The central idea of Einstein’s theory of gravity is the principle of equivalence. That is, objects will fall at the same rate under gravity regardless of their mass or composition. As long as there isn’t air resistance, a feather and a bowling ball dropped at the same time will strike the ground simultaneously. But what if one object is rotating and another is not? Will they fall at the same rate? We know that the rotation of a body can affect how things fall. When a body such as Earth rotates, it creates an effect known as frame dragging, which twists space and time slightly. Computer simulations of merging black holes show that two rotating black holes would merge at a different rate than if