On the classification of pyramidal central configurations

We present some results associated with the existence of central configurations (c.c.'s) in the classical gravitational $N$-body problem of Newton. We call a central configuration of five bodies, four of which are coplanar, a $pyramidal$ central configuration (p.c.c). It can be shown that there are only three types of p.c.c.'s, admitting one or more planes of symmetry, viz. (i) the case where the planar bodies lie at the vertices of a regular trapezoid, (ii) the case where the bodies lie at the vertices of a kite-shaped quadrilateral, and (iii) the case where the bodies lie at the vertices of a rectangle. In this paper we classify all p.c.c.'s with a rectangular base and, in fact, prove that there is only one such c.c., namely, the square-based pyramid with equal masses at the corners of the square. The classification of all p.c.c.'s satisfying either (i) or (ii) will be discussed in subsequent papers.