  A unique description of the Big Crunch-Big Bang transition is given at the
classical gravity level, along with a complete set of homogeneous, isotropic,
analytic solutions in scalar-tensor cosmology, with radiation and curvature.
All solutions repeat cyclically; they have been obtained by using conformal
gauge symmetry (Weyl symmetry) as a powerful tool in cosmology, and more
generally in gravity. The significance of the Big Crunch-Big Bang transition is
that it provides a model independent analytic resolution of the singularity, as
an unambiguous and unavoidable solution of the equations at the classical
gravitational physics level. It is controlled only by geometry (including
anisotropy) and only very general features of matter coupled to gravity, such
as kinetic energy of a scalar field, and radiation due to all forms of
relativistic matter. This analytic resolution of the singularity is due to an
attractor mechanism created by the leading terms in the cosmological equation.
It is unique, and it is unavoidable in classical relativity in a geodesically
complete geometry. Its counterpart in quantum gravity remains to be understood.
