Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic scales, the so-called quantum realm.

Excerpt: How does it come about that alongside of the idea of ponderable matter, which is derived by abstraction from everyday life, the physicists set the idea of the existence of another kind of matter, the ether? The explanation is probably to be sought in those phenomena which have given rise to the theory of action at a distance, and in the properties of light which have led to the undulatory theory. Let us devote a little while to the consideration of these two subjects.

Preface: (December, 1916) The present book is intended, as far as possible, to give an exact insight into the theory of Relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics. The work presumes a standard of education corresponding to that of a university matriculation examination, and, despite the shortness of the book, a f...

ETHER AND THE THEORY OF RELATIVITY. An Address delivered on May 5th, 1920, in the University of Leyden How does it come about that alongside of the idea of ponderable matter, which is derived by abstraction from everyday life, the physicists set the idea of the existence of another kind of matter, the ether? The explanation is probably to be sought in those phenomena which have given rise to the theory of action at a distance, and in the properties of light which have le...

Excerpt: Part I: The Special Theory of Relativity: // 01. Physical Meaning of Geometrical Propositions // 02. The System of Coordinates // 03. Space and Time in Classical Mechanics // 04. The Galilean System of Coordinates // 05. The Principle of Relativity (in the Restricted Sense) // 06. The Theorem of the Addition of Velocities employed in Classical Mechanics // 07. The Apparent Incompatibility of the Law of Propagation of Light with the Principle of Relativity // 08....

Abstract: Progress in the new information-theoretic process physics is reported in which the link to the phenomenology of general relativity is made. In process physics the fundamental assumption is that reality is to be modeled as self-organizing semantic (or internal or relational) information using a self-referentially limited neural network model. Previous progress in process physics included the demonstration that space and quantum physics are emergent and unified, ...