I am frequently asked, “If the Universe is expanding, what is it expanding into?” The answer is that it is not expanding into anything. Space itself grows.
With my spotty knowledge based on a 12 year watching cosmos 30 years ago, and then not paying enough attention in modern physics in college, I had assumed that the universe was the area with matter and energy, and what lied outside was just empty void and otherwise unknowable since we cannot see that far and there is nothing out there to reflect or emit light anyway.
