Alexander Friedmann (1888–1925): Russian physicist and mathematician who provided the first mathematical solutions (in 1922) showing that the universe could expand, based on Einstein's general relativity—laying groundwork for modern cosmology.
George Gaylord Simpson (1902–1984): American paleontologist renowned for his work on mammal evolution, intercontinental migrations, and integrating paleontology with the modern evolutionary synthesis.
1963: Valentina Tereshkova becomes the first woman in space.
On this day, Soviet cosmonaut Valentina Tereshkova launched aboard Vostok 6 from Baikonur Cosmodrome