The concept of the multiverse suggests the existence of multiple universes beyond our own. It is important to note that the multiverse is a speculative idea that is not currently confirmed by direct evidence. Different models of the multiverse propose different forms and sizes, so it's challenging to provide a definitive answer regarding its size in comparison to our universe.
However, it's worth mentioning a few common theories about the multiverse:
Level I Multiverse: In this type of multiverse, also known as the "Cosmic Inflation" multiverse, our universe is just one of many bubble-like regions that underwent rapid expansion during a period called cosmic inflation. Each bubble represents a separate universe with its own physical laws and properties. If this model is accurate, the size of the multiverse would be vast, potentially infinite, with an immense number of universes similar to or larger than our own.
Level II Multiverse: The Level II multiverse is based on the concept of an infinite or vastly large "landscape" of universes. This idea arises from string theory and the notion that the universe may have many possible configurations of fundamental particles and forces. According to this theory, each configuration represents a different universe within the multiverse. The size of the multiverse in this model would be either infinite or enormously larger than our observable universe.
Level III Multiverse: The Level III multiverse, also known as the "Many Worlds" interpretation of quantum mechanics, suggests that every quantum event leads to the creation of multiple universes. For example, in the famous Schrödinger's cat thought experiment, both the alive and dead states of the cat would exist in different branches of the multiverse. The size of the multiverse in this interpretation would depend on the frequency of quantum events and is difficult to quantify.
It's important to emphasize that the concept of the multiverse is still a subject of scientific investigation and debate. While these models provide intriguing possibilities, their precise size and nature remain speculative and are yet to be confirmed or directly observed.