14 ESSENTIALS OF BIOLOGY 



the internal heat of the earth, and other planets, will have become 

 completely dissipated. Oceans and atmospheres will become 

 solid materials and the crusts of the planets will become rigid. 

 Because of the immobility of these envelopes there will no longer 

 be tides and so tidal friction Vv^ill no longer affect the relative 

 distances of the sun, planets and satellites and the periods of 

 their revolutions and rotations. In that phase we may regard 

 the solar system as having become stabilized, or made, for the 

 energy received by it from the radiation of the stars may be 

 neglected. 



To an intelligent observer situated outside the solar system 

 and able to measure the motions of the various bodies there would 

 be absolute determination in those motions. (*' Stability," it 

 should be noted, does not involve the immobility of sun, planets 

 and satelHtes : bodies in uniform motion will continue in those 

 states, for no work is done by them in the absence of any resisting 

 media.) From any one phase in the solar system, as thus made, 

 any future or past phase could be predicted without error. 



Such an environment could not permit of life, as we know it, 

 or can imagine it, for it would be an environment in which all 

 energy-transformations would have ceased. The temperature, 

 for instance, would be that of cosmic space, and we have been 

 able to observe the behaviour of living things (of very simple 

 organic status) at temperatures only a few degrees higher than 

 that of cosmic space. At such temperatures some primitive 

 organisms, such as some seeds, or the spores of bacteria may 

 continue to live during the periods throughout which the very 

 low temperatures can be maintained. They do not function in 

 any way, or we may regard their rate of functioning as proceeding 

 " infinitely slowly." It is not merely because of the extreme 

 " cold " that life is thus suspended — it is because energy-trans- 

 formations between the organism and its environment have 

 practically ceased. 



The environing media of organisms are parts of the universe that 

 are incompletely made. In these parts there is available energy 

 that is undergoing dissipation : there is, for instance, radiation 

 that is about to transform in some way or other, and there are 

 chemical substances in such states that they can be oxidized, 

 or combined with other substances so as to generate energy as 

 heat, electrically, or in some other form. The environment in 



