In 1969, 1970, I looked at the surface of those neutron stars and wrote a paper about it in Copenhagen with Baym and Pethick who were great experts in statistical mechanics and we thought we could explain the surface structure of a neutron star, that there is ordinary matter at the very surface, and then as the density increases you get more and more neutrons. The protons absorb electrons and once you get to a high enough density you have almost pure neutrons. So that then again made me interested in finding out how these... the neutrons themselves would behave on the... in the inner part of that neutron star. They obviously at high density come close enough to each other to have nuclear interaction and we pretty well knew that nuclear interaction, because we know it generally between any nucleon and another nucleon - proton-proton proton-neutron, and neutron-neutron. And so on that basis I, with another postdoctoral student, Johnson, calculated the behavior of neutron star matter at high density, density several times the density of an ordinary nucleus, and my previous work of course on nuclear matter was useful for that. And we got an equation of state for neutron matter at... at these high densities, and then together with another student, in fact a student of Salpeter's, Malone, we calculated how a neutron star may be constructed, how the density changes from the center to the outside. It has the highest density of course at the center, but that density mustn't be too high because if it got too high then it would collapse into a Black Hole. And I think the calculations we did were satisfactory. We calculated that the neutron star would have a radius of about 10km and a mass a little bigger than the mass of the sun.