The Debate Between Einstein and Bohr

Beneath the complexities of our life, the world seems rather simple to the laws of Physics. As scientists started looking into the tiny building blocks of matter, all such certainty vanished away. The weird world of quantum mechanics startled us in more than one way. This journey down the rabbit hole became stranger than our common sense. It may be viewed as our descent into scientific madness. Albert Einstein along with several other luminaries like Niels Bohr was at the heart of these developments. Albert Einstein and Niels Bohr could not agree on the fundamental of quantum reality. Einstein had quantized ultra-violet light and Bohr had quantized the atom and are truly the fathers of quantum physics with Max Plank. It was the 1927 conference on quantum physics in Houston that really put the cat among the pigeons. The world witnessed a clash of titans.

Einstein showed that light also behaved like a particle. It questioned the reigning scientific orthodoxy that considered light only to be a wave and demonstrated that light also behaved like particles. This meant light behaved both like wave and particle. But with these new findings, the wheels of reality seemed to be coming off. It seemed to shake the ground on which we were standing. Bohr rightly said, ‘Anyone who is not shocked by quantum mechanics has not understood it’. The genius Einstein started thinking that quantum theory is incomplete. He was not the only one to think this way. Schrodinger also joined him. Other scientists also followed. Soon it was also noted that not just light but electrons, protons and other sub-atomic particles were also behaving like waves. But Einstein famously said ‘God does not play dice’ to show which side he had chosen. To him, reality cannot be both waves and particles. But Bohr opined that reality is neither wave nor particle until one decides to see it. It is our observation that summons reality into existence. Bohr said something truly weird. He said something like this: a spinning coin while in its spin is both heads and tails. It is only when it falls on one side, it becomes either heads or tails. The quantum world is the observer-created world. Before observation is made reality is ghostly. This means the debate between Einstein and Bohr struck the very heart of reality. Einstein again famously said, ‘does the moon cease to exist when I don’t look at it?”

Einstein along with his assistants Boris Podolsky and Nathan Rosen presented the famous EPR paradox. At the heart of their argument was quantum entanglement. Imagine to coins spinning around standing for two particles that are created together. Because they were created together they shared some common properties and are, therefore, entangled. Bohr’s interpretation is also called Copenhagen interpretation. It said that coins/ particles do not exist until we measure them. Now let us stop one of the coins and say that it reads heads. Because both the coins were entangled the other coin should instantaneously read tails. Einstein refused to believe in this faster-than-light communication between two particles. His special theory of relativity had made the speed of light the highest limit of speed. This means the instantaneous communication between the entangled particles would break the speed limit. Hence, he called it spooky action at a distance. He, therefore, taught that he has found a flaw in the Copenhagen interpretation. He believed that he had a better interpretation than that. He thought that whether the coins will read heads or tails was fixed long before we observed them. It is just hidden from us. He thinks entangled particles are more like a pair of gloves inside two boxes. The moment we open a box and find a left-handed glove, we will instantly know that the other box contains the right-handed glove. Therefore, there is no spooky action. They were already left-handed glove or right-handed glove before one of the boxes was opened.

The debate between Einstein and Bohr divided physicists between those that believed in objective reality and those that did not believe in it. There was no way to decide. But quantum applications were very successful. Hence, scientists choose to ignore Einstein’s objections. They even invented a phrase, ‘shut up and calculate’ to emphasize its applications. The debate about the reality of the quantum world was simply brushed aside. But Physicist John Bell had other ideas. He began asking the same fundamental questions: Did the quantum world exists only when it is observed or is there deeper truth waiting to be discovered? He produced what we know today as Bell’s incomplete theorem. It gave a death blow to Einstein’s view of quantum physics. Let us take the analogy to understand his theorem. When the rules are fixed before we begin to play a card game, the shrewd quantum dealer may cheat us by dealing the cards in a manner he always wins. When this happens, we are in Einstein’s world. The Cards are already stacked to let the shrewd quantum dealer win. But suppose we ask the shrewd quantum dealer to deal with the cards and then set the rules of the game. Now the dealer cannot stack the cards beforehand. If this is the case, we are in Bohr’s world. But what if we still lose the game? There is no sensible explanation. This suggests that each card is sending secret signals to the other cards \ across space and time. It defies all that we know. At the most, fundamental level, the reality is truly unknowable. Bell reduced this idea into a single mathematical equation in 1964 and showed that the quantum world was really weird and dizzy.

The next stage of quantum physics takes us to California where a group of new-age hippies became very fond of quantum physics. They began to mix quantum physics with eastern mysticism. We have famous work like the Tao of Physics of Fritjof Capra emerges out of their work. Their look began to tilt towards Bohr’s interpretation because it seems to support their esoteric beliefs and ideas. One of their Guru, John Clauser tried to seek experimental results to Bell’s theorem. It was later improved upon by Alain Aspect in Paris. Anton Zeilenger also refined the experiment. This indicates that finally, Bell’s equation was put to test. This test demonstrated that Einstein was wrong and Bohr was right. The world is indeed summoned into existence when we are looking at it. In a quantum sense, we may have to agree that the moon does not exist when we’re not looking.


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Hypocrisy is the tribute that vice pays to virtue.

- Fr Victor Ferrao