ZEEMANS DISCOVERY AND THE MASS OF THE ELECTRON

Citation
N. Robotti et F. Pastorino, ZEEMANS DISCOVERY AND THE MASS OF THE ELECTRON, Annals of Science, 55(2), 1998, pp. 161-183
Citations number
80
Categorie Soggetti
History & Philosophy of Sciences","History & Philosophy of Sciences","History & Philosophy of Sciences
Journal title
ISSN journal
00033790
Volume
55
Issue
2
Year of publication
1998
Pages
161 - 183
Database
ISI
SICI code
0003-3790(1998)55:2<161:ZDATMO>2.0.ZU;2-F
Abstract
In an article published recently in this journal, one of us reconstruc ted how in 1899 J. J. Thomson, after having measured the mass-to-charg e ratio of the corpuscle (which became our electron), achieved a measu rement of its charge and consequently an estimate of its mass, obtaini ng in this manner 'direct proof of the existence of particles smaller than the hydrogen atom'. In this paper, starting with an analysis of Z eeman's first measurements on the widening of spectral lines in a magn etic field, we show that the existence of masses smaller than the atom was already a matter of discussion in early 1897, and that a qualitat ive estimate of the mass of the electron was made even before Thomson' s measurements in 1899. In this process an important role was played b y a research programme on the structure of matter carried out by Stone y in the latter part of the nineteenth century. This had in many aspec ts anticipated Zeeman's experimental observations, and its conclusions were in part formalized in the so-called Larmor theorem.