The idea that the outer stars of a galaxy resp. the outer galaxies of a cluster of galaxies are rotating too fast around their gravitational centres and therefore can not be kept on their orbits by the gravitation of the baryonic matter leads to the assumption of extra matter, the u201edark matter", whose gravitation is suited to keep the outer stars/galaxies on their orbits.It is demonstrated that if the gravitational acceleration as a function of the distance from the gravitational centre is determined correctly, the observed orbital velocities can be explained solely by the baryonic matter and Newton’s laws and therefore u201edark matter" is not needed. It is not even necessary To explain the other effects ascribed to it, u201edark matter" is not neeeded either as the higher gravitational accelerations necessary for these effects are delivered solely by the baryonic matter.