We confront the big bang for the beginning of the universe with an equivalent picture of a slow freeze — a very cold and slowly evolving universe. In the freeze picture the masses of elementary particles increase and the gravitational constant decreases with cosmic time, while the Newtonian attraction remains unchanged. The freeze and big bang pictures both describe the same observations or physical reality. We present a simple “crossover model” without a big bang singularity. In the infinite past space–time is flat. Our model is compatible with present observations, describing the generation of primordial density fluctuations during inflation as well as the present transition to a dark energy-dominated universe. The early stages in the evolution of our universe are generally depicted as a big bang. The temperature of an early plasma of radiation and particles was much higher than the temperature of 2.7 K measured in the cosmic microwave background (CMB), exceeding in early stages by far the temperature of the sun or any other object in the present universe. This fireball resulted from a type of extremely fast primordial explosion — the big bang. Characteristic time scales of the early stages of the explosion were 10−3010−30 seconds or shorter, extremely tiny as compared to the present time scale of the cosmic expansion of around 1010 years. In this note we contrast the big bang picture with a very different alternative picture of a slow freeze. We present a specific “crossover model” which is described both in the freeze and big bang pictures. In the freeze picture the characteristic mass scale is set by a parameter

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