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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.
The term "physical constant" refers to the physical quantity, and not to the numerical value within any given system of units. For example, the speed of light is defined as having the numerical value of 299 792 458 when expressed in the SI unit metres per second, and as having the numerical value of 1 when expressed in the natural units Planck ...
The Planck constant, or Planck's constant, denoted by ,[ 1] is a fundamental physical constant [ 1] of foundational importance in quantum mechanics: a photon 's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a matter wave equals the Planck constant divided by the associated particle momentum.
The gravitational constant is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton 's law of universal gravitation and in Albert Einstein 's theory of general relativity. It is also known as the universal gravitational constant, the Newtonian constant of gravitation, or the Cavendish ...
The Avogadro constant, commonly denoted NA[ 1] or L, [ 2] is an SI defining constant with an exact value of 6.022 140 76 × 1023 mol−1 ( reciprocal moles ). [ 3][ 4] It is defined as the number of constituent particles (usually molecules, atoms, or ions) per mole ( SI unit) and used as a normalization factor in the amount of substance in a ...
A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]
The fine-structure constant, α, has several physical interpretations. α is: The ratio of two energies: the energy needed to overcome the electrostatic repulsion between two electrons a distance of d apart, and. the energy of a single photon of wavelength λ = 2πd (or of angular wavelength d; see Planck relation ): α = ( e 2 4 π ε 0 d ...
Some of the constants used in science are named after great scientists. By this convention, their names are immortalised. By this convention, their names are immortalised. Below is the list of the scientists whose names are used in physical constants.