Quantum Mechanics and the Bohr-Einstein Debate

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