Could a universal "Oort cloud" structure cause expansive acceleration? Could there be a giant sphere of invisible non-reactive matter (neutrinos?), left over from the big bang, so massive that it's gravity is pulling galaxies outward? I know the Oort cloud doesn't pull planets outward, but that's because the mass is small compared to the Sun, and not concentrated but distributed relatively evenly around the solar system. But if there was 73% of the universe's matter (the estimate I saw for the amount of mass-energy in the form of Dark Energy) as a thin sphere on the edge of the 'expansion radius' of the big bang, could it explain the acceleration we see? As the initial velocity of the 'cloud' slows due to the gravitational force of the inner universe, the distances between galaxies and the cloud would decrease and the gravitational force between galaxies and the cloud would increase, causing what would look like a continued outward acceleration (until everything smacked into each other, turning the universe into one giant hollow shell). Obviously I have no scientific basis for this hypothesis, it's just curiosity if it was even possible. I teach HS physics and we got into a discussion about this.