Without an early presence of black holes, it is impossible for galaxies to have formed. No galaxies, no heavy elements near Main Sequence Stars. No such elements near stable stars, no rocky planets that have the time to develop life. No life, no observers.
So, black holes are "fundamental" in the sense that a Universe without them would be a Universe without anyone to recognize that there were no black holes!
Black Holes.
Stephen Hawking's work on black holes has advanced our understanding of fundamental physics, leading to discoveries about the behavior of black holes and the nature of the universe. This knowledge has contributed to technological advancements and new insights into the fundamental laws of physics, which could have practical applications in the future. Additionally, Hawking's work inspires curiosity and innovation in scientific research and education worldwide.
String theory offers insights into the behavior of black holes by suggesting that the fundamental building blocks of the universe are tiny, vibrating strings. These strings can provide a more comprehensive understanding of how black holes interact with other particles and forces in the universe, leading to new perspectives on their behavior and properties.
Mass that has entered a black hole isn't destroyed. Instead, it is converted into gravitational energy. Thus, no fundamental laws about the universe are violated (i.e. the law of conservation of mass).
Even though black holes suck through parts of the universe, the universe is inevitably big, and growing so as the universe is being sucked into another dimension by black holes, it is also expanding.
There are already black holes within the universe
Black Holes' can 'eat' any type of matter in the Universe.
Probably stellar mass black holes
The universe likely contains millions upon millions of black holes.
No.
The black holes may not devour everything since the outward velocity of the matter in the universe may escapethe gravitational pull of the black holes. Stephen Hawkins reckons that even the mass in the black holes would diminish over time, though over trillions and trillions of years.
Stephen Hawking worked on understanding the nature of black holes, the origins of the universe, and the theory of everything in physics. He also focused on reconciling quantum mechanics and general relativity. In his work, he aimed to explain complex phenomena in the universe and deepen our understanding of the fundamental laws governing it.