178 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 7 



universe remains the same. In any chemical action the final products 

 weigh just as much as the constituents entering it. On one scale of a 

 balance put the coal you throw into your furnace, and pile on, if you 

 can, all the oxygen used in combustion. On the other scale put all 

 the ashes, and all the smoke and gases resulting from the fire. The 

 scales balance. 



In the nineteenth century was stated another great law, the Law of 

 the Conservation of Energy. No energy is ever created or destroyed. 

 Its form changes, its amount is unaltered. The sun's energy in the 

 form of light and heat comes racing down to us. It dries up (at 

 least we hope it will tomorrow) our sodden streets. The water, lifted 

 into the clouds, has the potential energy of a raised weight. The 

 winds carry it over Lake Erie and it falls as rain, losing some of its 

 energy in heat, but it is still higher than the Niagara Gorge. It enters 

 the turbines of the Ontario Hydro Electric Commission and its re- 

 maining energy is transformed into electrical energy and distributed at 

 high voltage all over Ontario. It runs our streetcars and lights 

 our cities. It enters our homes, runs our washing machines, our radios, 

 our refrigerators. It cooks our meals, toasts our bread, and heats 

 our bath water. It begins as heat, undergoes many transformations 

 and ends up as heat. None is lost. 



Nothing of him that doth fade 

 But doth suffer a sea-change 

 Into something rich and strange 



The twentieth century saw the two laws combined. In 1905 Einstein 

 propounded his theory of relativity which has revolutionized all our 

 thinking in the scientific realm ever since. He claimed that these two 

 conservation laws are two aspects of one more fundamental law, for 

 matter and energy are just two manifestations of the same thing. 

 Neither law taken alone is quite true, for matter can change into 

 energy and energy into matter. Together they are absolute. "The 

 total amount of matter and energy in the universe remains the same." 

 He went further and wrote down from theory the equation 



connecting energy E and mass m. If m is given in grams and c is 

 the velocity of light in centimeters per second, then E is given in 

 ergs. Since in these units c=3 X 10^°, this equation shows that a very 

 small bit of matter will yield an enormous amount of energy. One 

 kilogram (2.2 pounds) of matter, whether of coal or butter, if con- 

 verted entirely into energy would yield 25,000 million kilowatt hours 

 of energy ; thus 



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