"...there is an optimal balance, depending on the manner of man's life, between the density of human population and the tolerances of nature. This balance, in the case of the United States would seem to me to have been surpassed when the American population reached, at a very maximum, two hundred million people, and perhaps a good deal less."

Next Quote

With all reserve we advance the view that a supernova represents the transition of an ordinary star into a neutron star consisting mainly of neutrons. Such a star may possess a very small radius and an extremely high density. As neutrons can be packed much more closely than ordinary nuclei and electrons, the gravitational packing energy in a cold neutron star may become very large, and under certain conditions may far exceed the ordinary nuclear packing fractions.

— Fritz Zwicky