Along with the media and scientific publication inherent to the expedition to the observation of the solar eclipse of 29 May 1919, Eddington’s presence on the Island of Príncipe, in particular his stay at Roça Sundy, was documented by him in letters addressed to his mother and sister

What did Eddington see?

In this communication we aim to present a possible modulation of iconic sceneries through which Eddington went, founded on the integration of arguments from the History of Science, Mathematics and Architecture. The virtual visit to the sceneries is part of a scientific education experiment which, throughout the route in the Island of Príncipe, invites the visitor to interact with different dimensions of knowledge and the local reality.

The observations of the total solar eclipse made by the Royal Society expeditions of 1919 are one of the greatest experiments in physics.nThe observations from the two expeditions (to Sobral and to Principe) were made in different meteorological conditions, with different instruments and at different local times. This led to datasets of different quality and sizes that required different data analysis procedures. We revisit the original paper by Dyson, Eddington and Davidson published in the Philosophical Transactions of the Royal Society in 1920, with two goals in mind. On one hand, we examine the two data analyses procedures presenting a comparison of the two methods. The data from Principe was analysed in an ingenious way, making use of external data, trying to make the most of a small dataset. The larger dataset from Sobral was analysed in a more standard manner and provided the strongest constraint on the deflection of light at the Sun’s limb (1.9800±0.1200). The paper, however, does not detail the method used to compute the error. This leads to our second goal: to make a new computation of the uncertainties using the data available in the paper. For this, we carried out a Fisher matrix computation in a four-dimensional parameter space and found a consistent tighter constraint of (1.9600 ± 0.0600).

This presentation intends to share preliminary research regarding the 1912 Eclipse expeditions to Passa-Quatro, Brazil. An emblematic group photo, taken by the photographer Augusto Soucasoux on the occasion of this eclipse, will serve as a mechanism to map the expeditions, actors and agendas present. Properly characterising the 1912 expeditions is relevant to better understand the 1919 expeditions. Not only did the previous experience informed the planning of the latter but, comparing both endeavours enables us to understand in which ways the particular geopolitical circumstances, in place in 1919, influenced the planning of the expeditions. Finally, it is also the purpose of this presentation to demonstrate the relevance of the information mobilised and extracted from a visual source.

Final words by the E3GLOBAL project’s Scientific Coordination