Are the any thoughts on this paper (which I copied the first part of as a reference)? They seem to be saying the existance of a 4th spatial dimension would help resolve questions. But, I think I've read other places that speculation of this type is meaningless. Hierarchy Problem in the Shell-Universe Model Merab Gogberashvili Institute of Physics, Tamarashvili st. 6, 380077 Tbilisi, Georgia E-mail: firstname.lastname@example.org (February 7, 2008) In the model where the Universe is considered as a thin shell expanding in 5-dimensional hyper-space there is a possibility to obtain one scale for particle theory corresponding to the 5-dimensional cosmological constant and Universe thickness. Several authors in the physics literature speculated about the possibility that our Universe may be a thin membrane in a large dimensional hyper-Universe (for simplicity here we consider the case of five dimensions). This approach is an alternative to the conventional Kaluza-Klein picture that extra dimensions are curled up to an unobservable size. In this paper we want to consider Universe as a bubble expanding in five dimensional space-time. This model of shell-Universe does not contradict the present time experiments and are supported by at least two observed facts. First is the isotropic runaway of galaxies, which for close universe model is usually explained as an expansion of a bubble in five dimensions. Second is existence of preferred frame in the Universe where the relict background radiation is isotropic. In the framework of the close-Universe model without boundaries this can also be explained if the universe is 3-dimensional sphere and the mean velocity of the background radiation is zero with respect to its center in the fifth dimension. In shell-Universe models the expansion rate of the Universe should depend not only on the matter density on the shell, but also on the properties of matter in inner-outer regions. This can give rise to the effect similar to the hypothetical dark matter. Also some authors want to introduce action at a distance without ultrafast communication as a possible connection of matter through the fifth dimension.