I found myself thinking about this particular scenario after playing Portal 2 and seeing a Halloween decoration on the ceiling of a store: Let's say you portal this part of the ceiling And another area of the ceiling inside the store. What would happen to the object? Would it fall through the second portal towards the floor or remain where it is- remember gravity is acting equally (I would think) on both portals- so I'd figure there would be equal gravitational pull from the floor and the portal. What would happen? Would the answer change if you portaled outside the building? It would seem that the only variable here would be the actual gravitational pull- It would be stronger closer to ground/sea level.