সঠিক উত্তর হচ্ছে: ১৯১২
ব্যাখ্যা: Cosmic rays were discovered in 1912 by Victor Hess, when he found that an electroscope discharged more rapidly as he ascended in a balloon. He attributed this to a source of radiation entering the atmosphere from above, and in 1936 was awarded the Nobel prize for his discovery.
Source: srl.caltech.edu