gutenberg_org, en Henri Becquerel died #OTD in 1908.
He was the first person to discover evidence of radioactivity. For work in this field he, along with Marie Skłodowska-Curie and Pierre Curie, received the 1903 Nobel Prize in Physics, for the discovery of spontaneous radioactivity. The SI unit for radioactivity, the becquerel (Bq), is named after him. via @wikipedia
Photographic plate made by Henri Becquerel showing effects of exposure to radioactivity.