What is on the outside of our universe?

Question

Claire Anctil · Accepted Answer

As of now, there is no preferred center for our expanding universe. What is expanding is space and not the matter. So, in my opinion, the definition of outside of our universe is not yet definitive..

The definition of direction is local, not global, and there is no absolute frame of reference to fix any direction. Our universe is expanding evenly around no preferred center, contrary to the adage "the surface area is equal to the rate of change of a sphere's volume." Any definition of "outside" of our universe is not definitive, since all of these are not applicable to the expansion of our universe. I had generalized this for higher dimensional hyper sphere, long ago. The topic of what is outside could be discussed once there is a widely accepted definition of what is "outside of our universe."

Owen Atkinson · Answer

undefined The concept of what lies beyond the observable universe is speculative and not yet fully understood. Some theories suggest the existence of a multiverse or other dimensions, but these are currently hypothetical and have not been empirically confirmed.