1. Quantum Mechanics and the Bohr-Einstein Debate

2. Heroes of Quantum Mechanics

3. Heisenberg’s Breakthrough, 1925: Matrix Mechanics Theory built on observables, e.g., transition probabilities of quantum jumps Motions were described by terms represented not by straightforward numbers, but by matrices Three-man-paper: Heisenberg, Max Born, and Pascual Jordan pq-qp=h/2πi

4. De Broglie-Schrödinger’s Wave Mechanics Louis de Broglie: If light can behave like particles, why can’t matter (e.g., electrons) behave like waves? Schrödinger, 1925-1926: applied electron- as-wave concept to atomic theory Wave mechanics: quantization came about because only in certain orbit could electron wave have integral number of “vibrations.”

5. Reactions to Two Rival Theories Bohr supported Heisenberg’s while Einstein and Planck backed Schrödinger’s 1926: discovery of mathematical equivalence of the two theories Born’s probability interpretation: electron wave was not real wave, but only wave of probability Philosophical differences: Matrix Mechanics emphasized particle aspect, denied visualization, threatened determinism; wave mechanics gave a familiar, continuous, and causal world view

6. Bohr-Heisenberg Debate Heisenberg denied completely the wave aspect of quantum mechanics but Bohr thought that there was a particle-wave duality Heisenberg: uncertainty principle Δp Δq ≈ h/2π Bohr: complementarity: particle-wave duality is a fundamental fact of nature Copenhagen Interpretation: Uncertainty + Complementarity

7. Bohr-Einstein Debate Bohr advocated Copenhagen interpretation Einstein: admitted that quantum mechanics worked, but thought it was not complete—not the final word Different philosophies: Bohr was more empiricist believing that the goal of science as to organize our experience Einstein believed in fundamental unity and rationality of nature and the universe