In this paper, the effectiveness of GRT and of the use of the Riemann metrics for GRT and for the String Theory is discussed. We come to the conclusion that the invention of dark matter is a striking example of the incompetence of GRT and of the Riemann metric to explain many physical realities of the cosmos. Though, the Heaviside field for gravitation (or the gravitomagnetic field theory, or also called gyrogravitation) has found the origin of the constant speed of the stars in disc galaxies.

Keywords: gravitation, gravitomagnetism, gyrotation, dark matter, wormholes, Heaviside gravity, Maxwell analogy, GRT, String Theory, Riemann metric