The quantum-mechanical model, besides revolutionizing chemistry, shook the philosophical world because of its implications regarding determinism. Determinism is the idea that the outcomes of future events are determined by preceding events. The trajectory of a baseball, for example, is deterministic; that is, its trajectory—and therefore its landing place—is determined by its position, speed, and direction of travel. Before quantum mechanics, most scientists thought that fundamental particles—such as electrons and protons—also behaved deterministically. The implication of this belief was that the entire universe must behave deterministically—the future must be determined by preceding events. Quantum mechanics challenged this reasoning because fundamental particles do not behave deterministically—their future paths are not determined by preceding events. Some scientists struggled with this idea. Einstein himself refused to believe it, stating, "God does not play dice with the universe." Explain what Einstein meant by this statement.
Here, we are going to explain what einstein meant by the given statement.
Einstein of course believed in mathematical laws of nature, so his idea of a God was at best someone who formulated the laws and then left the universe alone to evolve according to these laws. He saw the hand of God in the precise nature of physical laws, in their mathematical beauty and elegance, and in their simplicity. To him, the very fact that there were natural laws that the human mind could discover was evidence of a God, not a God who superseded these laws but one who created them. Thus his use of the word God is to be interpreted as the existence of natural laws of great mathematical beauty, whatever form they might take.
This brings us to the second part of Einstein’s statement, the part about not playing dice. This relates to Einstein’s reaction to the part of Nature described by Quantum Mechanics, which is undoubtedly one of the pillars of modern physics. He felt that natural laws could not be like the throw of dice, with inherent randomness or probability. But this is exactly what Quantum Mechanics tells us – that at the fundamental level Nature is inherently random, codified in Heisenberg’s famous Uncertainty Principle.