Researchers at Uppsala University in Sweden have developed an interesting model of the universe. They describe and support their idea in a paper that uses the principles of string theory (according to which all matter is made up of tiny, vibrating strings) and simultaneously incorporates the phenomenon of dark energy (which is considered as a possible cause for the expansion of the cosmos).
According to their model, our universe is being carried along on the skin of a kind of bubble that is expanding in another dimension. Space and the bubble are far from the same thing; effectively we are merely passengers on the skin of a balloon. The balloon, the bubble, is here a five-dimensional anti-de Sitter space, that is, a spacetime with a negative cosmological constant. On the surface of its skin (a spherical brane), the researchers show, life appears to be playing out as we know it, in four dimensions and with the known laws of gravity. This is all just an appearance, because this is only how the universe looks to us poor four-dimensional observers who cannot see or measure the massless, five-dimensional gravitons that move effortlessly between the dimensions.