Editing Physical constant (section)

=== Natural units ===
{{main article |Natural units}}
It is possible to combine dimensional universal physical constants to define fixed quantities of any desired dimension, and this property has been used to construct various systems of natural units of measurement. Depending on the choice and arrangement of constants used, the resulting natural units may be convenient to an area of study. For example, Planck units, constructed from [[speed of light|''c'']], [[gravitational constant|''G'']], [[reduced Planck constant|''ħ'']], and [[Boltzmann constant|''k''<sub>B</sub>]] give conveniently sized measurement units for use in studies of [[quantum gravity]], and [[atomic units]], constructed from [[reduced Planck constant|''ħ'']], [[electron rest mass|''m''<sub>e</sub>]], [[elementary charge|''e'']] and 4''π''[[vacuum permittivity|''ε''<sub>0</sub>]] give convenient units in [[atomic physics]]. The choice of constants used leads to widely varying quantities.