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Dimensionless fundamental physical constants include: α, the fine-structure constant, (≈ 1 / 137 ). This is also the square of the electron charge, expressed in Planck units, which defines the scale of charge of elementary particles with charge. The electron charge is the coupling constant for the electromagnetic interaction.
This is a list of well-known dimensionless quantities illustrating their variety of forms and applications. The tables also include pure numbers, dimensionless ratios, or dimensionless physical constants; these topics are discussed in the article.
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The fine-structure constant α is the best known dimensionless fundamental physical constant. It is the value of the elementary charge squared expressed in Planck units . This value has become a standard example when discussing the derivability or non-derivability of physical constants.
It is a dimensionless quantity (dimensionless physical constant), independent of the system of units used, which is related to the strength of the coupling of an elementary charge e with the electromagnetic field, by the formula 4πε 0 ħcα = e 2.
A statement of this theorem is that any physical law can be expressed as an identity involving only dimensionless combinations (ratios or products) of the variables linked by the law (e. g., pressure and volume are linked by Boyle's Law – they are inversely proportional). If the dimensionless combinations' values changed with the systems of ...
Martin Rees formulates the fine-tuning of the universe in terms of the following six dimensionless physical constants. [1] [18] N, the ratio of the electromagnetic force to the gravitational force between a pair of protons, is approximately 10 36. According to Rees, if it were significantly smaller, only a small and short-lived universe could ...
The number 6.022 140 76 × 10 23 is a dimensionless physical constant known as the Avogadro number, commonly denoted N 0 [5] [6] and often confused with the constant. Both are named after the Italian physicist and chemist Amedeo Avogadro.