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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 2: History and Philosophy of Gravity

AGPhil 2.1: Hauptvortrag

Montag, 21. März 2022, 16:15–17:00, AGPhil-H14

To G or not to G: J. H. Poynting and the gravitational constant in the 19th century — •Isobel Falconer — University of St Andrews, UK

The increasing precision of gravitational measurement is sometimes given as a reason for the acceptance of the gravitational constant, G, in the late 19th century. However, as late as the 1890s, John Henry Poynting, the doyen of British workers on gravitation, persistently refused to cast measurement of the gravitational constant as his experimental aim; he preferred to present it as measurement of the mean density of the Earth. Despite his detailed analysis, in his Adams Prize Essay of 1894, of the improvements in experimental method that were enabling ever more precise measurement, he similarly interpreted all previous measurements as of the mean density of the earth. His reservations about G alert us to the mathematical, physical and metaphysical interpretative work involved in the shift that had occurred during the previous 100 years, from expressing the laws of physics as ratio equations to expressing them as functional relationships between algebraic symbols that denoted the numerical values of physical quantities.

This talk will encompass gravitational work in Britain, France, and Germany, in exploring the introduction of G into physics and some of the questions raised by Poynting's reservations about G as a useful physical construct.