The concept of multiple expanding universes is often associated with the idea of the multiverse, which is a hypothetical framework that suggests the existence of multiple universes, each with its own set of physical laws and properties. In such a scenario, where multiple universes are expanding, the question of what happens when two expanding universes come into contact is intriguing but remains largely speculative, as our current understanding of the multiverse is still a topic of ongoing research and exploration.
Different theories within the multiverse framework propose various possibilities for the behavior of neighboring expanding universes. Here are a few speculative ideas:
Bubble Collisions: One hypothesis is that universes in the multiverse may exist as separate "bubbles" within a larger space. If two expanding universes were to come into contact or collide, it is suggested that their interaction might lead to dramatic effects. This could potentially result in the creation of new universes or even influence the physical properties of the involved universes.
Cosmic Inflation: Inflationary cosmology, a theory explaining the rapid expansion of the early universe, also allows for the possibility of the existence of multiple expanding universes. According to this theory, the regions of spacetime that undergo inflation can give rise to distinct universes. In such a scenario, two expanding universes may not physically interact or touch each other, as they are already causally disconnected due to their rapid expansion.
String Theory: In certain formulations of string theory, which aims to provide a unified description of the fundamental forces of nature, the existence of extra dimensions beyond our familiar three spatial dimensions is proposed. These extra dimensions might allow for the existence of parallel universes or branes, which could potentially interact or come close to one another.
It's important to note that these ideas are still highly speculative, and there is currently no experimental evidence to support or refute the existence of a multiverse or how expanding universes might interact if they were to come into contact. The multiverse remains an active area of theoretical physics and cosmology, and further research and advancements are needed to gain a better understanding of its potential implications.