I've been studying astrophysics and I read that our universe is still expanding because the gravity is not enough compared to the dark energy present. And right now we are not sure whether are universe is flat, open or closed because we don't know the critical mass.
However what I don't understand is that while this universe is expanding, distance between the particles is increasing, doesn't that mean that their pull on each other i.e. is gravitational force is reducing? So shouldn't that mean that our universe is going to expand forever?