But Newton?s laws are invalid for galactic rotation or should we say not applicable. Newtons laws are valid mathmatical constructs, it is just the presumptions surrounding their application that are debate-able.. Newton?s gravity law was meant, specifically?.mea culpa. Newton?s UNIVERSAL law of gravitation is said by MS types to hold throughout the UNIVERSE. It explains binary star system motion, attraction of stars to form galaxies and what will bring the BB expansion to a halt (if there?s enough mass). But?.. an inverse square law can?t explain the stability of the arms of spiral galaxies. Robert