Quantum Theory contains the seminal works of quantum theory from the early years of the 20th Century, representing breakthroughs in science that radically altered the landscape of modern knowledge: Quantum Theory of Line-Spectra by Niels Bohr and The Origin and Development of the Quantum Theory by Max Planck. FLAME TREE's Great Works That Shape Our World is a new series of definitive books drawing on ancient, medieval and modern writing. Created to entertain, inform and enrich the new series brings infinite variety to refresh the mind, presented in beautiful editions for the modern market. Each book features a new, accessible introduction placing the book in context both as part of the new series, and its special contribution to the advancement of human understanding. New Introductions specially written for these editions examine the significance of each work, their impact at time of publication, and their influence today. Created to entertain, inform and enrich the new series brings infinite variety to refresh the mind, presented in beautiful editions for the modern market. Each book features a new, accessible introduction placing the book in context both as part of the new series, and its special contribution to the advancement of human understanding. New Introductions specially written for these editions examine the significance of each work, their impact at time of publication, and their influence today. AUTHORS: Max Karl Ernst Ludwig Planck was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of quantum theory, which revolutionised human understanding of atomic and subatomic processes. Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research.