What is Fine structure constant: Definition and 58 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. S

    Varying Fine Structure Constant?

    This question may have been asked a thousand times on here so please diredt me to the relevant post if that is the case. During a particle physics lecture I was told that although the fine structure constant is widely regarded as being 1/137 at normal lab energies, it seems to tend towards...
  2. N

    Nuclear efficiency and the fine structure constant?

    I find in Martin Rees "Just Six Numbers" that hydrogen undergoes fusion to helium with a mass energy conversion of .007, that is, the mass of the helium formed is less than the mass of the hydrogen by this ratio. Is it a coincidence that this number is the same as the fine structure...
  3. Hans de Vries

    An exact expression for the fine structure constant

    Just for the record: \ \alpha^{-\frac{1}{2}}\ +\ \alpha^\frac{1}{2}\mu\ =\ e^{\pi^2/4} Where \alpha, the fine-structure constant = 1/137.03599911 (46) and \mu=1+\frac{\alpha}{2\pi} is Schwingers first term of the electrons magnetic moment anomaly which is a function of \alpha as...
  4. Hans de Vries

    An exact? expression for the fine structure constant

    Just for the record: \ \alpha^{-\frac{1}{2}}\ +\ \alpha^\frac{1}{2}\ \mu\ =\ e^{\pi^2/4} Where \alpha, the fine-structure constant = 1/137.03599911 (46) and \mu=1+\frac{\alpha}{2\pi} is Schwingers first term of the electrons magnetic moment anomaly. Fill in 1/137.03599911 for...
  5. W

    Coulomb's Force Law and the Fine Structure Constant - Variance?

    *** PART I. *** THREE QUESTIONS ON "COULOMB'S LAW" The value of the constant "K" in what appears to be the "ORIGINAL" Coulomb's Law depends upon the nature of the medium. [ K = 1/4pi*epsilon ] where epsilon is the "absolute permittivity of the medium". In many modern books, I...
  6. W

    Is Boltzman's Constant related to the Fine Structure Constant?

    Is Boltzmann's Constant related to the Fine Structure Constant? Is Boltzmann's constant related to the Fine Structure Constant and if so how? Thanks in advance for your time and assistance.
  7. K

    Fine structure constant changes over time

    In this month's edition of the "New Scientist" magazine (July 2004), there is an article which says that the fine structure constant alpha was smaller in the past ( alpha = e^2/ hbar c), and the speed of light was greater. Since the speed of light can be given by the ratio of E/B (electric...
  8. V

    Fine structure constant has geometrical nature

    In the previous theme I spoke, that tangential energy of the dipole of speed is proportional to its square. Accordingly, tangential energy of radial resonance oscillations of the energy ring is proportional to the total square of all dipoles of speed in the ring. See file "dipole of speed.pdf"...
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