and inertial mass, together with the time dilation of special relativity, and a consequence of these—the Gravitational redshift. Bohr showed that, in order for Einstein's experiment to function, the box would have to be suspended on a spring in the middle of a gravitational field. In order to obtain a measurement of the weight of the box, a pointer would have to be attached to the box which corresponded with the index on a scale. After the release of a photon, a mass could be added to the box to restore it to its original position and this would allow us to determine the energy that was lost when the photon left. The box is immersed in a gravitational field of strength , and the gravitational redshift affects the speed of the clock, yielding uncertainty in the time required for the pointer to return to its original position. Bohr gave the following calculation establishing the uncertainty relation . Let the uncertainty in the mass be denoted by . Let the error in the position of the pointer be . Adding the load to the box imparts a momentum that we can measure with an accuracy , where ≈ . Clearly , and therefore . By the redshift formula (which follows from the principle of equivalence and the time dilation), the uncertainty in the time is , and , and so . We have therefore proven the claimed . More recent analyses of the photon box debate questions Bohr’s understanding of Einstein’s thought experiment, referring instead to a prelude to the EPR paper, focusing on inseparability rather than indeterminism being at issue. Post-revolution: Second stage The second phase of Einstein's "debate" with Bohr and the orthodox interpretation is characterized by an acceptance of the fact that it is, as a practical matter, impossible to simultaneously determine the values of certain incompatible quantities, but the rejection that this implies that these quantities do not actually have precise values. Einstein rejects the probabilistic interpretation of Born and insists that quantum probabilities are epistemic and not ontological in nature. As a consequence, the theory must be incomplete in some way. He recognizes the great value of the theory, but suggests that it "does not tell the whole story", and, while providing an appropriate description at a certain level, it gives no information on the more fundamental underlying level: I have the greatest consideration for