IS THERE INTELLIGENT LIFE ON EARTH? 273 



the U. S. Bureau of Mines (1970), and brings us up-to-date through 1968. Here 

 the reserves of various commodities are shown by the thin horizontal bars in 

 various appropriate units and scales. The scales of the various groups of bars go 

 to larger exponents upward, and all project to zero off the page to the left. I 

 have taken optimistic figures for reserves, often including those which will only 

 become available at substantially higher than current prices or inferred beyond 

 measured reserves, or both. Over these thin reserve lines are shown wider, lighter 

 bars, indicating expected average global demand to the end of the century. 

 Figure 4 also shows where reserves are and where they are not adequate to meet 

 average demands expected to the end of the century. A good many are not 

 adequate, although they may well be increased by discovery of yet undiscovered 

 resources or mining of lower grades, as suggested by several reserve bars that 

 show different end points for quantities available at different prices. Figure 4 

 represents the world as a whole. Figure 5 shows similar data for the United 

 States. 



From the same data, Fig. 6 shows, on a global basis, apparent mineral 

 lifetimes, although not for quite the same group of commodities. For all 

 commodities shown in Fig. 6, I have again used conservative estimates of 

 demand rates and have looked at the apparent mineral lifetimes from 1968 

 onward in terms of three categories. The solid line on the left represents 

 optimistically estimated current reserves, the dotted line in the middle gives the 

 extended lifetimes for five times current reserves, and the solid line on the right 

 represents an extension to 10 times current reserves. See where these lifetimes 

 lead: We still run into severe shortages by the middle or end of the 21st century, 

 some of them coming early on. How far we will be able to extend these 

 resources is a matter not only of economics and technology but of the discovery, 

 through application of geological principles, of presently unknown reserves. 

 Although these variables are all uncertain, in the case of petroleum we can infer 

 on rather good geological grounds that about five times currently known reserves 

 of petroleum will be found, leading to a tapering off and decline in petroleum 

 production beginning probably around 1990 to 2000. If we add oil shale and the 

 so-called tar sands, then we are warranted in raising total reserves of 

 petroleum-type products up to about 10 times those now known, although that 

 is probably about as far as we can take petroleum. So you can relax and quit 

 worrying about smog from gasoline by year 2040 or thereabouts. It will be gone 

 or on a declining curve. 



In the case of coal, the probability of about 10 times known reserves is 

 pretty good, which takes us up to around 2150, although this will go 

 much faster if it comes under heavy pressure to replace energy needed as crude 

 petroleum and natural gas are used up. A longer range hope is to develop a clean 

 breeder reactor and eventually a fusion reactor that will make available much 

 larger quantities of energy. But then it will be important to have ample 

 inventories of helium so that this energy can be transferred from its place of 

 generation in superconductive lines without loss of energy en route and to 



