In this paper we present an alternative and classical force of gravitation without dark matter or dark energy hypotheses. This model has common points with MOND but may be considered as an alternative to this theory. Indeed the laws of classical physics are respected. This model is a consequence of a study of forces which lead to conic trajectories and we compare our results with the Bertrand's theorem. At end an important part of this work is to purpose an experiment on the Earth, in order to valid or invalid our results.