I graduated physics, but I'm almost a layman when it comes to general relativity. Still, I wonder if another possible explanation for stuff that don't match theory could be the basic assumption about our current cosmology. That the space is flat where there's no matter. Since there's a relation between the geometry of the space and the matter within, would it be unreasonable to believe that space itself could be curved independently of the matter we can observed? Maybe for other reasons, yet unknown?