we all know the that the universe is exapnding. But where it is expanding?
It is expanding everywhere. If you mean what is it expanding INTO, then there is no such thing. It is not expanding INTO anything.
Why should the universe be located in any larger space?. It does not need to be anywhere. Internal distances can simply expand without there being any exterior.
Think of the universe as comprising all space. It is impossible to view it from the "outside" because there is no outside. So you must understand expansion differently from the way one does when one can view something from outside in the context of a surrounding space.
Changes in the geometry of space are experienced and measured by creatures living within that space.
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