The idea that the Universe is held together by gravity forces despite the expansion is ridiculous, IMO, because the expansion is likely to happen at lightspeed and that photons, regardless, beam toward the edges of it, meaning a definite drain on the more central parts of the Universe. All in all, this means that the Universe loses mass and that this makes it more easy for the Universe to expand, going at maximum speed!
Note: this is my opinion only. I don't know to what degree I agree with other scientists, just that I've heard enough about the expansion of the Universe for a good 20 years!
Note2: this has first been published to the ScientificBlog777 just moments ago.