Let's start with what is the universe: the **universe** is everything that exists - galaxies, stars, planets, matter, energies, etc. So the universe is composed of atomic components and the energies between them. That means that our universe is composed entities "positioned" relatively to each other in some space.

Even if everything is relative and space is infinite, there aren't any bounds like the start or end of space. How can be this space in nothing? It is supposed to be in something, forming something like atoms are forming complex structures. But if it's in something then where is this something? So that would be infinite recursion and if this recursion ends somewhere it would be again nothing. 

Do we exist? If we do, then where?