proved to be wrong about light quanta. Although Bohr and Einstein disagreed, they were great friends all their lives and enjoyed using each other as a foil. The year 1913 brought the Bohr model of the hydrogen atom, which made use of the quantum to explain the atomic spectrum although at the time Bohr did not believe the atom to be wave-like but like a solar system so that the equations he used were for rotational orbits of particles similar to planets, yet Planck’s constant had been invented for light radiation in black bodies. Einstein was at first skeptical about using h for a solar system style atom, but quickly changed his mind and admitted his shift in mindset. From 1913 to 1919, Einstein studied and revised Arnold Sommerfeld’s extension of the Bohr atom to include the Stark effect and Zeeman effect. The coefficients Einstein created during this time are still named for him and still in use today. The quantum revolution The quantum revolution of the mid-1920s occurred under the direction of both Einstein and Bohr, and their post-revolutionary debates were about making sense of the change. The shocks for Einstein began in 1925 when Werner Heisenberg introduced matrix equations that removed the Newtonian elements of space and time from any underlying reality. However, when Erwin Schrödinger sent a preprint of his new equation to Einstein, Einstein wrote back hailing his equation as a decisive advance of “true genius.” But the next shock came in 1926 when Max Born proposed that mechanics were to be understood as a probability without any causal explanation. Both Einstein and Erwin Schrödinger rejected this interpretation with its renunciation of causality which had been a key feature of science previous to Quantum Mechanics and was still a feature of General Relativity. In a 1926 letter to Max Born, Einstein wrote: "quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the “old one”. I, at any rate, am convinced that He [God] is not playing at dice." At first, even Heisenberg had heated disputes with Bohr that his matrix mechanics was not compatible with the Schrödinger Equation. And Bohr was at first opposed to the Uncertainty Principle. But by the Fifth Solvay Conference held in October 1927 Heisenberg