The Development of Elementary Quantum Theory from 1900 to 1927

TL;DR

This paper reviews the historical development of elementary quantum theory from 1900 to 1927, highlighting key ideas, conceptual shifts, and contributions by major physicists leading to the 1925/26 formulation.

Contribution

It provides a detailed historical analysis of the evolution of quantum theory, emphasizing original publications and the conceptual breakthroughs that shaped its development.

Findings

Key contributions by Einstein, Born, and Jordan identified

Transition from classical to quantum concepts explained

Mathematical representations of quantum laws discussed

Abstract

Planck's introduction of the quantum of action in 1900 was followed by 25 years of trial and error in quest of the understanding of the quantum world; different ideas and directions had to be pursued until the path leading to the elementary quantum theory was discovered. Radical changes away from traditional perceptions about natural phenomena were necessary, the entire system of basic concepts in classical physics had to be abandoned and replaced by a new mode of thought. Continuity and determinism of classical laws were no longer applicable on the quantum scale, where dynamical behaviour proceeds by discontinuous and statistical quantum transitions. Albert Einstein laid the essential foundations for the new concept; Max Born made the decisive step further leading to the breakthrough in 1925. The development of the ideas, which eventually resulted in the elementary quantum theory in 1925/26, will be described, relying on original publications and letters written during that period in time by the major contributors. The fundamental laws of Quantum Theory derived by Max Born and Pascual Jordan may mathematically be represented in many different ways, and particular emphasis is given to the distinction between physical content and mathematical representation.