Henri Becquerel first observed the phenomenon of uranium radioactivity. He intended to conduct an experiment on the fluorescence of uranium salts, but instead abandoned the experiment and left the photographic plate with the uranium salt chip on it in a drawer. A few days later, on March 1st, he developed the plate anyway, attempting to detect a faint ring of fluorescence, but to his surprise, he clearly saw the shape of the chip (caused by the uranium’s nuclear radiation).
