system
Given the following post, respond as if you're commenting on Reddit:
human
If all of the mass in the universe was to be inside of one black hole right now would the event horizon be larger, smaller or the same size as the universe is right now?

also if this was possible would this effect the rate at which the universe expands (especially if the event horizon of this black hole is larger than what the universe is right now)
gpt
That black hole cannot form. In fact, that mass is already inside its own Schwarzschild radius: if you do the calculation that radius is about equal to the radius of the observable Universe, so you can tell already something doesn't add up.

An intuitive understanding for this is perhaps as such: the uniform distribution of matter that we see in the observable Universe continues on at least for a good bit beyond the cosmological horizon. All points of the Universe are mostly identical and none is special. This matter beyond the horizon pulls on you as much as does the matter inside. The overall effect is that this can make the Universe itself expand or contract (depending on the proportions of the various types of energy you can have in your Universe) but you cannot seal off one part of the Universe from the rest of it with an event horizon (which is what a black hole is) because that contradicts the fact that all points of the Universe are equal and are to be treated equally.