How does cosmic inflation lead to the idea of multiple bubble universes?

In the context of cosmology, the idea of multiple bubble universes arises from the mechanics of inflation. During the early universe, space-time underwent exponential expansion driven by vacuum energy. In many inflationary models, the transition from this high-energy "false vacuum" state to a lower-energy "true vacuum" state does not occur everywhere simultaneously.12

Instead, this transition happens at different times in different locations. While some regions exit inflation to become ordinary, expanding universes, other regions continue to inflate eternally. This process generates an infinite number of post-inflationary regions, often visualized as expanding bubbles within a common, inflating background.2

When these bubble universes collide, they may leave detectable imprints, such as circular disturbances, on the cosmic microwave background. This framework is frequently linked to the anthropic principle, as it suggests that physical constants may vary across these different bubbles, explaining why our specific universe possesses conditions compatible with life.2