I have a few questions so I hope it is okay if I ask them all here in this thread. They are all related somewhat. According to brane cosmology, our 4-D universe is embedded inside a higher dimensional space, a hyperspace if you will, called the bulk. The reason we cannot perceive or interact with the bulk is because we are "stuck" in our brane. Lets say that we somehow became unstuck and were able to navigate into the higher dimensional space, what would we perceive? Would we be able to see into our 3d brane universe from the outside? Would we be able to interact with things IN the brane? All this is just like asking, what would we perceive if we took a ride on a photon or went into a black hole. I dont mean to suggest that it is actually possible to leave our brane. While we are on the subject, in brane cosmology, how many spacial dimensions does the higher dimensional space have? In brane cosmology, are there still compactified dimensions in our own brane universe? Would there effectively be extra spacial dimensions inside AND outside our universe? One more thing if its alright. The universe's expansion is described as a metric expansion of space, where the the expansion is intrinsic and therefore does not need or refer to anything out side the universe to expand. But if we live in a higher dimensional bulk as described in brane cosmology, would it be appropriate to say that the universe is actually expanding into this higher dimensional bulk?