The Problem of the Earth’s Figure: Measurement, Theory, and Evidence in Physical Geodesy

My PhD project explores the epistemology of measurement in physical geodesy through an in-depth study of its foundational measurement problem. I present a novel historical analysis of how scientists successfully measured the earth's figure and gravity field, highlighting the problem's central role in the histories of Newtonian gravitation physics, statistics, and modern earth science, as well as its unique importance for our epistemological understanding of measurement, theorizing, and theory-testing.

Different geodetic measurement operations sketched in: Pierre Bouguer and Charles-Marie de La Condamine in La figure de la terre, Paris 1749.

Research Summary

Understanding the inferential structure and justification of scientific measurements is a crucial problem for scientists and philosophers of science alike. However, the classical views that have informed philosophical theories of measurement are almost exclusively based on laboratory physics or behavioural science. My work aims to enrich our understanding of measurement by focusing on the history of physical geodesy - the science concerned with modelling and measuring the earth's shape and gravitational field. The earth is a large and partially inaccessible physical system, while it is often impossible to shield geodetic measurements from confounding perturbations. These contexts distinguish geodetic measurement from classical examples used to illustrate the structure and development of scientific measurement. In my project, I provide novel historical analyses of central developments in physical geodesy, including the construction of the first mathematical models and measurements of planetary figures (1680-1730), geodesy's central role in confirming Newtonian particle-to-particle gravitation (1755-1820), responses to persistent discordances (1820-1870), and the eventual agreement on a unified model of the earth's figure and gravitational field (1880-1930).

Hydrostatic derivation of planetary equilibrium figure in: Alexis Clairaut, Théorie de la figure de la terre : tirée des principes de l'hydrostatique, Paris 1743.

Published research from this project:

*Winner of the 2022 APS History and Philosophy of Physics Essay Price

*Winner of the 2021 Du Châtelet Price in Philosophy of Physics