Fine-structure constant
…c ) − 1 . Its numerical value is approximately 0.0072973525643 ≈ 137.035999177−1, with a relative uncertainty of 1.6×10−10. The constant was named by Arnold Sommerfeld, who introduced it in 1916 when extending the Bohr model of the atom. α quantified the gap in the fine structure of the spectral lines of the hydrogen…