The concept of multiverses, which posits the existence of multiple universes beyond our own, is a topic that is still the subject of scientific inquiry and speculation. Different theories propose various ideas about the nature and properties of multiverses, but currently, there is no consensus on whether they have a definitive beginning or end, or if they continue indefinitely.
One theory, known as eternal inflation, suggests that the process of cosmic inflation, which is the rapid expansion of the universe, may give rise to the formation of multiple universes within a larger multiverse. According to this theory, inflation continues eternally, creating an infinite number of universes with different physical laws and properties. In this view, the multiverse would not have a definite beginning or end but would exist in a perpetual state of inflation.
Another perspective is provided by the cyclic model, which proposes that our universe goes through cycles of expansion and contraction. According to this idea, each cycle starts with a big bang and ends with a big crunch, followed by a new big bang, forming an eternal cycle of universes.
It's important to note that these theories are highly speculative and are still being explored and refined by physicists and cosmologists. The nature of multiverses and their temporal properties are areas of active research, and our understanding may evolve as new evidence and theories emerge.
Ultimately, the question of whether multiverses have a beginning and an end or continue indefinitely is still an open question in scientific exploration.