Magic number: A partial history of the fine-structure constant.
The magic number considered in this article is \(\alpha= 1/137\), which is called Sommerfeld's fine-structure constant in most textbooks of atomic and quantum physics. Even before \(\alpha\) was turned into a spectroscopic quantity, this dimensionless combination of the natural constants \(e\), \(c\), and \(h\) had been discussed by some chemists (Lewis and Adams) and physicists (Birge, Stanley). After Sommerfeld's insertion of the constant into his famous fine-structure formula for hydrogen-like atoms in 1915, \(\alpha\) was considered just as another atomic parameter until 1929, when Eddington suggested that it was more than a spectroscopic constant. He claimed that \(\alpha^{-1}\) was an integer (137) that could be derived from fundamental mathematical and epistemological considerations. An important part of the article deals with different responses to Eddington's theory, including Max Born's hostile reactions after 1935. The paper ends with the discussion of geophysical and astrophysical arguments suggesting a variation of the fine-structure constant in time.
scientific article; zbMATH DE number 1969267