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Twin2Design Inc.
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WERNER HEISENBERG (1901 - 1976)
While Einstein believed that randomness is a reflection of our ignorance of some fundamental property of reality, Bohr believed that the probability distributions are fundamental and irreducible, and depend on which measurements we choose to perform. There is no objective reality underneath determining the outcome. Not only is there a veil hiding the clockwork, but the clockwork is different depending on how you lift the veil.
But Bohr was compelled to modify his understanding of the uncertainty principle after another thought experiment by Einstein. In 1935, Einstein, Podolski and Rosen published an analysis of widely separated entangled particles. Measuring one particle, Einstein realized, would alter the probability distribution of the other, yet here the other particle could not possibly be disturbed. This example led Bohr to revise his understanding of the principle, concluding that the uncertainty was not caused by a direct interaction.[7].
But Einstein came to much more far reaching conclusions from the same thought experiment. He felt that a complete description of reality would have to predict the results of experiments from locally changing deterministic quantities, and therefore would have to include more information than the maximum possible allowed by the uncertainty principle.
In 1964 John Bell showed that this assumption can be tested, since it implies a certain inequality between the probability of different experiments. Experimental results confirm the predictions of quantum mechanics, ruling out local hidden variables.
Albert Einstein was not happy with the uncertainty principle, and he challenged Niels Bohr and Werner Heisenberg with many thought experiments designed to test it. The most famous went as follows (see also Bohr-Einstein debates):
Consider a box filled with light. The box has a shutter, which opens and quickly closes by a clock at a precise time, and some of the light escapes. We can set the clock so that the time that the energy escapes is known. To measure the amount of energy that leaves, Einstein proposed weighing the box just after the emission. The missing energy will lessen the weight of the box. If the box is mounted on a scale, it is naively possible to adjust the parameters so that the uncertainty principle is violated.
Bohr spent a day considering this setup, but eventually realized that if the scale and the box are placed in a gravitational field, then the uncertainty of the position of the clock in the gravitational field will alter the rate, and this introduces the right amount of uncertainty.
The Copenhagen interpretation of quantum mechanics and Heisenberg's Uncertainty Principle were seen as twin targets by detractors who believed in an underlying determinism and realism. Within the Copenhagen interpretation of quantum mechanics, there is no fundamental reality which the quantum state is describing, just a prescription for calculating experimental results. There is no way to say what the state of a system fundamentally is, only what the result of observations might be.
