What is behind the Universe being observed?

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We know that our Solar system is part of a vast galaxy. We also know that there are approximately 100 to 200 billion galaxies in “close proximity " to Earth. This is what scientists call the observable Universe. But what lies beyond what is observable? There are more galaxies out there, and these galaxies go on forever? Are these galaxies part of one Universe, or are they part of many other universes? In this regard, the question arises: our universe is all that is and we live in the multiverse? Is the universe or Multiverse just incredibly large or is it infinite?