(December 21, 1898)
The radioactive chemical element radium, a silvery white metal used to cure cancer, was discovered on this day in 1898 by future Nobel Prize winners Marie and Pierre Curie, who had just found polonium.
photo source: wikimedia.org
(Died on December 21, 2017) Bruce McCandless II, US astronaut who conducted the first untethered spacewalk (b. 1937).