There are one or more black holes in the center of galaxies in the universe, but the universe itself is not a black hole, and even light cannot escape from the black hole. If the universe is a black hole, strong pressure will make it impossible for all civilizations to exist. Black holes are in the middle and old age of the universe, and their temperature (energy) is very high. Some people say that the big bang singularity where black holes gather is the critical point of energy, so it can explode. In his later years, black holes became the main celestial bodies in the universe. Finally, the black holes devour each other and return to the singularity of BIGBANG, and so on.

At present, the existence of black holes can be basically determined. Although the characteristics of black holes make it difficult to be directly observed, human beings can determine the existence of black holes with the help of the special operation mode and special optical phenomena of stars. The stars in the center of the Milky Way move around the center at a high speed, so there must be some kind of celestial body with great gravity in the center of the Milky Way. Sometimes, scientists can even see the "back" of the star, but in life, we will find that light travels in a straight line. Seeing the back of the star also shows that there is some kind of celestial body with great gravity in the universe.

In fact, the propagation of light is not a straight line, but around the shortest distance in space. Supergravity celestial bodies cause space-time to bend, and the propagation of light in curved space-time is also "curved". Humans can now observe the universe with all kinds of visible light and electromagnetic waves. Although they are also bent by some massive celestial bodies in the universe, they can still be captured by humans. In the event horizon of a black hole, light cannot escape and cannot be observed.

The universe is composed of many levels of celestial structures, such as star system, galaxy, week group, supercluster and so on. The number of black holes is also very large, at least there is a black hole in the center of every galaxy. If the universe is a black hole, the pressure will be so great that all galaxies and civilizations will be squeezed together and become a "singularity" when the universe is created.