Do you have any idea what a degree in Philosophy in Physics involves? Neither do most people. But Thornton has a PhD in it, as well as bachelors and masters degrees in physics. So she’s scary smart, but she’s also scary tough. Part of the astronaut class of 1985, she flew four missions aboard three different shuttles and logged 975 hours aloft—21 of them spent outside the spacecraft conducting spacewalks. On her third mission, in 1993, she helpedcapture and repair the Hubble Space Telescope, marking that flight as one of the most scientifically consequential ones of the entire shuttle program. She’s now associate dean of engineering at the University of Virginia. Here’s betting she’s a really, really tough grader.

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