A physical constant is a physical quantity that is generally believed to be both universal in nature and constant in time. It can be contrasted with a mathematical constant, which is a fixed numerical value, but does not directly involve any physical measurement.
There are many physical constants in science, some of the most widely recognized being the speed of light in vacuum c, the gravitational constant G, Planck's constant h, the electric constant ε0, and the elementary charge e. Physical constants can take many dimensional forms: the speed of light signifies a maximum speed limit of the Universe and is expressed dimensionally as length divided by time; while the fine-structure constant α, which characterizes the strength of the electromagnetic interaction, is dimensionless.
Read more about Physical Constant: Dimensional and Dimensionless Physical Constants, How Constant Are The Physical Constants?, Anthropic Principle, Table of Universal Constants, Table of Electromagnetic Constants, Table of Atomic and Nuclear Constants, Table of Physico-chemical Constants, Table of Adopted Values, Natural Units
Famous quotes containing the words physical and/or constant:
“A woman may very well form a friendship with a man, but for this to endure, it must be assisted by a little physical antipathy.”
—Friedrich Nietzsche (1844–1900)
“There is a constant in the average American imagination and taste, for which the past must be preserved and celebrated in full-scale authentic copy; a philosophy of immortality as duplication. It dominates the relation with the self, with the past, not infrequently with the present, always with History and, even, with the European tradition.”
—Umberto Eco (b. 1932)