Elements of cosmology

Abstract

The fundamental force keeping solar systems, binary stars, and galaxies together is the force of gravity (as opposed to electric, magnetic, and nuclear forces), and it is not unreasonable to suppose that the force governing the large-scale motions of the entire universe is primarily gravitational. If there is some other force governing these motions, there has to date been no evidence for it, neither in the solar system, nor in the observable galaxies. By the universe we mean all detectable components in the sky: stars, galaxies, constellations, pulsars, quasars, as well as such things as cosmic rays and background radiation. If this directly observable universe is part of a much grander system of universe-within-universes (C.V.I. Charlier’s hypothesis¹) then there is little we can say.