Fine structure constant Definition and 5 Discussions

In physics, the fine-structure constant, also known as Sommerfeld's constant, commonly denoted by α (the Greek letter alpha), is a fundamental physical constant which quantifies the strength of the electromagnetic interaction between elementary charged particles. It is a dimensionless quantity related to the elementary charge e, which denotes the strength of the coupling of an elementary charged particle with the electromagnetic field, by the formula 4πε0ħcα = e2. As a dimensionless quantity, its numerical value, approximately 1/137, is independent of the system of units used.
While there are multiple physical interpretations for α, it received its name from Arnold Sommerfeld, who introduced it in 1916, when extending the Bohr model of the atom. α quantifies the gap in the fine structure of the spectral lines of the hydrogen atom, which had been measured precisely by Michelson and Morley in 1887.

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  1. Auto-Didact

    A Quantization isn't fundamental

    This thread is a direct shoot-off of this post from the thread Atiyah's arithmetic physics. Manasson V. 2008, Are Particles Self-Organized Systems? The author convincingly demonstrates that practically everything known about particle physics, including the SM itself, can be derived from first...
  2. John Greger

    Identify spectral lines

    Homework Statement The Ca spectrum below, recorded using a Fourier Transform Spectrometer (FTS), shows the resolved ##3d4s ^3D - 3d4p ^3D## multiplet. The wavenumbers and their relative intensities are given in the table. Identify all the lines and determine the fine structure constants in the...
  3. P

    I Calculating the fine structure constant in Feynman diagrams

    Griffith's Introduction to Elementary Particles, if I understand it correctly, states that in QED, the fine structure constant contributes less and less to the strength of the EM interaction as we add more and more vertices since the constant is so small (1/137). However, in QCD, since the...
  4. S

    I Systematic redshift?

    Hi everyone, I am new to observations and observational terms! I am reading the paper "constraining the time variation of the fine-structure constant" by Srianand et. al in the section "constraining alpha with QSO absorption lines" there is a sentence saying "... rest wavelengths of MG II ...
  5. mikenw

    B Dipole pattern for Fine Structure Constant?

    Can someone describe for me the dipole pattern that was detected related to the fine structure constant? This thread talks about that pattern some. What I am trying to understand is how that dipole is oriented relative to the observer on Earth? Are we talking about a toroidal shape with a...