Isotropy

ISOTROPY, a property of certain substances, consisting in the fact that their various physical constants, taken in different directions, maintain their constant magnitude. All gases, liquids, as well as substances in a glassy state are isotropic, provided they are annealed. In isotropic substances, their properties can be represented geometrically by a sphere. This means that if we take some point A in the substance and along different directions lay off certain physical constants, which generally speaking change in the substance depending on direction, then the ends of the lines graphically representing the constant being studied, or as they say, the ends of vectors representing these physical quantities, will lie on the surface of a sphere, the center of which is at the given point A. Thus, if we study thermal conductivity in different directions, the speed of light, the speed of sound, etc., then in isotropic substances these magnitudes are the same in all directions.