 in Florence, I already presented the analysis of the solar microscopes, focusing on the technical realizations of the functional principle on the one hand, and on the particular observation situation for ready-made preparations on the other. In this contribution, I am going to return to these instruments and the practice with them, however, my focus will be of course a different one:
I will discuss in more detail what was projected and how this changes the observation situation. The focus here is particularly on the dynamic projections, which were carried out with both water animalcule and salt solutions which were - according to the historical actors in the 18th century - among the most beautiful projections that can be made with the solar microscope. In this analysis, I will rely on practical experiences made with a reconstructed solar microscope. In particular, I will discuss material as well as aesthetic aspects of these projections. Moreover, I am going to argue that the projections of the dynamics both in living creatures and in crystallizations were used to claim a specific significance with respect to the representation of nature.

Scientific Precision and Public Perception: The Case of the Historic Lens Replacement
Author: James Gort
In
1905, a National Observatory for Canada was constructed to house a 15-inch equatorial telescope and other instruments in its complex, with a goal of providing precision timekeeping and setting a “prime meridian” for Canada. Of particular note, a Warner and Swasey telescope with a John A. Brashear lens was purchased and used for the study of the moon, spectroscopic binary stars, and other scientific pursuits. Curiously, the Brashear objective was unceremoniously replaced in 1958 with the world's largest apochromat. But there was no announcement or mention in the Observatory Annual Reports. Why replace the Brashear lens, produced by one of the world’s most renown optical companies? And why was there no major announcement? Public perception of its poor visual performance was touted as the reason in a plea for Government funds. So was the Brashear lens defective? Was it assembled backwards? Was it insufficient for the precision measurement of spectral lines and double stars, with public outreach a cover story? Or was there something else to hide? The personal papers and daily journals of the principal actors are examined to uncover the truth.

The Curious Mistake of Ibn al-Haytham, the Founder of Modern Optics : Modeling the Rainbow with a Concave Mirror
Author: Sena Aydin
Ibn al-Haytham (d. 1040) revolutionized the history of science by developing a new concept of controlled experiment. This approach to experimentation, defined with the term "i'tibār" in his masterpiece Kitāb al-Menāẓir appears as an explicit and original methodological tool involving the use of artificially constructed instruments. Ibn al-Haytham, who is considered to be the founder of modern optics, also wrote a treatise entitled Maqāla Fi al-Hāla wa Kavs-i Kuzah, in which he discusses the rainbow and the halo. In this work, he explains the formation of the rainbow as an image formed in a concave mirror and argues that the light rays coming from a distant light source will form concentric circles around that point by reflecting on any point on the axis of the concave mirror. Thus, he concludes that the rainbow is the result of the reflection in the cloud. Ibn al-Haytham's explanation is erroneous in that it does not include the concept of refraction. On the other hand, Ibn al-Haytham's main contribution to the development of the rainbow and halo problem was indirectly through his redefinition of the methodology of science and the refraction experiments he organized in his Kitāb al-Menāẓir. In this study, we will examine the model chosen by the founder of modern optics and question the possible reasons why Ibn al-Haytham chose a concave mirror instead of a glass sphere to model a raindrop.