The similarity of our universe to a black hole 1. The universe is expanding, but, in turn, black holes can also grow rather quickly in size due to the absorption of mass. 2. Nobody knows where the border of the Universe is - we know only about cosmological horizon. The border of the universe has never been seen, and can we ever get to it? The limits of the black hole, the event horizon, no one and nothing can leave, not even the light. 3. Another interesting point - in the center of the black hole there is a singularity, which is a point in space-time, where the density of matter is so high that the laws of physics that are familiar to us no longer work in it. The same singularity is also present in the cosmological model of the Universe - in the Big Bang Theory. 4. Among the similarities there is also spherical symmetry, in which, if an object is inside a black hole, then wherever it looks, it will be the same everywhere - there is only a black hole around. In the Universe, too, at sufficiently large distances, wherever you look, all is the same everywhere. 5. Scientists have noticed that the Schwarzschild radius for the observable universe coincides with the radius of the black hole event horizon. The essence of this statement is that if an object with a certain mass is less than the Schwarzschild radius for this mass, then it will be a black hole. For example, if you calculate such a radius for the Earth, then, in order for the Earth to turn into a black hole, it is necessary that this radius is slightly less than a centimeter. The logic is that the radius of the observable Universe and its mass are such that it should be a black hole, by analogy with the fact that our planet was one and a half centimeters in diameter. Our world and the black holes themselves are described mathematically by the same Einstein equations, maybe this is just a coincidence? Hypothesis (https://bit.ly/3E7Y9QF). A particularly interesting version is that each black hole contains its own universe, and they all exist like a bubble in a bubble, and parallel worlds, possibly very close to us. Matter from one universe is absorbed, drawn into another, and there, in a parallel universe, it seems to them that scientists are seeing some kind of Big Bang - the Big Rebound, which may be the cause of the expanding universe. It turns out that everything in the world is cyclical. One state passes into another, and our Universe was born in the same way.