I was thinking yesterday about the fact that the universe is supposedly expanding at an ever increasing rate and i thought of i reason why. I'm pretty sure its wrong but so far nobody could explain to me why. If you assume that the there is an infinetly big nothingness for our current universe to expand into, i.e that there is no point where the universe will hit a wall and stop growing; then i thought you could explain it using pressure. So if this infinetly big space has nothing in it then the pressure must be infinetly low because of P=m/V, where as our current universe has a much smaller volum and much more mass meaning it must therefore have a greater pressure which would mean that our universe would be being pushed outwards due to the pressure differenece, and thus would accelerate because a=F/m there fore as long as there is a force it must accelerate. Can someone try to find where i went wong because it is really bothering me?