Final answer:
The question involves concepts from quantum physics and cosmology, such as the anthropic principle and the fate of the universe, touching on the speculative possibility of a multiverse and various end scenarios like the Big Freeze and Heat Death.
Step-by-step explanation:
The topic you've touched upon involves elements of quantum physics and cosmology. The notion that an observer is required for something to exist is a philosophical interpretation of quantum mechanics called the 'observer effect'. The idea of the anthropic principle suggests that the universe's properties are such because we are here to observe them. Existence and nonexistence, as well as the passage of time, have different interpretations in various physical theories.
Regarding the ultimate fate of the universe, scientists have coined terms like the Big Freeze, Heat Death, Big Rip, and Big Crunch, which predict various scenarios for the universe's end, considering the observable expansion and energy distribution. The discovery of dark energy has shifted some of these theories, relegating concerns about events like the Big Crunch to a lower priority. Our understanding of time, especially considering quantum gravity, implies there is a finite limit to how short time intervals can be, affecting our conception of the universe's beginnings.
When discussing the possibility of multiple universes or a multiverse, this moves towards speculative and philosophical realms. However, these ideas offer intriguing implications regarding the physical laws in our universe and perhaps others within the hypothetical multiverse. Future advancements in physics may help us understand why our universe has its specific properties without needing to resort to the anthropic principle.