By 1926, Albert Einstein had become completely unforgiving of quantum mechanics’ probabilistic interpretation of the universe and would step away from it forever. In Einstein’s mind, the universe must ultimately obey laws of physics that are fundamentally deterministic, and with respect to this, he would be uncompromising. Einstein made this most clear in response to a letter Max Born (1882–1970) had written to him when he said:
Quantum mechanics is very impressive. But an inner voice tells me that it is not yet the real thing. The theory produces a good deal but hardly brings us closer to the secret of the Old One. I am at all events convinced that He does not play dice.
Indeed, for the last 30 years of Einstein’s life (even including the last moments just before his death on April 18, 1955), his scientific endeavors were committed to this vision as he focused on finding a unified field theory. Among other things, such a theory was to unify gravity (as described by Einstein’s very own general relativity) and electromagnetism (as described by Maxwell’s equations), and most importantly, it was to rid physics of the “quantum uncertainty.”
Nonetheless, Einstein’s relationship with quantum wasn’t always so strained, and in fact, he led the way in its development for some 20 years, as it transitioned from quantum theory into quantum mechanics. So, what happened?