system
Given the following post, respond as if you're commenting on Reddit:
human
Two Questions. First, Black holes are said to have infinite density. If that's the case, wouldn't their gravitational influence instantaneously suck in the entire universe? Second. If a singularity just 1 dimension, how does a black hole have spin? Don't they need multiple dimensions to rotate?

To further clarify. 

The first question. If they had infinite density, wouldnt that mean that an object at the event horizon would feel the same powerful pull as an object 50 light years away, or even further?

The second question. I think i did a well enough job asking but if you need me to be more clear about the question, i'll gladly update with an edit.
gpt
The characterisation of a singularity in any particular way is not very useful for knowing about what's really going on inside a black hole.

There are good reasons to expect that there are no singularities and the existence of singularities in General Relativity is generally taken to mean we can't trust it once we get close to the singularity. Additionally there is very little reason to expect the interior of a real black hole is anything like the interior in the non-dynamical black holes we often talk about.

Real black holes have to form, and they interact with their environment. So they are dynamical. There is good evidence, but it wasn't immediately obvious, that the exterior of the stationary black holes describes the exterior of real black holes well though.

When we talk about the rotation of a black hole, you do yourself a disservice by imagining that this has anything to do with a rotating object inside the horizon. 

To talk about what the rotation means from a physical point of view let me first give an analogy, Imagine you have some object that isn't perfectly level, so in some places it is higher and other places it is lower. If the object isn't changing this height is "non-dynamical" but if you are moving around the object the height you're at will be changing. We call a perspective where the height isn't changing under your feet a stationary perspective.

How does this relate to rotating black holes? Well something that is stationary closer to the black hole will be orbiting the black hole according to something stationary further away. Furthermore, if you throw something into the black hole which has some angular momentum the rotation of that closer observer will speed up. It will in fact speed up in exactly the same way as if you imagine the horizon was a rotating object which gained the angular momentum of what fell in.