Transcript: Stellar fusion cannot be understood without the quantum theory of matter. In classical physics the electrical repulsion force between two protons as they approach each other is an insurmountable barrier, but in the quantum theory there’s a finite probability that the protons will ignore the barrier and be able to fuse. This problem was worked out in the 1930s by Hans Bethe, a German physicist who immigrated to Cornell University. Bethe calculated the probability that protons would fuse and then was able to realize that the small amount of mass-energy released was sufficient to power the fusion reaction in the Sun and other stars. The paper he wrote on the subject gave him a prize with which he helped his parents and family escape from Nazi Germany. The same work subsequently won him the Noble Prize.