PAST CHANGES IN THE UNIVERSE. 



353 



mersed) without becoming to some extent dissi- 

 pated in the gravific medium : for it seems incred- 

 ible how two media should be immersed in each 

 other without interfering with each other's mo- 

 tions at all. If we admit that the waves of heat, 

 though no perceptible diminution occurs in plane- 

 tary distances, are at last in the course of ages 

 frittered away or dissipated in the gravific medium 

 in which the ether is immersed, then, since ener- 

 gy cannot be annihilated, the full equivalent of 

 heat-energy (represented by the waves) is finally 

 converted into gravific energy (by dissipation in 

 the gravific medium). The energy, therefore, 

 which came from the gravific medium, and was 

 converted into heat-energy in the action of grav- 

 ity at the approach of the masses, is finally re- 

 stored to the gravific medium again, in the frit- 

 tering away of the waves of heat in that medium. 

 Thus the total amounts of gravific energy and of 

 heat-energy may remain constant in the universe, 

 the one being convertible into the other, and back 

 again. It may be observed that, besides the above 

 apparently unavoidable conversion of heat-ener- 

 gy into gravific energy by dissipation of the heat- 

 waves in the gravific medium (and the consequent 

 equalization of the energy in the two media), it 

 would seem a reasonable conclusion that two me- 

 dia (the gravific medium and the heat-conveying 

 medium), immersed in each other, must naturally 

 maintain an equilibrium of motion or energy be- 

 tween themselves, as, for example, is known to be 

 the fact in the case of two gases immersed in each 

 other or mixed, however diverse their qualities 

 may be. It should be observed that the gravific 

 medium must be constituted as a gas (according 

 to the kinetic theory) in order to accord with the 

 observed effects of gravity. 



These considerations would point to the gen- 

 eral conclusion that recurring changes take place 

 in the universe whereby the continuance of use- 

 ful activity and life is insured, and the deadlock 

 of useless inaction and uniform repose prevented. 

 In other words, they would lead to the inference 

 that physical causation is not so constituted as to 

 defeat itself and bring the operations of the uni- 

 verse to a standstill. 



It should be noted that, as a matter of theo- 

 retic principle, the problem of recurring changes 

 in the universe undoubtedly admits of solution, 

 since it is an admitted dynamical principle that 

 masses immersed in media whose particles are in 

 a state of translatory motion must themselves in- 

 evitably acquire some translatory motion, and the 

 stellar masses moving freely in straight lines in 

 the gravific medium represent (as it were) a larger 



95 



scale gas immersed in a smaller scale gas (viz., 

 the gravific medium). It is a mere question of 

 scale, and dynamical principles are (admittedly) 

 independent of scale. The difficulty, if any, would 

 therefore be one of degree, not of principle. There 

 might be a difficulty in accounting for the high 

 value of the translatory motion of the stellar mass- 

 es that observation appears to point to. But it 

 should be noted that it does not follow that the 

 value of the translatory motion we observe is the 

 true mean value ; for it might be exceptionally 

 above it. For it is known that the translatory 

 motion of the molecules of gases (or of any bod- 

 ies moving freely among each other according to 

 kinetic theory) varies from zero toward infinity. 

 It might therefore well be that the translatory 

 motion we observe in our immediate neighbor- 

 hood might be exceptionally above the mean val- 

 ue, and we happen to observe this particular val- 

 ue because it is suited to the conditions of life (or 

 the low translatory motion, on account of the fee- 

 ble heat developed, would not be so suited). 1 



1 Possibly there may be some supplementary cause 

 tending to produce translatory motion in the stars. 

 The spectroscope shows the molecules of matter to 

 possess a considerable complexity, or their parts have 

 a considerable capacity for taking up motion. It would 

 appear reasonable to conclude that the molecules of 

 matter of the universe, immersed in a medium con- 

 stituted according to the kinetic theory, must ac- 

 quire also in their parts a certain degree of motion, 

 owing to the dynamic action of the impinging parti- 

 cles of the medium in which they are immersed. The 

 intensity of motion thus acquired would (as is known) 

 be greater in proportion as the parts of the molecule 

 which are capable of motion are smaller ; and this mo- 

 tion of the parts of the molecules would apparently 

 tend to produce translatory motion in the molecules 

 as wholes — much as the development of motion in the 

 parts of the molecules of a gas (as occurs when they 

 are exposed to the pulsations of waves of heat) is 

 known to produce translatory motion in the molecules 

 as wholes, thereby producing expansion in the volume 

 of gas. Indeed, a balance (as is known) tends to es- 

 tablish itself between the energy of the translatory 

 motion of the molecules as wholes, and the energy of 

 the motion of their parts (internal motions). Thus, 

 the throwing of the parts of molecules into motion 

 (from any cause) would tend to produce motion in the 

 molecules as wholes. In principle, therefore, the de- 

 velopment of motion in the smaller parts of matter, 

 tends to produce translatory motion in the larger 

 parts (and that whatever the relative scale may be). 

 This might possibly have its application as an auxilia- 

 ry cause for the development of translatory motion in 

 the larger scale parts of matter (represented by the 

 stellar masses), through the intermediary of the 

 smaller parts (molecules), and the minute, moving 

 particles of the medium in which these smaller parts 

 are immersed. 



Another point may, perhaps, be worth noticing 

 here. When the molecules of a compound gas (im- 



