I get that the universe can be expanding, and that there might be different methods to calculate/measure this that have discrepancies. But that the rate of expansion is accelerating, how in the world is that possible?
I don't think it's not possible, I just find it surprising based on the layman understanding that gravity is a dominant force at long distances, leading me to believe that expansion should be slowing.
I also have the layman awareness of some kind of missing mass sometimes explained by "dark matter." But I did not see the additional explanation that this "dark matter" also acts as a repulsive force to accelerate the expansion. Maybe large scale structures manage to create propulsive forces that happen to point away from the center? Anyhow I would love to know what the mechanism is there.
As far as I understand dark energy/matter is not established, it's just a placeholder as we don't quite know what's missing in our formulas. Isn't it like that?
It's a pretty well accepted fact.