The fate of the universe, especially in terms of black holes and their evolution, is a topic of significant speculation and study in cosmology. Black holes are indeed regions of space where gravity is so strong that nothing, not even light, can escape. They are formed when massive stars collapse under their own gravity at the end of their life cycles, resulting in a state where all the star’s mass is compacted into an incredibly small area with enormous gravitational pull.
The concept of black holes merging is well-supported by astrophysical observations. When black holes collide, they can coalesce to form a larger black hole, releasing gravitational waves in the process, as confirmed by detections from observatories like LIGO and Virgo. This merging process can occur repeatedly over vast timescales as galaxies interact and merge.
As the universe continues to expand and evolve, the fate of black holes and the long-term condition of the universe are subjects tackled by theories like the Big Freeze and the Big Rip. The Big Freeze scenario suggests that the universe will continue expanding, stars will eventually exhaust their fuel, and galaxies will recede from each other faster than new stars can form, ultimately resulting in a cold, dark universe filled with inactive remnants like black holes and depleted stars.
Regarding the vision of all black holes merging into one or starting a new universe, this aligns with theoretical concepts like cosmic natural selection or the hypothesis of black holes as seeds for new universes. Some speculative theories propose that under certain conditions, the singularity within a black hole might represent the birth of a new universe, with its own distinct spacetime. However, these ideas are currently beyond experimental verification and remain in the realm of theoretical physics.
Ultimately, the current understanding, following the laws of thermodynamics and the absence of an unknown cosmological mechanism, suggests that black holes will slowly evaporate over an extraordinarily long timescale due to Hawking radiation. This process would leave behind a universe that corresponds more closely with the Big Freeze scenario: a dark, cold expanse with incredibly sparse matter and the remnants of evaporated black holes. This aligns more with the notion of eventual darkness rather than the rebirth of a new universe initiated by black holes.