  We formulate a predictive theory at the level of forces of activated
relaxation in hard sphere fluids and thermal liquids that covers in a unified
manner the apparent Arrhenius, crossover and deeply supercooled regimes. The
alpha relaxation event involves coupled cage-scale hopping and a long range
collective elastic distortion of the surrounding liquid, which results in two
inter-related, but distinct, barriers. The strongly temperature and density
dependent collective barrier is associated with a growing length scale, the
shear modulus and density fluctuations. Thermal liquids are mapped to an
effective hard sphere fluid based on matching long wavelength density
fluctuation amplitudes, resulting in a zeroth order quasi-universal
description. The theory is devoid of fit parameters, has no divergences at
finite temperature nor below jamming, and captures the key features of the
alpha time of molecular liquids from picoseconds to hundreds of seconds.
