Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. The scale factor
or cosmic scale factor parameter of the Friedmann equations is a
function of time which represents the relative expansion of the
universe. It is sometimes called the Robertson-Walker scale factor. It
relates the comoving distances for an expanding universe with the
distances at a reference time arbitrarily taken to be the present.The
evolution of the scale factor is a dynamical question, determined by the
equations of general relativity, which are presented in the case of a
locally isotropic, locally homogeneous universe by the Friedmann
equations.
