According to the things I've been reading, while most forces and particles can be trapped on a brane, gravity can escape it and thus provide a means of interaction with other branes and the bulk. The reasoning given is that since gravity is woven into spacetime and has a component in the dimension of time in addition to the 3 spatial dimensions (according to relativity), it should be able to exist in all dimensions other than our familiar 3. I'd like to know how this can be considered a logical conclusion, and there are two reasons for my confusion. Firstly, in relativity, gravity is shown to act in the dimension of time, which is not a spatial dimension, yet in the context of branes, it is said that gravity can escape the lower dimensional brane and penetrate the higher spatial dimensions outside the brane. Relativity does not, to the extent of my limited knowledge, show penetration of gravity into higher spatial dimensions. Secondly, if the nature of the additional dimensions (to our 3) that gravity can penetrate somehow does not matter (spatial or time), how can it be concluded that just because gravity can penetrate one additional dimension that it can penetrate any number of additional dimensions. Is this all somehow known? Or is it just that because it has demonstrated this ability in one instance that physicists believe it, if anything, can apply its ability with respect to other dimensions?