ABSTRACT
Newtonian celestial mechanics is based on Newton's law of universal gravitation and the laws of Newtonian mechanics. The simplest problem of Newtonian celestial mechanics is the problem of two bodies. The trajectories of the two-body problem are conic sections. Most practical problems of celestial mechanics are to a certain extent close to the two-body problem, enabling them to be solved by the perturbation theory techniques. It is to be noted that in celestial mechanics there are many efficient methods enabling one to derive in analytical form the approximate solutions of the equations of the disturbed motion. Generalization of the vectorial form may be carried out with the aid of tensors. Tensors represent sets of quantities changing by a simple linear law in transforming from one reference system to another. Tensors enable one to define operations remaining invariant under the transformation of coordinates.
