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(ÿ-sot -rŏ-pee) The property by which all directions appear indistinguishable to an observer expanding with the Universe. Isotropy about every point in space implies homogeneity but the reverse is not necessarily true. See cosmological principle.



identity of the physical properties of a medium in all directions (the opposite of anisotropy).

All gases, liquids, and solids are isotropic in the amorphous state in all physical properties. Most physical properties in crystals are anisotropic. However, the isotropy of the properties of a crystal increases with increasing symmetry. Thus, the elasticity, strength, and electro-optical properties are anisotropic in highly symmetrical crystals (diamond, germanium, and rock salt), but the index of refraction, electrical conductivity, and coefficient of thermal expansion are isotropic (in less symmetrical crystals, these properties are likewise anisotropic).

Homogeneous polycrystals are usually isotropic with respect to all properties, if their properties are studied in a volume that is considerably larger than the grain size.



The quality of a property which does not depend on the direction along which it is measured, or of a medium or entity whose properties do not depend on the direction along which they are measured.