I can't think that it would be terrible of me to say - and it is occasionally true - that I need physics more than friends.

When all thermonuclear sources of energy are exhausted a sufficiently heavy star will collapse. Unless fission due to rotation, the radiation of mass, or the blowing off of mass by radiation, reduce the star's mass to the order of that of the sun, this contraction will continue indefinitely.

It is proper to the role of the scientist that he not merely find new truth and communicate it to his fellows, but that he teach, that he try to bring the most honest and intelligible account of new knowledge to all who will try to learn.

When you see something that is technically sweet, you go ahead and do it and you argue about what to do about it only after you have had your technical success. That is the way it was with the atomic bomb.

[About the great synthesis of atomic physics in the 1920s:] It was a heroic time. It was not the doing of any one man; it involved the collaboration of scores of scientists from many different lands. But from the first to last the deeply creative, subtle and critical spirit of Niels Bohr guided, restrained, deepened and finally transmuted the enterprise.

Maybe General Groves was right. Maybe we should just banish thinking forever.

Both the man of science and the man of action live always at the edge of mystery, surrounded by it.