by Jack Sarfatti
This is the title of a short 1931 letter by Einstein, Tolman and Podolsky that appeared in the Physical Review (37, 780-81). They argue that there is no arrow of time distinguishing past from future in quantum reality.
It will hence be concluded that the principles of quantum mechanics actually involve an uncertainty in the description of past events which is analogous to the uncertainty in the prediction of future events.
If, as I argue in this book, our minds are quantum wave functions of our material bodies, then this uncertainty about the past explains the fallibility of our memories. The writing of historical records is an irreversible process in classical reality in which we can, in the best of cases, ignore quantum uncertainty. If not, we would really be part of an apparently nightmarish reality worse than George Orwell's 1984 in which past history really is uncertain. In fact, the many-worlds picture of quantum reality says that there are many actual pasts as well as many actual presents and futures. If we could travel back in time we would be forced to switch between these different parallel universes in order to avoid paradoxes.
This paper is a precursor to the seminal Einstein- Podolsky-Rosen (EPR) paper of 1935 that led to the recognition of the importance of faster-than-light quantum influences. Both papers describe thought experiments on pairs of particles. The 1931 paper shows that the ability to exactly reconstruct the past motion for one particle would violate the Heisenberg uncertainty principle for energy and time for the second particle. The essential part of the argument is that "there can be no method for measuring the momentum of a particle without changing its value". Similarly, the 1935 EPR paper shows that it is possible to violate the Heisenberg uncertainty principle for momentum and position for the second particle by different free choices of measurements on the first in the absence of a faster-than-light influence between the two particles.
Therefore, the only way to keep the Heisenberg uncertainty principle is to recognize the objective reality of faster-than-light action at a distance. David Bohm's theory shows the detailed mechanism of the faster-than-light nonlocal quantum force which is qualitatively different from the local strong, electromagnetic-weak and gravitational "gauge" forces.
The 1931 paper is also interesting because it shows the common fallacy that quantum effects are only important on the tiny scale of atoms and below.
Finally, it is of special interest to emphasize the remarkable conclusion that the principles of quantum mechanics would actually impose limitations on the localization in time of a macroscopic phenomenon such as the opening and closing of a shutter.