8 



LAWS OF ENERGY 



to be expended on its environment at least equal to the amount of 

 energy rendered available. 



A weight resting on the ground may be considered as representing a body 

 having degraded energy. Its energy potential is the same as its environ- 

 ment. No work could be got from it without the previous expenditure of 

 work on it. If a certain amount of work were done in raising it from the 

 ground, then the same amount of work would be recovered on letting it fall 

 to the ground (taking into account the mechanical equivalent of the degraded 

 heat). On the other hand, a weight resting on a ledge above the ground may 

 perform work in falling if sufficient free energy be applied to tip it over. The 

 quantity of work done in tipping over the weight bears no relation whatever 

 to the amount of energy liberated in falling. 



The following scheme may help to make the matter clear : 



Total Energy of the Universe 



(1) V 



Available for work, 

 i.e., Free Kinetic Energy 



i (2) 



Not directly available for work 



i (4) 



Potential Energy 

 Add trigger Energy from (1) 



i (3) 



Degraded Heat 

 (Entropy) 

 Totally unavailable 



Free Energy 

 Total Available Energy 



Total Unavailable 

 Energy 



(3) Called " bound " energy by Helmholtz in 1882. 

 (3 + 4) Called "' bound '' energy by later workers. 



(4) Called " bound " energy by Physicists. 



One of the most important problems in biology is the means by 

 which potential energy is translated into work and the mechanism 

 by which this translation is controlled. 



" The struggle for existence is the struggle for free energy " (Boltzmann). 



Of potential energy there is an abundant supply. Some of it, 

 e.g. that of coal, requires the employment of only small quantities 

 of free energy to render it immediately available for work, while 

 other varieties, e.g. that of radio-active minerals, have their energy 

 boimd in such a way that it is evolved with excessive slowness. 

 Uranium contains the same amount of energy as 250,000 times or 



more of its weight of coal, but little more than part 



10,000,000,000 



