Why do we live in a 3D universe anyway and what does it mean when they say that String Theory would theorize a 10 dimensional universe?
All the work I have studied so far states that the supposed other 7 dimensions of the 10 of string theory are smaller then a quark.
Here is a paper that says if the gravity component is a defect on our 3D brane from a 7D brane and if spacetime is curved significantly enough the
other spatial dimensions may not necessarily be small after all.
Wow thats kinda cool.
Another view, pioneered by Randall and Raman Sundrum, holds that if gravity is localized on a 3D defect in the larger multi-dimensional universe
and if spacetime is sufficiently warped, then the other spatial dimensions might be large after all. But why is our "local gravity" apparently a 3D
defect in a 10D universe? Why not a 4D defect or some other dimensionality?