 The number of water molecules in 1 m3 of water is approximately 1028.These leads to the prediction formula_38, which means that on average one would have to wait 1083s (1076 years) to see a single ice nucleus forming in 1 m3 of water at -20 °C!This is a rate of homogeneous nucleation estimated for a model of water, not real water — in experiments one cannot grow nuclei of water and so cannot directly determine the values of the barrier formula_5, or the dynamic parameters such as formula_10, for real water.