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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.
Dimensionless quantities, or quantities of dimension one, [1] are quantities implicitly defined in a manner that prevents their aggregation into units of measurement. [ 2 ] [ 3 ] Typically expressed as ratios that align with another system, these quantities do not necessitate explicitly defined units .
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 ...
Martin Rees, in his book Just Six Numbers, [21] mulls over the following six dimensionless constants, whose values he deems fundamental to present-day physical theory and the known structure of the universe: N ≈ 10 36: the ratio of the electrostatic and the gravitational forces between two protons.
Richard Feynman, one of the originators and early developers of the theory of quantum electrodynamics (QED), referred to the fine-structure constant in these terms: There is a most profound and beautiful question associated with the observed coupling constant, e – the amplitude for a real electron to emit or absorb a real photon.
Pages in category "Dimensionless quantities of chemistry" The following 4 pages are in this category, out of 4 total. This list may not reflect recent changes. M.
Dimensionless quantities of chemistry (4 P) Countable quantities (1 C, 4 P) ... Dimensionless quantity * List of dimensionless quantities; D. Strain (mechanics) N.
A physical constant, sometimes fundamental physical constant or universal constant, is a physical quantity that cannot be explained by a theory and therefore must be measured experimentally. It is distinct from a mathematical constant , which has a fixed numerical value, but does not directly involve any physical measurement.