"In a spiral galaxy, the ratio of dark-to-light matter is about a factor of 10. That's probably a good number for the ratio of our ignorance-to-knowledge. We're out of kindergarten, but only in about third grade." —Vera Rubin, born OTD in 1928. . . . . . . . . . #womeninscience #science #darkmatter #sciencehero #otd #hbd #happybirthday #womenscientist #galaxy #spiral #universe #space #knowledge #knowing #education #learn #discovery #learning #onthisday