Physics
Scientific paper
Jan 1974
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1974aipc...16..157b&link_type=abstract
CAUSALITY AND PHYSICAL THEORIES. AIP Conference Proceedings, Volume 16, pp. 157-175 (1974).
Physics
Scientific paper
Life in general, and man's memory in particular, determine a preferred direction in time (``time arrow''). It is made plausible that the time direction in which the entropy increases is this same time arrow.
In quantum theory, wave functions describe not real (single) physical systems, but ensembles of systems. Reduction of wave packets corresponds to treating a system as a member of a new ensemble. Similarly, splitting an electromagnetic field into IN-field plus retarded field, or into OUT-field plus advanced field, corresponds to different ensembles describing a scattering on which only partial information is available. Our desire to ascribe a source to any light observed is the reason for usually preferring retarded fields over advanced fields. Independent of the fact that retardation of light waves is shown experimentally by Fizeau's measurement of the velocity of light, Afterthought One shows that an eye-object interaction by advanced fields would violate the second law of thermodynamics. This would relate the time arrow of electromagnetism to the one of life. A puzzle remains when this is applied to light traveling between stars and interstellar dust.
The time arrow of cosmology (time direction of expansion of the universe) is sometimes related to the time arrow of life by an extension of Olbers' paradox. An example worked out in Afterthought Two shows that this generalization of Olbers' paradox is not justified. Afterthought Three contains some speculations about possible correlations between the time arrows of cosmology and of life.
The time arrow of quantum theory is determined by the fact that quantum theory in general predicts future probabilities, and that it can retrodict (postdict) probabilities of the past only under specific conditions that often are not satisfied. This asymmetry becomes more understandable when quantum theory is applied to sequences of nonideal (irreproducible) measurements separated by the use of gadgetry that prepares chosen initial conditions for the next measurement. The entering here of choice indicates a relation between the mind with its built-in time arrow, and the choice of the ensembles to which quantum theory then is applied objectively.
We shall now return to the style of yesterday's meeting, talking about generalities. The only difference is that I will be thinking in terms of quantum theory instead of classical theory. Therefore the word Indeterminism in the title of this talk.
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