Quantum Theorycontains 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 Worldis 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, specially written for these editions, placing the book in context both as part of the new series, and highlighting its special contribution to the advancement of human understanding; they examine the significance of each work, their impact at time of publication, and their influence today.