If we look at our own solar system, our sun is pushing gasses outwards as solar winds. Our Galaxy has what around 100 billion stars? All which most likely follow suit expelling their own atmospheres outwards as solar winds. The ratio of stars being born to stars dying is something like 350:1 that's a steady increase of gas production (recycled I mean). Thats a lot of gas, so essentially galaxies steadily increase thrust, pushing themselves away from each other by pumping gas into the "space" expanding space between them. I just don't understand the need for dark energy... the recipe for expansion seems to be clear. What am I missing?