8 Responses. > 1  the Moon takes an elliptical path around the Earth. The planets make nearly elliptical orbits around the Sun, close enough for reasonable approximations, but the Moonâs Orbit around the Earth is sufficiently influenced by the Sun that it follows a path detectably different from an ellipse.
Quick Answer. In 1896, French scientist Antoine Henri Becquerel discovered radioactivity which was an early contribution to atomic theory. He discovered this phenomenon while experimenting with uranium and a photographic plate. Continue Reading.
The SI unit for radioactivity, the becquerel (Bq), is named after him. Roentgen discovered X-rays on November 8, 1895. The press reported this on January 5, 1896, shortly before Becquerel did his famous experiment. Thus radioactivity was discovered the following year but within a year of the discovery of X-rays.