In the vast universe, our existence is like a blink of an eye. Human needs are completely ignored by the universe, and nature exerts its powerful power on the scale of space and time in an unpredictable way. Perhaps the only comfort we can get is that we will ask endless questions about where we are and seek their answers. One of the questions is what is the profound connection between this special environment and the magnificent cosmic picture composed of stars, galaxies and black holes.
Many cosmic phenomena may potentially affect the existence of life, but some of them will be more obvious, and black holes are one of them. No other celestial body in the universe can convert matter into energy so efficiently. No other celestial body can let matter travel through tens of thousands of light years at a speed close to the speed of light like a black hole. In addition, black holes can trap nearby substances, and no one is spared. They are the ultimate competitive diners in the universe, just like a "gourmet", who often gobble up food instead of chewing it slowly.
Matter falling into a black hole will not disappear quietly. As we get closer and closer to the horizon (the surface of a black hole), matter will move at a very high speed. If the black hole itself is rotating, then the matter falling into the black hole will rotate at a very high speed. When these substances collide with any other substances, their huge kinetic energy will be converted into the kinetic energy of atoms and subatomic particles, releasing electromagnetic radiation. These massive particles and photons can escape from the black hole and surge out before reaching the horizon. A rough analogy is the noise generated by bathtub drainage. As water enters the drainage pipe and violently impacts the molecules in the air, some kinetic energy will be converted into sound waves. Sound waves move much faster than water and can escape from the drainage pipe. For a huge black hole, the energy released in such a "digestion" process is enough to have a wide impact on the surrounding galaxies.
Matter is "fed" into a supermassive black hole, just like clothes occasionally shake in a washing machine to make a sound. This process is called "loading cycle". The duty cycle of a black hole represents the transition speed of the black hole from swallowing matter to restoring calm. At present, the supermassive black hole in the center of the Milky Way is in a calm state, but it will also change with time. Astronomers speculate that there is a correlation between the load period of the black hole in the center of the Milky Way and the overall state of the Milky Way.