Fine-Structure Constant

fine-structure constant

[′fīn ‚strək·chər ′kän·stənt]

(physics)

A fundamental dimensionless constant, equal to e ²/(4πε₀ℏ c) in International System (SI) units and to e ²/(ℏ c) in centimeter-gram-second (cgs) electrostatic units, where e is the elementary charge, ℏ is Planck's constant divided by 2π, c is the speed of light, and ε₀ is the electric constant; numerically, it is equal to 0.007 297 352 533 ± 0.000 000 000 027 or to 1/(137.035 999 76 ± 0.000 000 50); symbolized α. Also known as Sommerfeld fine-structure constant.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Fine-Structure Constant

(α), a dimensionless quantity formed from universal physical constants: α = e²/hc ≠ 1/137, where e is the elementary electric charge, h is Planck’s constant, and c is the speed of light in a vacuum. According to the most accurate measurements, which are based on the Josephson effect, α^–1 = 137.0359 ± 0.0004. The constant α is called the fine-structure constant because it determines the fine structure of the energy levels of an atom in the sense that the magnitude of the fine-structure splitting is proportional to α². In quantum electrodynamics, α is a natural parameter that characterizes the strength of the electromagnetic interaction.

References in periodicals archive ?

Some controversial measurements suggest, however, that the fine-structure constant may be different in different parts of the universe.

Constant connections: new units based on fundamental properties of the universe will make measurements more precise

Magic number: A partial history of the fine-structure constant. Arch.

An essay on numerology of the proton to electron mass ratio

Recent observations of light from distant quasars (luminous sources thought to be caused by material heating up as it swirls around a black hole) hint that the fine-structure constant varies over the sky at large distances.

Does electromagnetic force's strength change in white dwarf star's gravitational field?

Dziuba, Determination of the von Klitzing Constant and the Fine-Structure Constant Through a Comparison of the Quantized Hall Resistance and the Ohm Derived from the NIST Calculable Capacitor, Metrologia 35, 83-96 (1998).

Initial NIST AC QHR measurements

Kilmister's masterly reconstruction of Eddington's attempts to determine the fine-structure constant shows how and why Eddington's programme, like Kepler's, finally degenerated.

Eddington's Search for a Fundamental Theory: A Key to the Universe

[5.] Fine-structure constant. Wikipedia, http://en.wikipedia.org/wiki/Finestructure.constant

Laboratory instrument for detecting the earth's time-retarded transverse vector potential

Dr Berengut, of the University of New South Wales School of Physics, said the team's previous research on light from distant quasars suggests that alpha - known as the fine-structure constant - may vary across the universe.

30,000 times greater gravity white dwarf star contradicts theory of nature

In recent years, astrophysical data have indicated that the fine-structure constant called alpha has increased since the early universe.

Terrific timekeeper: optical atomic clock beats world standard

The lead article in the annual Buyer's Guide of the American Institute of Physics features five pages of values of the fundamental physical constants, such as the speed of light, the Newtonian constant of gravitation, the Planck constant, the fine-structure constant, and energy-unit conversion factors.

Buyers guide features NIST Data product. (General Developments)

Webb (University of New South Wales, Australia) and his colleagues tracked the fine-structure constant, denoted by the lowercase Greek letter alpha ([alpha]).

New physics from ancient quasars?

The numerical value of the fine-structure constant a was often denoted to be a mystery, a magic number and an enigma.

A new theoretical derivation of the fine structure constant

Since 2001, Flambaum and his colleagues have presented growing evidence that another constant, known as alpha or the fine-structure constant, has also varied (SN: 10/6/01, p.