I have just recently learned of repulsive gravity and I have 2 questions that need clearing up. 1. For an object that generates repulsive gravity, what does that object do to space-time? If normal gravity is when the object bends paths through space-time towards itself, then what does something like a white-hole do to the fabric of space-time? 2. The book that opened me up to repulsive gravity was briane greenes the fabric of the cosmos. In one part he sets up a situation like this, you are trapped in jail and the only way to get released is if you can make one jack-in-a-box weigh more than another that is exactly the same. He said that you would compress the jack-in-a-box'x spring to make it weigh more. At first I thought that that generates potential energy, therefore making the box weigh more. But in the notes it says that, though the energy increase does cuase the box to weigh more, it is mainly the pressure. He says matter, energy, and pressure cause gravity. My question is what exactly does he mean by "pressure" that makes it any different from an increase in energy?