Niels Bohr: The Man, His Science, and the World They Changed
The Questioners: Physicists and the Quantum Theory
Thirty Years that Shook Physics
One achievement that stands apart, in the complex history of ideas of the twentieth century, is the development of our concept of the structure of matter. It was a steady development, which penetrated deeper and deeper into the inner structure of the atom, ever broadening with each step our understanding of material things. Modern scientific progress is usually described as a series of revolutions and upheavals, in which old ideas are destroyed by a new theory. This description, however, overlooks the fundamental fact that scientific development is intrinsically evolutionary. Indeed, each of the new “revolutionary” ideas in modern science was a refinement of the old system of thought, a generalization or an extension. Relativity did not replace Newton’s mechanics—orbits of satellites are still calculated with Newton’s theory—but extended its application to extreme velocities and established the general validity of a common conceptual basis for both systems of mechanics and electricity. Quantum theory came perhaps nearest to being revolutionary, but even its ideas, such as the uncertainty principle, must be considered as a refinement, an application of mechanics to very small systems; quantum theory did not change the validity of classical mechanics to the motion of bodies of larger size.
Although the steady and incessant growth of our understanding of material structure may have helped to steady the minds of the scientists who live in this century of upheaval, it clearly did not have that effect on society itself. Growth of this kind necessarily brings with it more and more ways of dealing with new materials—new forms of energy and new ways of using them. This again, necessarily, changes the quality of life at an ever-increasing rate. We are left at odds with our accepted system of values when we face the new human problems created by this change.
Nothing could be better suited to illustrate this problem than a study of the life of Niels Bohr. Bohr was a great physicist. He ranks with the greatest figures in the history of science, with Galileo, Newton, Maxwell, and Einstein. It was he who began the development of our concepts of the structure of matter and kept this development going for half a century. To a greater degree than any other scientist, he was involved in the human consequences of his science, in its impact on politics and society.
Bohr was born in 1885; his life as a scientist began about 1905 and lasted for fifty-seven years. In 1905 Einstein published his first paper on special relativity, only a few years after Planck’s great discovery of the quantum of action. Niels Bohr had the luck to be alive at this important moment, or perhaps it was mankind’s luck that he was present at this critical point in the history of science. What a time to be a physicist! Bohr began his work when the structure of the atom was still unknown, and ended it when atomic physics had reached maturity, when the atomic nucleus was …