ONE of the most astounding things in nature is the enormous energy which the sun is continually dispensing as radiation to surrounding space. The earth, as viewed from the sun, is a mere point in space, and receives no more than 1/2,200,000,000 of the radiant energy which the sun is outpouring so lavishly. Yet out of this small fraction of the total radiation, practically all the terrestrial activities of wind and wave, tropical hurricanes and avalanches of ice on alpine slopes and the no less potent but milder forces which clothe the earth with verdure, originate.
If we include all the planets in the solar system, and assess the outgoing solar rays at the maximum tariff imposed by the obstructions in their path, it still remains true that only 1/100,000,000 of their power is directly utilized in maintaining the thermal equilibrium and life of the attendant orbs, dependent from day to day for these gifts upon the dispenser of all of this bounty.
The solar outpouring for even a single day is inconceivably great, yet the same flux of energy has been going on ceaselessly and with very little change in its absolute intensity for at least a hundred million years, as the records of geologic time attest. If only one part of solar radiant energy in one hundred million is directly utilized, what becomes of the other ninety-nine million, nine hundred and ninety-nine thousand, nine hundred and ninety-nine? Remember, also, that our sun is but one among hundreds of millions of stars made known to us by our photographic telescopes, all outpouring similar torrents of energy, and the question comes home to us accentuated with many millionfold intensity.
Professor Comstock has shown that the theoretical and observed distributions of luminosity among the brighter stars may be reconciled, if we suppose either that the intrinsically brightest stars have a "distinct tendency to cluster about the sun," or else that "there is a sensible absorption of light in its transmission through space, of such average amount that a star having a parallax of a tenth of a second appears one magnitude fainter than it would appear in the absence of absorption." Other modes of attacking the problem must be invoked in order to decide between these alternatives.
- George C. Comstock, "The Luminosity of the Brighter Lucid Stars," Publications of the Astronomical and Astrophysical Society of America, Vol. 1, p. 307.