  Taking into account only luminous objects, the kinematics of clusters of
galaxies, galaxies and their interior, require a much higher mass than the
luminous one to explain the observations. This situation has provoked more than
30 years of intense research and has stimulated hypothesis like the dark
matter. Also new mechanical theories, different from Newton (like the Modified
Newtonian Dynamics), have been proposed. We here present an alternative:
theoretical and observational data strongly suggest the existence of a
universal field of minimum acceleration of the order of c/t, c the speed of
light and t the age of the Universe. We keep our reasoning within the present
state of the art of Quantum Mechanics, Relativity and Newtonian Mechanics. With
this approach the kinematics of the luminous objects are explained without any
additional assumption. At the same time the sizes of all structures in the
Universe, from protons up to the Universe, are explained as due to the constant
action of this field.
