 Good question, Luke. We're here to find out. The turbulence which shakes planes and, at its worst, injures people is, in simple terms, a sudden swirling of air. You can picture what happens in our atmosphere by imagining the swirling fluid when you stir a cup of coffee or empty the bathtub. To find out whether it's getting worse, I spoke to Paul Williams, Professor of Atmospheric Science at the University of Reading.