I once had my friend calculate the probability of a single pair of hydrogen nuclei fusing in the reaction of 2H2 with O2 in a balloon (which produces a cool boom resulting in water vapor). Despite the enormous number of atoms, and the fact that at the high energy tail of the distribution some fraction of atoms should be going really fast, the probability that any were going fast enough to fuse was e^-somethinghuge.
I once had my friend calculate the probability of a single pair of hydrogen nuclei fusing in the reaction of 2H2 with O2 in a balloon (which produces a cool boom resulting in water vapor). Despite the enormous number of atoms, and the fact that at the high energy tail of the distribution some fraction of atoms should be going really fast, the probability that any were going fast enough to fuse was e^-somethinghuge.