Dark Matter

Gravitational force manifested in its affect on rotational velocity is what indicates the presence of dark matter in individual galaxies. Newtonian mechanics is generally used to derive the relationship between rotational velocity and gravitational force. In Newtonian mechanics, mass is associated with gravitation. At the same time, in such galaxies there appears to be insufficient gravitational mass to account for the size of the gravitational force deduced from rotational velocity. The general theory of relativity encompasses Newtonian mechanics and also indicates that reference frames provide the means to develop spacetime curvature that expresses the gravitational field. It is reasonable to conclude that because of the more fundamental character of the general theory of relativity, the reference frames that are a key element of the general theory form the basis for understanding gravitation, and not mass.