science like string theory say there are 11 or so others say curved 4d. honestly i do not think there is a limit. it is just the same thing cut up different ways. you can express 11 dimensions in a sequential one dimentional list. personaly i go with four because it is practical. why bother with dimensions you cannot experience. on a side note one of my hypothesises about dark matter is that it is leaking gravity from a higher dimension. for instance how much would a two dimensiomal slice of our universe weigh? well now think of how much the next dimension would weigh compared to ours if we are but a two(three) dimensional slice in comparison. with that in mind i think that even with the inverse square law some of the gravity would reach us.