On one occasion, physicist Ludwik Silberstein: The famous astrophysicist Subrahmanyan Chandrasekhar heard this story directly from Eddington. It is described in Berenstein 1973, p. 192.

“Only the inertia of tradition”: Eddington 1920. Quoted also in full in the 1988 edition of The Internal Constitution of the Stars (Cambridge: Cambridge University Press), in the foreword (by S. Chandrasekhar), p. x.

the strong, attractive nuclear force: At distances that are very small compared to the size of the nucleus, the nuclear force itself becomes repulsive, because particles such as protons (fermions) resist being crowded. This quantum effect is known as the Pauli exclusion principle.

Using this quantum mechanical effect: The probability of penetrating the barrier created by the Coulomb force increases exponentially with increasing energy of the particles. At the same time, the distribution of the particles at a given temperature is such that at high energies the number of particles decreases exponentially. The product of these two factors results in a peak (known as the Gamow peak) at which the nuclear reaction is most likely to occur. These ideas were first published in the late 1920s.

In a remarkable paper published: Bethe 1939.