How does science determine the edge of the universe?

“If the multiverse theory is true and other universes truly exist, and let’s say we had the technology to escape our universe and go into interuniversal space…since time only exists because of the big bang and there are other “times”…

“If the multiverse theory is true and other universes truly exist, and let’s say we had the technology to escape our universe and go into interuniversal space…since time only exists because of the big bang and there are other “times” in different universes same as our own then what about the area in between the universes does time exist there?” – Barrows0re

“With the theory, or fact, that the universe is expanding how does science determine the edge of the universe? And once the energy/forces which drives the expansion is spent and the universe begins to shrink what is left in it’s place? The same void/nothingness before expansion? Thank you.” – patrick pegasus