Perspective on quantum mechanical tunneling.
People have been asking for the math. So here it is. The Sun`s core temp is ~13.6 MK. For hydrogen nuclei the Coulomb barrier is roughly 0.1 MeV. This corresponds to a temperature in excess of 1 GK! Luckily, tunneling and the distribution of speeds among nuclei lower the actual temperature required. So without tunneling even the Sun`s core isn`t hot enough for fusion
