Hi Cookie, I’m not an astronomer but I’ll try to answer. Black holes don’t have enough gravitational power to pull in the whole universe and if they did – well I really have no idea what would happen but it’d either be really cool or really horrible (and probably the latter…).
A great question! Black holes have an event horizon. That means that anything that passes this boundary cannot escape from the black hole (this includes light and matter). Anything outside the boundary is relatively safe.
What would happen if the entire universe was sucked in?…this will not happen, however, No one really knows what is inside a black hole. The very centre is likely a ‘singularity’ and will have a huge mass. I think, in short, we would be squished.
Black holes are very compact, and therefore VERY heavy bodies in space. Because
they are so heavy, the gravitational force they produce is very high, so they are
able to suck in everything, even light waves, the fastest thing in the universe. However,
while gravitational force is larger for heavy objects, it reduces as you get further away from it.
This is just like on earth, where if you throw a ball on earth, if falls back to the ground, but if you get far enough into space and throw the ball it would just keep going. Black holes have what is known as an ‘event horizon’ – if you are closer to the black hole than the event horizon, then the gravitational force is too strong and you would be sucked in. If you are outside of the event horizon, the
gravitational force is too weak because you are too far away, and your momentum will stop you being sucked in. Only when things get too close are they sucked into black holes, and because there aren’t too many black holes out
there, most of the universe is not within the event horizon of any black hole, so is not sucked in.
Because black holes don’t work that way. Black holes have a lot of mass in it, so much so that an object can not escape from it once it is inside the black hole because it can’t afford the gravitational pull. That’s why massive stars also become black holes, it is sort of their death, they can not handle with their gravity any more and they shrink. Therefore, there is no way a black hole can suck the entire universe, sleep peacefully 🙂 If you enter in black hole zone, you might not find a way out though, that I don’t promise!