ioo Master Minds of Modern Science 



He knew that the opportunity would not arrive for nearly 

 four years — that the world would have to wait for his 

 proof until the total eclipse of the sun on May 29, 1919. 

 Although, at the date of his lecture, all Europe was 

 plunged in the horrors of the Great War, Einstein's state- 

 ment caused a tremendous sensation and was eagerly 

 discussed in all countries. Scientists everywhere awaited 

 anxiously the time of test. 



At last the War was over and the great day approached. 

 Telescopes and cameras were ready at several points along 

 the line of total eclipse, one point being a small island 

 called Principe, off the coast of Africa. You will under- 

 stand that it is only when the disc of the sun is obscured 

 by the passage of the moon that the stars closest to the 

 sun become visible, and so only then can they be photo- 

 graphed. These photographs would enable astronomers 

 to learn whether the rays from stars passing close to the 

 great bulk of the sun were actually bent. The proof 

 would be secured if the distances of these stars, as recorded 

 on the photographic plate, were greater than could be 

 expected from their actual positions. 



The eclipse came and passed, and within a few weeks 

 Einstein's theory was proved to be perfectly correct. 

 Newspapers all over the world proclaimed to their readers 

 that light -rays did bend. A new truth had been estab- 

 lished, and Einstein was rightfully acclaimed as the 

 greatest and most original thinker of the twentieth 

 century. 



You may wonder why the phenomenon was not 

 observed long ago. The reason is that the bend or 

 deflection is almost infinitesimal. Einstein stated that it 

 would be found to be seven-tenths of a second of arc. 

 This corresponds to the thickness of a match seen at a 

 distance of about nine hundred yards. One's wonder is 

 divided between the brain that could calculate so tiny a 

 deflection and the instruments that could detect it. 



