IS THERE INTELLIGENT LIFE ON EARTH? 



277 



30 



a 



.c 



O 



> 



Mineral production (U. S. total) 



X 



111 

 O — 1.5 Q 



1.0 



o 

 ro 



O 



H 



Q 

 HI 



0.5 = 

 a. 



O 

 0.0 " 



1960 



Fig. 7 Energy use compared with mineral production (slightly modified after 

 T. S. Lovering in Resources and Man, 1969). 



difficulties are involved in the application of nuclear energy to the increase of 

 our resource inventory. Nevertheless, this is an avenue of some promise that 

 ought to be explored to the full with all proper safeguards. 



But what about substitution and synthesis? There are, of course, some 

 intrinsic limitations. To begin with, 84 of the 90 naturally occurring elements on 

 the earth already have some commercial use. Second, the synthesis of elements is 

 very difficult to do on the earth. In fact, we know of no metals that can be 

 synthesized except at such temperatures and pressures as prevail in exploding 

 stars, and we have no means of maintaining those pressures and temperatures for 

 times sufficient to create new metal elements here on the earth. Whatever we do 

 in the way of substitution has to be in terms either of substituting common 

 elements for uncommon ones or of substituting new compounds produced 

 through the applications of materials science and technology from common raw 

 materials. Neither of these offers much help with the problem of finding suitable 

 substitutes for things like helium, mercury, gold, germanium, uranium, thorium, 

 tin, and other metals that have unique properties for which there are no 

 satisfactory substitutes and for which the creation of substitutes having such 

 properties is difficult to envisage. A substitute for gold, for instance, which is 

 critical in a number of electronic applications and particularly in the 

 development of high-speed computers, would be very difficult to find. Although 

 we often hear about the substitution of aluminum for copper in transmission 

 lines and some other applications, aluminum is a very unsatisfactory substitute 

 for many of the applications of copper in small machinery and electrical devices. 

 Thus opportunities to relieve pressures through substitution and synthesis are 

 also limited, even though they should be pursued to the limit. Materials science 

 and engineering along with recycling and improved methods of geological 

 exploration are among our main hopes. 



As for marine mineral resources, often referred to as a "veritable 

 cornucopia," they are of two main kinds — those which are found as dissolved 



