  In the context of the half-centenary of Hagedorn temperature and the
statistical bootstrap model (SBM) we present a short account of how these
insights coincided with the establishment of the hot big-bang model (BBM) and
helped resolve some of the early philosophical difficulties. We then turn
attention to the present day context and show the dominance of strong
interaction quark and gluon degrees of freedom in the early stage, helping to
characterize the properties of the hot Universe. We focus attention on the
current experimental insights about cosmic microwave background (CMB)
temperature fluctuation, and develop a much improved understanding of the
neutrino freeze-out, in this way paving the path to the opening of a direct
connection of quark-gluon plasma (QGP) physics in the early Universe with the
QCD-lattice, and the study of the properties of QGP formed in the laboratory.
