The concept of a multiverse suggests the existence of multiple universes or regions of space-time that may have different properties, physical laws, or initial conditions. However, the nature of what might occupy the space between these universes, if anything at all, is highly speculative and not well-defined within current scientific understanding. The concept of the multiverse is still a topic of ongoing research and exploration, and different theoretical frameworks propose various possibilities for the structure of the multiverse.
Here are a few different perspectives on what could occupy the space between universes:
Empty Space: One possibility is that the space between universes is simply empty, devoid of matter, energy, or any other discernible entities. This would imply a vast expanse of nothingness between the individual universes.
Higher-Dimensional Space: Some theories, such as string theory and brane cosmology, suggest the existence of additional spatial dimensions beyond the three dimensions of space we commonly experience. In this context, the space between universes could potentially be occupied by higher-dimensional structures or entities that are beyond our current understanding.
Quantum Foam and Fluctuations: Quantum mechanics and theories of quantum gravity propose that space-time is not a continuous and smooth entity but rather has a quantum nature. At the smallest scales, space-time might exhibit a foamy or fluctuating structure known as the quantum foam. In this view, the space between universes could be a complex and dynamic environment influenced by quantum fluctuations.
Other Universes or Structures: Some cosmological theories, such as eternal inflation or bubble universes, propose the existence of an ever-expanding or inflating multiverse where new universes constantly emerge. In this scenario, the space between universes would be occupied by other universes, regions of space-time, or structures associated with the multiverse.
It's important to note that these ideas about the nature of the multiverse and the space between universes are highly speculative and are still the subject of active scientific research and theoretical exploration. At present, there is no definitive experimental evidence or consensus on the existence of a multiverse or the properties of the space between universes.