Fundamental Physical Constants - Constants which occur naturally in the field of physics, such as the electronic charge, the velocity of light, the Avogadro number, Planck's constant, The Rydberg constant, the fine structure constant, the gravitatinonal constant, and so on. With the apparent exception of the gravitational constant, the fundamental constants are interdependent, and a precise knowledge of only a small number is all that is needed to establish the values of the entire group.