# If space expansion keeps accelerating, what would happen when the Hubble length gets smaller than the radius of a blackhole?

I am wondering what would happen if our universe expansion keeps accelerating and finally one day, the Hubble distance gets smaller than the radius of a black hole. For example, at time t, two points whose distance between each other is 1km, shift away from each other at the speed of light because of the space expansion. If there is a black hole that has an event horizon of radius exactly 1 km, would it be possible that in such a universe, things that slightly enters the event horizon at the time t would be spat out because of acceleration of space expansion? Because after, say a tiny while, the space expansion makes two points that are 0.99 km from each other separate the speed of light so the event horizon of the black hole shrinks and things in the original event horizon is no longer in it?

Though this example is an extreme case, I am wondering that in general, would the acceleration of space expansion shrink the radius of the event horizons of black holes?

• I think you are describing what is sometimes called the "Big Rip" en.wikipedia.org/wiki/Big_Rip . I would also be interested in knowing more about physics in such an environment. Edit: However, this can happen with a fixed Hubble constant, so maybe some clarification is needed. Dec 4, 2018 at 5:14

Hubble length is defined as $$H_d=c/H_0$$ since Hubble constant gets smaller Hubble distance($$H_d$$) should increase, not decrease.