216 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



The energy thrown out with the sunlight is several billion times 

 greater than the total interchange of energy which takes place on the 

 earth. The sun gives off continually enormous quantities of it, and 

 its supply, of whatever unknown kind it may be, must finally be 

 exhausted. It would cool down more and more, and our civilization, 

 after terrible struggles, would meet with disaster more and more 

 amidst the ever-present ice. 



Thus the two fundamental physical laws lead, it is seen, to essen- 

 tially gloomy consequences, but, with all the respect that is due to 

 their sublime results and to their precision, it is only right to ask 

 whether they are really established with such ideal exactness as to 

 enable one to draw conclusions applicable to epochs immensely re- 

 mote, and to comprehend the very plan of creation. Before accept- 

 ing these consequences, it will be well to submit these inexorable laws 

 to a much more searching scrutiny. That the law of gravitation will 

 not support an examination carried to extreme limits, nearly all as- 

 tronomers agree in admitting. The most striking deviation from this 

 law is offered us by the moon, which undergoes an inexplicable ac- 

 celeration, not less than 6 seconds per century. An analogous anom- 

 aly, more marked and still more complicated, has also been recog- 

 nized in the motion of Encke's comet. The orbit of Mercury pre- 

 sents an inexplicable perihelic rotation, attaining 40 seconds per 

 century, and its eccentricity is not augmented with the rapidity which 

 the law of gravitation demands. The orbit of Mars is subject to 

 anomalies of the same nature, while the inclination of the orbit of 

 Venus increases too rapidly by 10 seconds every century. Terrestrial 

 gravity presents, even from the point of view of direction, a diurnal 

 and annual oscillation of a fraction of a second, which is not to be 

 explained alone by the attraction of the moon or of the sun.^ It is 

 true that these are relatively small and isolated deviations, and that in 

 general the law of gravitation suffices for the calculation of the mo- 

 tions of the stars with a sufficient approximation, always assuming 

 that the cosmic ether is absolutely devoid of friction. This latter, 

 however, is far from being accepted by physicists. When one con- 

 siders that the periodic comets, even the smallest ones, apparently 

 undergo no frictional resistance, that they are capable of penetrating 

 the solar corona at a speed of 5,500 kilometers per second, without 

 undergoing appreciable loss, one is obliged to admit that the law of 

 gravitation is not sufficient, but that forces unknown, though hinted 

 at by Kepler, act upon the stars in motion, and tend to offset the ef- 

 fects due to friction of the cosmic ether. It is a fact that no trace, 

 however slight, of a beginning of the falling of the planets toward 

 the sun, as the law of Newton predicts, has yet been shown. The same 



^G. H. Darwin, Tides, 1898, p. 125; O. Hecker, Publications of the Royal Prussian 

 Geodetic Institute, No. 82, 1907. 



