Guarded deeply in a Paris cellar is a long platinum bar. When its temperature is that of melting ice (0° Centigrade, 32° Fahrenheit) two marks on that bar are exactly one metre apart. That Paris metre is the modulus of the world's weights and measures.* If the standard bar were lost, and all its master duplicates in the capitals of civilized countries, scientists would be hard put to recalculate the metre distance, except. . . .
That exception is the fact that Professor Albert Abraham Michelson of the University of Chicago has very accurately...
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