J.AXLARY, 1929 



EVOLUTION 



Page Seven 



How Long Will the World Last? 



SCIENTIFIC men have dittered much 

 in the last fifty years as to the past 

 age and probable future of the earth. The 

 mathematician «as correct, but the phys- 

 icist gave him the wrong material for his 

 sum. How can he be sure that he now 

 has the right material? He cannot be 

 absolutely sure, but I will explain how 

 little room for doubt there now is about 

 the matter. There is a general agreement 

 about the point, and the skepticism of peo- 

 ple who know no more about the subject 

 than they know about the arteries of a cod- 

 fish, is as idle as the crackling of thorns 

 under the pot. 



Until twenty years ago we had three 

 chief ways of determining the age of the 

 earth which is closely connected with the 

 question how long it will be fitted to sus- 

 tain life. The water of the ocean was 

 originally fresh, because its salts are being 

 actually conveyed into it today by the 

 rivers. The water itself notoriously evap- 

 orates, leaving the salt behind, and re- 

 turns, with a fresh burden of salt, in the 

 rivers. In other words, the proportion of 

 salt in the ocean is steadily increasing, 

 and by analysis of the water of many 

 rivers we can ascertain, roundly, what 

 quantity of salt is added to it yearly. Ob- 

 viously, the further we go back in past 

 time, the less salt there would be in the 

 ocean, and it is a fairly simple mathem- 

 atical sura to determine how far back we 

 must go to find the waters of the earth 

 free from salt. Somewhere about seventy 

 million years, said the experts. 



There was always a recognized weak- 

 ness in this estimate. It supposes that 

 through all geological time the rivers bore 

 to the sea much the same proportion as 

 they do today. The same weakness, one 

 may say the same unjustifiable assump- 

 tion, lay in the purely geological method 

 of calculating the age of the earth. The 

 rivers bear mud and sand and stones to 

 the sea ; where new strata are formed, and 

 patient investigation can find what bur- 

 den of sediment the great rivers transfer 

 from the land to the ocean-bottom every 

 year. American geologists have thus cal- 

 culated how much of their precious land 

 is deposited on the floor of the Atlantic 

 and Pacific every year. When the majority 

 of geologists working along this line reach- 

 ed a conclusion not very different — be- 

 tween fifty and a hundred million years 

 for the formation of the stratified rocks 

 of the earth, it seemed impressive. 



The fallacy or weakness in both cases 

 is to suppose that during all geological 

 time the rivers bore, on the average, much 

 the same load of sediment to the seas as 

 they do today. It is a big assumption in 

 the case of a globe which, as we now 

 know, has had so many ups and downs 

 in the course of its life. 



Another mischief was that, on a third 



By JOSEPH McCABE 



and quite independent line of reasoning, 

 Lord Kelvin gave a figure for the age oi 

 the sun which seemed to harmonize with, 

 and confirm the geological estimate. In 

 those days men could see no substantial 

 source of the heat of the sun and the stars 

 except the compression of the matter com- 

 posing the'globes, and Kelvin started from 

 this theory. We now know a source of 

 heat which is enormously more effective 

 and would sustain the temperature of the 

 sun during a period of time twenty times 

 as long as the longest period assigned by 

 Kelvin. 



This source is radio-active matter (ura- 

 nium, thorium, etc.), the heat-producing 

 quality of which we realize as an absolute 

 fact in the laboratory. We have only to 

 suppose that the interior of the stars is 

 composed of masses of these heavy and 

 unstable metals, and we have, since we 

 know their weight, a source of heat which 

 will last for billions of years. 



It is always amusing to listen to the 

 gentleman who prides himself on his com- 

 mon sense and asks us to be skeptical about 

 these estimates and theories. Most of his 

 own opinions about cosmogony are infer- 

 ences drawn by imperfectly educated derv- 

 ishes from bad translations of forged doc- 

 uments of an age of colossal ignorance; 

 but his opinons are sacred enough to be 

 protected by gunmen if necessary, while 

 he can smile at an opinion laboriously 

 reached by a thousand mathematicians of 

 almost magical skill, profoundly critical 

 judgment, and years of the most learned 

 calculations. The mathematician asks the 

 physical astronomer — though the two 

 branches are really combined, since every 

 astronomer is a good mathematician — what 

 the probability is that vast stores of radio- 

 active matter exist in the sun. We can- 

 not prove it, as we can prove the existence 

 in the sun of oxygen or iron, because our 

 instruments analyze only the glowing sur- 

 face of the sun. But it is an elementary 

 truth of astronomy that the lighter ele- 

 ments remain at the surface of a globe 

 and the heavier elements lie below — it is 

 just as natural a process as when you 

 see the stones brought down by a river 

 remain in its bed while sand is taken out 

 to the seashore and the fine mud borne far 

 out to sea — and no one with any knowl- 

 edge of these matters can have any doubt 

 that there must be vast quantities of the 

 heavy radio-active metals in the interior of 

 the sun. 



A few grains of uranium notoriously 

 give off heat and other forms of energy, 

 and one has at once a vague idea of the 

 possibility if we suppose that billions of 

 tons of this material exists in the sun. 

 But we have another matter to take into 

 account ; the terrific pressure put upon the 

 central matter of the sun and stars bv the 

 mass of the globe. As the total weight of 



the sun is well known, this pressure in the 

 interior can be calculated, and the effect 

 on the material can be gathered. The 

 state of matter in the interior of the sun, 

 or even of the earth, is beyond the power 

 of our imagination, but the abstract form- 

 ulae of the mathematician can penetrate 

 to the very heart of it, and for those who 

 are interested in these matters the modern 

 analysis of the interior of stars is as im- 

 pressive as it is fascinating. 



The total energy poured out by the sun 

 every minute or year is known. The 

 amount of radio-active matter needed to 

 give off that energy — astronomers now say 

 lo be converted into that energy — is 

 known. The weight of the sun is known. 

 Naturally one must not regard this con- 

 clusion as "mathematical" in the same 

 sense as the addition of \-our bank-balance 

 is. For most of us it is enough that the 

 masters of this branch of science have, 

 after ten or more years of critical and 

 laborious estimates, agreed that the sun will 

 probably continue to give light and heat 

 enough to support life on this planet for 

 a future period which is nearer two hun- 

 dred million years than one hundred. 



What matters to us is the value of this 

 conclusion to our human outlook on life. 

 We count our civilization as five or six 

 thousand years old, and it is still so foul 

 with injustices and stupidities that many 

 wonder occasionally if the human endeavor 

 is not futile: if history is not going to be 

 always a series of advances and retrogres- 

 sions into Dark Ages. On the ovher hand . 

 we have the thoughtless crowd and the im- 

 perfectly or wrongly educated people who 

 seem incapable of visualizing any higher 

 civilization than ours. 



I am confident that much of this 

 thoughtless attitude could be corrected if 

 the school planted so deeply in the minds 

 of pupils this new conception of the mean- 

 ing of life that they could never wholly 

 forget it. What are five thousand years 

 in face of this stupendous future of the 

 race? We learn a healthy contempt of 

 our own institutions; and by a healthy 

 contempt I mean the sure and steady real- 

 ization that every institution or idea of 

 which we may be proud today is child- 

 like in comparison with the ideas and in- 

 stitutions of the future. We may be fully 

 human, but we are the infants of civiliza- 

 tion. It has hardly yet begun. Tens if 

 not hundreds of millions of years of 

 scientifically ordered life lie before us. 

 —U. R. V. Bulletin. 



RUBE: What do you think about this 

 here Evolution ? 



YOKEL: It's a good idea — but can they 

 enforce it? 



— American Boy Magazine. 



