 At these extremely small distances, quantum mechanics plays a dominating role. A proton travels as a wave, described by Schrodinger's equation. As a wave, its exact location is not completely knowable. The square of the particle's wave function gives us the probability for materializing as a particle at any particular location and time. Most of the time, it will be found at the most probable location. But we see that some of the wave function is on the far side of the barrier. The wave amplitude is significantly smaller, but the frequency is the same. The small amplitude indicates that there is a small probability that it will materialize there. But having the same frequency indicates that it will have the full particle energy. The phenomenon is called tunneling. At the Sun's temperature, the probability that a proton will tunnel through the barrier is quite small, but 193 orders of magnitude more likely than classical physics would have it. Protons will cross the barrier and overlap many times before they actually trigger a fusion event. To be exact, converting probabilities to rates, we see that on average, there are a million successful tunnelings through the Coulomb barrier to get one fusion. This is because, in order to fuse, a pion transfer between the two protons or something similar has to occur in the extremely short period of time that the protons are in contact. This particle sharing in the nucleus is similar to the electron sharing that binds molecules. We cover how this works in the Higgs-Boson segment of the How Small Is It? video book. In addition, one of the protons has to eject a neutrino and a positron to become a neutron. All these nuclear processes are sensitive to proton energies, that is, temperature. To conclude, we see that small increases in the colliding proton's energy driven by increases in temperature will increase collisions, cross-sections, Coulomb barrier penetration rates, and fusion rates for overlapping protons. The accumulative effect makes the hydrogen burn rate exponentially sensitive to temperature.