But such opacity is merely a front for the study of friction. And, according to Jennifer R. Vail, friction is ‘the unsung hero of the material world’. Because ‘the way we experience the world, whether through greater efficiency, flight or space exploration, has been shaped by our understanding of friction’. Well, as Vail explains, the mastery of fire is really the mastery of friction, right? Especially because, as Vail notes, ‘friction is ignored in high school physics classes’, and therefore she must explain everything.