ABSTRACT
Although radioactivity is primordial in the universe and is associated with the origin of all things such as the chemical elements, stars, the solar system, and the earth, less than 100 years have elapsed since the discovery of uranic rays by Henri Becquerel (1852-1908) on Saturday, February 29, 1896, a date which marks the beginning of a new era in the history of mankind. Historians contending for scripta manent may prefer the following Monday, March 2, when Becquerel reported at the weekly session of the Academy of Sciences in Paris on the "invisible radiation emitted by phosphorescent substances". I This paper announced that uranium salts spontaneously blacken a photographic plate, even without the stimulus of solar light, which was initially thought to be at the origin of the phenomenon.
