How can there be a multi-verse when universe means 'one' or 'everything' you'll have to correct me if I'm wrong. But if the universe means everything how can you have two everything's and the universe is bigger than what out equipment detects today and if there is a galaxy outside our viewing range it's still in the universe, the universe is massive and if the is something outside the universe doesn't that make it apart of the universe as is is something in nothing outside of everything so it become everything.
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You are confusing semantics with reality. Until relatively recently, our Milky Way Galaxy was considered to be "all there was", until Emmanuel Kant coined the term "island universe" for nebulae that had been observed, but considered to be part of the Milky Way. It can be seen from this that the term "universe" has changed several times in the past, and reality should not be defined by the meaning of a particular word. The possibility of a Multiverse stems from string theory and is a natural consequence of several theories coming together. In fact, it has been stated by several physicists(including myself, by the way) that it would be very much more difficult to make sense of our own Universe without recourse to something outside it. It solves many problems and answers so many questions that the vast majority of cosmologists accept at least a version of it. You are right about two "everythings" though this could be extended to three. We live in a bubble that is about 93 billion light years in diameter (the Observable Universe) which is contained in a very much larger Universe. This in turn appears to be part of a Multiverse in which there are an unknown number of other universes, some of which may be similar to our own, and some of which may be radically different. Don't be side-tracked by supposed meanings of words. After all, there are several languages around th world that have no word for snow. We in the Northern Hemisphere at this time of the year know only too well that it exists!