Vera Rubin's observations of the speeds of stars at the edges of spiral galaxies implied an unseen mass, which we now call dark matter. She was born #OTD in 1928. 🌌 . . . . . . . . . #womeninscience #science #birthday #otd #darkmatter #astronomy #galaxy #space #cosmos #mondaymotivation #dark #matter #unknown #universe #questions #discovery #happybirthday #onthisday #sciencehistory #women #womancrush #whatsoutthere #stars