- A simple calculation shows that from the classical theory follows that we should find a broadening of the beam with the maximum intensity on the place of the beam without field. However, from the quantum theory follows that we should find there no intensity at all, and deflected molecules on both sides. The beam should split up in two beams corresponding to the two orientations of the magnet. The experiment decided in favor of the quantum theory.
- "Shall we do it?" "Well, then let's go, we shall do it!" Otto Stern asking, Walther Gerlach answering.
- As quoted in The Historical Development of Quantum Theory: Its Foundation and the Rise of Its Difficulties, 1900-1925 (2001) by Jagdish Mehra, p. 437.