Is seemingly empty space considered part of the universe? This basic question can eradicate what I believe to be a huge mistaken concept that scientists have believed for too long now.
Let me put it another way: Is the space between the Milky Way and Canis Major Dwarf (our galaxy and a close neighbor) part of the universe? Is the empty space beyond IOK-1 (One of the furthest known galaxies) considered part of the universe? What about the space space in a direct line from that galaxy and a different galaxy?
A basic definition of the word "universe" is: "the totality of all the things that exist; creation; the cosmos". In short, the universe is everything that exists everywhere and for all time. So I think we must say yes, empty space qualifies as part of the universe.
Wait a minute! The basic idea of the Big Bang (a theory for the creation of the universe) is that everything started from an "explosion" and has been expanding outward ever since.
But expanding into what? If we have agreed that empty space is, in fact part of the universe, then we face a problem of definitions. The universe can not expand into itself.
I am not saying (in this post) that the Big Bang did not occur. I am saying that it can not be the explanation of the formation of the universe.