I am not aware of any models of the universe that posit an infinite mass. Edit: Also, "observable universe" is a frequently misunderstood concept. Just because

I am not aware of any models of the universe that posit an infinite mass. Edit: Also, "observable universe" is a frequently misunderstood concept. Just because something is now outside the observable universe (the distance between them and us is big enough so that the rate of expansion of the universe between us and them is higher than the speed of light) doesn't mean that we aren't, today, receiving light from a long time ago when the object was closer. If you go far enough back in time you can "see" the entire universe . As time passes, more and more mass moves outside of the observable universe since the size of the sphere is constant relative to the rate of expansion.