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CHAPTER VIII \^ 6sS t' 



THE MASTER OF RELATIVITY 

 77^ Wor& awrf Li/fe 0/ Albert Einstein 



IN 1831 Urbain Leverrier, a young man of twenty, 

 was admitted into the Polytechnic School of Paris. 

 Five years later he distinguished himself by writing 

 some clever papers on chemistry and astronomy, with 

 the result that he was offered the post of teacher of 

 astronomy in the Polytechnic. He soon became known 

 for his original work in this science, and was elected a 

 member of the French Academy. His principal work was 

 careful observation of the movements of the planets, 

 especially of Uranus, which at that time was believed 

 to be the last and outermost of the solar system, but 

 Leverrier by his calculations decided that there must 

 be still another planet farther out in space. 



Shortly after Leverrier had written a paper announ- 

 cing his belief in the existence of this planet, it was 

 discovered by another astronomer, Gottfried Galle, of 

 Berlin. Neptune, as it is named, though eight times 

 larger than the earth, revolves at a distance of three 

 thousand million miles from the sun, and is therefore so 

 tiny a speck that it had hitherto escaped observation. 



Now there is another planet which, like Uranus, has 

 shown a slight irregularity in its movement. This is 

 Mercury, the innermost planet of our system, a tiny body 

 only three times the size of the moon ; it circles around 

 the sun in a year which is only eighty- eight of our days. 

 It is so near the sun that it is very rarely visible to the 

 naked eye. 



Mercury's irregularity is a very small matter, yet the 



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