**Fine structure constant**

In physics,
the **fine structure constant**
(usually denoted *α*, the Greek letter alpha) is a
fundamental physical constant, namely the __coupling constant__
characterizing the strength of the electromagnetic interaction. Being a dimensionless
quantity, it has constant numerical value in all systems of units. Arnold Sommerfeld introduced the fine-structure
constant in 1916.

The current
recommended value of *α* is 7.29735257×10^{−3}.
^{[1]}

**Содержание**

- 1 Definition
- 2 Bohr model
- 3 See also
- 4 References
- 5 External links

**Definition**

Some
equivalent definitions of *α* in terms of other fundamental
physical constants are:

where:

*e*is the elementary charge;*h*is the Planck constant;*ħ*=*h*/2π is the Dirac constant or reduced Planck constant;*c*is the speed of light in vacuum;*ε*_{0}is the electric constant;*m*_{S}is the__Stoney mass__;- is the gravitoelectric
gravitational constant of
__selfconsistent gravitational constants__; - is the
__gravitational constant__; - µ
_{0}is the vacuum permeability; *k*_{e}is the Coulomb constant;*R*_{K}is the von Klitzing constant;*Z*_{0}is the impedance of free space;*q*_{p}is the Planck charge;*m*_{P}is the__Planck mass__;*M*_{p}is the mass of proton;*M*_{e}is the mass of electron;*G*_{s}is the__strong gravitational constant__;- β is the
__magnetic coupling constant__.

In electrostatic
cgs units, the unit of electric
charge, the statcoulomb, is defined so that the Coulomb constant, *k*_{e},
or the permittivity factor, 4π*ε*_{0}, is 1 and dimensionless. Then
the expression of the fine structure constant becomes the abbreviated

an expression
commonly appearing in physics literature.

**Bohr model**

In the Bohr
model of hydrogen atom *α* is connected to the atom parameters for the
first energy level

where is the speed of electron’s matter at the Bohr
radius .

On the other hand

where is the Compton wavelength of the electron, is the classical electron radius, is the Rydberg
constant for wavelength.

The next
equation for *α** * is

where is the magnetic flux quantum, is the electron magnetic flux for the first
energy level,

is the magnetic field in electron disc with
flat surface area , and is __velocity
circulation quantum__ for electron.

Another
equation for *α** * is

where m^{2}/s

is the
strong gravitational torsion flux quantum, which is related to proton and to
its velocity circulation quantum,

and the strong
gravitational electron torsion flux for the first energy level of hydrogen atom
is

while is the __gravitational torsion
field__ of __strong gravitation__ in
electron disc.

The Bohr
model for __hydrogen system__ at the
level of star introduces
*α* in such way:

where and – mass of the star-analogue of proton and the
planet-analogue of electron, respectively, – stellar Dirac constant, – __characteristic speed__ of
stars matter.

**See also**

Many of
articles in Vikiversity make reference to the fine structure constant, or
discuss its relationship to other physical quantities. Examples are:

__Planck scale____Stoney scale____Strong gravitational constant____Selfconsistent gravitational constants____Selfconsistent electromagnetic constants____Gravitational characteristic impedance of free space____Magnetic coupling constant____Monopoles__

**References**

- "CODATA
Value: fine-structure constant". The NIST Reference on
Constants, Units, and Uncertainty. US National Institute of Standards and
Technology. June 2011. Retrieved
2011-06-23.

**External**** links**

- Fine structure constant in Russian
- Wikipedia article fine-structure constant

Source: http://sergf.ru/fscen.htm