Carl Sagan
Astronomer
Carl Sagan is here because he made the hardest ideas plain without making them small. Cosmos, the pale blue dot, the baloney detection kit. I read him when I want a claim to earn the belief I am giving it.
He was born in Brooklyn in 1934, worked on the Mariner, Viking, and Voyager missions, made Cosmos for PBS in 1980, and co-founded The Planetary Society. He died in 1996. In this photograph he stands next to a Viking lander.
Photograph by NASA/JPL. Public domain. Source. Cropped from the original.