WHAT IS OUTSIDE THE KNOWN UNIVERSE

It's one of the most compelling questions you could possibly ask, one that humanity has been asking since basically the beginning of time. What's beyond the known limits? What's past the edge of our maps? The ultimate version of this question is, what lies outside the boundary of the Universe? To answer the question of what's outside the universe, we first need to define exactly what we mean by "universe". If you take it to mean literally all the things that could possibly exist in all of space and time, then there can't be anything outside the universe. Even if you imagine something outside that volume, then whatever is outside also has to be included in the universe. Even if the universe is a formless, shapeless, nameless void of absolutely nothing, that's still a thing and is counted on the list of "all the things"- and, hence, is, by definition, a part of the universe. If the universe is infinite in size, you don't really need to worry about this conundrum. The universe, being all there is, is infinitely big and has no edge, so there's no outside to even talk about. Sure there's an outside to our observable patch of the universe. The cosmos is only so old, and light only travels so fast. So, in the history of the universe, we haven't received light from every galaxy. The current width of the observable universe is about 90 billion light-years. And presumably beyond the boundary there are other random stars and galaxies. But past that? It's difficult to calculate with any degree of certainty. Cosmologists aren't sure if the universe is infinitely big or just extremely large. Current observations and measurements of the curvature of the universe indicate that it is almost perfectly flat. You might think this means the universe is infinite. But even in the case of a flat universe, the cosmos doesn't have to be infinitely big. The universe could be completely flat yet closed in on itself. Even assuming that the universe is finite, it doesn't necessarily suggest there is an edge or an outside. The universe doesn't need that outside perspective in order to exist. The universe simply is. It is entirely mathematically self-consistent to define a three-dimensional universe without requiring an outside to that universe. It's sounds impossible for there to be a finite universe that has nothing outside it. It could very well be that our universe does indeed have an "outside". But again this doesn't have to be the case. There's nothing in mathematics that describes the universe that demands an outside.