Socratic social network Quora recently questioned the effect of zero gravity on breasts. Faced with the slightly rude query, "Do female astronauts wear bras in space?" NASA astronaut trainer Robert Frost cited physics: "Even though there is no noticeable pull from gravity, there is still inertia. So while they are running on the treadmill, their rib cage is constantly changing its direction of motion and other more delicate parts are resisting those changes." Thus, sports bras. Now you know.