Karina+Week+9

While reading the piece by Niels Bohr on his discussion with Einstein on “Epistemological Problems in Atomic Physics”, I found that there was much information there but the paper dragged on and on and I found that I was getting almost nowhere. I was intrigued however, with the discussion between two of the men accredited as great physicists, which would have centered on their disagreements about certain aspects of their field. “From the very beginning the main point under debate has been the attitude to take to the departure from customary principles of natural philosophy characteristic of the novel development of physics which was initiated in the first year of this century by Planck's discovery of the universal quantum of action.” Both Albert Einstein and Niels Bohr are well known physicists of the 20th century who, while contributing monumentally to their field, disagreed about the interpretations of quantum theory beginning at the fifth Solvay Conference and ending at Einstein’s death in 1955. Bohr introduced the idea that an electron could drop from a higher-energy level (or orbit) to a lower one, emitting a photon (light quantum) of discrete energy as the result. This theory became the basis for quantum theory (which was radically different from the interpretations of classical physics). // Bohr’s argument has been summarized by Max Jammer in “The Philosophy of Quantum Mechanics” as // // “1. Indivisibility of the quantum of action. (quantum postulate”). // // 2. Discontinuity (or indivisibility) of elementary processes. // // 3. Uncontrollability of interaction between object and instrument. // // 4. Impossibility of a (strict) spatio-temporal and at the same time causal description. // // 5. Renunciation of the classical mode of description.”  // // (as quoted in Horner, 1987, 106)  // Anyway…Einstein's great original contribution to quantum theory (I905) was just the recognition of how physical phenomena like the photo-effect may depend directly on individual quantum effects.  Einstein also believed it was possible to measure properties such as the position and momentum of a particle or its energy at the same point in time (using classical physics). If these measurements were possible, then it would show that both Bohr’s idea of complementarity, which refers to the duality of light (wave-like and particle-like properties) where measurements made on a system reveal it to have either particle-like or wave-like properties, and Heisenberg’s uncertainty principle (certain physical characteristics, such as momentum and position, cannot both be known at the same time) were wrong and that the quantum theory proposed by Bohr, called the Copenhagen Interpretation, was wrong. Einstein’s famous quote, “God does not play dice.” sums up his disagreement with Bohr and his dislike of the uncertainty principal and the discontinuity of Bohr’s theory. Einstein attempted to prove Bohr wrong by modifying the double slit experiment, saying that it was possible to tell which slit a particle passed through. Bohr disproved that argument by showing that, “//there was a change in momentum of the electron as it passed through the slit due to interaction between the electron and the screen. The width of the slit which effects the position of the electron and the wave cone brings a degree of uncertainty into the position of the electron as its momentum changes. This uncertainty was consistent with Heisenberg’s uncertainty principle…”// Another attempt of Einstein to disprove quantum theory was described in the correspondence to Einstein by Bohr, and involved the complex “Clock in the Box Experiment”. This experiment in short was, “//This involved a box with a hole in one wall covered by a shutter which could be opened and closed by a clock mechanism inside the box. The box also contained radiation which would add to the weight of the box. The box would be weighed and then at a given moment the clock would open the shutter allowing a single photon of radiation to escape. The box could then be re-weighed, the difference between the two weights telling us the amount of energy that escaped using the formula e=mc2. Under the uncertainty principle it is not possible to obtain an exact measurement of the energy of the released photon and the time at which it was released.” //Bohr’s reply was to point out the impracticalities of making the required measurements and to show that uncertainty is involved in the experiment and thus Einstein’s experiment did not do the intended of disproving the uncertainly principle. (More detail is in the discussion between Bohr and Einstein.) Einstein never accepted the limits that Bohr argued were on the knowledge of the quantum world, yet was never able to get around those limits. So while Einstein was not able to disprove Bohr’s theory, that does not mean he was entirely wrong.