Harold F. Blum

Dimensions and Probability of Life

TIFE constitutes a very thin layer of matter on the L Earths surface, the biosphere: continuous cyclic change provides for maintenance, replication and other activities of this system; carbon dioxide is reduced by photosynthesis with concurrent formation of high-energy compounds that are then oxidized in the metabolism of living organisms, carbon dioxide being returned to the atmosphere. At present a balance is maintained with virtually no change in biosphere and atmosphere of the total amount of matter taking part in this cycle. The energy for photosynthesis is provided by continuous inflow of radiant energy from the Sun; an equal amount of energy being re-radiated from the Earth, but in the form of a larger number of quanta of lower energy than those received. The net increase in number of quanta may be regarded as a decrease in order with attendant increase in probability and entropy of a Sun-Earth system of which the biosphere system is a part. Thus, increase in order may occur in the biosphere, without contradiction of the second law of thermodynamics, so long as this average increase is less than the average decrease of order in the Sun-Earth system. If one were to think of the biosphere as an open system continuously replicated in exact quantity and patternthe same total amount of information being maintained -one would assume that no over-all change in order occurred in this system, the only change in entropy being in the Sun-Earth system. But evolution of the biosphere has been going on for millenia, and this has certainly involved increase in orderly arrangement and decrease in entropy, which has, of course, been compensated by corresponding increase in entropy within the including Sun-Earth system. We may represent the changes pertaining to the SunEarth system by:

Evolution in the Biosphere

(2) Environmental Influences on Man (Dr. Crawford H. Greenewalt, chairman of the Board, E. 1. du Pont de N emours and Co., and regent of the Smithsonian Institution): Dr. Ian McTaggart Cowan, dean of the faculty of graduate studics, University of British Columbia; Prof. J. Robert Oppenheimcr, profcssor of physics and director of the Institute of Advanced Study, Princeton, fOlm<3rly dirflctor of the Los Alamos ScientifiC Laboratory.

Probability of Life

DR. FREMLINS analogy to probabilities of bridge hands seems far from applicable to evolutionary processes of the kind considered in my article. Before dealing a bridge hand the pack is thoroughly shuffled to avoid retention of patterns of arrangement of the cards. In evolution each step is predicated on an existing pattern which has been formulated in the course of previous evolutionary steps, the pattern being copied (by one means or another) and so retained between steps. Thus, the probability of a given step is to be reckoned in terms of existing pattern, not in terms of a shuffled arrangement as for a bridge hand. The analogy to computer operation used in my article seems more suitable and leads to a very different point of view.