  This paper gives a compilation of physical mechanisms which have been
proposed to explain the spectral red-shift of distant astronomical objects.
Over sixty selected mechanisms are listed for the purpose of quantitative
comparisons. Some of these mechanisms may not completely account for all
astrophysical observations but are relevant to particular situations such as
the solar limb red-shift, the red-shift of quasars or the cosmological
red-shift. However, this paper focuses mainly on the 59 mechanisms giving a
quantitative description of the cosmological redshift-distance relationship. A
description is given for each mechanism including its properties, limits of
applicability, functional relationships and comments.
