History of quantum mechanics in the context of "Niels Bohr"

In physics, mechanics is the study of objects, their interaction, and motion; classical mechanics is mechanics limited to non-relativistic and non-quantum approximations. Most of the techniques of classical mechanics were developed before 1900 so the term classical mechanics refers to that historical era as well as the approximations. Other fields of physics that were developed in the same era, that use the same approximations, and are also considered "classical" include thermodynamics (see history of thermodynamics) and electromagnetism (see history of electromagnetism).

The critical historical event in classical mechanics was the publication by Isaac Newton of his laws of motion and his associated development of the mathematical techniques of calculus in 1678. Analytic tools of mechanics grew through the next two centuries, including the development of Hamiltonian mechanics and the action principles, concepts critical to the development of quantum mechanics and of relativity.

The Principles of Quantum Mechanics is an influential monograph written by Paul Dirac and first published by Oxford University Press in 1930. In this book, Dirac presents quantum mechanics in a formal, logically consistent, and axiomatic fashion, making the book the first of its kind. Its 82 sections contain 785 equations with no diagrams. Nor does it have an index, a bibliography, or a list of suggestions for further reading. The first half of the book lays down the foundations of quantum mechanics while the second half focuses on its applications. Dirac did not pursue a historical approach to the subject. Nor did he discuss at length the philosophy of quantum mechanics.